The thesis “Ancillary Ligand Effects on the Anticancer Activity of Ruthenium (II) Piano Stool Complexes” is an effort to design better antitumor metallodrugs based on ruthenium(II) complexes with various H-bond donor/acceptor ligands and to understand their mechanism of action. Chapter 1 presents a brief review of metallodrugs and their mechanism of action. Different classes of metallodrugs are discussed. A short discussion on ruthenium based anticancer drugs and their established mechanism of action is also included in this chapter. Chapter 2 deals with the synthesis, characterization and anticancer activity of Ru(II) complexes with P(III) and P(V) ligands. The effect of a strong hydrogen bond acceptor on the cytotoxicity of the complexes has been investigated which allows comparison of complexes with ligands possessing a strong hydrogen bond donor or hydrogen bond acceptor. Partial oxidation of the tertiary phosphine ligands leads to a decrease in cytotoxicity of the ligand, while coordination to ruthenium resulted in a significant increase in the cytotoxicity. A molecular mechanism of action for these complexes was suggested on the basis of various biophysical studies. These complexes bind DNA through non-intercalative interactions which lead to the destabilization of the double helix of the DNA and also unwinding of the negatively supercoiled DNA. Results show that the presence of a hydrogen bond acceptor on the ligand is not capable of enhancing interactions with DNA in comparison with hydrogen bond donor groups. Cellular studies of these complexes showed that inhibition of DNA synthesis and apoptosis occur on treatment with these complexes. Interestingly, these complexes are found to be not only cytotoxic but also antimetastatic. Chapter 3 deals with the synthesis, characterization and anticancer activity of Ru(II) complexes with biologically active S containing heterocyclic ligands and their mechanistic study. Complexation of ruthenium with mercaptobenzothiazole (MBT) gave the most cytotoxic complex (H3) in the series. Heterocyclic Ru(II) complexes behave differently as evidenced by cellular and biophysical studies. Unlike phosphine complexes, H3 shows biphasic melting of DNA at higher concentrations which suggests two different types of interaction with DNA. Chapter 4 deals with synthesis and characterization of water soluble multiruthenated hydrophilic ruthenium(II) complexes with urotropine. An increase in cytotoxicity and binding affinity has been observed with increase in the number of ruthenium atoms per molecule. The complex with three ruthenium atoms showed the best activity. However cytotoxicity of the complexes decreases with decrease in the lipophilicity of the complexes. Chapter 5 describes studies on the interaction of Ru complexes with water, ss-DNA, AMP, GMP and GSH by various spectroscopic techniques. Hydrolysis of Ru-Cl bond in the complexes correlates with the cytotoxicity. Chapter 6 reports the summary of the observations of the thesis and the future prospects of metallodrugs.

El treball de tesi s'emmarca dins del camp de la bioinorgànica, disciplina que estudia les propietats estructurals i de reactivitat dels centres actius dels enzims, servint-se de models síntètics de baix pes molecular per tal d'intentar reproduïr la reactivitat presentada per l'enzim i conèixer els mecanismes de reacció a nivell molecular que tenen lloc en els processos biològics.1 Més concretament el treball posa especial èmfasi en els processos d'activació d'oxigen molecular que tenen lloc en les metaloproteïnes de Coure del Tipus 3, com són l'hemocianina i la tirosinasa, ambdues presentant un complex dinuclear de Cu(I)) en el centre actiu de la forma reduïda, capaç d'activar l'O2 cap a espècies de tipus peròxid.2 Un altre camp d'interès ha estat l'estudi dels processos d'activació d'enllaços C-H no activats en hidrocarburs, tant per la seva importàcia a nivell industrial com per comprendre els mecanismes intrínsecs d'aquesta activació a través de metalls de trancisió.3,4 Durant el treball de tesi presentat s'ha desenvolupat la síntesi de nous complexes de Coure(I), Coure(II) y Cu(III) utilitzant lligands macrocíclics de tipus triaza i hexaaza, i s'han estudiat la seves propietats estructurals així com la seva reactivitat. La reacció dels lligands triazacíclics H32m, H2Me33m i H33m amb sals de coure(II) dóna lloc a una reacció de desproporció de Cu(II) per obtenir-se en quantitats equimolars un complex organometàl·lic de Cu(III) i un complex de Cu(I). La caracterizació estructural exhaustiva dels complexes del tipus aryl-Cu(III) evidencia la formació d'un enllaç organometàl·lic entre l'àtom de Cu(III) i el carboni més próxim de l'anell aromàtic del lligand. Aquesta reacció, a més de representar una nova forma de desproporció en la química del Cu, suposa l'activació d'un enllaç C-H aromàtic a temperatura ambient que, mitjançant l'estudi cinètic d'aquesta desproporció per espectroscòpia UV-Vis, dels càlcul de l'efecte cinètic isotòpic utilitzant el lligand deuterat en el C-H de l'anell, juntament amb el recolzament teòrics dels càlculs DFT per a la optimització de geometries d'intermedis de reacció, ens permeten proposar un mecanisme de reacció pel nostre sistema, on l'activació de l'enllaç C-H aromàtic transcorre per la formació d'un enllaç de tipus agòstic C-H ? Cu(II),5 seguit de la desprotonació del C-H aromàtic per acció d'una base i posterior transferència electrònica per obtenir el complex organometàlic de Cu(III) i el complex de de Cu(I). En quant a la reactivitat d'aquests complexes organometàl·lics aryl-Cu(III) s'ha observat que una base en medi aquós causa la inestabilitat d'aquests compostos, evolucionant cap a la inserció d'un àtom d'oxigen sobre la posició activada de l'anell aromàtic, per a donar lloc a un complex dinuclear de Cu(II) amb dos grups fenoxo actuant de pont entre els àtoms metàl·lics. La reacció transcorre per un intermedi colorejat, caracteritzat com el complex ayl-Cu(III) monodesprotonat en una de les seves amines benzíliques, els quals s'observen igualment en la reacció dels correponents complexos de Cu(I) amb oxigen molecular (O2). És en els nostres sistemes en els quals es descriu per primera vegada la participació d'intermedis organometàl·lics Cu(III)-C en processos d'hidroxilació aromàtica, tals com el desenvolupat per l'enzim tirosinasa o per alguns dels seus models químics de síntesi.6,7,8 S'han estudiat les propietats magnètiques dels quatre bis(fenoxo)complexes de Cu(II) descrits, obtenint-se uns acoplaments de tipus antiferromagnètic o ferromagnètic de diversa magnitud, depenent del solapament orbitalari a l'enllaç Cu-O, a través del qual es produeix el superintercanvi. Nous complexos de Cu(I) sintetitzats amb lligands hexaazamacrocíclics han estat estudiats, i posant especial èmfasi a la seva reactivitat respecta a l'activació d'oxigen molecular (O2). S'ha observat una reactivitat diferenciada segons la concentració de complex de Cu(I) utilitzada, de manera que a altes concentracions s'obté un carbonato complex tetranuclear de Cu(II) per fixació de CO2 atmosfèric, mentre que a baixes concentracions s'observa la hidroxilació aromàtica intramolecular d'un dels anells benzílics del lligand, reacció que presumiblement transcorre per atac electrofílic d'un peroxo complex intermedi sobre el sistema ? de l'anell.6Els resultats obtinguts en aquest treball ens mostren la facilitat per activar enllaços C-H aromàtics per metalls de transició de la primera sèrie (Cu, Ni) quan aquests estan suficientment pròxims a l'enllaç C-H, en unes condicions de reacció molt suaus (1atm., temperatura ambient). Els nous complexos organometàl·lics Aryl-Cu(III) són el producte d'una nova reacció de desproporció de Cu(II), així com un posició aromàtica activada que podria ser el punt de partida per l'estudi de funcionalització selectiva d'aquests grups aromàtics. / In the present thesis the synthesis of novel Cu(I), Cu(II) and Cu(III) complexes containing triaza and hexaaza macrocyclic ligands is described, as well as the study of their structural and reactivity properties. Ligands H32m, H2Me33m and H33m react with Cu(II) salts at room temperature in CH3CN to afford an organometallic Cu(III) complex and a Cu(I) complex in equimolar amounts, constituting a new disproportionation reaction for Cu(II). An exhaustive structural characterization of Aryl-Cu(III) complexes shows the formation of an organometallic between theCu(III) center and the carbon form the aromatic ring. This reaction represents a novel disproportionation in copper chemistry and moreover, evidenciates the activation of an aromatic C-H bond at room temperature. Throughout kinetic studies by UV-Vis spectroscopy, determination of the KIE value by using the corresponding deuterated ligand and theoretical calculations at DFT level for the optimization of intermediate geometries, we have proposed a mechanism for this disproportionation reaction: the aromatic C-H bond activation occurs through the formation of an agostic C-H ? Cu(II) interaction, followed by the deprotonation of the aromatic proton by the action of a base and final electron transfer to obtain the Cu(III) and Cu(I) final complexes. The organometallic Cu(III) synthesized are stable in protic media, but react with aqueous base to afford the insertion of an oxygen atom at the C-Cu(III) bond and finally obtain a dinuclear Cu(II) complex where two phenoxo groups are bridging between the metal centers. The reaction undergoes through the formation of a colored intermediate characterized as an Aryl-Cu(III) complex deprotonated in one of the benzylic amines. These intermediates are also observed in the reaction of the corresponding Cu(I) complexes with molecular oxygen (O2). The intermediacy of organometallic aryl-Cu(III) in aromatic hydroxylation processes such as the reactivity displayed by tyrosinase or some synthetic model systems, is first described in the present work. Magnetic properties for the four bis(phenoxo)Cu(II) complexes have alse been investigated. Different magnetic couplings are observed yielding ferromagnetic and antiferromagnetic behavior of variable magnitudes, depending on orbital overlapping on the Cu-O bond, through which the superexchange occurs. Novel Cu(I) complexes containing the hexaazamacrocyclic ligand H33+33m have been studied, with special attention on the reactivity towards the O2 activation. It has been observed a differential reactivity depending on the concentration of Cu(I) complex: if high Cu(I) concentration are used the product obtained consists on a tetranuclear carbonato complex by atmospheric CO2 fixation, while if low concentrations are used the intramolecular aromatic hydroxylation is observed, reaction that is proposed to undergo through an electrophilic attack of the peroxo group to the ? system of the aromatic ring.

No description available.

The hydrophobicity of a surface is an important property in many areas of science and engineering. This is especially the case in mineral processing, where differences in surface hydrophobicity lie at the heart of the separation process of flotation. Chemicals are used to increase and decrease the natural hydrophobicity of minerals to attain a better separation between valuable and worthless material. Polymers are often used to reduce mineral surface hydrophobicity. Decades of empirically based decision making have produced a list of effective depressants. However the detailed study of how these polymer depressants affect surface hydrophobicity and mineral recovery lags behind applied investigations. The aim of this thesis was to study the adsorption of commonly used depressants on model surfaces and to interrogate the action of these polymers in reducing surface hydrophobicity. We have modelled the degree of hydrophobicity of common minerals in order to study polymer depressants with methods not commonly used in studies of surface characterisation in flotation. The model surfaces (self-assembled monolayers, SAMs) allowed us to use the quartz crystal microbalance with dissipation monitoring (QCM-D) to study the adsorption of polymers. The QCM-D can be used to obtain adsorption isotherms, adsorption kinetics, water content of adsorbed layers, and information on the conformation of the adsorbed polymer. The results from the QCM-D were correlated with the contact angle data from the captive bubble measurements, with which we assessed the hydrophobicity of the surface before and after polymer adsorption. Three of the polymers layers were probed with dynamic dewetting studies, in order to test other modes of depressant action. Three types of polymers were studied - a polyacrylamide (Polymer-H), a polyelectrolyte CMC (carboxymethyl cellulose) and a group of dextrins (Dextrin-TY, a phenyl succinate substituted dextrin (PS Dextrin) and a styrene oxide substituted dextrin (SO Dextrin)). These polymers are commonly used or have potential to be used in the depression of talc and graphite. Polymer-H was used to investigate the hydrophobic bonding between a non-ionic polymer depressant and chemically inert and non charged surfaces by probing the influence of substrate hydrophobicity on polymer adsorption and reduction of contact angle. Three different model surfaces were used (mixed self-assembled 0.5 SAM, 0.7 SAM or single self-assembled 1.0 SAM monolayers) with advancing contact angles between 75?? and 119??. The study of Polymer-H found that the substrate hydrophobicity is an important factor in adsorption of this polymer and the change in contact angle upon adsorption depends on adsorbed amount. The effectiveness of Polymer-H to reduce surface hydrophobicity was established to correlate with its conformation and morphology. CMC was investigated to find out how a stimulus responsive polymer depressant can be used in flotation. It was established that the adsorbed amount and rate of adsorption of CMC increase with decreasing of pH or increasing of ionic strength. It was shown that the surface hydrophobicity of a CMC pre-adsorbed layer changes with the environment and these alterations are fully reversible. A switch of ionic strength (from 10-2 M KCl to 10-1 M KCl) caused partial dehydration of the adsorbed layer and a decrease of the receding contact angle by 20??. A pH switch (pH = 9 to pH = 3) resulted in a 40?? change in receding contact angle. The CMC investigation showed that the use of a stimulus responsive polymer presents opportunities for exploiting solution conditions as a means to effect a better mineral separation in flotation The adsorption of three dextrin-based polymers on a model hydrophobic surface has been characterized using the quartz crystal microbalance with dissipation monitoring (QCM-D). The three polymers (one standard dextrin and two dextrins with different aromatic group substitutions) exhibited varying affinities and capacity for adsorption on the hydrophobic substrate. The effect of the three polymers on the static contact angle of the surface was studied using captive bubble contact angle measurements. The three polymers were seen to reduce the receding contact angle by similar amounts (approximately 14 degrees) in spite of having varying adsorbed amounts and differences in adsorbed layer water content. Although no differences were observed in the ability of the polymers to reduce the static contact angle, measurements of the dewetting dynamics between a rising air bubble and the polymer covered substrate yielded stark differences between the polymers, with one polymer slowing the dewetting dynamics by an order of magnitude more than the other two polymers. The differences in dewetting behaviour correlate with the adsorbed layer characteristics determined by QCM-D. / Thesis (PhD)--University of South Australia, 2010

Thyroxine is the main secretory hormone of thyroid gland and it is produced in thyroglobulin by thyroid peroxidase/hydrogen peroxide/iodide system. After biosynthesis and secretion of thyroxine, it undergoes multiple metabolic reactions. The most important metabolic pathway is the stepwise deiodination from the inner ring or outer ring. Removal of one of the outer ring or phenolic ring iodines of biologically less active T4, leads to the formation of 3,5,3'-triiodothyronine or T3, a compound which is biologically more active. On the other hand, removal of one of the inner ring or tyrosyl ring iodines gives 3,3',5'-triiodothyronine (3,3',5'-T3 or rT3) which is a biologically inactive thyroid hormone. Three enzymes involved in this activation and inactivation pathway of thyroid hormones are known as iodothyronine deiodinases (IDs), which are dimeric integral-membrane selenoproteins. Depending upon the sequence and substrate specificity, three iodothyronine deiodinase enzymes have been identified, iodothyronine deiodinase-1 (ID-1), iodothyronine deiodinase-2 (ID-2) and iodothyronine deiodinase-3 (ID-3). ID-1 can catalyze both inner ring and outer ring deiodination of thyroid hormones whereas, ID-2 is selective to the outer ring deiodination. The type-1 and -2 deiodinases (ID-1 and ID-2) produces the biologically active hormone 3,5,3′-triiodothyronine (T3). These two enzymes also convert 3,3′,5′-triiodothyronine (reverse T3 or rT3) to 3,3′-diiodothyronine (3,3′-T2) by outer-ring deiodination (Scheme 1). The type-3 deiodinase (ID-3) catalyzes the convertion of T4 to rT3 by an inner-ring deiodination pathway. Apart from deiodination, there are several alternate pathways of thyroid hormone metabolism, which include sulfate conjugation and glucoronidation of the phenolic hydroxyl group of iodothyronines, the oxidative deamination and decarboxylation of the alanine side chain to form thyroacetic acid and thyronamines, respectively. Glucoronidation and sulfate conjugation changes the physico-chemical properties of iodothyronines dramatically. This thesis consists of five chapters. The first chapter provides a general introduction of biosynthesis of thyroid hormones and followed by deiodination by three iodothyronine deiodinase enzyme. This chapter also provides an overview of thyroid hormone transport and different transport proteins and their mode of binding with thyroid hormones. Apart from this, this chapter also provides a brief overview on other thyroid hormone metabolites. In the second chapter of the thesis, initial attempts in the development of different iodothyronine deiodinase mimics have been discussed. Goto et al have shown that the sterically hindered selenol 1 converts the thyroxine derivative 3 (N¬butyrylthyroxine methyl ester) to the corresponding triiodo derivative 4 by an outer-ring deiodination (Scheme 2). Although the reaction was carried out in organic solvent and a relatively higher temperature (50 °C) and longer reaction time (7 days) were required for about 65% deiodination, this study also provides an experimental evidence for the formation of selenenyl iodide (2) in the deiodination of a thyroxine derivative by an organoselenol. However, only one iodine was removed from the outer ring of 3, no inner ring deiodination was detected (Scheme 2). Interestingly, when compound 5 was treated with selenol 1 under similar conditions, no deiodination was observed (Scheme 3). This leads to assumption that presence of free phenolic hydroxyl group is important for the deiodinase activity. Based on this experimental observation, they proposed a mechanism which involves an enol¬keto tautomerism of the phenolic hydroxyl group. In the case of thyroxine, the outer-ring can undergo enol-keto tautomerism, whereas due to lack of free hydroxyl group, the inner ring cannot undergo similar kind of tautomerism. The enol-keto tautomerism probably makes the outer ring iodines more reactive than the inner ring iodines of thyroxine. We have developed tthe first chemmical modell for the inneer ring deioddination of TT4 and T3 by type 33 deiodinase . We have shown that naphthyl-baseed selenol 6 bearing a thhiol group in the cloose proximitty to the sellenium act aas an excelleent model foor ID-3 by selectively deiodinatting T4 andd T3 to prodduce rT3 annd 3,3'-T2, rrespectively,, under physiological relevant conditions. When 2 equuivalent of ccompound 66 was emplooyed in the assay, an almost quuantitative cconversion oof T4 to rT3 was observeed within 300 hours and there was no indicaation of the fformation off T3 or 3,3'-TT2. When the selenol group was repplaced with a thiol group in compouund 7, the ddeiodinase activity wwas decreassed. On thee other handd, when thee thiol groupp was replaaced with selenol mmoiety in commpound 8, thhe deiodinasse activity drramatically iincreased wiithout any change iin the selecttivity. Comppounds 10 and 11 havving N-methhylamino grooup were found too be more aactive than the correspponding unssubstituted ccompounds 7 and 8, respectively. However, introduction of a secondary amine adjacent to the selenol moiety into the compound 9 significantly reduces the deiodinase activity. In the third chapter synthesis, deiodinase activity and mechanism of deiodination of a series of peri-substituted naphthalene derivatives is discussed. Iodobenzene was used as halogen bond donor for the DFT calculations. From the orbital analysis it is observed that there is perfect orbital symmetry match between the HOMO of compound 8 (selenolate form) and LUMO of iodobenzene. When the selenolate form of 1-selenonaphthol interacts with iodobenzene, a halogen bonded adduct is formed. The negative charge on the selenium center decreases as it donates electron pair to the σ* orbital of C–I bond in iodobenzene and as a consequence the positive charge on the iodine center decreases (Figure 1). Addition of iodobenzene to 1-selenonaphthol led to a significant downfield shift in 77Se NMR spectrum of 1-selenonaphthol and with an increase in the concentration of iodobenzene, more downfield shift in the signal was observed. Figure 1. The charges obtained from Natural Bond Orbital (NBO) analysis for the selenolate form of (a) 1-selenonaphthol (b) iodobenzene, (c) halogen-bonded adduct On the basis of experimental end theoretical data, a mechanism for the deiodination of T4 by compound 8 is proposed. According to the mechanism, the initial interaction of one of the selenol moieties with an iodine leads to the formation of halogen bond. The transfer of electron density from selenium to the σ* orbital of the C−I bond generates a σ-hole or partial positive charge on the selenium atom, which facilitates an interaction between the halogen bonded selenium atom and the free selenol (selenolate) moiety (intermediate 12). The selenium−selenium interaction (chalcogen bond) strengthens the halogen bond, leading to a heterolytic cleavage of the C−I bond. The protonation of the resulting carbanion leads to the formation of rT3. On the other hand, the formation of an Se−Se bond produces the diselenide 13 with elimination of iodide as HI. The reductive cleavage of the Se−Se bond in compound 13 regenerates the diselenol 8 (Figure 2). In the fourth chapter deiodination of sulfated thyroid hormones is discussed. Sulfate conjugation is an important step in in the irreversible inactivation of thyroid hormones. Sulfate conjugation of the phenolic hydroxyl group stimulates the inner ring deiodination of T4 and T3 but it blocks the outer ring deiodination of T4 by ID-1. The thyroxine sulfate (T4S) undergoes faster deiodination as compared to the parent thyroid hormone T4. Only ID-1 catalyzes the deiodination of sulfated thyroid hormones. In contrast, ID-2 and ID-3 do not accept T4S and/or T3S as substrate. We have shown that iodothyronine sulfates can be readily deiodinated by synthetic deiodinase model compound 8 and its derivatives. In contrast to the inner ring-selective deiodination of T4, the synthetic compounds loses the selectivity and mediate both inner and outer-ring deiodination of T4S and outer ring deiodination of rT3S. From this study, we have also proposed that the enol-keto tautomerism is probably not required for the outer ring deiodination and the strength of halogen bonding controls the regioselective deiodination by model compounds. In the fifth chapter, the mechanism of inhibition of iodothyronine deiodinases by PTU and IAA is discussed with the help of model compounds. In the model study, it has been observed that compound 8 does not form a stable Se-I intermediate (14), which is essential for the formation of Se-S covalent bond with PTU. As a consequence, the deiodination of T4 by compound 8 is not inhibited by PTU. This study supports the proposal that ID-3 does not follow a ping-pong bi-substrate pathway for deiodination and may not form a stable E-Se-I intermediate, which is responsible for the insensitivity of ID-3 towards PTU. The biphenyl based diselenol 15 reacts with IAA and iodoacetamide to form the corresponding carboxymethylated product 17. On the other hand, compound 8 does not undergo the expected carboxymethylation by IAA and iodoacetamide, but they readily deiodinate both IAA and iodoacetamide. Based on this model study, a possible model is proposed for the insensitivity of ID-3 towards IAA. Iopanoic acid (18) is a well known radiocontrast agent and is used as adjunctive therapy with PTU and CBZ for the treatment of thyrotoxicosis.[9] We show in this chapter that iopanoic acid undergoes monodeiodination by compound 8 under physiological relevant conditions. The deiodinated products (19 and 20) from iopanoic acid are characterized by NMR spectroscopy and single crystal X-ray crystallography. It is observed that after monodeiodination, the strength of halogen bonding decreases and therefore, the monodeiodinated products do not undergo further deiodination.

The present thesis deals with different aspects of the chemistry of oxovanadium(IV) complexes, their interaction with DNA and protein and photo-induced DNA and protein cleavage activity and photocytotoxicity. Chapter I presents a general introduction on various modes of interactions of organic compounds and transition metal complexes capable of targeting DNA leading to DNA strand scission, emphasizing particularly the photo-induced DNA cleavage activities for their potential application in PDT. The mechanistic pathways associated with the DNA cleavage are discussed. A comparison has been made on the advantages of photoactive metal complexes over organic conjugates. Objective of the present investigation is also dealt in this Chapter. Chapter II of the thesis deals with the synthesis, characterization, DNA binding and photo-induced DNA cleavage activity of ternary oxovanadium(IV) complexes of N-salicylidene-S-methyldithiocarbazate (salmdtc) and phenanthroline bases to explore the photo-induced DNA cleavage activity in UV-A light of 365 nm. Chapter III presents the synthesis, characterization, DNA binding and photo-induced DNA cleavage activity of ternary oxovanadium(IV) complexes containing N-salicylidene-L-methionate (salmet) and N-salicylidene-L-tryptophanate (saltrp) Schiff bases and phenanthroline bases. The objective of this work is to investigate the photo-induced DNA cleavage activity in near-IR light and to see the effect of pendant thiomethyl and indole moieties in the DNA cleavage reactions. Chapter IV deals with the synthesis, characterization, DNA binding, red-light induced DNA cleavage activity and photocytotoxicity of ternary oxovanadium(IV) complexes having N-salicylidene-L-arginine (sal-argH) and N-salicylidene-L-lysine (sal-lysH) Schiff bases and phenanthroline bases. The important results include the visible light-induced DNA cleavage activity and photocytotoxicity of the complexes in human cervical HeLa cancer cells. Chapter V describes the synthesis, characterization, DNA binding and photo-induced DNA and protein cleavage activity and photocytotoxicity of oxovanadium(IV) complexes containing bis(2-benzimidazolylmethyl)amine and phenanthroline bases. The significant results include DNA cleavage activity in near-IR light and photocytotoxicity of the dppz complex in non-small cell lung carcinoma/human lung adenocarcinoma A549 cells in visible light. Further, we have studied the protein cleavage activity of the complexes in UV-A light of 365 nm by using bovine serum albumin (BSA) and lysozyme. Finally, Chapter VI presents the binary oxovanadium(IV) complexes of phenanthroline bases. We have studied their synthesis, characterization, DNA binding and photo-induced DNA and protein cleavage activity and photocytotoxicity. Photocytotoxicity of dppz complex has been studied in human cervical HeLa cancer cells in visible light. Photo-induced protein cleavage activity of the complexes has been studied in UV-A light of 365 nm by using BSA and lysozyme. The references have been compiled at the end of each chapter and indicated as superscript numbers in the text. The complexes presented in this thesis are represented by bold-faced numbers. Crystallographic data of the complexes, characterized structurally by single crystal X-ray crystallography, 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 omission that might have happened due to oversight or mistake is regretted.

Angiotensin converting enzyme (ACE) catalyzes the conversion of angiotensin I (Ang I) to angiotensin II (AngII). ACE also cleaves the terminal dipeptide of vasodilating hormone bradykinin (a nonapeptide) to its inactive form. Therefore, inhibition of ACE is one of the treatments of hypertension. A number of ACE inhibitory antihypertensive drugs are known. ‘Oxidative stress’ is another disease state caused by an imbalance in the production of oxidants and antioxidants in the body. A number of studies suggest that hypertension and oxidative stress are interdependent. Therefore, ACE inhibitors having antioxidant property are considered beneficial for the treatment of hypertension. Generally, selenium compounds exhibit better antioxidant behavior than their sulfur analogues. Therefore, we have synthesized a number of selenium analogues of captopril, an ACE inhibitor used as antihypertensive drug. Similar to captopril, the selenium analogues of captopril exhibited excellent ACE inhibition property. It was observed that these compounds are very good scavengers of peroxynitrite (PN), a strong oxidizing as well as nitrating agent found in vivo. The orientation of the chiral centers in these compounds was found to be very important for their ACE inhibition behavior. A number of selenocysteine- and cysteine-containing dipeptides and tripeptides were synthesized as inhibitors of ACE. It was observed that the ACE inhibition properties of these compounds depend on various factors such as orientation of the amino functionality, substitution at the C-terminal of the inhibitor, ring size of the proline moiety or the availability of the terminal acid group in carboxylate form etc. A structure-function correlation was drawn for the ACE inhibition properties of the peptide-based selenium-or sulfur-containing compounds. These studies reveal that the antioxidant properties do not depend on the side-chain functional groups, but they depend on the availability of selenium or sulfur centers. Selenium-based compounds were found to be better antioxidants than those containing sulfur moieties. In conclusion, the present study reveals that the replacement of sulfur atom in captopril and its analogues by selenium enhances the antioxidant activity. The reaction products of lactoperoxidase (LPO)-catalyzed iodination of Ang II were separated and characterized. It was observed that LPO-catalyzed iodination of Ang II takes place preferentially at the tyrosine residue. LPO-catalyzed iodination of Ang II is inhibited by commonly used antithyroid drugs such as MMI, MTU, PTU and also by antihypertensive drug captopril. It was also observed that the monoiodo Ang I is a better substrate for ACE compared to the natural substrate Ang I. The site of nitration of Ang II by PN was also determined by MS-MS analyses. This study reveals that the nitration takes place at the tyrosine residue.

Scorpionate and terpyridine ligands are of importance in inorganic chemistry for their metal-binding properties. Tris-pyrazolylborate (Scorpionate) ligands that show facial binding mode and steric protection have been extensively used to synthesize complexes modeling the active site structure and biological function of various metalloproteins and as catalysts in C-H and NO activation and carbine transfer reactions. Terpyridine and modified terpyridine ligands showing meridional binding mode have been used in bioinorganic chemistry where Pt-terpyridine complexes are known to inhibit the activity of thiordoxin reductase (TrxR) besides showing interaction with G-quadruplex. The thesis work stems from our interest to use these ligand systems to design and prepare new 3-d metal-based photodynamic therapeutic (PDT) agents to explore their visible light-induced DNA cleavage activity and photocytotoxicity. Efforts have been made in this thesis work to design and synthesize Co(II) and Cu(II) complexes having scorpionate (Tpph) abd terpyridine (tpy) ligands. Ternary 3d-metal complexes having Tpph and planar phenanthroline bases have been synthesized and structurally characterized. The steric encumbrance of Tpph has led to the reduction in chemical nuclease activity along with enhanced photo-induced DNA cleavage activity, particularly of the Cu(II) and Co(II) complexes. The Co(II), Cu(II) and Zn(II) complexes of Tpph and a pyridyl ligand having a photoactive naphthalilmide moiety show molecular light-switch effect on binding to calf thymus DNA or BSA protein. The complexes do not show any chemical nuclease activity. The Cu(II) complex shows significant DNA cleavage activity in red light. The Co(II) complex displays significant photocytotoxicity in UV-A light. Ternary Cu(II) complexes of ph-tpy and heterocycylic bases are prepared and their DNA binding and cleavage activity studied. The complexes are avid binders to CT-DNA. The dipyridoquinoxaline (dpq) and dipyridophenazine (dppz) complexes are photocleavers of DNA in visible light. A significant enhancement in cytotoxicity in HeLa cancer cells is observed on exposure of the dppz complex to light. The binary Cu(II) complexes are also prepared to reduce the dark toxicity using phenyl and pyrenyl substituted terpyridine ligands. The pyrenyl substituted complex shows DNA cleavage activity in the visible light, low dark toxicity and unprecedented photocytotoxicity in visible light. The copper(II) complexes generally show dark cellular toxicity due to the presence of reducing thiols. The present terpyridine copper(II) complex having pendant pyrenyl moiety shows significant PDT effect that is similar to that of the PDT drug Photofrin. Binary Co(II) complexes show efficient DNA cleavage activity in visible light, significant photocytotoxicity in visible light and cytosolic uptake behaviour. Considering the bio-essential nature of the cobalt and copper ions, the present study opens up new strategies for designing and developing 3d-metal-based photosensitizers for their potential applications in PDT.

<p>The development of new materials has been inspired by lessons learned from natural systems. In the area of underwater adhesion and adhesives, inspiration has come from the complex protein adhesives generated by marine organism such as barnacle and mussels. These protein systems have a high incorporation of a unique amino acid, dihydroxyphenylalanine, and provides the unique adhesive qualities synthetic systems strive to emulate.</p> <p>By understanding how marine mussels stick to a variety of surfaces, new strategies can be explored for preventing the adhesion of biological organisms to various substrates. A continuous concern for marine vessels is the detrimental impact caused by biofouling on the hull of the ship. Fuel consumption can increase as the vessel’s drag increasing fuel consumption and non-native species can be introduced into new environments. Taking inspiration from catechol curing, new oxidative surfaces were investigated as potential antifouling coatings.</p> <p>Further insight into the marine mussels ability to apply and cure its adhesive on a variety of substrate has also inspired various synthetic polymers. The catechol moiety can be incorporated into a polymer backbone to give a new solvent based adhesive. Further investigation of the poly(styrene-co-(3,4-dihydroxystyrene)) adhesive system was done to formulate an underwater adhesive for unique use cases. A terpolymer was also explored as an ideal adhesive taking inspiration from the mussels by incorporating flexible, stiff, and sticky components to give a tunable adhesive.</p> <p>Having a strong bonding synthetic adhesive that can be used on a laboratory scale is good for academic investigation, but not of use outside the lab if it cannot easily be produced on a commercial scale. With the goal of large scale synthesis, a new polymerization method was introduced addressing some of the issues currently preventing commercial scale production.</p><br>

In der vorliegenden Arbeit werden unter Verwendung von Hydrotris(pyrazolyl)-boraten (Tp) als tripodale Zuschauerliganden Modellsysteme für unterschiedliche Nicht-Häm-Eisenenzyme entwickelt und untersucht. Dabei steht im ersten Schritt die Syntheseoptimierung und Implementierung der noch nicht für biomimetische Studien verwendeten TpMes und TpMes* Liganden im Vordergrund. Darauffolgend werden geeignete Metall-Chloro-Vorläuferkomplexe [TpMesMCl] synthetisiert. Das Koordinationsverhalten des TpMes*-Liganden gegenüber zweiwertigen Übergangsmetallionen wird systematisch untersucht und eine Reihe von heteroleptischen [TpMes*MCl] und homoleptischen [(TpMes*)2M] Komplexen synthetisiert und charakterisiert. Die Modellverbindungen [TpMesFeCysOEt] und [TpMesFeCysAm], welche Cysteinatethylester und Cysteaminat als Substratliganden tragen, dienen jeweils als strukturelles sowie funktionelles Modell für die Cystein- und die Cysteamindioxygenase. Die Mesitylreste des TpMes-Liganden bilden eine schützende, becherartige Struktur um das Eisenzentrum. Die Reaktionsprodukte können so unter anderem erstmalig kristallografisch charakterisiert werden. Zudem wird ein Intermediat in der Reaktion von [TpMes*FeCysAm] mit O2 beobachtet und eingehend untersucht. Die Eisen(II)komplexe [TpMesFeOBzR], die neben dem Tp-Liganden unterschiedlich substituierte Benzoate tragen, zeigen bemerkenswerte Ähnlichkeit zum Ruhezustand von Lipoxygenasen. Mit tert-Butylhydroperoxid (tBuOOH) können temperaturempfindliche Spezies beobachtet werden, die den mononuklearen [TpMesFe(OOtBu)(OBzR)] Alkylperoxiden zugeordnet werden. Im letzten Teil dieser Arbeit wird [TpMesFeACC] als Modell für die 1-Aminocyclopropansäureoxidase dargestellt. Es ist möglich, reaktive Spezies mit tBuOOH und meta-Chlorperbenzoesäure (mCPBA) zu beobachten. Zudem liefert die elektrochemische in-situ-Aktivierung von Sauerstoff in Folge Hinweise auf (Hydro-)-peroxidkomplexe bei der Reaktion von [TpMesFeACC] mit dem Superoxidradikalanion. / In the present work model systems for different non-heme iron enzymes are developed and investigated with the help of hydrotris(pyrazolyl) borates (Tp) as tripodal spectator ligands. The first part focusses on the optimization of the synthesis and implementation of the TpMes and TpMes* ligands for biomimetic studies. Following this, suitable precursor complexes [TpMesMCl] are prepared. The coordination behavior of the so far rarely used TpMes* ligand towards divalent transition metal ions is systematically investigated and several heteroleptic [TpMes*MCl] and homoleptic [(TpMes*)2M] complexes are synthesized and characterized. The model complexes [TpMesFeCysOEt] and [TpMesFeCysAm], which carry cysteinate ethylester and cysteaminate as substrate ligands, serve as structural and functional models for the cysteine and cysteamine dioxygenase, respectively. The mesityl residues of the TpMes ligand form a protective, cup-like structure around the iron center. The reaction products could be characterized crystallographically for the first time. An intermediate in the reaction of [TpMes*FeCysAm] with O2 is intensively studied. The iron(II) complexes [TpMesFeOBzR], which in addition to the Tp ligand carry substituted benzoates, show remarkable similarities to the resting state of lipoxygenases. With tert-butyl hydroperoxide (tBuOOH) temperature-sensitive species are observed, which are assigned to the mononuclear [TpMesFe(OOtBu)(OBzR)] alkylperoxides. In the last part of this work, [TpMesFeACC] is presented as a model for 1-aminocyclopropan-1-carboxylic acid oxidase. It is possible to observe reactive species with tBuOOH and meta-chloroperbenzoic acid (mCPBA). In addition, the electrochemical in-situ activation of oxygen provides evidence for (hydro-)peroxide complexes in the reaction of [TpMesFeACC] with the superoxide radical anion.