Treatment of the diethyl ester of o-phenylenebis(oxamic acid) (opbaH2Et2, 1) with 5/6 equivalent of MeNH2 in abs. EtOH results in the exclusive formation of the ethyl ester of o-phenylene(N′-methyl oxamide)(oxamic acid) (opooH3EtMe, 2) in ca. 50% yield. Treatment of 2 with four equivalents of [Me4N]OH followed by the addition of Cu(ClO4)2·6H2O gave [Me4N]2[Cu(opooMe)]·H2O (3A) in ca. 80% yield. As 3A appears to be a hygroscopic solid, the related [nBu4N]+ salts [nBu4N]2[M(opooMe)]·H2O (M = Cu (3B), Ni (4)) have been synthesized. By addition of two equivalents of [Cu(pmdta)(NO3)2] to a MeCN solution of 3B the novel asymmetric trinuclear complex [Cu3(opooMe)(pmdta)2](NO3)2 (5) could be obtained in ca. 90% yield. Compounds 2, 3A, 3B, 4 and 5 have been characterized by elemental analysis and NMR/IR spectroscopy. Furthermore, the solid state structures of 3A in the form of [Me4N]2[Cu(opooMe)]·MeOH (3A′), 3B in the form of [nBu4N]2[Cu(opooMe)] (3B′), 4 in the form of [nBu4N]2[Ni(opooMe)]·1.25H2O (4′) and 5 in the form of [Cu3(opooMe)(pmdta)2] (NO3)2·3MeCN (5′), respectively, have been determined by single-crystal X-ray diffraction studies. By controlled cocrystallization, diamagnetically diluted 3B (1%) in the host lattice of 4 (99%) in the form of single crystals have been made available, allowing single crystal EPR studies to extract all components of the g-factor and the tensors of onsite CuA and transferred NA hyperfine interaction. Out of these studies the spin density distribution of the [Cu(opooMe)]2− complex fragment could be determined. The magnetic properties of 5 were studied by susceptibility measurements versus temperature. An intramolecular J parameter of −65 cm−1 has been obtained, unexpectedly, as 5 should possess two different J values due to its two different spacers between the adjacent CuII ions, namely an oxamate (C2NO3) and an oxamidate (C2N2O2) fragment. This unexpected result is explained by a summarizing discussion of the experimentally obtained EPR results (spin density distribution) of 3B, the geometries of the terminal [Cu(pmdta)]2+ fragments of 5 determined by X-ray crystallographic studies and accompanying quantum chemical calculations of the spin density distribution of the mononuclear [Cu(opooMe)]2− and of the magnetic exchange interactions of trinuclear [Cu3(opooMe)(pmdta)2]2+ complex fragments. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Treatment of the diethyl ester of o-phenylenebis(oxamic acid) (opbaH2Et2, 1) with 5/6 equivalent of MeNH2 in abs. EtOH results in the exclusive formation of the ethyl ester of o-phenylene(N′-methyl oxamide)(oxamic acid) (opooH3EtMe, 2) in ca. 50% yield. Treatment of 2 with four equivalents of [Me4N]OH followed by the addition of Cu(ClO4)2·6H2O gave [Me4N]2[Cu(opooMe)]·H2O (3A) in ca. 80% yield. As 3A appears to be a hygroscopic solid, the related [nBu4N]+ salts [nBu4N]2[M(opooMe)]·H2O (M = Cu (3B), Ni (4)) have been synthesized. By addition of two equivalents of [Cu(pmdta)(NO3)2] to a MeCN solution of 3B the novel asymmetric trinuclear complex [Cu3(opooMe)(pmdta)2](NO3)2 (5) could be obtained in ca. 90% yield. Compounds 2, 3A, 3B, 4 and 5 have been characterized by elemental analysis and NMR/IR spectroscopy. Furthermore, the solid state structures of 3A in the form of [Me4N]2[Cu(opooMe)]·MeOH (3A′), 3B in the form of [nBu4N]2[Cu(opooMe)] (3B′), 4 in the form of [nBu4N]2[Ni(opooMe)]·1.25H2O (4′) and 5 in the form of [Cu3(opooMe)(pmdta)2] (NO3)2·3MeCN (5′), respectively, have been determined by single-crystal X-ray diffraction studies. By controlled cocrystallization, diamagnetically diluted 3B (1%) in the host lattice of 4 (99%) in the form of single crystals have been made available, allowing single crystal EPR studies to extract all components of the g-factor and the tensors of onsite CuA and transferred NA hyperfine interaction. Out of these studies the spin density distribution of the [Cu(opooMe)]2− complex fragment could be determined. The magnetic properties of 5 were studied by susceptibility measurements versus temperature. An intramolecular J parameter of −65 cm−1 has been obtained, unexpectedly, as 5 should possess two different J values due to its two different spacers between the adjacent CuII ions, namely an oxamate (C2NO3) and an oxamidate (C2N2O2) fragment. This unexpected result is explained by a summarizing discussion of the experimentally obtained EPR results (spin density distribution) of 3B, the geometries of the terminal [Cu(pmdta)]2+ fragments of 5 determined by X-ray crystallographic studies and accompanying quantum chemical calculations of the spin density distribution of the mononuclear [Cu(opooMe)]2− and of the magnetic exchange interactions of trinuclear [Cu3(opooMe)(pmdta)2]2+ complex fragments. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

<p style="text-align: justify; ">Reactions of 3,5-dimethylpyrazole-1-carboxamidinium&nbsp;nitrate (dpca∙HNO3) and 4-acetyl-3-amino-5-methylpyrazole (aamp) with transition metals under different reaction conditions are presented. The template reaction of aamp with triethyl orthoformate (teof) in the presence of metal ion is described. Besides, condensation of aamp with thiosemicarbazide (tsc) and the coordination of its product to copper(II) ion is also described. Twelve new complex compounds are synthesized and fully characterized. The characterization of two other, already known complexes is significantly enriched. The influence of HSAB interactions between the metal ions and ligators on the structures of obtained compounds is studied. The influence of the reaction conditions on the composition, structure and quality of crystals obtained in the reactions is investigated. Compounds are characterized by structural&nbsp;analysis, elemental analysis, molar conductivity data, infrared spectrometry and thermal analysis. Some selected complexes are characterized by UV-Vis spectra, magnetic measurements and biological activity tests, too.</p> / <p> Reactions of 3,5-dimethylpyrazole-1-carboxamidinium&nbsp;nitrate (dpca∙HNO3) and 4-acetyl-3-amino-5-methylpyrazole (aamp) with transition metals under different reaction conditions are presented. The template reaction of aamp with triethyl orthoformate (teof) in the presence of metal ion is described. Besides, condensation of aamp with thiosemicarbazide (tsc) and the coordination of its product to copper(II) ion is also described. Twelve new complex compounds are synthesized and fully characterized. The characterization of two other, already known complexes is significantly enriched. The influence of HSAB interactions between the metal ions and ligators on the structures of obtained compounds is studied. The influence of the reaction conditions on the composition, structure and quality of crystals obtained in the reactions is investigated. Compounds are characterized by structural<br /> analysis, elemental analysis, molar conductivity data, infrared spectrometry and thermal analysis. Some selected complexes are characterized by UV-Vis spectra, magnetic measurements and biological activity tests, too</p>

Use of metal based anticancer medication began with the clinical approval of cisplatin in 1978. Research led to the development of six platinum based drug candidates which are in use around the world. However there is a great need to develop better treatment strategies. The present work entitled “Cytotoxicity of Metal Based Anticancer Active Complexes and Their Targeted Delivery Using Nanoparticles” is an effort to prepare cytotoxic metal complexes based on platinum(IV) and copper(II) and deliver them selectively to cancer cells using a targeting ligand, biotin, with two different delivery vehicles, viz. PEGylated polyamidoamine dendrimer (PAMAM) and gold nanoparticles (AuNPs). Chapter 1 provides a brief introduction to cancer and its characteristic features, followed by a short description about different treatment modalities in clinical practice. An account of the development of anticancer drugs starting from purely organic drugs to the field of metal based anticancer drugs is discussed. An overview of the available targeting strategies are discussed with specific examples. The section ends with the scope of the present work. Platinum based anticancer drugs currently in use contain platinum in the +2 oxidation state. These drugs showed side effects and are often ineffective against resistant cells, especially in the latter stages of treatment. A recent focus of metal based anticancer drug research is the development of platinum(IV) systems which shows promise to have greater activity in cancer cells in a reducing environment. Reported platinum(IV) dual drugs contain the components of “cisplatin” or an analogue along with an active organic drug. But there are no known dual drugs based on platinum(IV) that would generate a cytotoxic metal complex along with cisplatin. In Chapter 2, a bimetallic dual drug (M4) (Figure 1), the first of its kind, with components of cisplatin and copper bis(thiosemicarbazone) has been prepared (Figure 1). The components and the bimetallic complex were characterized using several spectroscopic techniques. The dual drug M4 was found to be highly cytotoxic (IC50 1.3 M) against HeLa cells and was better than cisplatin (IC50 6.8 M). The bimetallic complex turned out to be better than the mixture (IC50 7.2 M) of individual drugs which indicated possible synergism of the released cisplatin and the copper bis(thiosemicarbazone) from the dual drug. Figure 1: Structure of the platinum(IV) and copper bis(thiosemicarbazone) complexes. A novel approach towards conjugation of platinum(IV) drugs to a carrier has been developed using a malonate moiety (Figure 2). The bis(butyric acid) complex, Pt(NH3)2(OCOC3H7)2Cl2 (M1), was taken as model complex to demonstrate the conjugation strategy. The complex M4 was also conjugated to the partially PEGylated 5th generation PAMAM dendrimers. Figure 2: Schematic representation of the platinum(IV) drug conjugated PAMAM dendrimer. The cytotoxicity of M4 was reduced to a small extent on conjugation to the dendrimer. In the presence of 5 mM sodium ascorbate as a reducing agent, sustained release (40 %) of the drug was shown to occur over a period of 48 h by the drug release study. The reduction in cytotoxicity of the dendrimer conjugates could be due to incomplete release of the active drug. Unfortunately, no enhanced activity was observed with the additional targeting ligand, biotin. The drug uptake study revealed that the dendrimer conjugates were successful in entering cancer cells. There was no preferential uptake with biotin conjugated dendrimers which explained the similar cytotoxicity of dendrimer conjugates with and without biotin. Different delivery vehicles showed varied efficiency in delivering the pay load (drugs) to the cancer site. In this connection, PEGylated gold nanoparticles have shown good promise as a drug delivery vehicle. In Chapter 3, M1 and M4 are both conjugated to malonate functionalized PEGylated gold nanoparticles (30 nm). Biotin was also attached to the AuNPs for targeting HeLa cells. Figure 3: Schematic representation of the platinum(IV) drug and biotin conjugated AuNPs. The AuNPs were highly stable in water without agglomeration. There was no shift in the Surface Plasmon Resonance (SPR) band after conjugation of the drug molecules and targeting ligands. TEM images and DLS measurements showed there was no change in particle size. Drug conjugated AuNPs were also very stable in high salt concentrations as well as over a large range of pH. AuNPs with M1 were found to be less cytotoxic than the parent drug. Biotinylated AuNPs with M1 were more potent than non-biotinylated nanoparticles and increased cytotoxicity (35 %) was observed with biotin conjugation. Surprisingly, the enhanced activity of biotinylated AuNPs could not be correlated to the drug uptake study. The cytotoxicity of the bimetallic dual drug containing AuNPs were about 10-fold less and no increased activity was observed with the biotinylated conjugates. The reduced activity of AuNPs with the bimetallic drug was due to incomplete release from the AuNPs (20 % release after 48 h). But the release kinetics was very slow and sustained which might increase in vivo activity. The unexpected lower activity of biotinylated conjugates with copper bis(thiosemicarbazone) was suggestive of interference between bis(thiosemicarbazone) complex and the biotin receptor resulting in reduced drug uptake. Copper bis(thiosemicarbazone) complexes hold very good promise as a class of non-platinum anticancer drug candidates. However, they lack selectivity towards malignant cells. Recently, CuATSM has shown hypoxia selectivity and very good cytotoxicity resulting in 64CuATSM being used in advanced stages of clinical trials for imaging hypoxic cells. In Chapter 4, a copper bis(thiosemicarbazone) complex analogous to Cu(ATSM) with a redox active cleavable disulfide linker and a terminal carboxylic acid group (CuATSM-SS-COOH) was synthesised and characterised spectroscopically. The complex was highly cytotoxic and has an IC50 value (6.9 M) similar to that of cisplatin against HeLa cells. The complex was conjugated to PEGylated gold nanoparticles by amide coupling between the acid group from the drug molecule and the amine on the AuNPs (20 nm) for smart drug delivery. The gold nanoparticles were decorated with biotin for targeted delivery to the HeLa cells. Figure 4: Schematic representation of the CuATSM-SS-COOH and biotin decorated AuNPs. The CuATSM-SS-COOH was insoluble in water but conjugation to PEGylated gold nanoparticles made it water soluble. The drug molecules and biotin conjugated AuNPs were highly stable which was confirmed by TEM and DLS measurements. Similar to the study described in the previous chapter, these AuNPs were also stable in a wide range of pH and salt concentrations. In vitro glutathione (GSH) triggered release study demonstrated substantial release of the cytotoxic agent from the AuNPs (60 %) over a period of 48 h. In vitro cell viability study with HeLa cells showed reduced cytotoxicity (IC50 15 M) of AuNPs with and without biotin containing drug conjugates relative to the parent copper complex (IC50 6.9 M). The reduction of the cytotoxicity correlated well with the released amount of the active drug from the nanoconjugates over the same time period. In vivo studies demonstrated the effectiveness of these nanoparticle carriers as suitable vehicles as they exhibited nearly four-fold reduction of tumor volume without significant loss in body weight. Moreover, the biotin targeted nanoparticle showed significant (p < 0.5) reduction in tumor volume compared to the non-targeted gold nanoparticles. Thus, this smart linking strategy Can be extended to other cytotoxic complexes that suffer from non-specificity, low aqueous solubility and toxicity. Multinuclear anticancer active complexes do not act in the same way as that of their corresponding mononuclear analogues. In the case of multinuclear platinum complexes, the activity not only depends on the active moiety but also on the spacer length between the moieties. In Chapter 5, a series of multinuclear copper bis(thiosemicarbazone) complexes were prepared and characterised using different techniques. Figure 5: General structures of binuclear copper bis(thiosemicarbazone) complexes. All the complexes showed redox activity and have a very high negative reduction potential, i.e. these compounds would not be easily reduced in the biological medium and would remain as copper(II) species. As the concentration of the reducing agents are more within cancer cells, once these complexes are inside cells they would be reduced to Cu(I). These compounds were shown to be highly lipophilic from the large log P values. Unfortunately, these binuclear complexes were less active than similar mononuclear complexes. One possible reason for the reduced cytotoxicity of these complexes could be adherence of the complexes to the cell membrane due to the high lipophilicity of these complexes. Out of five different methylene spacers between two bis(thiosemicrarbazone) moieties, the complex with a three carbon spacer was shown to be the most active against HeLa cells. The complexes with five and six methylene spacers turn out to be noncytotoxic. Further experiments are necessary to reveal the mechanism of action in these complexes. In summary, bimetallic complexes can be very active and may be a way of overcoming drug resistance in platinum based therapy. A dual drug can be delivered using a malonate moiety and a disulfide linker. Gold nanoparticles are good delivery vehicles for these dual drugs and show great potential for improvement and translation to the next stage. (For figures pl refer the abstract pdf file)

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.