Tyrosine (4-hydroxyphenylalanine) is one of the naturally occurring 22 amino acids. The importance of tyrosine is due to the presence of its phenolic side chain. In biological systems, the tyrosyl residue in proteins is found to be sulfated, phosphorylated and nitrated. Upon oxidation with dioxygenases, Tyr residue forms dopaquinone which undergoes a series of reactions ultimately leading to the formation of melanin. Tyr is also a precursor to neurotransmitters (catechol amines namely dopamine, epinephrine and norepinephrine) and thyroid harmones T4 and T3. Tyr residue is also found to be cross linked with other amino acid residues in the active site of certain proteins. Tyr-Tyr cross link has also been associated with neurodegenerative diseases. Tyr residue in proteins has been targeted widely for site selective modifications. A series of chemical modifications like acylation, allylation, ene-type reaction, iodination with radiolabeled iodine, formation of Tyr-Tyr cross link with oxidants and aminoalkylation have been carried out on surface exposed Tyr residues in proteins. Apart from these chemical modifications of Tyr on protein surface, a couple of free Tyr-based scaffolds have also been developed for different applications. Similar to tyrosine-based scaffolds, several phenolate-based scaffolds have also been developed for various applications. Several phenolate-based binuclear metal complexes have been developed as mimics of the active site of metalloenzymes. Moreover, by varying the substituent in the phenolate scaffold, the redox properties of metal bound in these systems can be tuned. The thesis consists of five chapters. The first chapter gives general idea about tyrosine-and phenolate-based scaffolds. The first chapter also gives introduction to zinc(II)-containing enzymes metallo-β-lactamases (mβls) and phosphotriesterase (PTE) and their functional mimics. The importance of copper(II)-containing enzyme, catechol oxidase and its mimics has also been discussed. The significance and formation of o-dityrosine (Tyr-Tyr cross link) has also been briefly discussed. In chapters 2 and 3, a couple of phenolate-based ligands and their corresponding zinc(II)- and copper(II)- complexes have been synthesized and have been checked as mimics of zinc(II)-containing enzymes (mβl and PTE) and copper-containing enzyme catechol oxidase, respectively. In chapter 4, a series of tyrosine-based ligands have been designed and their in situ copper(II) complexes have been tested as mimics of catechol oxidase. In chapter 5, the effect of neighboring amino acid in the formation of Tyr-Tyr cross link has been studied. In chapter 2, a couple of zinc(II) complexes have been synthesized and studied as mimic of zinc(II)-containing enzymes mβl and PTE. Metallo-β-lactamases (mβls) are zinc(II)-containing enzymes which exist in both mono- and binuclear forms. Mβls are capable of hydrolyzing β-lactam ring in antibiotics and make them inactive (Scheme 1(A)). To date, an effective inhibitor for this enzyme is not known. Hence, in order to understand the nature of the enzyme a couple of synthetic mimics are known. However, in most of the synthetic mimics both the metal ions are in symmetrical environment. Therefore, we have attempted to design a few unsymmetrical phenolate- based ligands and their zinc(II) complexes. The unsymmetrical phenolate-based ligands HL1 and HL2 have been synthesized by sequential mannich reaction with formaldehyde and two different amines. Complexes 1 and 2 are obtained from ligands HL1 and HL2, respectively (Figure 1). For comparative purpose, the symmetrical ligands HL3 and HL4, and their zinc(II)-complexes 3 and 4 have been synthesized by reported procedures (Figure 1). The efficiency of the complexes 1-4 towards the hydrolysis of oxacillin has been studied. It has been observed that the binuclear zinc(II) complexes with metal-bound water molecule 1 and 4 are able to hydrolyze oxacillin at much faster rates compared to that of mononuclear complexes 2 and 3. However, between 1 and 4, there is no appreciable change in activity, indicating that the slight change in ligand environment has no significant role. PTE is a binuclear zinc(II)-containing enzyme, capable of hydrolyzing toxic organphosphotriesters to less toxic diesters (Scheme 1(B)). As the binuclear active site of mβl is comparable with that of phosphotriesterase (PTE), PTE activity of complexes 1-4 has been studied. Although the binuclear zinc(II)-complexes 1 and 4 are able to hydrolyze PNPDPP (p-nitrophenyl diphenyl phosphate) initially, these complexes are not able to effect complete hydrolysis. This is due to the inhibition of complexes 1 and 4 by hydrolyzed product, diester. However with mononuclear complexes 2 and 3 no such inhibitions is possible, and are capable of hydrolyzing PNPDPP at comparatively faster rates than 1 and 4. Scheme 1. Function of metallo-β-lactamase and phosphotriesterase. (A) Hydrolysis of β-lactam ring in antibiotics by metallo-β-lactamase. (B) Hydrolysis of organophosphotriesters to diesters by phosphotriesterase. Figure 1. Chemical structures of ligands HL1-HL4 and their corresponding zinc(II)complexes 1-4. In chapter 3, a couple of copper(II) complexes have been synthesized and their catechol oxidase activity has been studied. Catechol oxidase belongs to the class of oxidoreductase and it catalyzes the oxidation of a wide range of o-diphenols to o-quinones through the reduction of molecular oxygen to water (Scheme 2). A four new µ4-oxo-bridged tetranuclear copper(II) complexes (5-8) have been synthesized (Figure 2). The ability of these complexes to catalyze the oxidation of 3,5-DTBC (3,5-Di-tert-butylcatechol) to 3,5-DTBQ (3,5-Di-tert-butylquinone) has been studied. A detailed kinetic study has been carried out which reveals that the complexes with exogenous acetate ligands (5 and 6) are better catechol oxidase mimics compared to complexes with exogenous chloride ligands (7 and 8). This observation is due to the labile nature of acetate compared to chloride, as the displacement of exogenous ligand is essential for the binding of substrate to the catalyst. Based on mass spectral analysis a plausible mechanism has been proposed for the oxidation of 3,5-DTBC by these complexes. Scheme 2. Oxidation of catechol by catechol oxidase. Figure 2. Chemical structures of copper(II) complexes 5-8. In chapter 4, by following the analogy between phenol and tyrosine, a series of binucleating ligands of tyrosine or tyrosyl dipeptides (Figures 3 and 4) have been synthesized by Mannich reaction under mild conditions. The in situ complexation of these fifteen new binucleating ligands (HL5-HL19) with copper(II) chloride has been observed. In situ complexation was followed by UV-visible and mass spectral analysis. These in situ complexes were able to oxidize 3,5-DTBC at slower rate compared to that of the tetranuclear complexes reported in chapter 3. The catecholase activity has also been tested with the addition of base. A slight enhancement in activity of in situ complexes has been observed in the presence of base. Based on mass spectral evidences, a plausible mechanism for the oxidation of catechol by these in situ complexes has been proposed. Figure 3. Binucleating ligands (Mannich bases) of boc-protected tyrosine and tyrosyl dipeptides. Figure 4. Binucleating ligands (Mannich bases) of boc-deprotected tyrosyl dipeptides. In chapter 5 of the thesis, the effect of neighboring amino acid residue in the formation of o,o-dityrosine (Tyr-Tyr cross link) has been studied. o,o’-Dityrosine is a specific marker for oxidative/nitrosative stress. The increase in concentration of dityrosine is associated with several disease states. A detailed study has been carried out in order to find out the effect of neighboring amino acid residues in the rate of formation of dityrosine of several tyrosyl dipeptides. The formation of dityrosine has been carried out with horseradish peroxidase(HRP) and H2O2 (Scheme 3). Except Cys-Tyr, all other tyrosyl dipeptides, form corresponding dityrosine with HRP/ H2O2. With Cys-Tyr, the formation of corresponding disulfide is observed. The appreciably higher rate of dityrosine formation of Phe-Tyr is attributed to the presence of strong hydrophobic environment around the active site of HRP. Among the polar tyrosyl peptides, the positively charged peptides (Arg-Tyr, Lys-Tyr) undergo dityrosine formation at much faster rate compared to that of negatively charged dipepptides (Asp-Tyr, Glu-Tyr). This trend is in accordance with the pKa of neighboring amino acid residues. The positively charged neighboring residues with higher pKa stabilizes ionized tyrosine, hence the rate of dityrosine formation is higher for them. As positively charged neighboring residue enhances the rate of dityrosine formation, the effect of externally added L-Arg has been studied. A coupling of a few biologically relevant tyrosine derivatives has been studied. The derivatives in which one of the ortho-positions of tyrosine is blocked, does not undergo coupling under the experimental conditions employed. Scheme 3. Formation of dityrosine of Ile-Tyr from Ile-Tyr in the presence of H2O2 catalyzed by HRP. (For structural formula and figures pl refer the abstract pdf file)

No description available.

Neste trabalho, alguns novos complexos imínicos de cobre(II) com ligantes inspirados em biomoléculas como oxindóis, contendo grupos indólicos, imidazólicos ou pirrólicos com diferentes características estruturais, foram sintetizados e caracterizados por análise elementar, espectrometria ESI-MS e espectroscopias IV, UVNis e EPR. As possíveis interações desses complexos de cobre com a albumina humana (HSA) e com o plasma sanguíneo foram estudadas através das técnicas EPR, CD e SDS-PAGE, indicando que estas ocorrem principalmente no sítio N-terminal da proteína. Suas reatividades frente a compostos biológicos relevantes, tais como glutationa, ascorbato e peróxido de hidrogênio, também foram verificadas. Alguns dos complexos estudados podem ser ativados por glutationa, ascorbato ou peróxido de hidrogênio, sendo capazes de gerar espécies reativas de oxigênio em concentrações significativas, na presença desses redutores ou oxidantes biológicos. Adicionalmente, as propriedades pró-oxidantes de tais complexos foram investigadas, visando elucidar estudos prévios de suas atividades pró-apoptótica e antitumoral. Alguns destes complexos foram mais eficientes em causar danos oxidativos à 2-deoxi-D-ribose, enquanto outros foram mais eficientes em causar oxidantes na proteína HSA, com formação de grupos carbonílicos, principalmente em presença de H202. Experimentos de CD complementaram estes resultados, indicando que somente alguns complexos causaram modificações na α-hélice da proteína. Experimentos de EPR com captador de spin, na presença de HSA e H202, mostraram a formação de quantidades apreciáveis de radicais hidroxil e radicais de carbono, em presença de peróxido de hidrogênio. Além disso, os complexos apresentaram notável habilidade de ligação ao DNA e conseqüente atividade nuclease, promovendo clivagens nas duas fitas. Experimentos de fluorescência, EPR, gel de eletroforese marcado com α-32P-UTP e CD foram ainda realizados, visando elucidar o mecanismo de ação destes complexos no meio biológico. Estes experimentos indicaram que eles podem se associar ao DNA, através de suas bases ou pela interação com a deoxi-ribose, já que promoveram danos oxidativos nestes substratos. Entretanto, não catalisam a hidrólise dos grupos fosfato, atuando, portanto, predominantemente por um mecanismo oxidativo. Através de CD, poucas perturbações na elipsicidade do DNA foram observadas, o que indica que estes complexos provavelmente estão localizadas nas cavidades ou alças do ácido nucléico. / Some novel imine-copper(II) complexes with ligands inspired in biomolecules such as oxindoles, containing indole, pirrole or imidazole moieties with different structural features were synthesized, and characterized by elemental analysis, IV, UV/Vis and EPR spectroscopies, and ESI-MS spectrommetry. Interactions of these complexes with human serum albumin (HSA) and human plasma were verified by EPR, CD and SDS-PAGE techniques, showing that they occur mainly at the N-terminal site of the protein. Their reactivity towards biological relevant compounds, such as glutathione, ascorbate and hydrogen peroxide were also verified; some of them are capable of generating ROS in significant concentrations, in the presence of these reducing or oxidant agents. Additionally, the activity of such copper(II) complexes in promoting oxidative damage to different substrates was investigated, in order to elucidate previous studies on their pro-apoptotic and antitumoral activity. Some of these complexes were much more efficient to cause oxidative damage to 2-deoxy-D-ribose, especially in the presence of hydrogen peroxide. On the contrary, others were more active in causing damage to HSA protein, with the formation of carbonyl groups. Experiments by CD corroborated these results, since only some of the complexes caused modifications in the protein -helix. EPR spin trapping experiments, in the presence of HSA and H2O2, showed significant generation of hydroxyl as well as carbon centered radicals. Moreover, all the complexes showed remarkable ability to bind to DNA, promoting double-strand cleavage, upon H2O2 activation. In order to investigate their mechanism of action, fluorescence, EPR, gel-electrophoresis with labeled α-32P-UTP and CD experiments were carried out. The results indicated that these complexes can bind to DNA through its bases or can interact with the deoxi-ribose rings, promoting oxidative damage to those substrates. On the contrary, they do not catalyze the hydrolysis of phosphate groups. By CD spectroscopy, little perturbations on the helicity conformation of the DNA were observed, indicating that these complexes are probably located in the grooves.

Neste trabalho, alguns novos complexos imínicos de cobre(II) com ligantes inspirados em biomoléculas como oxindóis, contendo grupos indólicos, imidazólicos ou pirrólicos com diferentes características estruturais, foram sintetizados e caracterizados por análise elementar, espectrometria ESI-MS e espectroscopias IV, UVNis e EPR. As possíveis interações desses complexos de cobre com a albumina humana (HSA) e com o plasma sanguíneo foram estudadas através das técnicas EPR, CD e SDS-PAGE, indicando que estas ocorrem principalmente no sítio N-terminal da proteína. Suas reatividades frente a compostos biológicos relevantes, tais como glutationa, ascorbato e peróxido de hidrogênio, também foram verificadas. Alguns dos complexos estudados podem ser ativados por glutationa, ascorbato ou peróxido de hidrogênio, sendo capazes de gerar espécies reativas de oxigênio em concentrações significativas, na presença desses redutores ou oxidantes biológicos. Adicionalmente, as propriedades pró-oxidantes de tais complexos foram investigadas, visando elucidar estudos prévios de suas atividades pró-apoptótica e antitumoral. Alguns destes complexos foram mais eficientes em causar danos oxidativos à 2-deoxi-D-ribose, enquanto outros foram mais eficientes em causar oxidantes na proteína HSA, com formação de grupos carbonílicos, principalmente em presença de H202. Experimentos de CD complementaram estes resultados, indicando que somente alguns complexos causaram modificações na α-hélice da proteína. Experimentos de EPR com captador de spin, na presença de HSA e H202, mostraram a formação de quantidades apreciáveis de radicais hidroxil e radicais de carbono, em presença de peróxido de hidrogênio. Além disso, os complexos apresentaram notável habilidade de ligação ao DNA e conseqüente atividade nuclease, promovendo clivagens nas duas fitas. Experimentos de fluorescência, EPR, gel de eletroforese marcado com α-32P-UTP e CD foram ainda realizados, visando elucidar o mecanismo de ação destes complexos no meio biológico. Estes experimentos indicaram que eles podem se associar ao DNA, através de suas bases ou pela interação com a deoxi-ribose, já que promoveram danos oxidativos nestes substratos. Entretanto, não catalisam a hidrólise dos grupos fosfato, atuando, portanto, predominantemente por um mecanismo oxidativo. Através de CD, poucas perturbações na elipsicidade do DNA foram observadas, o que indica que estes complexos provavelmente estão localizadas nas cavidades ou alças do ácido nucléico. / Some novel imine-copper(II) complexes with ligands inspired in biomolecules such as oxindoles, containing indole, pirrole or imidazole moieties with different structural features were synthesized, and characterized by elemental analysis, IV, UV/Vis and EPR spectroscopies, and ESI-MS spectrommetry. Interactions of these complexes with human serum albumin (HSA) and human plasma were verified by EPR, CD and SDS-PAGE techniques, showing that they occur mainly at the N-terminal site of the protein. Their reactivity towards biological relevant compounds, such as glutathione, ascorbate and hydrogen peroxide were also verified; some of them are capable of generating ROS in significant concentrations, in the presence of these reducing or oxidant agents. Additionally, the activity of such copper(II) complexes in promoting oxidative damage to different substrates was investigated, in order to elucidate previous studies on their pro-apoptotic and antitumoral activity. Some of these complexes were much more efficient to cause oxidative damage to 2-deoxy-D-ribose, especially in the presence of hydrogen peroxide. On the contrary, others were more active in causing damage to HSA protein, with the formation of carbonyl groups. Experiments by CD corroborated these results, since only some of the complexes caused modifications in the protein -helix. EPR spin trapping experiments, in the presence of HSA and H2O2, showed significant generation of hydroxyl as well as carbon centered radicals. Moreover, all the complexes showed remarkable ability to bind to DNA, promoting double-strand cleavage, upon H2O2 activation. In order to investigate their mechanism of action, fluorescence, EPR, gel-electrophoresis with labeled α-32P-UTP and CD experiments were carried out. The results indicated that these complexes can bind to DNA through its bases or can interact with the deoxi-ribose rings, promoting oxidative damage to those substrates. On the contrary, they do not catalyze the hydrolysis of phosphate groups. By CD spectroscopy, little perturbations on the helicity conformation of the DNA were observed, indicating that these complexes are probably located in the grooves.

Des ligands diiminopyrrolides portant deux substituants N-méthylbenzyle chiraux ont été préparés par condensation du 1H-pyrrole-2,5-dicarbaldéhyde et de la S-méthylbenzylamine. La réaction de ce ligand avec du Cu(OMe)2 en présence de 2 équivalents de pyridylméthanol ou de diméthylaminoéthanol a donné les catalyseurs dimèriques de Cu(II) L2Cu2(μ-OR)2. L'application de ces complexes dans la polymérisation du rac-lactide a permis d’obtenir respectivement des PLA isotactiques (Pm = 0,73) et atactiques (Pm = 0,50). Les études cinétiques menées sur ces deux complexes ont indiqué la présence de deux espèces actives différentes. Les résultats de GPC obtenus pour le catalyseur cuivrique contenant deux pyridylméthoxyde pontant indiquent la croissance d'une seule chaîne par dimère (un des alcoolates reste en tant que ligand spectateur), alors que dans le cas du complexe portant deux diméthylaminoéthoxydes, les deux alcoolate attaquent le lactide. Un mécanisme de "ligand mediated chain-end control", se faisant par l'épimérisation du site catalytique par rapport à la chiralité de la dernière molecule de lactide insérée, est proposé. La présence d'un "bras" iminé coordonné et non coordonné facilite l'épimérisation car celle-ci ne nécessite qu'une dissociation / ré-coordination. Les effets du ligand (encombrement stérique) sur l'activité et le stéréocontrôle du catalyseur ont été étudiés par utilisations de divers substituants sur l’imine : benzyle, bromobenzyle, xylyle, diphénylméthyle et cyclohexyle. Les subtituants imino-benzyle, -bromobenzyle et -cyclohexyle one été les seuls fournissant les catalyseurs de cuivre dimèrique désiré avec le pyridylméthoxyde. Les complexes portant les groupes benzyle et cyclohexyle ont produit du PLA isotactique. La chiralité portée par le liguand n'était donc pas requise pour le stéréocontrôle. Le complexe bromobenzyl-substitué a été le seul à fournir un site catalytique achirale avec les deux imines coordinées et produit un PLA atactique. Des complexes monoiminopyrrolidiques de cuivre(II) avec des ligands pyridylméthoxydes ont été préparés avec des substituants imino N-naphtyle, -diphénylméthyle, -xylyle et -2,6-diisopropylphényle. Ils ont démontré un stéréocontrôle réduit, qui est présument due à une épimérisation plus lente (une rotation autour de la liaison Cu-pyrrole est désormais nécessaire). Tous les complexes ont fourni des PLA isotactiques, mais le stéréocontrôle obtenu n'a pas dépassé celui des complexes diiminopyrrolidiques. La substitution de la position 5 du pyrrole par un Chlore conduit à une perte d'activité tandis qu'un substituant méthyle fournit un PLA atactique. Les ligands phénoxy-imine ont été préparés par condensation de dérivée de salicylaldéhydes et d’une amine (benzyle, cyclohexyle, xylyle et diphénylméthyle). Leurs complexes de Cuivre(II) portant soit un ligand diméthylaminoéthoxyde ou pyridylméthoxyde étaient structurellement similaires aux complexes iminopyrrolidiques. Tous les complexes étaient actifs dans la polymérisation du rac-lactide, mais bien que les résultats GPC indiquaient la croissance d'une seule chaîne par dimère pour les complexes de pyridylméthoxyde et ainsi une espèce active similaire, seul du PLA atactique était produit. Un analogue de zinc du complexe de cuivre isotactique avec le ligand N,N'-bis (méthylbenzyl-diiminopyrrolide) a été préparé et structurellement caractérisé, mais a produit du PLA hétérotactique (Pr = 0,75). Les complexes de zinc de 2,4-di-tert-butyl-6-aminométhylphénol, où les substituants amino sont le N,N,N',N'-tétraméthyldiéthylènetriamine ou le di-(2-picolyl)amine ont été préparés et structurellement caractérisés. Ils ont montré un centre zincique tétrahédrique chiral avec un "bras" coordiné et un non coordinné pour l'éthylènediamine et un centre zincique pentacoordiné avec les deux groupes picolylamine. Les analyses par RMN ont indiqué une épimérisation rapide du centre métallique, sur l'échelle de temps de la RMN. Les deux complexes de zinc sont hautement actifs dans la polymérisation du lactide et atteignent une conversion complète en seulement quelques minutes, les plaçant parmi les catalyseurs de zinc les plus actifs connus à ce jour. Un PLA légèrement isotactique (Pm jusqu'à 0,6) a été obtenu pour les deux complexes, démontrant en principe l'avantage de l'introduction d'un site catalytique capable de s’épimériser. Le complexe substitué par le ligand picolylaminique présentait une suppression du stéréocontrôle à des concentrations élevées de catalyseur, qui n'est pas entièrement compris. La polymérisation en masse du lactide a été réalisée avec des complexes de manganèse diamino-diphénolate suivant un mécanisme de coordination-insertion. Leur activité était faible et seul un PLA hétérotactique a été obtenu. Des complexes tri / tétradentate de phénoxy-imine-cuivrique ont également été utilisés dans la polymérisation en masse, en suivant un mécanisme de monomère activé et utilisant de l'alcool benzylique en tant que co-initiateur. Les polymérisations étaient stables dans l'air et en présence d'eau ou d'acide acétique, mais le contrôle du poids moléculaire du polymère était faible du à des réactions de transestérification intramoléculaire aisées. Des PLA hétérotactiques étonnamment élevées ont été obtenues dans le monomère fondu (Pr jusqu'à 0,85), mais il n'y avait aucune preuve que le site basique additionnel des ligands participe au stéréocontrôle. / Diiminopyrrolide ligands bearing two chiral N-methylbenzyl substituents were prepared by a condensation reaction of the 1H-pyrrole-2,5-dicarbaldehyde and S-methylbenzylamine. Reaction of the ligand with Cu(OMe)2 in the presence of 2 equiv of pyridylmethanol or dimethylaminoethanol yielded the dimeric Cu(II) catalysts L2Cu2(μ-OR)2. Application of these complexes in rac-lactide polymerization gave isotactic (Pm = 0.73) and atactic (Pm = 0.50) PLA, respectively. Kinetic studies conducted on these two complexes indicated the presence of two different active species. GPC results obtained for the copper catalyst containing two pyridylmethoxide bridges indicate the growth of only one chain per dimer (thus one alkoxide remains as a spectator ligand), while in the complex bearing two dimethylaminoethoxides both alkoxides inserted lactide. A ligand mediated chain-end control mechanism, which is accomplished by the epimerization of the catalytic site based on the chirality of the last inserted unit, is proposed. The presence of a coordinated and an uncoordinated imine “arms” facilitates epimerization since it requires only dissociation/re-coordination. The effects of the ligand framework (steric bulk) on activity and stereocontrol of the catalyst were investigated by variation of the imine substituents to benzyl, bromobenzyl, xylyl, diphenylmethyl and cyclohexyl. Benzyl, bromobenzyl and cyclohexyl were the only imine substituents providing the desired dimeric copper catalyst with pyridylmethoxide. Benzyl and cyclohexyl substituted complexes produced isotactic PLA. Substituent chirality was thus not required for stereocontrol. The bromobenzyl-substituted complex was the only one providing an atactic catalytic site with both imines coordinated and produced atactic PLA. Monoiminopyrrolide copper(II) complexes with pyridylmethoxide ligands were prepared with naphtyl, diphenylmethyl, xylyl and 2,6-diisopropylphenyl N-substituents. They showed reduced stereocontrol which is assumed to be due to slower epimerization (rotation around the Cu-pyrrole bond is now required). All complexes provided isotactic PLA, but the stereocontrol did not surpass that of the diiminopyrrolide complexes. Substitution of the 5-position of the pyrrole by chloride led to loss of activity while a methyl substituent provided atactic PLA. Phenoxy-imine ligands were prepared by a condensation reaction of the salicylaldehyde derivative and the desired amine (benzyl, cyclohexyl, xylyl and diphenylmethyl). Their complexes bearing either dimethylaminoethoxide or pyridylmethoxide ligands were structurally similar to the iminopyrrolide complexes. All complexes were active in rac-lactide polymerization, but although GPC results indicated the growth of only one chain per dimer for the pyridylmethoxide complexes and thus indicated a similar active species, only atactic PLA was produced. A zinc analog of the isotactic copper complex with the N,N’-bis(methylbenzyldiiminopyrrolide ligand was prepared and structurally characterized, but produced heterotactic PLA (Pr = 0.75). Zinc complexes with 2,4-di-tert-butyl-6-aminomethyl-phenol ligands with amino = N,N,N’,N’-tetramethyldiethylenetriamine or di-(2-picolyl)amine substituents were prepared and structurally characterized. They showed a chiral tetrahedral zinc center with one coordinated and one uncoordinated for the ethylenediamine substituents and a five-coordinated zinc center with both amino groups coordinated for picolylamine. NMR investigations indicated fast epimerization of the metal center on the NMR time scale. Both zinc complexes are highly active in lactide polymerization and reach full conversion in only a few minutes, placing them among the most active zinc catalysts known. Slightly isotactic PLA (Pm up to 0.6) was obtained for both complexes, showing in proof-of-principle the advantage of introducing catalytic site epimerization. The picolylamine-substituted complex showed a suppression of stereocontrol at high catalyst concentrations, which is not fully understood. Bulk polymerization of lactide was conducted with manganese diamino-diphenolate complexes following a coordination-insertion mechanism. Their activity was low and only heterotactic PLA was obtained. Tri/tetradentate phenoxy-imine copper complexes were likewise used in bulk polymerization, following an activated monomer mechanism with benzyl alcohol as co-initiator. Polymerizations were stable in air and in the presence of water or acetic acid, but polymer molecular weight control was low with evidence for facile intramolecular transesterification reactions. Surprisingly high heterotacticities were obtained in molten monomer (Pr up to 0.85), but there was no evidence that the additional basic site on the ligand participates in stereocontrol.

In recent years, copper radioisotopes have been extensively studied for their suitable coordination and physical properties. Nuclides 61 Cu, 64 Cu and 67 Cu are used in nuclear medicine - in diagnostic as well as in therapeutic applications. The aim of the Thesis is a study of the coordination properties of divalent copper as a stepping stone for the next potential applications. The presented Thesis consists of two thematic parts. The first part deals with the synthesis of cyclam derivatives. Sixteen new macrocyclic ligands with different phosphorus acid coordinating pendant arms (phosphinate, phosphonate, germinal P-C-P) were prepared; an analogous ligand endowed by carboxylic acid pendant arm as well as tetramethylcyclam without coordinating arm were prepared for comparison. The influence of the nature of coordinating acid pendant arms on selectivity and on the rate of copper(II) complexation was studied in detail. The protonation constants of the free ligands and the stability constants of the complexes with selected transition metal ions were determined by potentiometric titrations and by 1 H and 31 P NMR spectroscopy. Kinetic properties - i.e. studies of the formation rate and kinetic inertness of the copper(II) complexes - were performed by UV-Vis spectroscopy. The formation kinetics of the selected...

Influenza A is involved in hundreds of thousands of deaths globally every year resulting from viral infection-related complications. Previous efforts to subdue the virus by preventing proper function of wild-type (WT) neuraminidase (N), and M2 proteins using oseltamivir and amantadine (AMT) or rimantadine (RMT), respectively, exhibited success initially. Over time, these drugs began exhibiting mixed success as the virus developed drug resistance. M2 is a proton channel responsible for the acidification of the viral interior which facilitates release of the viral RNA into the host. M2 has a His37-tetrad that is the selective filter for protons. This protein has been demonstrated to be a feasible target for organic compounds. However, due to a mutation from serine to asparagine at residue 31 of M2, which is found in the majority of influenza strains circulating in humans, AMT and RMT block is insufficient. From simulations, it is unclear whether the insensitivity results from weak binding or incomplete block. The question of how the S31N mutation caused MT and RMT insensitivity in M2 is addressed here by analyzing the binding kinetics of AMT and RMT using the two-electrode voltage clamp electrophysiology method. The dissociation rate constant (k2) is dramatically increased compared to WT for both AMT and RMT, by 1500-fold and 17000-fold respectively. Testing of AMT at 10 mM demonstrates complete block, albeit weak, of the S31N M2 channel. At 10 mM, RMT does not reach complete block even though the binding site is saturated. When RMT is in the bound state, it is not blocking all the current, and is binding without block. These results motivated the development of novel M2 blockers using copper complexes focusing on the His37 complex in M2. I hypothesized that copper complexes would bind with the imidazole of a histidine in the His37 complex and prevent proton conductance. The His37 complex is highly conserved in the M2 channel and, therefore, would be important target for influenza therapeutics. By derivatizing the amines of known M2 blockers, AMT and cyclooctyalmine, to form the iminodiacetate or iminodiacetamide, we have synthesized Cu(II) containing complexes and characterized them by NMR, IR, MS, UV–vis, and inductively coupled plasma mass spectroscopy (ICP-MS). The copper complexes, but not the copper-free ligands, demonstrated H37-specific blocking of M2 channel currents and low micromolar anti-viral efficacies in both Amt-sensitive and Amt-resistant IAV strains with, for the best case, nearly 10-fold less cytotoxicity than CuCl2. Isothermal titration calorimetry was used to obtain enthalpies that showed the copper complexes bind to one imidazole and curve fitting to the electrophysiology data provided rate constants for binding in the M2 channel. Computational chemistry was used to obtain binding geometries and energies of the copper complexes to the His37-tetrad. The results show that the copper complexes do bind with the His37 complex and prevent proton conductance and influenza infection.

Anticancer active metal complexes such as cisplatin are routinely used for treating various cancers since 1978. However, the side effects of cisplatin overwhelm its therapeutic potential, especially in the latter stages of treatment. The nonspecific cytotoxicity of drugs could be avoided if targeted delivery to cancer cells is achieved using two different methodologies namely, enhanced permeability and retention in solid tumors (EPR) and receptor mediated endocytosis using a homing agent (RME). Ru(II)-arene complexes which are delivered specifically into cancer cells by the transferrin enzyme are less toxic compared to other metal complexes. The thesis describes the synthesis and use of Ru(II)-η6cymene complexes with different ancillary ligands which modulates the anticancer activity and the utility of two macromolecular vehicles in directed drug delivery. Ru(II)-η6cymene complexes with different heterocyclic ancillary ligands are synthesized and their anticancer activity tested against various cancer cell lines. Ruthenium complexes with mercaptobenzothiazoles are found to be quite active against the H460 cell lines that overexpress transferrin receptors and non-cytotoxic to the normal cell line, HEL299. Biophysical studies show that complexes (H1 and H8) can unwind the pBR322 DNA and inhibit the Topo IIα enzyme. A unique biphasic melting curve of CT DNA is observed in the presence of H1 which is attributed to formation of a dinuclear species (H20). Half-sandwich complexes of 6-thioguanine (6-TG) have also been prepared to improve the delivery and efficacy of 6-TG which is used in spite of a deleterious photoreaction. The Ru complexes cytotoxic to several leukemia cell lines. As they are photostable and anticancer active, they are better than 6-TG. Anticancer activity exhibiting piazselenols are used as ancillary ligands to make Ru(II)-arene complexes. Unfortunately, 1H NMR spectra suggests that piazselenol complexes dissociate in solution. However, the nitro substituted piazselenol and its Ru complex show the greatest cytotoxicity (<0.1 µM) against the A2780 cell line. The utility of PAMAM dendrimers and hyper branched polymers (hybramers) conjugated with a homing agent to target cancer cells by EPR and RME is probed. A cytotoxic copper complex (CuATSM) is covalently attached to the macromolecules through a disulfide linker, cleaved in the presence of GSH. Targeting efficacy of the folic acid-dendrimer conjugates is checked against two glioma cell lines. The folic acid-dendrimer conjugate is more active compared to dendrimer conjugate without folic acid against folate-receptor-overexpressing LN18 cell line. Biotin conjugated dendrimer shows better accumulation in HeLa cells, which require high amounts of biotin for growth. In vivo studies demonstrate that the conjugate can cross the blood-brain barrier. These studies suggest that PAMAM dendrimer can be used as a targeted delivery vehicle for cytotoxic metal complexes. Hyperbranched polymers decorated with propargyl groups and hydrophilic OH terminated TEG groups are attached to biotin and a cytotoxic Cu complex. (CuATSM-SS-CONH-N3) through ‘click’ reactions and tested against the HeLa cell line. On the basis of the studies conducted, it is concluded that targeted delivery of cytotoxic metal complexes are possible in the case of Ru(II) half-sandwich complexes and macromolecular vehicles like dendrimers are suitable for specifically delivering copper complexes into cancer cells.

The thesis is divided into four chapters Chapter 1 provides a brief introduction to the metal-nucleic acid interactions, the role of synthetic models to understand them with both solution (potentiometric) and solid state (Crystallographic) studies. Further the work done in the area of nucleobase [purines and pyrimidines] metal complexes and nucleotide metal complexes are briefly reviewed. Chapter 2 contains an account of synthesis and characterizations of metal [Cu/Co] purine [adenine] complexes and is divided into two sections Viz., Section I and Section II. Section I Five crystals structures of copper adenine dimeric complexes are synthesized and characterized with 1, 10-phenanthroline as coligand. The first ternary [Cu2(phen)2(µ-ade)2Cl2].3H2O complex (2a) crystallizes in the orthorhombic space group Pna21. In the crystal structure of 2a it has been observed that the five and six membered rings of adenine are arranged in such a way that the five membered ring nitrogen atoms N9 and N9A are coordinated to Cu1 while the nitrogen atoms N3 and N3A are coordinated with Cu2 center. This is the first time such co-ordination is observed for the copper-adenine dimeric complexes, while the earlier report shows an alternate coordination. In the complex adenine-adenine dimer formation is observed, mediated via N-H···N hydrogen bond interactions which give rise to a corrugated sheet like pattern along the bc plane. The 1,10-phenanthroline rings and water molecules are packed in the grooves of these corrugated sheets via non covalent interactions. The second ternary [Cu2(phen)2 (µ-ade)(µ-Cl)Cl2].5H2O complex (2b) obtained under same reactant conditions, as 2a, by changing the ratio of the reactants, is the unique example of a dimeric copper complex with one adenine acting as a bridging ligand. The complex 2b crystallizes in the monoclinic centric space group P21/c. Interestingly, the crystal packing of complex 2b does not show any direct adenine-adenine hydrogen bond interactions as was seen for 2a, but adenine moieties of neighboring molecules interact indirectly, mediated via N-H···O and O-H···N hydrogen bonds through solvent water molecules forming a zig-zag pattern. It is interesting to note that two hydrogen bond networks are running across the body diagonal like “X” mediated by the nitrogen atoms of the adenine base and the chlorine atom, axially coordinated to copper centre. Similarly the water molecule O4 and N7 are involved in forming a four membered ring at the body center through the non covalent interactions. As seen for the complex 2a, complex 2b also depicts the presence of slipped π-π stacking intra and intermolecular interactions for the 1,10-phenanthroline rings. The third complex [Cu2(phen)2(µ-ade)2(H2O)2](ClO4)2 complex (2c), obtained by post synthetic modification of 2a, crystallizes in the monoclinic space group Cc. The adenine moieties forms a dimer mediated via N-H···N hydrogen bonds at the pseudo two fold and are connected to the neighboring dimers through the possible hydrogen bond between the nitrogen atom N1 and the axially coordinated oxygen atom O1 of the water molecule. The perchlorate anions are trapped in the pockets surrounded by the adenine and 1,10-phenanthroline moieties. The Nitrogen atom N6, N6A of the adenine bases forms hydrogen bond with N7, N7A of the five membered rings of adenine bases and the oxygen atom O4, O7 of both perchlorate ions, the other oxygen atoms O3, O5 from Cl1 and O8 of Cl2 are involved in C-H···O hydrogen bonds but the remaining oxygen atoms O6, O9 and O10 of the perchlorate ions are not involved in hydrogen bond network. Thus the dimerization involves axial oxygen atoms and the five and six membered nitrogen atoms N7 and N1. The 1,10-phenanthroline rings show both intra as well as intermolecular slipped π-π stacking interactions. The fourth complex [Cu2(phen)2(µ-ade)2(H2O)2](BF4)2 complex (2c), obtained by post synthetic modification of 2a, crystallizes in the monoclinic space group Cc. The adenine moiety forms intermolecular N-H···N hydrogen bonds with the neighboring adenine moieties at the pseudo two fold and is connected to the neighboring dimers through the N-H···O hydrogen bond via axial water molecule. The dimerization of the neighboring adenine moieties is favored through the hydrogen bond between the oxygen atom O2 of Cu2 and N1 of the six membered ring, in return the oxygen atom O1 of second molecule is hydrogen bonded to the nitrogen N7 of the five membered ring of the first molecule. Interestingly the three fluorine atoms F1, F2 and F3 are involved in hydrogen bond and in the second BF4 ion only two fluorine atoms F6 and F7 are involved where F1 and F6 acts as a bifurcated hydrogen bond acceptor while the remaining fluorine atoms are not taking part. Here too, as in the previous case of 2c 1,10-phenanthroline rings show both intra as well as intermolecular slipped π-π stacking interactions. The fifth complex [Cu2(phen)2(µ-ade)2(H2O)2](PF6)2 complex (2c), obtained by post synthetic modification of 2a, crystallizes in the monoclinic space group Cc. The adenine moiety forms intermolecular N-H···N hydrogen bonds with the neighboring adenine moieties at the pseudo two fold and is connected to the neighboring dimers through the N-H···O hydrogen bond via axial water molecule. As observed in the previous structure of 2c and 2d the dimerization of the neighboring molecule is favored through the hydrogen bond between the oxygen atom O2 of Cu2 and N1 of the six membered ring, in return the oxygen atom O1 of second molecule is hydrogen bonded to the nitrogen N7 of the five membered ring of the first molecule. Interestingly the nitrogen atom N6 of the six membered ring is involved in four hydrogen bonds, Where one H is hydrogen bonded to N1 of the neighboring base while the second hydrogen atom is being shared by three fluorine atoms belonging to the second PF6 ion and in turn all these three fluorine atoms acts as bifurcated acceptor of the hydrogen bond with the carbon atoms of 1,10-phenanthroline. It is noteworthy that the fluorine atoms F3, F4, F5 and F6 are involved in single hydrogen bonds with the 1,10-phenanthroline carbon atoms. At the same time the rest of the fluorine atoms are not involved in any non covalent interactions. Here too, as in the previous cases of 2c and 2d 1,10-phenanthroline rings show both intra as well as intermolecular slipped π-π stacking interactions. The complexes 2c, 2d and 2e are isostructural. All the three complexes crystallized in the noncentric space group Cc as the precursor complex 2a [Pna21] with the difference being the nature of the complex, 2a being neutral whereas 2c, 2d and 2e are complex salts. All the three complexes have similar bond lengths between the coordinating atoms and the central copper metal but they differ in the angles subtended by the ligands at the copper centres which are also reflected in the dihedral angle between the planes of the coordinating ligands. Though the molecular structure of the three complexes differs only in the nature of the counter ion, the crystal packing analysis reveals the finer differences. The interaction of adenine with neighboring adenine is same for the three complexes 2c, 2d and 2e but differs from the precursor complex 2a. Section II covers the synthesis and characterization of cobalt adenine binary and ternary complexes with 1,10-phenanthroline and 2,2’-bipyridyl as coligands for the ternary complexes. The first binary [Co2(µ-Hade)2(µ-H2O)2(H2O)4](NO3)4·2H2O complex (2f) crystallizes in the centric space group P21/c. Though there were four water molecules, coordinated to the metal Co centres, available for intra molecular hydrogen bond interactions with the base nitrogen atoms the orientation of the coordinated bases is not favorable to enable the C-H···O hydrogen bond formation, but intermolecular hydrogen bonds were observed. The structure is stabilized mainly through the O-H···O and N-H···O hydrogen bond interactions between the neighboring molecules via nitrate ions. Interestingly there is an absence of any direct adenine-adenine interactions. The terminally coordinated water molecule O2 forms hydrogen bond with nitrate anion on both sides, which in turn the nitrates hold the bases of two different molecules as the network is running -N6-O10-O9-O2-O5-N6-. Both the nitrate anion oxygen atoms are involved in hydrogen bond where all the oxygen atoms are bifurcated acceptor. The nitrate ions with nitrogen atoms N10 and N11 are making a nine and eight membered ring through hydrogen bond with adenine nitrogen atoms [N6 and N7] and coordinated water molecules [O2 and O3] respectively. The second binary [Co(Hade)2(H2O)4]SO4·5H2O complex (2g) crystallizes in the centric space group P21/n. Interestingly, only one adenine [N3A] is involved in forming the O-H···N intramolecular hydrogen bond with the water molecule while the adenine on other side is not in favorable orientation. All the water molecules coordinated to the metal center are involved in forming hydrogen bonds where O1, O2 and O4 form two hydrogen bonds while, O3 forms three hydrogen bonds. The water molecule and sulphate ions are trapped in between the adenine bases and forming an interesting network of hydrogen bond running in opposite directions. In general the sulphate and the water molecule are holding the symmetry related molecules connecting the nitrogen atoms N6 and N7 of the adenine. The crystal structure of 2g shows the presence of intermolecular π-π stacking interaction between the six membered rings of the neighboring adenine molecules along a axis. These stacked adenine moieties looks like a zig- zag pattern when viewed down a axis. Here too as in previous case of 2f there are no adenine-adenine interactions present. It is noteworthy that both of these complexes[differing only in the nature of salts i.e. CoNO3 and CoSO4] differ in the adenine coordination to the cobalt centre [N9 and N3 co-ordination in 2f; N9 coordination in 2g]. The third ternary [Co2(µ-ade)2(µ-OH)2(phen)2](NO3)2·6H2O complex (2h) was synthesized by a one pot reaction and crystallizes in the triclinic space group P-1. Though there are two hydroxyl ions coordinated to the metal centre there is no favorable intramolecular hydrogen bond formation. The adenine moieties of 2h interact with each other forming a dimer at the inversion centre, which looks like a zig -zag sheet pattern, via N-H···N hydrogen bond. In addition to this the hydroxyl O1 forms hydrogen bond with water oxygen and the oxygen atom of the disordered nitrate anion. These chains are further linked to neighboring chains by N-H···O hydrogen bond and a slipped π-π interaction between the 1,10-phenanthroline rings forming a sheet like pattern. The fourth ternary [Co2(µ-ade)2(µ-OH)2(phen)2](OTs)2·6H2O complex (2i) , was also synthesized by a one pot reaction and crystallizes in the triclinic space group P-1. Similar to previous case though there are two hydroxyl groups bridging the metal centres as dimers, no intramolecular hydrogen bonds were observed. The adenine moieties interact with each other forming a zig-zag pattern via N-H···N hydrogen bond like in the previous structure 2h. Interestingly, contrary to the previous case where two such zig- zag sheets interacted with each other through slipped π-π stacking between the 1,10-phenanthroline rings, no such interaction was found among the neighboring sheets. Instead, the 1,10-phenanthroline rings interact with tosylate counter ion through C-H···O hydrogen bonds. Down the c axis projection, at the inversion centre tosylate ion and the water molecules form an eight membered ring where the water oxygen O1W acts as a donor in the two hydrogen bonds and the oxygen atom O2 of the tosylate acts as bifurcated acceptor. On the other side, the tosylate oxygens form a twelve membered ring with the water oxygen atom O2W. Thus, eight membered and twelve membered rings are formed alternately and both are subtending an angle of 113°. It is noteworthy that the tosylate ion is parallel to the adenine base while perpendicular to the 1,10-phenanthroline rings favoring the π-π and C-H···π stacking interactions between the neighboring zig zag chains. The fifth ternary [Co2(µ-ade)2(µ-OH)2(bpy)2](NO3)2·6H2O complex (2j) synthesized via one pot reaction and crystallizes in the triclinic space group P21/n. Similar to previous two cases there are two hydroxyl groups bridging the metal centres as dimers, no intramolecular hydrogen bonds were observed in the present case. The adenine moieties interact with each other forming a zig-zag pattern via N-H···N hydrogen bond as observed in the previous two structures 2h and 2i. The adenine also interacts with nitrate ion through N-H···O hydrogen bond. The nitrate groups are oriented parallel to the adenine base. The adenine base nitrogen atom N6 is involved in holding the neighboring adenine nitrogen atom N7 in addition to the nitrate oxygen atoms O3 and from the same nitrate the other oxygen atoms O4 is involved in hydrogen bond with the carbon atom C8 thus forming a nine membered ring. These chains interact with the parallel chains by slipped π-π stacking interaction similar to that observed in complex 2h. Chapter 3 describes the syntheses and characterizations of copper pyrimidine [uracil, cytosine and thymine] ternary complexes with 1,10-phenanthroline as coligand. The first polymeric [Cu(phen)(µ-ura)(H2O)]n·H2O complex (3a) crystallizes in the monoclinic space group P21/c. The protons of the water oxygen O1W is oriented towards the uracil rings enabling O-H···O intramolecular hydrogen bonds with O2 as a bifurcated bond acceptor of the uracil on either sides and the chain extends to infinity along the c axis. The structure is stabilized by slipped π-π stacking interactions between the 1,10-phenanthroline rings of neighboring polymeric chains. Each polymeric chain also interacts through C-H···O hydrogen bond between the neighboring chains. The second polymeric [Cu(phen)(µ-ura)(H2O)]n·MeOH complex (3b) is isostructural to (3a) and crystallizes in the monoclinic space group P21/c. Similar to 3a the coordinated water oxygen O1w is oriented towards the uracil rings enabling O-H···O intramolecular hydrogen bonds with O2, as a bifurcated hydrogen bond acceptor, of the uracil on either sides and the chain extends to infinity along the c axis. The structure is stabilized by slipped π-π stacking interactions between the 1,10-phenanthroline rings of neighboring polymeric chains. Each polymeric chain also interacts through C-H···O hydrogen bond between the neighboring chains. Both these complexes differ only in the lattice solvent molecule i.e. water for 3a and methanol for 3b. These complexes are the first example of direct uracil to metal coordination structurally characterized. Also, both the ring nitrogen atoms N1 and N3 are involved in coordination to the metal. The third polymeric [Cu4(cytosine)3Cl3(OH)2]n·14H2O complex 3c is the first polymeric complex known with cytosine and 1,10-phenanthroline as coligands. It crystallizes in the orthorhombic centric space group Pbca. Out of the four, three copper centres adopts square pyramidal [4+1] geometry {τ = 0.17 [Cu1], 0.028 [Cu3] and 0.053 [Cu4]}, whereas the fourth copper centre exhibits distorted trigonal bypyramidal [3+2] geometry. {[τ = 0.66 [Cu2]}. Two copper centres Cu1 and Cu3 have same co-ordination environment viz., the basal plane of the square pyramid is formed by cytosine [N1and N1A], 1,10-phenanthroline [N7, N8 and N11, N12] and chlorine ligands [Cl1, Cl3] while the axial site is occupied by other chlorine atom [Cl2] which act as a bridge between Cu1 and Cu3 in the polymeric chain. The cytosine ring attached to Cu1 and Cu3 act as tridentate ligand co-ordinating to two other copper centres [Cu2, Cu4] via O2, O2A and N3, N3A respectively. Thus remaining three sites of Cu2 are occupied by 1,10-phenanthroline [N9, N10] and a bridged hydroxyl [O1D] moiety. The hydroxyl moiety [O1D] acts as a bridging ligand between Cu2 and Cu4. Thus the basal plane of the trigonal bipyramid for Cu2 is formed by N9, O2 and O2A while axial sites are occupied by N10 and O1D. The basal plane for Cu4 is formed by N3, N3A, O1D and N3C [from third cytosine ligand] while the axial site is occupied by a hydroxyl ion [O1]. The structure is stabilized by slipped π-π intra molecular stacking interactions between the 1,10-phenanthroline rings. The cytosine moieties interact with each other through bifurcated N-H···O hydrogen bond where the proton of N6c is involved with O2 and O2A of the other two cytosine moieties coordinated to the same copper centre. The neighboring chains of the polymer are linked by inter molecular slipped π-π stacking interactions between the cytosine ring attached to Cu4 and the 1,10-phenanthroline rings. The chains are also connected through C-H···Cl hydrogen bonds where the chlorine atom Cl4 is involved in the bifurcated hydrogen bond one as intramolecular and the second as intermolecular. Both the Nitrogen atoms [N6, N6A] of different cytosine are involved in the noncovalent interactions, with the water [O41, O10W] as intermolecular hydrogen bond as well as intramolecular hydrogen bond with chlorine atoms [Cl4, Cl4* (* symmetry generated)] respectively. The water molecules pack between the polymeric chains via noncovalent interactions. Thus this complex is the first example of its kind where all the possible binding modes of cytosine are utilized. The fourth [Cu2(Phen)2(thy) (µ-OH)2(H2O)].HCO3·4.5H2O complex (3d) obtained as the minor product along with 3e crystallizes in the triclinic space group P1 with two molecules in the asymmetric unit. The structure displays the presence of a pseudo centre of inversion between the two molecules. But careful analysis of the structure reveals that the two different tautomeric forms of thymine are coordinated to the two copper centres in each molecule, thus making it a cocrystal. The molecule shows the presence of O-H···O intramolecular hydrogen bond between the thymine oxygen and the bridged hydroxyl ion. The structure is stabilized by slipped π-π stacking and C-H···π interactions between the 1,10-phenanthroline rings of neighboring molecules. The molecules also interact with solvent molecules and counter ions through non covalent C-H···O interactions. The fifth [Cu2(Phen)2(thy)(µ-OH)2(H2O)]Cl·3H2O complex (3e) which was the major product along with 3d also crystallizes in the triclinic space group P1 with two molecules in the asymmetric unit. The difference between 3d and 3e is the change in the nature of counter ion i.e. HCO3- for 3d and Cl- for 3e. Similar to 3d the two different tautomeric forms of thymine are coordinated to the two copper centres in each molecule, thus making it a cocrystal. The molecule shows the presence of O-H···O intramolecular hydrogen bond between the thymine oxygen and bridged hydroxyl ion. The structure is stabilized by slipped π-π stacking and C-H···π interactions between the 1,10-phenanthroline rings of neighboring molecules. The molecules also interact with solvent molecules and counter ions through non covalent C-H···O and C-H···Cl interactions. The sixth Cu(phen)(thy)2 complex (3e) was obtained just by changing the pH in the reaction condition for 3d and 3e and crystallizes in the monoclinic centric space group C2/c. Here a different tautomer of thymine other than that observed for 3d and 3e was coordinated to the central copper metal. The structure is mainly stabilized by slipped π-π stacking between the 1,10-phenanthroline rings of neighboring molecules as well as between the thymine rings. The thymine molecules also interact with neighboring thymine molecules through non covalent N-H···O interactions. These thymine thymine interactions were absent in 3d and 3e. Chapter 4 presents the synthesis and characterization of ternary copper 5’-Adenosine monophosphoric acid (5’-AMP)/ 5’-cytidine monophosphoric acid (5’-CMP) complexes with 2,2’-bipyridine/1,10-1,10-phenanthroline as coligands. The first Cu(bpy)(5’-AMP)2·2H2O complex (4a), obtained at pH = 3.0, crystallizes in the triclinic space group P1 with two molecules in the asymmetric unit Viz., complex A and Complex B. The phosphate group of 5’-AMP which has two protons in the uncoordinated state gets monodeprotonated at one hydroxyl group during the complex formation and is co-ordinated to the copper centre. Thus in each complex the charge on the central copper atom is balanced by 5’-AMP monodeprotonated ligand. The environment around both copper centres is same, Cu1 and Cu2 exhibits square planar geometry. The least square plane analysis reveals that the ribose sugar moieties adopt envelope conformation. The ΦCN angle, which is the torsion angle of the base with respect to sugar, are 84(2)°, 41(2) ° for complex A and - 43(2)°, 47(2) ° for complex B suggesting a anti conformation about the glycosyl bond for all the four 5’-AMP ligands. All the four ribose ring are puckered with one carbon atom of the ring,[C4’ and C3’A for complex A, C4’B and C3’C for complex B], displaced from the best four atom plane of furanose ring on the same side as C5’. [C4’ = -0.539(2) Å, C3’A = - 0.539(2) Å for complex A; C4’B = 0.509(17) Å, C3’C = 0.535(20) Å for complex B], suggesting in each complex, the confirmation of the ribose sugar of two 5’-AMP ligands are different. [C4’ endo and C3’A endo for complex A; C4’B endo and C3’C endo for complex B] Both the complexes A and B are stabilized by C-H···O intramolecular interaction between the adenine base and the phosphate oxygen atom. The structure is stabilized through a complicated network of C-H···O and N-H···O hydrogen bond interactions between the neighboring molecules where the oxygen atoms of the water molecules are involved in forming the network of bifurcated hydrogen bond. The adenine rings interact with each other through the N-H···N hydrogen bonds forming a dimer between the N6-N7 and N7-N6 similar to the base pairing observed in the DNA molecule, in addition to this the atom N6 is involved in forming a bifurcated hydrogen bond with the O7 atom of the phosphate group. Additionally, there is a presence of slipped π···π stacking interaction, between the bipyridine rings and adenine rings in a -B-A:A-B- fashion [B= 2,2’-bipyridine and A:A= adenine adenine adduct]. The second {Cu2(bpy)2(µ-5’-AMP)2(H2O)2·2[Cu(bpy)(5’-AMP)(H2O)2]·10H2O} complex (4b) is a cocrystal obtained at pH = 6.0, crystallizes in the monoclinic space group C2. The crystal structure of 4b can be described as a cocrystal made up of one dimeric [complex D] and two monomeric [complex M] copper (II) complexes. Both the complexes are ternary with 5‘-AMP and 2,2’- bipyridine as co ligands. These complexes are neutral in nature with the charge on the copper centres balanced by the 5’-AMP ligands. The asymmetric unit consists of half of this two component cocrystal system. The basal plane for the monomeric complex M is formed by two nitrogen atoms [N10A, N11A] from the 2, 2’-bipyridine , one water molecule [O1A] and a phosphate oxygen atom [O9A] from one of the 5’-AMP ligand, while the axial site is occupied by the other water molecule, O1W. The basal plane for the dimeric complex D is formed by two nitrogen atoms [N10, N11] from the 2, 2’- bipyridine , and two phosphate oxygen atom [O9 andO7] from two bridging 5’-AMP ligand, while the axial site is occupied by the other water molecule O2A. The 5’-AMP ligand bridges the two copper centres to form the dimeric complex. It is noteworthy that both the axial water molecules of complex D are on the same side. The least square plane reveals that the ribose sugar moieties adopt envelope conformation. The ΦCN angle, which is the torsion angle of the base with respect to sugar, 72(1)° for complex D and 77(1)° for complex M, suggest an anti conformation for both the complexes about the glycosyl bonds. The ribose rings are puckered in both complex D and M, with C3’ and C3’A displaced from the best four atom plane of furanose ring. C3’ deviates from the sugar plane by 0.604(13) Å which is opposite to C5’, imply C3’ exo conformation for the ribose ring. While for the ribose moiety in complex M, C3’A deviates from the sugar plane by 0.585(11)Å which is on the same side of C5’, confirm C3’A endo conformation for the ribose ring. The conformation around the C4’-C5’ bond described by the angles ΦOO [O1’-C4’-C5’-O5’= -60(1)°] and ΦOC [C3’-C4’-C5’-O5’= -179.8(9)°] is gauche trans, a rare conformation, for the complex D while around the C4’A-C5’A bond the angles ΦOO [O1’A- C4’A-C5’A-O5’A= -59(1)°] and ΦOC [C3’A-C4’A-C5’A-O5’A = 57(1)°] suggest the commonly observed gauche gauche conformation. The structure is stabilized through the extensive network of C-H···O and N-H···O hydrogen bond interactions between the neighboring molecules. The adenine rings interact with each other through the N-H···N hydrogen bonds forming a dimer between N6-N7 and N7- N6, mimicking the base pair observed in the DNA molecule, in addition to this N6 is involved in the formation of a bifurcated hydrogen bond with the O8 atom of the phosphate group. Additionally, there is a presence of slipped π···π stacking interaction, between the bipyridine rings and adenine rings in a -B-B-A:A-B-B- fashion [B= bipyridine and A:A= adenine adenine adduct]. The third [Cu2(bpy)2(µ-5’-AMP)2]·14H2O complex 4c crystallizes in the triclinic space group P1 with one molecule in the asymmetric unit. The complex is neutral in nature with the charge on the copper centres being balanced by the 5’-AMP ligands. It is noteworthy that both the axial water molecules of complex are on the opposite side to each other which is in contradiction to the orientation of the water molecule in dimeric complex D of the molecule 4b. The least square plane analysis of the ribose sugar moiety reveals that the sugar moiety adopts envelope conformation. The ΦCN angle, which is the torsion angle of the base with respect to sugar, is 2(4)° for one 5’-AMP ligand and 69(4)° for other 5’-AMP ligand, suggesting an anti conformation for both the complexes about the glycosyl bonds. The ribose rings are puckered in both the ligands, with C3’ and C2’A displaced from the best four atom plane of furanose ring. C3’ deviates from the sugar plane by -0.624(3)Å which is on the same side of C5’, reveals C3’ endo conformation for the ribose ring. While for the other ribose moiety, C2’A deviates from the sugar plane by 0.509(3)Å which is on the same side of C5’, confirms C2’A endo conformation for the ribose ring. The conformation around the C4’-C5’ bond described by the angles ΦOO [O1’-C4’-C5’-O5’= - 76(3)°] and ΦOC [C3’-C4’-C5’-O5’= 41(3)°] is gauche gauche for one of the 5’-AMP ligand. Also around the C4’A-C5’A bond the torsion angles ΦOO [O1’A-C4’A-C5’A-O5’A= -59(2)°] and ΦOC [C3’A-C4’A-C5’A-O5’A = 59(3)°] suggest the commonly observed gauche gauche conformation for the other 5’-AMP ligand. The complex is stabilized by C-H···O and N-H···O intramolecular interactions between the adenine base and the phosphate oxygen atom. The phosphate oxygen atoms O8 and O8A become bifurcated by hydrogen bonding to O1W and O4W. In turn by symmetry relation it forms a sheet like structure extending to infinity. The adenine also interacts with the bipyridine ring with slipped π···π stacking interaction. The structure is stabilized by extensive net work of C-H···O and N-H···O hydrogen bond interactions between the neighboring molecules. The adenine rings interact with each other through the N-H···N hydrogen bonds forming a dimer between N6-N7 and N7- N6, mimicking the base pair observed in the DNA molecules, in addition to this N6 is involved in the formation of a hydrogen bond with the O8 atom of the phosphate group. Very interestingly, the axially coordinated water molecules O1A, O2A along with the phosphate oxygen atoms O8, O8A and water molecules O1W, O4W form a six membered ring in the chair conformation of a cyclohexane ring through hydrogen bonds mediated by the water molecules. Additionally, there is a presence of slipped π···π stacking interaction, between the bipyridine rings and adenine rings in a –B-B-A:A-B-B- fashion [B= bipyridine and A:A= adenine adenine adduct]. This is similar to previous two structures. All the three structures show the presence of different coordinating nature of phosphate groups obtained just by varying the pH conditions. The presence of cocrystal suggests that more than one type of coordination can exists at the same time. The fourth [Cu2(bpy)2(µ-5'CMP)(µ3-5'CMP)(Cl)]n·3H2O polymeric complex (4d) crystallizes in the Orthorhombic space group P212121. The polymer can be described as follows. There are two 5’-CMP ligand in the asymmetric unit viz., I and II. I acts as bidentate bridging ligand co-ordinating through base [N3] and phosphate oxygen [O9] to Cu1 and Cu2 respectively. II acts as a tridentate ligand co-ordinating to Cu1 through phosphate oxygen [O7A] while to Cu2 through the base [N3A] and phosphate oxygen [O9A]. Thus ligand I connects Cu1 and Cu2 forming a chain along the a axis while this chain is extended in b axis direction via ligand II. The least square plane analysis of the ribose sugar moiety reveals that both sugar moieties adopt envelope conformation. The ΦCN angle, which is the torsion angle of the base with respect to sugar, are 40.0(8)° [for ligand I] and 19.2(8)° [For ligand II] suggesting an anti conformation for both sugar moieties about the glycosyl bond. Both the ribose ring adopt a puckered confirmation with C2’ and C3’A displaced from the best four atom plane of furanose ring by 0.511(7) Å and 0.461(7) Å for ligand I and II respectively. Both the atoms C2’ and C3’A are on the same side as C5’, hence the conformation is C2’ endo [for ligand I] and C3’A endo [for ligand II] respectively. The conformation around the C4’-C5’ bond described by the angles ΦOO [O1’-C4’-C5’-O5’= -86.0(6)°{for I} and O1’A-C4’A-C5’A-O5’A= -72.8(2)°{for II}] and ΦOC [C3’-C4’-C5’-O5’= 33.9(8)°{for I} and C3’A-C4’A-C5’A-O5’A = 45.6(6)°{for II}] is gauche gauche for both the ribose rings in the polymeric complex. The polymeric strand is stabilized by N-H···O intramolecular interaction between the cytosine base and the phosphate oxygen atom. The cytosine base also interacts with the axial Chlorine atom to form N-H···Cl hydrogen bond. The structure is stabilized through the extensive network of N-H···O, C-H···O and O-H···O hydrogen bond interactions between the water molecules and polymerizing, making the sheets to run in third direction. The chlorine atom Cl1 at the same time along with the water molecule O1W and O8W of the phosphate group forms an envelope shape five membered ring [Cl1-O2W-O8-O1W-O3W-Cl1] via hydrogen bond. Thus the water molecules, the phosphate oxygen atoms, the chlorine atoms and the nitrogen atoms of the base make the network of hydrogen bonds in three dimension. In the three dimensional network the copper atoms, the base and the sugar with the phosphate are running anti parallel direction pushing the bipyridyl ring on the outer side, thus remaining as the back bone of the sheet. Additionally, there is a presence of slipped π···π stacking interaction, both intra and inter strand, between the 2, 2’-bipyridine rings. Thus the bipyridine rings, stacked

The present thesis deals with different aspects of the chemistry and photo-biology of various ferrocene-conjugated metal complexes, their interaction with double helical DNA, DNA photocleavage and photo-enhanced cytotoxicity in visible light. Phenyl analogues of the active complexes have been synthesized and used for comparison in biological assays. Chapter I provides an introduction to the potential of metal complexes as photochemotherapeutic agents with special reference to organometallic compounds. A brief overview of Photodynamic Therapy (PDT) as a new modality of cancer treatment has been given. Various modes of non-covalent interactions of small molecules with duplex DNA are mentioned. Recent reports on the metal-based photocytotoxic and DNA cleaving agents including photoactivatable organometallic compounds are discussed. The objective of the present investigation is also presented in this chapter. Chapter II presents the synthesis, characterization, structure, DNA binding, DNA photocleavage, photocytotoxicity, mechanism of cell death and cellular localization of ferrocene-conjugated L-methionine reduced Schiff base Cu(II) complexes of phenanthroline bases. To explore the role of the ferrocenyl moiety the phenyl analogues of the ferrocenyl complexes are synthesized and used as controls for comparison purpose. Chapter III deals with the photo-induced DNA cleavage and photo-enhanced cytotoxicity of ferrocene-appended L-tryptophan Cu(II) complexes of heterocyclic bases. The synthesis, characterization, structural comparisons, DNA binding, DNA photocleavage, photocytotoxic activity and cell death mechanism in visible light are discussed in detail. Chapter IV describes the synthesis, characterization and structure of ferrocenylmethyl-L-tyrosine Cu(II) complexes of phenanthroline bases. The complexes are evaluated for DNA binding, DNA photocleavage and photocytotoxic activity in visible light. The cellular localization of the complexes and the mechanism of cell death induced by the complexes are also discussed. Chapter V presents the photocytotoxic effect of ferrocene-conjugated L-amino acid reduced Schiff base Cu(II) complexes of anthracenyl/pyrenyl imidazophenanthroline. The ability of the complexes to bind to double helical DNA and cleave it under photo-illumination conditions is described. Evaluation of the complexes as photochemotherapeutic agents and comparison with currently clinically available drug Photofrin are presented. The mechanism of cancer cell death and cellular localization of the complexes are studied by fluorescence microscopy. Chapter VI describes the synthesis, characterization and photochemotherapeutic efficacy of Cu(II) complexes having ferrocene-appended L-amino acid reduced Schiff base ligands and the naturally occurring polyphenol curcumin. Stabilization of curcumin by complexation to metal for improved photodynamic effect in cancer cells is described with comparison to the parent dye and clinically used drug Photofrin. The mechanism of cell death induced by the copper complexes and their localization in cancer cells are also presented. Finally, the summary of the dissertation and conclusions drawn from the present investigations are presented. The references in the text have been indicated as superscript numbers and compiled at the end of each chapter. The complexes presented in this thesis are represented by bold-faced numbers. Crystallographic data of the structurally characterized complexes are given in CIF format in the enclosed CD (Appendix-I). Due acknowledgements have been made wherever the work described is based on the findings of other investigators. Any unintentional omission that might have happened due to oversight or mistake is regretted.