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A series of bimetallic (Ru^II, Pt<sup>II</sup) complexes were synthesized with the general formula [(tpy)RuCl(BL)PtCl₂](PF₆) (tpy = 2,2':6',2"-terpyridine and BL = bridging ligand) and their spectroscopic, electrochemical, and DNA binding properties studied. The bridging ligands used in these complexes were 2,3-bis(2'-pyridyl)pyrazine (dpp), 2,3-bis(2'-pyridyl)quinoxaline (dpq) and 2,3-bis(2'-pyridyl)benzoquinoxaline (dpb). These complexes combine light-absorbing Ru^II-polypyridyl chromophores and a cis-PtCl₂ structural motif known to bind DNA. The Ru-bound chloride may be substituted, enabling further modification of the spectroscopic properties. The synthesis of [(tpy)RuCl(BL)PtCl₂](PF₆) utilizes a building block approach that allows modifications to the series of complexes within the general synthetic scheme. This illustrates the applicability of this scheme to the development of new series of complexes. The lowest-energy absorption for the three complexes is assigned to a Ru(dπ) → BL(π*) charge transfer transition. This transition shifts to lower energy as the ligand is varied from dpp to dpq to dpb. The first and second reductions are BL^0/- and BL^-/2- based and shift to more positive potentials from dpp to dpq to dpb. The Ru^II/III redox couple remains at a nearly constant potential for the series. All three compounds show DNA binding when incubated with linearized plasmid DNA. Adduct formation was assessed by agarose gel electrophoresis as a retardation of band migration. / Master of Science

The goal of this research was to develop an understanding of the impact of component modifications on spectroscopic properties, DNA interaction, and bioactivity of tridentate, terpyridine containing ruthenium-based chromophores and chromophore coupled cisplatin analogs. The coupling of a light absorbing unit to a bioactive site offers the potential for developing supramolecules with multifunctional interactions with DNA and other biomolecules. A series of supramolecular complexes of the form [(TL)RuCl(dpp)](PF₆) and [(TL)RuCl(BL)PtCl₂](PF₆) with the BL (bridging ligand) = 2,3-bis(2-pyridyl)pyrazine (dpp) and varying TL (terminal ligand) (tpy = 2,2'':6'',2''-terpyridine, MePhtpy = 4''-(4-methylphenyl)- 2,2'':6'',2''- terpyridine, or tBu3tpy = 4,4'',4''-tri-tert-butyl-2,2'':6'',2''-terpyridine) have been designed and developed. The investigations described in this thesis were focused on the design and development of multifunctional supramolecules with improved DNA interaction and antibacterial properties. The impact of component modifications on photophysical and biological properties of the designed the supramolecular complexes was investigated. A series of supramolecular complexes of the type, [(TL)RuCl(dpp)](PF₆) and [(TL)RuCl(dpp)PtCl₂](PF₆), have been synthesized using a building block approach. Electronic absorption spectroscopy of these types of complexes displayed intense ligand-based transitions in the UV region and metal to ligand charge transfer (MLCT) transitions in the visible region. The Ru to dpp MLCT transitions in RuIIPtII bimetallic complexes were found to be red-shifted relative to the monometallic synthons. The MLCT transitions for [(TL)RuCl(dpp)](PF₆) and [(TL)RuCl(dpp)PtCl₂](PF₆) were centered at ca. 520 and 545 nm, in CH₃CN respectively. The RuIIPtII bimetallic complexes with (TL = tpy, MePhtpy, and tBu3tpy) displayed reversible RuII/III couples at 1.10, 1.10, and 1.01 V vs. Ag/AgCl, respectively. The tpy0/- reductions occurred for TL = tpy, MePhtpy, and tBu3tpy at -1.43, -1.44, and -1.59 V vs. Ag/AgCl, respectively. The RuIIPtII complexes displayed a more positive potential for the dpp0/- couples (-0.50 -0.55, -0.59 V for tpy, MePhtpy, and tBu3tpy, repectively) relative to their monometallic synthons (-1.15, -1.16, and -1.22 V), consistent with the coordination of electron deficient Pt(II) metal center. This research also presents first extensive DNA photocleavage studies of these relatively unexplored tridentate, tpy-containing chromophores. The DNA binding and photocleavage properties of a series of homoleptic and heteroleptic chromophores and RuIIPtII bimetallic complexes were investigated using agarose gel electrophoresis and equilibrium dialysis experiments. The heteroleptic complexes, [(MePhtpy)RuCl(dpp)](PF₆), [(tpy)RuCl(dpp)](PF6), and [(tBu3tpy)RuCl(dpp)](PF6), were found to photocleave DNA more efficiently than homoleptic complexes, [Ru(MePhtpy)2]2+, [Ru(tpy)2]2+, and [Ru(tBu₃tpy)2]2+, in the presence of oxygen. Coupling of [(TL)RuCl(BL)] subunit to a cis-PtIICl2 site provides for the application of typically shorter lived RuII(tpy) based chromophores in DNA photocleavage. The [(TL)RuCl(dpp)PtCl₂]+, complexes displayed covalent binding to DNA and photocleavage upon irradiation with visible light modulated by TL identity. The impact of component modifications on antibacterial properties of the designed molecules was explored for the first time. Both the RuIIPtII bimetallic complexes and their monometallic analogs displayed antibacterial properties. [(MePhtpy)RuCl(dpp)](PF₆) was found to be the most efficient antibacterial agent in the series of monometallic and RuIIPtII bimetallic complexes, displaying cell growth inhibition at 0.05 mM concentration compared to 0.1 mM concentration of [(MePhtpy)RuCl(dpp)PtCl₂](PF₆) needed to display the similar effect. A direct correlation was found to exist between the DNA interaction and bactericidal properties of the designed supramolecules. The effects of light on antibacterial properties of [(MePhtpy)RuCl(dpp)](PF₆) were also briefly examined. This complex represents the first inorganic chromophore-based photodynamic antibacterial agent. / Ph. D.

The goal of this research was to develop structurally diverse polyazine-bridged Ru(II),Pt(II) trimetallic and tetrametallic supramolecular complexes and study the impact of component variation on the redox, spectroscopic, and excited state properties that influence photoinduced charged separation and multielectron reduction.  These complexes are active photocatalysts for H2O reduction to H2.  Tetrametallic complexes with the supramolecular architecture [{(TL)2Ru(dpp)}2Ru(BL")PtCl2]6+ (Ru3Pt; TL = phen = 1,10-phenanthroline or Ph2phen = 4,7-diphenyl-1,10-phenanthroline; BL" = dpp = 2,3-bis(2-pyridyl)pyrazine or dpq = 2,3-bis(2-pyridyl)quinoxaline) feature a trimetallic dpp-bridged Ru(II) light absorber coupled to a cis-PtCl2 reactive metal center.  Trimetallic complexes with one less Ru-based light absorbing unit, [{(Ph2phen)2Ru(dpp)Ru(bpy)(BL")PtCl2]4+ (Ru2Pt; BL" = dpp or dpq), represent  a new supramolecular architecture that was designed and synthesized to provide less complex systems for excited state analysis.  Both the Ru3Pt and Ru2Pt systems have a remote Ru center separated from the reactive Pt site designed to provide extended 3MLCT lifetimes relative to directly coupled [(TL)2Ru(BL)PtCl2]2+ systems. The building block synthetic method used in constructing supramolecules provides the ability to purify and analyze the properties following each synthetic step, allowing sub-unit variation and structural diversity.  Building a knowledge base about the properties of smaller, less complicated structures is critical in understanding the electrochemistry, spectroscopy, and excited state dynamics of multi-metallic, multi-ligand complexes.  Electrochemical analysis of the [{(TL)2Ru(dpp)}2Ru(BL")PtCl2]6+ complexes suggests a HOMO localized on the terminal Ru centers (E1/2 (RuII/III) = 1.56-1.63 V vs. Ag/AgCl) and a LUMO localized on the remote BL" coordinated to the reactive Pt site, with the energy dictated by the BL" identity (E1/2 = "0.32 or "0.33 V for BL" = dpp or E1/2 = "0.02 or "0.05 V for BL" = dpq).  This provides spatially separated HOMOs and LUMOs which predict lowest-lying charge separated states.  The complexes are robust UV and visible light absorbers due to multiple broad, overlapping ligand centered and metal-to-ligand charge transfer (MLCT) transitions.  The lowest energy 1MLCT absorption is centered around 540-550 nm for the four tetrametallic complexes with high molar absorptivity (31,000-42,000 M"1cm"1).  BL" variation has only a small impact on the electronic absorption spectroscopy, while the TL variation greatly enhances the absorptivity between 350 nm and 500 nm from 29,000 to 42,000 M"1cm"1 for complexes with TL = phen and Ph2phen, respectively.   The tetrametallic [{(TL)2Ru(dpp)}2Ru(BL")PtCl2]6+ complexes exhibit unusual excited state dynamics as well as spatially separated HOMOs and LUMOs. The lowest lying optically populated state is a terminal Ru\'¼-dpp MLCT in all the Ru3Pt and Ru2Pt systems reported herein.  The terminal Ru(dÀ) based HOMO and BL"(À*) based LUMO suggests a lower lying terminal Ru\'BL" CS state in all systems.  Because the lowest lying terminal Ru(dÀ)\'BL"(À*) 3CS (charge separated) state is optically inaccessible, indirect population occurs.  The tetrametallic [{(TL)2Ru(dpp)}2Ru(BL")PtCl2]6+ complexes have similar excited state lifetimes (Ä) of 75-83 ns, and they exhibit quantum yields of emission  ("em) of 7.1 x 10"4 (when BL" = dpp) and 3.2-3.7 x 10"4 (when BL" = dpq).  The lifetimes are shortened and the emission quantum yields are quenched in comparison to the [{(TL)2Ru(dpp)}2Ru(BL")]6+ models which possess the same emissive terminal Ru\'¼-dpp 3MLCT state with Ä = 110 ns and "em = 1.0-1.1 x 10"3.   In marked contrast to the large number of Ru polyazine systems studied, both monometallic and supramolecular complexes, the lowest lying 3MLCT state of the Ru3Pt complexes is not populated with unit efficiency due to 3CS state population from the emissive terminal Ru(dÀ)\'dpp(À*) 3CT state and a higher energy 3MLCT state, likely the central Ru(dÀ)\'BL"(À*) 3CT state.  The degree of population of this state is strongly dependent on the LUMO energy or driving force for population.  Stabilization of the BL" = dpq(À*) compared to higher energy dpp(À*) provides a larger driving force for intramolecular electron transfer to populate the 3CS state, resulting in ca. 40 % and 95 % population of the emissive state when BL" = dpq and dpp, respectively.  This suggests ca. 60 % and 5 % indirect population of the non-emissive 3CS state via a higher-lying 3MLCT state and the terminal Ru\'dpp 3MLCT emissive state when BL" = dpq and dpp, respectively.  These complexes violate Kasha\'s rule, an unusual occurrence for Ru(II) polyazine complexes, as the emissive state is not populated with unit efficiency.  Instead, the degree of population of the emissive state is dependent on the excitation wavelength. The Ru3Pt complexes are active photocatalysts for H2O reduction to H2.  In the presence of light and the sacrificial electron donor, DMA (N,N-dimethylaniline), the tetrametallic complexes collect electrons on the ligand À* orbitals of the central Ru to serve as photoinitiated electron collectors.  The photocatalytic activity in H2 production is drastically impacted by BL" identity, consistent with the enhanced driving force for charge separation to move electrons toward the cis-PtCl2 moiety.  After photolysis for 10 h, 15 ± 1 ¼mol (66 ± 4 TON) and 4 ± 1 ¼mol (18 ± 1 TON) of H2 were produced using [{(phen)2Ru(dpp)}2Ru(dpq)PtCl2]6+ and [{(phen)2Ru(dpp)}2Ru(dpp)PtCl2]6+, respectively.  Varying TL to Ph2phen serves to enhance light absorptivity and subsequently increase H2 production to 21 ± 1 ¼mol (94 ± 6 TON) and 5 ± 1 ¼mol (23 ± 2 TON) using [{(Ph2phen)2Ru(dpp)}2Ru(dpq)PtCl2]6+ and [{(Ph2phen)2Ru(dpp)}2Ru(dpp)PtCl2]6+, respectively.  The identity of BL" greatly influences the ability to direct the flow of charge through the supramolecular architecture impacting photocatalysis, while the identity of TL serves to fine tune the light absorbing and excited state properties. Due to the complicated excited state properties imparted by the large number of MLCT transitions in the [{(TL)2Ru(dpp)}2Ru(BL")PtCl2]6+ complexes, the analogous [(Ph2phen)2Ru(dpp)Ru(bpy)(BL")PtCl2]4+ complexes were designed and a synthetic scheme developed.  The trimetallics possess similar electronic absorption spectroscopy with fewer terminal metal-based transitions due to removal of one (TL)2RuII(dpp) sub-unit and allow for distinguishable spectroscopic shifts resulting from perturbation of specific sub-units and the related molecular orbitals.  The trimetallic complexes exhibit similar redox properties with the HOMO localized on the terminal Ru and the LUMO localized on the remote BL", providing a low lying 3CS state.  Similar degrees of emission quenching are observed with the trimetallic complexes and their [(Ph2phen)2Ru(dpp)Ru(bpy)(BL")]4+ models as was observed in the tetrametallic complexes.  The values of Ä and "em measured for [(Ph2phen)2Ru(dpp)Ru(bpy)(dpp)PtCl2]4+ were 90 ns and 1.1 x 10"3, respectively, and these values were 100 ns and 5.2 x 10"4 for [(Ph2phen)2Ru(dpp)Ru(bpy)(dpq)PtCl2]4+.  Similar to the Ru3Pt systems, the lifetimes are shortened and the emission is quenched compared to the [(Ph2phen)2"Ru(dpp)Ru(bpy)(BL")]4+ models (Ä = 120 ns and "em = 1.50 x 10"3, regardless of BL" identity).  These values provide ca. 98 % and 45 % population of the emissive state in the Ru2Pt systems for BL" = dpp and dpq, respectively, suggesting ca. 2 % and 55 % population of the non-emissive 3CS state for BL" = dpp and dpq, respectively.  This supports the use of this new Ru2Pt motif as models to study the excited state dynamics.  A substantial difference was observed between the excitation and absorption spectra for [(Ph2phen)2Ru(dpp)Ru(bpy)(dpq)PtCl2]4+, consistent with non-unity population of the emissive 3MLCT excited state. The simplified electronic absorption spectroscopy allowed the use of nanosecond transient absorption (TA) spectroscopy to analyze the excited state, and strong evidence of violation of Kasha\'s rule through partial population of the terminal Ru(À)\'BL"(À*) 3CS state (Ä = 25 ns)  in addition to the emissive terminal Ru(dÀ)\'dpp(À*) 3MLCT state (Ä = 120 ns) was observed through excitation-based emission spectroscopy and time-resolved TA spectroscopy. The synthesis, electrochemistry, electronic absorption spectroscopy, and steady-state and time-resolved emission spectroscopy for the [2Ru(BL")PtCl2]6+ and [(Ph2phen)2Ru(dpp)Ru(bpy)(BL")PtCl2]4+ complexes as well as photocatalytic H2 production with [2Ru(BL")PtCl2]6+ and transient absorption spectroscopy of [(Ph2phen)2Ru(dpp)Ru(bpy)(BL")PtCl2]4+, are reported herein.  The work discussed within this dissertation provides in depth knowledge about the effects of component modification on the excited state dynamics and photocatalytic activity of structurally diverse Ru3Pt and Ru2Pt supramolecular complexes that is important in developing photochemical molecular devices.  Unusual excited state dynamics make it clear that much remains to be uncovered about structure-property relationship in these complex mixed-metal, mixed-ligand supramolecular motifs.  These supramolecular motifs also have applications in photodynamic therapy drug development and are currently under investigation by members of the Brewer research group. / Ph. D.

Dans un contexte où l’énergie représente un enjeu majeur pour les pays et organisations à économies émergentes et développées, la recherche de nouvelles sources renouvelables et la démocratisation des vecteurs énergétiques permettant l’approvisionnement mondial de façon durable constitue un devoir pour la communauté scientifique internationale. D’ailleurs, il serait essentiel que les nombreuses disciplines de la chimie concertent leurs efforts. Plus particulièrement, la croissance de la recherche en chimie de coordination orientée vers la photosynthèse artificielle ainsi que le développement de matériaux fonctionnels démontre l’importance indéniable de ce champ de recherche. Ce travail présente dans un premier temps l’étude des différentes voies de synthèse d’hydroxyamidines, un ligand chélatant aux propriétés de coordination prometteuses ne recevant que très peu d’attention de la part de la communauté scientifique. Dans un deuxième temps, nous présenterons le développement d’une stratégie d’assemblage de leurs complexes supramoléculaires impliquant des métaux de transition abondants et peu dispendieux de la première rangée. Dans un troisième temps, il sera question de l’investigation de leurs propriétés photophysiques et électrochimiques à des fins d’applications au sein de matériaux fonctionnels. Pour ce faire, les différentes voies de synthèse des hydroxyamidines et de leurs amidines correspondantes qui ont précédemment été étudiées par les membres du groupe seront tout d’abord perfectionnées, puis investiguées afin de déterminer leur versatilité. Ensuite, les propriétés de complexation des amox résultantes comportant des motifs sélectionnés seront déterminées pour enfin étudier les propriétés photophysiques et électrochimiques d’une série de complexes de métaux de transition de la première rangée. En somme, plusieurs designs qu’offrent les amox et bis-amox sont étudiés et les propriétés des architectures résultantes de leur auto-assemblage sont déterminées. / In a context where energy supply represents a major challenge for countries and organizations with emerging and developed economies, the search for new renewable resources and the democratization of energy vectors allowing sustainable worldwide supply is a responsibility for the international scientific community. Besides, it would be essential that the many disciplines of chemistry concerted their efforts. In particular, the growth of research in coordination chemistry oriented toward artificial photosynthesis and the development of functional materials demonstrates the undeniable importance of this field of research. The first part of the work presents different synthetic routes to hydroxyamidines, a chelating ligand with promising properties and receiving very little attention from the scientific community. Secondly, we present the development of a strategy of assembly of their supramolecular complexes involving abundant and cheap first row transition metal. Thirdly, we will discuss the investigation of their photophysical and electrochemical properties for their purposes in functional materials applications. To do this, the different synthesis routes of hydroxyamidines and their corresponding amidines which have previously been studied by other members of the group will first be improved then investigated to determine their versatility. Next, the complexing properties of the resulting amox having selected patterns will be determined to finally study the photophysical and electrochemical properties of a series of first row transition metal complexes. In sum, the various designs offered by amox and the bis-amox complexes are studied and the properties of the resulting architectures of their self-assemblies are determined.