Le monoxyde d'azote (NO•) est connu pour son rôle dans de nombreux processus biologiques et physiologiques. Il peut cependant avoir des effets antagonistes selon sa concentration dans le milieu. Le développement de sources exogènes capables de relarguer localement et quantitativement NO• est donc nécessaire pour profiter pleinement de son potentiel thérapeutique. La chimiothérapie photoactivée offre une approche intéressante qui consiste en l'irradiation de systèmes photosensibles non toxiques dans l'obscurité, mais capables de déclencher la mort cellulaire sous activation à la lumière. Cette thèse s'articule autour de trois complexes de ruthénium nitrosyle (RuNO) à ligands polypyridines, développés dans la perspective d'étudier leur comportement par excitation mono- et biphotonique. La fonctionnalisation des ligands polypyridines par des groupements riches en électrons permet d'envisager une excitation à 2 photons dans la fenêtre thérapeutique afin de traiter de manière locale des tumeurs plus profondes. Un état de l'art sur ces enjeux et cette thématique est dressé dans le premier chapitre. Dans le deuxième chapitre, une étude théorique comparative de plusieurs complexes RuNO à ligand bipyridine fonctionnalisée par des fluorènes permet de sélectionner le meilleur candidat pour la photolibération de NO•. Dans le troisième chapitre, la synthèse et la caractérisation de [Ru(terpy)(F2bpy)(NO)](PF6)3 (terpy = 2,2':6',2''-terpyridine; F2bpy = 4,4'-bis(9,9'-dibutyl-9H-fluoren-2-yl)-2,2'-bipyridine) sont décrites. Sont ensuite présentées dans le quatrième chapitre la synthèse et la caractérisation de [Ru(terpy)(MP2bpy)(NO)](PF6)3 (T0B2) et [Ru(MPterpy)(MP2bpy)(NO)](PF6)3 (T1B2), avec MP2bpy = 4,4'-bis(4-méthoxyphényl)-2,2'-bipyridine et MPterpy = 4'-(4-méthoxyphényl)-2,2':6',2''-terpyridine. Dans le cinquième chapitre, les propriétés photophysiques de [Ru(terpy)(F2bpy)(NO)](PF6)3 sous excitation à un photon et à deux photons sont étudiées, la libération de NO• est mise en évidence (détermination du rendement quantique фNO et de la section efficace σ) et le photoproduit est caractérisé. Le comportement des complexes T0B2 et T1B2 sous irradiation monophotonique est étudié dans le sixième chapitre, à travers la photolibération de NO•, la caractérisation de leur photoproduit et la détermination de фNO. / Nitric oxide (NO•) is known for its role in many biological and physiological processes. Nonetheless its effects are opposite according to the concentration in the media. The development of exogeneous sources able to release locally and quantitatively NO• is therefore necessary to fully benefit from its therapeutic potential. Photoactivated chemotherapy offers an interesting approach consisting in the irradiation of non toxic photoreactive systems in the dark, but able to trigger cell death when irradiated with light. This thesis is based on three ruthenium nitrosyl complexes (RuNO) with polypyridyl ligands, developed in view of studying their behavior under mono- and biphotonic excitation. The functionalization of polypyridyl ligands by electron-rich groups enables to consider a two-photon excitation in the therapeutic window in order to access deeper tumors locally. A state of art on those stakes and on this theme is addressed in the first chapter. In the second chapter, a comparative theoretical study of several RuNO complexes with a bipyridine ligand functionalized with fluorene enables to select the best candidate for NO• photorelease. In the third chapter, the synthesis and the characterization of [Ru(terpy)(F2bpy)(NO)](PF6)3 (terpy = 2,2':6',2''-terpyridine; F2bpy = 4,4'-bis(9,9'-dibutyl-9H-fluoren-2-yl)-2,2'-bipyridine) are detailed. In the fourth chapter are presented the synthesis and characterization of [Ru(terpy)(MP2bpy)(NO)](PF6)3 (T0B2) and [Ru(MPterpy)(MP2bpy)(NO)](PF6)3 (T1B2), with MP2bpy = 4,4'-bis(4-methoxyphenyl)-2,2'-bipyridine et MPterpy = 4'-(4-methoxyphenyl)-2,2':6',2''-terpyridine. In the fifth chapter, the photophysical properties of [Ru(terpy)(F2bpy)(NO)](PF6)3 under one-photon and two-photon excitation are studied, NO• release is demonstrated (determination of the quantum yield фNO and the cross section σ) and the photoproduct is characterized. The behavior of T0B2 and T1B2 under monophotonic irradiation is described in the sixth chapter, through the photorelease of NO•, the characterization of their photoproduct, and the determination of фNO.

The present thesis deals with different aspects of the chemistry and photo-biology of various ferrocene-conjugates, their interaction with double helical DNA, DNA photocleavage and photo-enhanced cytotoxicity in visible light, localization and cellular uptake to study the mechanism of cell death. Phenyl analogues of the active complexes have been synthesized and used for comparison in biological assays. Chapter I presents an overview of cancer and its types, various treatments for cancer. A general overview on the Photodynamic Therapy, a new modality of light activated cancer treatment and its various possible mechanism of action, has been made. The promise of photoactivated chemotherapy is discussed with recently developed metal based antitumor agents. Biological applications of few ferrocene conjugates as anticancer and anti-malarial agents 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 and cellular localization of ferrocene-conjugated dipicolylamine oxovanadium(IV) complexes of curcumin. To explore the role of the ferrocenyl moiety the phenyl analogue of the ferrocenyl complexes is synthesized and used as a control for comparison purpose. Chapter III deals with the photo-induced DNA cleavage and photo-enhanced cytotoxicity of ferrocene-conjugated oxovanadium(IV) complexes of heterocyclic bases. The synthesis, characterization, structural comparisons, DNA binding, DNA photocleavage and photocytotoxic activity in visible light are discussed in detail. Chapter IV describes the synthesis, characterization and structure of ferrocene-conjugated oxovanadium(IV) complexes of acetylacetonate derivatives. The complexes are evaluated for DNA binding, DNA photocleavage and photocytotoxic activity in HeLa, MCF-7, 3T3 cells in visible light. The fluorescent nature of the complexes is used to study the cellular localization of the complexes and the mechanism of cell death induced by the complexes is also discussed. Chapter V presents the photocytotoxic effect of ferrocene-conjugated oxovanadium(IV) complexes of different curcuminoids in HeLa , HepG2 and 3T3 cells. Curcumin based fluorescence has been successfully used to study the cellular uptake and localization behavior of the complexes. The positive role of the ferrocenyl complex is evident from the ~4 fold increase in its photocytotoxicity compared to the phenyl analogue. The apoptotic mode of cell death is evident from nuclear co-staining using Hoechst dye. Chapter VI describes the synthesis, characterization and photochemotherapeutic efficacy of ferrocene conjugates of N-alkyl pyridinium salts. Mitochondria targeting property of ferrocene compound having n-butyltriphenylphosphonium group has been studied by JC-1 assay. FACS analysis showed significant sub G1/G0 phase cell-cycle arrest in cancer cells on visible light treatment. 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. INDEX WORDS: Ferrocene conjugates Crystal structure DNA binding DNA photocleavage Photocytotoxicity Vanadium Cellular Imaging