Le travail présenté dans ce mémoire est dédié à l'élaboration de complexes de ruthénium(II) photo-commutables originaux incorporant le couple photochrome Diméthyldihydropyrène (DHP) / Cyclophanediène (CPD), pour de futurs dispositifs moléculaires optoélectroniques.Dans le but de réaliser des systèmes complexes pouvant reproduire les fonctions d'un circuit logique, une stratégie intéressante repose sur l'association de molécules photo-commutables et de complexes métalliques. Cependant, cette stratégie se confronte à certains obstacles majeurs, généralement associés à la perte des propriétés de commutation des photochromes organiques. En réponse aux précédents résultats confirmant cette tendance, deux nouvelles familles de complexes terpyridiniques de ruthénium(II) à base de DHP ont été synthétisées. Sachant que la présence de fonction pyridinium améliore significativement les propriétés d'isomérisation du cœur DHP, les centres métalliques ont été connectés soit via un lien benzyle pyridinium (Ru-Lpy+tpy) soit via un lien aryle pyridinium (Ru-LZincke). Bien que fonctionnant à plus faible énergie, le complexe Ru-LZincke présente des performances amoindries, en revanche les complexes Ru-Lpy+tpy affichent une préservation notable de leurs propriétés de commutation. Suite à la découverte d'une photo-réactivité originale favorisée par la présence du centre métallique, une famille analogue à base de complexes bipyridiniques de ruthénium(II) (Ru-Lpy+bpy) a été étudiée. Même si les mécanismes ne sont pas complètement rationalisés, les complexes Ru-Lpy+bpy se sont révélés être de remarquables candidats pour la réalisation de photo-commutateurs réversibles quantitativement dans le domaine du visible. / The work of this thesis is devoted to the development of original photo-switchable ruthenium(II) complexes incorporating the photochromic Dimethyldihydropyrene (DHP) / Cyclophanediene (CPD), for future optoelectronic molecular devices.In order to realize complex systems capable of reproducing the functions of a logic circuit, an interesting strategy is based on the association of photo-switchable molecules and metal complexes. However, this strategy is confronted with some major obstacles, generally associated with the loss of the switching properties of organic photochromes. In response to previous results confirming this trend, two new families of DHP-based terpyridine ruthenium(II) complexes have been synthesized. Since the presence of pyridinium function significantly improves the isomerization properties of the DHP core, the metal centers were connected either via a pyridinium benzyl linkage (Ru-Lpy+tpy) or via an aryl pyridinium linkage (Ru-LZincke). Although operating at lower energy, Ru-LZincke complex exhibits lessened performance, whereas Ru-Lpy+tpy complexes exhibit a notable preservation of their switching properties. Following the discovery of an original photo-reactivity favored by the presence of metal center, an analogue family based on ruthenium (II) bipyridine complexes (Ru-Lpy+bpy) was studied. Even if the mechanisms are not completely rationalized, Ru-Lpy+bpy complexes have proved to be remarkable candidates for the realization of quantitatively reversible photo-switches in the visible domain.

Interactions of Metal Cations in Bioorganic Environment Computational Study Using Quantum Mechanics and Molecular Mechanics Tools Zdeněk Futera Biologically relevant interactions of piano-stool ruthenium(II) complexes with ds-DNA are studied by QM/MM computational technique. The whole re- action mechanism is divided into three phases - hydration of [RuII (η6 - benzene)(en)Cl]+ , consequent binding DNA and final intra-strand cross-link formation between two adjacent guanines. Free energy profiles of all reactions are explored by QM/MM MD umbrella sampling approach where the Ru(II) complex is described by DFT. For that purpose, special QM/MM software was developed to couple Gaussian and Amber programs. Calculated free energy barriers of Ru(II) hydration as well as DNA binding process are in good agreement with experimentally determined rate constants. Reaction pathway for cross-link formation was predicted that is feasible from both thermodynamical and kinetical point of view.

Orientadora: Profa. Dra. Paula Homem de Mello / Tese (doutorado) - Universidade Federal do ABC. Programa de Pós-Graduação em Ciência e Tecnologia/Química, 2017. / Pesquisas sobre dispositivos fotovoltaicos têm como objetivo aumentar sua eficiência, durabilidade e baixar seus custos de fabricação. Entre os dispositivos fotovoltaicos estão as células solares sensibilizadas por corantes (DSSC). Sendo o corante um dos parâmetros mais estudados e importantes das DSSC, este trabalho teve como objetivo principal estudar, utilizando métodos de química computacional, as propriedades eletrônicas de alguns corantes baseados em complexos de rutênio(II). Neste trabalho, as propriedades eletrônicas do N3 (cis-Ru[(dcbH2)2(NCS)2], dcbH2 = ácido 2,2¿-bipiridina-4,4¿-dicarboxílico), foram calculadas e comparadas com isômeros do N719 (N3 duplamente desprotonado) e com corantes mono (mMS) e dimetil substituídos (dMS), em relação aos grupos carboxílicos do N3. Os resultados sugerem que os isômeros do N719 se encontram em equilíbrio à temperatura ambiente. Os grupos mMS, dMS e desprotonados derivados do N3 apresentam menores energias de oxirredução, quando o metil ou o carboxilato, respectivamente, estão localizados em oposição à bipiridina. A correlação com dados experimentais dos corantes N3, C101, N945 e K19 sugere que as diferenças de energias de orbitais e grupos doadores/aceptores afetam a eficiência da DSSCs. Para ter um parâmetro de comparação entre os níveis de energia eletrônicos do corante e as bandas do semicondutor, foi realizado o cálculo de TD-DFT para o cluster Ti42O77H18. O estudo metodológico para verificar o efeito de diferentes funcionais e da inclusão do efeito do solvente na obtenção do espectro eletrônico de absorção mostrou que podem ocorrer variações significativas. Os funcionais M06 e B3LYP se mostraram bastante adequados para a previsão do gap HOMO-LUMO, mas para a previsão do espectro como um todo, o funcional CAM-B3LYP é o mais adequado para os complexos de rutênio(II) aqui estudados. / Research on photovoltaic devices aims to increase their efficiency and durability, as well as lower their manufacturing costs. Among the photovoltaic devices, there are the dyes-sensitized solar cells (DSSC). The dye is one of the most studied and important parameter of DSSC; so, in this work, we had as main objective to study, using computational chemistry methods, the electronic properties of some dyes based on ruthenium(II) complexes. In this work, the electronic properties of N3 (cis-Ru[(dcbH2)2(NCS)2], dcbH2 = 2,2'-bipyridine-4,4'-dicarboxylic acid) were calculated and compared with N719 isomers (N3 double-deprotonated), mono (mMS) and dimethyl substituted (dMS) dyes. The results suggest that N719 isomers are in equilibrium at room temperature. The mMS, dMS and deprotonated N3-derived groups exhibit lower oxidation energy when methyl or carboxylate, respectively, are located in opposition to bipyridine group. Correlation with experimental data of N3, C101, N945 and K19 dyes suggest that differences in orbital energies and donor / acceptor groups affect the efficiency of DSSCs. In order to establish a comparison parameter between the electronic energy levels of the dye and the semiconductor bands, the calculation of TD-DFT for the Ti42O77H18 cluster was performed. The methodological study to verify the effect of different functionals and the inclusion of the solvent effect in obtaining the electronic spectrum showed that significant variations can occur. M06 and B3LYP functionals are recommended to estimate HOMO-LUMO gap, but CAM-B3LYP functional is the most suitable for the prediction of the whole spectrum characteristics for the ruthenium(II) complexes studied here.

This thesis explores the design, synthesis and optoelectronic properties of supramolecular photoactive materials based on chiral iridium(III) and ruthenium(II) metalloligands. Our design strategies aim to create a high concentration of chromophoric units that, when self-assembled in well-defined geometrical arrangements, exhibit emergent photophysical properties.

Ce mémoire est consacré à la synthèse et la caractérisation de complexes bis-terdentates de ruthénium pour leur potentielle utilisation dans des triades photosensibles, ou pour la fabrication de dispositifs photosensibles. La première partie se concentre sur les propriétés photophysiques de deux complexes de RuII bis-terdentates. Le premier est un complexe homoleptique, formé de ligands tridentates comprenant deux sous-unités carbène (CNC), le second est un complexe hétéroleptique composé d'un ligand CNC et d'une terpyridine. Ce complexe hétéroleptique est luminescent à température ambiante, contrairement à ses deux complexes parents homoleptiques. Les propriétés électrochimiques et photoélectrochimiques de complexes de type [M(tpy)2]2+ (M=FeII ou RuII), dont les ligands terpyridine sont substitués par des groupements thiols, sont étudiées dans une seconde partie. Ces complexes électropolymérisent de manière organisée sur des électrodes d'or, par oxydation des thiols en disulfures. Ces propriétés ont été utilisées pour construire des diades [RuII]-[FeII] sur des électrodes d'or, dont le photocourant a pu être mesuré. Dans le dernier chapitre, les propriétés photophysiques et d'électropolymérisation du complexe de ruthénium décrit dans le chapitre 2 sont utilisées pour tenter de fabriquer un transistor pho-toactivable. / This thesis deals with the synthesis and characterization of several bis-terdentate complexes, and their potential use for the construction of photoactive molecular triads, or the fabrication of photoactive devices. The first chapter focuses on the photophysical properties of two new bis-terdentate RuII com-plexes. The first one is a homoleptic complex containing two N-heterocyclic carbene-based ligands (CNC) allowing close-to-perfect octahedral coordination geometry. The second one is a heteroleptic complex bearing a CNC ligand and an ancillary terpyridine ligand. This second complex displays room temperature luminescence whereas both homoleptic terpyridine-based and CNC-based RuII complexes are only luminescent at 77 K. The second chapter describes the electrochemical properties of a [M(tpy)2]2+-type (M = RuII or FeII) complex bearing thiol groups on both of the terpyridines are described. These complexes display electropolymerization properties through oxidation of thiols into disulfides. This phenomenon happens only on gold, suggesting that the polymer chains organize on the surface of the electrodes. Moreover, self-assembled monolayers of the RuII complexes were formed on gold, and their ability to exchange charges with the electrode upon irradiation was studied. Finally, self-organisation and electropolymerization properties were used to form [RuII]-[FeII] diads on a gold surface, and their photoresponse was recorded. The last chapter describes the attempts to construct a molecular photosensitive device by electropolymerizing the RuII complexes depicted in the second chapter in nanogaps between gold electrodes.

This thesis was conducted as cotutelle-de-thèse between the Université de Montréal and the Universität Würzburg (Germany). Cette thèse a été réalisée en cotutelle de thèse entre l'Université de Montréal et l'Universität Würzburg (Allemagne). / Cette thèse étudie la conception de différentes ligands pour les complexes de Ru(II) et leur activité comme photosensibilisateur (PS) dans l'évolution photocatalytique de l'hydrogène. Le système catalytique contient généralement un catalyseur, un donneur d'électron sacrificiel (SED) et un PS, qui doit présenter une forte absorption et luminescence et un comportement redox réversible. Les substituants pyridine attracteurs d'électrons sur le récepteur d'ions métalliques terpyridine entraînent une augmentation de la durée de vie de l'état excité et du rendement quantique (Φ = 74*10-5; τ = 3.8 ns) et permettent au complexe III-C1 de présenter une activité en tant que PS. Bien que la fréquence (TOFmax) et le nombre de cycle catalytique (TON) soient relativement faibles (TOFmax = 57 mmolH2 molPS-1 min 1; TON(44 h) = 134 mmolH2 molPS-1), le système catalytique a une longue durée de vie, ne perdant que 20% de son activité au cours de 12 jours. De manière intéressante, la conception hétérolytique dans III-C1 s'avère être bénéfique pour la performance en tant que PS, malgré des propriétés photophysiques et électrochimiques comparables à celles du complexe homoleptique IV-C2 (TOFmax = 35 mmolH2 molPS-1 min-1; TON(24 h) = 14 mmolH2 molPS-1). L'extinction réductive de la PS excitée par le SED est identifiée comme l'étape limitant la vitesse dans les deux cas. Par conséquent, les ligands sont modifiés pour être plus accepteurs d'électrons, soit par N-méthylation des substituants pyridine périphériques, soit par introduction d'un cycle pyrimidine dans le récepteur d'ion métallique, ce qui conduit à une augmentation des durées de vie des états excités (τ = 9–40 ns) et des rendements quantiques de luminescence (Φ = 40–400*10-5). Cependant, le caractère plus accepteur d'électrons des ligands entraîne également des potentiels de réduction décalés anodiquement, ce qui conduit à un manque de force motrice pour le transfert d'électrons du PS réduit au catalyseur. Ainsi, cette étape de transfert d'électrons s'avère être un facteur limitant de la performance globale du PS. Alors que des TOFmax plus élevés dans les expériences d'évolution de l'hydrogène sont observés pour les PS contenant le motif pyrimidine (TOFmax = 300–715 mmolH2 molPS-1 min-1), la longévité de ces systèmes est réduite avec des temps de demi-vie de 2–6 h. L'expansion des ligands contenant le motif pyrimidine en complexes dinucléaires conduit à une absorptivité plus forte (ε = 100–135*103 L mol-1 cm-1), une luminescence accrue (τ = 90–125 ns, Φ = 210–350*10-5) et peut également entraîner un TOFmax plus élevé si la force motrice est suffisante pour le transfert d'électrons vers le catalyseur (1500 mmolH2 molPS-1 min-1). En comparant des complexes avec des forces motrices similaires, une luminescence plus forte se traduit par un TOFmax plus élevé. Outre les considérations thermodynamiques, les effets cinétiques et l'efficacité du transfert d'électrons sont supposés avoir un impact sur l'activité observée dans l'évolution de l'hydrogène. En résumé, ce travail montre que la conception ciblée de ligands peut faire du groupe précédemment négligé des complexes de Ru(II) avec des ligands tridentés des candidats attrayants pour une utilisation comme PS dans l'évolution photocatalytique de l'hydrogène. / This thesis investigates different ligand designs for Ru(II) complexes and the activity of the complexes as photosensitizer (PS) in photocatalytic hydrogen evolution. The catalytic system typically contains a catalyst, a sacrificial electron donor (SED) and a PS, which needs to exhibit strong absorption and luminescence, as well as reversible redox behavior. Electron-withdrawing pyridine substituents on the terpyridine metal ion receptor result in an increase of excited-state lifetime and quantum yield (Φ = 74*10-5; τ = 3.8 ns) and lead to complex III-C1 exhibiting activity as PS. While the turn-over frequency (TOFmax) and turn-over number (TON) are relatively low (TOFmax = 57 mmolH2 molPS-1 min-1; TON(44 h) = 134 mmolH2 molPS-1), the catalytic system is long-lived, losing only 20% of its activity over the course of 12 days. Interestingly, the heteroleptic design in III-C1 proves to be beneficial for the performance as PS, despite III-C1 having comparable photophysical and electrochemical properties as the homoleptic complex IV-C2 (TOFmax = 35 mmolH2 molPS-1 min-1; TON(24 h) = 14 mmolH2 molPS-1). Reductive quenching of the excited PS by the SED is identified as rate-limiting step in both cases. Hence, the ligands are designed to be more electron-accepting either via N-methylation of the peripheral pyridine substituents or introduction of a pyrimidine ring in the metal ion receptor, leading to increased excited-state lifetimes (τ = 9–40 ns) and luminescence quantum yields (Φ = 40–400*10-5). However, the more electron-accepting character of the ligands also results in anodically shifted reduction potentials, leading to a lack of driving force for the electron transfer from the reduced PS to the catalyst. Hence, this electron transfer step is found to be a limiting factor to the overall performance of the PS. While higher TOFmax in hydrogen evolution experiments are observed for pyrimidine-containing PS (TOFmax = 300–715 mmolH2 molPS-1 min-1), the longevity for these systems is reduced with half-life times of 2–6 h. Expansion of the pyrimidine-containing ligands to dinuclear complexes yields a stronger absorptivity (ε = 100–135*103 L mol-1 cm-1), increased luminescence (τ = 90–125 ns, Φ = 210–350*10-5) and can also result in higher TOFmax given sufficient driving force for electron transfer to the catalyst (TOFmax = 1500 mmolH2 molPS-1 min-1). When comparing complexes with similar driving forces, stronger luminescence is reflected in a higher TOFmax. Besides thermodynamic considerations, kinetic effects and electron transfer efficiency are assumed to impact the observed activity in hydrogen evolution. In summary, this work shows that targeted ligand design can make the previously disregarded group of Ru(II) complexes with tridentate ligands attractive candidates for use as PS in photocatalytic hydrogen evolution. / In dieser Arbeit werden verschiedene Liganden für Ru(II)-Komplexe und die Aktivität der Komplexe als Photosensibilisatoren (PS) in der photokatalytischen Wasserstoffentwicklung untersucht. Das katalytische System besteht typischerweise aus einem Katalysator, einem Opferelektronendonator (SED) und einem PS, welcher eine starke Absorption und Lumineszenz sowie ein reversibles Redoxverhalten aufweisen sollte. Elektronenziehende Pyridin-Substituenten am Terpyridin-Metallionenrezeptor resultieren in einer Erhöhung der Lebensdauer des angeregten Zustands sowie der Quantenausbeute (Φ = 74*10-5; τ = 3.8 ns), was dazu führt, dass Komplex III-C1 als PS aktiv ist. Während die Wechselzahl (TOFmax) und der Umsatz (TON) relativ niedrig sind (TOFmax = 57 mmolH2 molPS-1 min-1; TON(44 h) = 134 mmolH2 molPS 1), ist das katalytische System langlebig und verliert im Laufe von 12 Tagen nur 20% seiner Aktivität. Das heteroleptische Design in III-C1 erweist sich als vorteilhaft für die Leistung als PS, obwohl III-C1 vergleichbare photophysikalische und elektrochemische Eigenschaften besitzt wie der homoleptische Komplex IV-C2 (TOFmax = 35 mmolH2 molPS-1 min-1; TON(24 h) = 14 mmolH2 molPS-1). In beiden Fällen erweist sich das reduktive Lumineszenzlöschen des angeregten PS durch den SED als geschwindigkeitsbestimmender Schritt. Daher werden die Liganden entweder durch N-Methylierung der peripheren Pyridin-Substituenten oder durch Einführung eines Pyrimidinrings in den Metallionenrezeptor elektronenziehender gestaltet, was zu erhöhten Lebensdauern des angeregten Zustands (τ = 9–40 ns) und Lumineszenzquantenausbeuten (Φ = 40–400*10-5) führt. Der stärker elektronenziehende Charakter der Liganden führt allerdings auch zu anodisch verschobenen Reduktionspotentialen, wodurch die treibende Kraft für den Elektronentransfer vom reduzierten PS zum Katalysator reduziert wird. Daher erweist sich dieser Elektronentransferschritt als ein limitierender Faktor für die Gesamtleistung des PS. Während höhere TOFmax in Wasserstoffproduktionsexperimenten für Pyrimidin-haltige PS beobachtet werden (TOFmax = 300–715 mmolH2 molPS-1 min-1), ist die Langlebigkeit für diese Systeme mit Halbwertszeiten von 2–6 h deutlich reduziert. Die Erweiterung der Pyrimidin-haltigen Liganden zu zweikernigen Komplexen führt zu einem stärkeren Absorptionsvermögen (ε = 100–135*103 L mol-1 cm-1), erhöhter Lumineszenz (τ = 90–125 ns, Φ = 210–350*10-5) und kann bei ausreichender treibender Kraft für den Elektronentransfer zum Katalysator auch zu einer höheren TOFmax führen (TOFmax = 1500 mmolH2 molPS-1 min-1). Beim Vergleich von Komplexen mit ähnlichen treibenden Kräften spiegelt sich die stärkere Lumineszenz in einem höheren TOFmax wider. Es wird angenommen, dass neben thermodynamischen Faktoren auch kinetische Effekte und die Effizienz des Elektronentransfers die beobachtete Aktivität bei der Wasserstoffentwicklung beeinflussen. Zusammenfassend zeigt diese Arbeit, dass gezieltes Ligandendesign die bisher vernachlässigte Gruppe der Ru(II)-Komplexe mit tridentaten Liganden zu attraktiven Kandidaten für den Einsatz als PS in der photokatalytischen Wasserstoffentwicklung machen kann.

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.

Introduction The chemistry of transitional metal complexes bearing σ-bonded H−X (X = H, Si, C) species/fragments, the so called σ-complexes, are key intermediates in catalytic processes such as hydrogenation, hydrosilylation, alkane functionalization etc. Particularly, the σ-H2 complexes form the best-known group of σ-complexes in which H2 is bound to the metal center in η2-fashion. Several well characterized examples of η2-silane and η2-borane complexes have also been reported. Moreover, in recent years, the carbon analogues of these complexes in which alkanes are coordinated through η2-C-H bonds to the metal center have been attracting the attention of organometallic chemists. An approach towards direct functionalization of σ-bonds in simple alkanes is the heterolytic activation of the C−H bond using highly electrophilic complexes. After all, for fine catalyst design and the selective functionalization of H−H, silanes or simple alkanes, it is necessary to understand the bonding nature of these σ-complexes in depth. Objectives The objectives of this work are as follows a) An attempt to stabilize and gain insights into the bonding nature and reactivity behavior of various sigma ligands on ruthenium center [Ru(η2-HX)(Tpms)(PPh3)2][OTf], (X = H, SiR (R = Me3 or Me2Ph) and CH3). b) Synthesis, characterization and reactivity studies of electrophilic ruthenium(II) complexes bearing (C6F5)2PCH2CH2P(C6F5)2 (dfppe) ligand towards heterolysis of H2. c) An approach towards preparation of insoluble molecular clusters from [Ru(P(OH)3)(dppe)2][OTf]2 complex and Zn, Cd and Cu acetates to realize σ-bond activation under heterogeneous conditions. Significant results In our attempts to gain insights into the bonding nature and reactivity behavior of σ-H2, silane and methane complexes, we followed two strategies to generate these complexes in solution. First, we synthesized and well characterized two new Ru(II)-complexes [RuH(Tpms)(PPh3)2] and [Ru(OTf)(Tpms)(PPh3)2], (OTf = trifluoromethane sulfonate) where Ru-H and Ru-OTf are the key reactive centers, followed by their subsequent reactions with electrophilic reagents such as HOTf, Me3SiOTf and CH3OTf and with H2, PhMe2SiH and CH4 at low temperature, respectively. These reactions finally resulted in the characterization of σ-H2 and σ-silane complexes, however, no σ-methane complex was observed even at low temperature (Scheme 1). Scheme 1 In order to realize highly eletrophilic metal complexes, a chelating fluorinated phosphine ligand 1,2-bis-(pentafluorophenylphosphino)ethane, (C6F5)2PCH2CH2P(C6F5)2 (dfppe) was employed and the synthesis and structural characterization of a series of new, Ru(II) hydride complexes [RuH(P(OMe)3)(bpy)(dfppe)][OTf], cis-[RuH2(dfppe)(PPh3)2] and [RuH(CO)Cl(PPh3)(dfppe)] were accomplished. Protonation reaction of the hydride complexes [RuH(P(OMe)3)(bpy)(dfppe)][OTf] (Scheme 2) and [RuH(CO)Cl(PPh3)(dfppe)] (Scheme 3) with HOTf at low temperature gave free H2 and five-coordinate species [Ru(P(OMe)3)(bpy)(dfppe)][OTf]2 and [Ru(CO)Cl(PPh3)(dfppe)][OTf], respectively. Surprisingly, in all these reactions, dihydrogen complexes are formed which were unobservable in which the H2 ligand was found to be highly labile. Reaction of is-[Ru(bpy)(dfppe)(OH2)(P(OMe)3)][OTf]2 with H2 however, resulted in the heterolytic activation of the H–H bond and concomitant protonation of H2O to give the corresponding hydride complex cis-[Ru(H)(bpy)(dfppe)(P(OMe)3)][OTf] and H3O+ (Scheme 2) . Scheme 2 Scheme 3 In an attempt to prepare insoluble molecular clusters in order to realize σ-bond activation under heterogeneous conditions, we studied the reactivity of highly electrophilic [Ru(P(OH)3)(dppe)2]2+ (dppe = (C6H5)2PCH2CH2P(C6H5)2) complex with various metal acetates. Usage of Zn(OAc)2.2H2O afforded a novel [Ru2(dppe)4P2(OH)2O4Zn2(OAc)(DMP)(OTf)][OTf]2 (Ru-Zn ) soluble bimetallic complex (Scheme 4) which was characterized in detail by NMR and single crystal X-ray crystallography. To achieve the expected insoluble molecular cluster further studies are required to tune the electronics and the sterics around the phosphorous acid moiety. Scheme 4