Tris Diimine Complexes Research Articles

Improving the Accuracy in the Prediction of Transition-Metal Spin-State Energetics Using a Robust Variation-Based Approach: Density Functional Theory, CASPT2 and MC-PDFT Applied to the Case Study of Tris-Diimine Fe(II) Complexes.

Designing ligands for transition metal complexes with a specified low-spin, high-spin or spin-crossover behavior is challenging. A major advance was recently made by Phan et al. [J. Am. Chem. Soc. 2017, 139, 6437-6447] who showed that the spin state of a homoleptic tris-diimine Fe(II) complex can be predicted from the N-N distance in the free diimine. They could thus predict the change in magnetic behavior on passing from the complexes of 2,2'-bipyridine (bpy), 2,2'-biimidazole (bim) and 2,2'-bis-2-imidazoline (bimz) ligands to those obtained with the modified analogs 4,5-diazafluoren-9-one (dafo), 1,1'-(α,α'-o-xylyl)-2,2'-bisimidazole (xbim) and 2,3,5,6,8,9-hexahydrodiimidazo[1,2-a:2', 1'-c]pyrazine (etbimz), respectively. Theoretically, the challenge lies in the accurate determination of the HS-LS zero-point energy difference ΔEHL°. The issue can be circumvented by using a variation-based approach, wherein ΔEHL° is not directly evaluated but obtained from the estimate of its variation Δ(ΔEHL°) in series of related systems, which include one whose ΔEHL° is accurately known [Phys. Chem. Chem. Phys. 2013, 15, 3752-3763; J. Phys. Chem. A 2022, 126, 6221-6235]. In this study, density functional theory (DFT), second-order multireference perturbation theory in its CASPT2 formulation, multiconfigurational pair DFT (MC-PDFT) and its hybrid formulation (HMC-PDFT) have been applied to the determination of Δ(ΔEHL°) in the pairs of complexes , , , and , . In DFT, we used several semilocal functionals and their global hybrids, as well as their D2, D3, D3BJ and D4 dispersion-corrected forms; and in MC-PDFT, different translated and fully translated functionals. The results are consistent with one another and in very good agreement with experiments. They show small to vanishing dependence on key details of the methods used: namely, the exact-exchange contribution to global hybrids; the ionization potential-electron affinity shift and basis sets used in the CASPT2 calculations; and the active spaces employed for the CASSCF wave functions used in the MC-PDFT and HMC-PDFT calculations. Insights into the change in the spin-state energetics accompanying the ligand exchanges were gained through a complexation energy analysis. Using the accurate CCSD(T) estimate of the HS-LS adiabatic energy difference in [J. Chem. Theory Comput. 2012, 8, 4216-4231], the Δ(ΔEHL°)-approach has been applied to the determination of ΔEHL° in the diimine complexes. The CASPT2 and DFT-D2 methods only give results in agreement with experiments. This suggests for the other methods a limitation in their treatment of dispersion which prevents them from accurately describing the spin-state energetics change accompanying the passing from with the tetragonal arrangement of its nitrile ligands to the tris-diimine complexes with the trigonal packing of their bulkier ligands.

Exploration of the Pharmacophore for Cytoskeletal Targeting Ruthenium Polypyridyl Complexes.

Ruthenium(II) trisdiimine complexes of the formula, [Ru(dip)n (L-L)3-n ]2+ , where n=0-3; dip=4,7-diphenyl-1,10-phenanthroline; L-L=2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen) were prepared and tested for cytotoxicity in two cell lines (H358, MCF7). Cellular uptake and subcellular localization were determined by harvesting treated cells and determining the ruthenium concentration in whole or fractionated cells (cytosolic, nuclear, mitochondrial/ ER/Golgi, and cytoskeletal proteins) by Ru ICP-MS. The logP values for the chloride salts of these complexes were measured and the data were analyzed to determine the role of lipophilicity versus structure in the various biological assays. Cellular uptake increased with lipophilicity but shows the biggest jump when the complex contains two or more dip ligands. Significantly, preferential cytoskeletal localization is also correlated with increased cytotoxicity. All of the RPCs promote tubulin polymerization in vitro, but [Ru(dip)2 phen]2+ and [Ru(dip)3 ]2+ show the strongest activity. Analysis of the pellet formed by centrifugation of MTs formed in the presence of [Ru(dip)2 phen]2+ establish a binding stoichiometry of one RPC per tubulin heterodimer. Complexes of the general formula [Ru(dip)2 (L-L)]2+ possess the necessary characteristics to target the cytoskeleton in live cells and increase cytotoxicity, however the nature of the L-L ligand does influence the extent of the effect.

Defect Density-Dependent Electron Injection from Excited-State Ru(II) Tris-Diimine Complexes into Defect-Controlled Oxide Semiconductors

Dye-sensitized solar cells and photocatalysts that consist of a light-absorbing dye and a wide gap oxide semiconductor substrate have been studied extensively as a means of solar energy conversion....

Visible-Light-Driven Water Oxidation Using Anatase Titania Modified with First-Row Transition-Metal-Oxide Nanoclusters

Composites comprising nanocrystalline anatase TiO2 and nanoclusters of first-row transition-metal oxides (MOx; M = Mn, Fe, Co, or Ni), which can potentially function as water oxidation catalysts, were applied as photocatalysts for water oxidation under visible light (480 < λ < 900 nm). Although TiO2 showed no visible light absorption, each of the MOx/TiO2 composites was capable of absorbing visible light. Activities during visible-light-driven water oxidation were examined using these materials in the presence of Ag+ as an electron acceptor. Co and Ni were found to be effective modifiers and promoted water oxidation with TiO2, whereas CoOx/TiO2 exhibited the highest activity. The catalytic activities of the MOx series during “dark” water oxidation were also investigated, employing an established photochemical water oxidation scheme with a Ru(II) trisdiimine complex as a redox photosensitizer in conjunction with weak visible light illumination. Under these conditions, the effect of light absorption by MOx/...

Judicious Design of Cationic, Cyclometalated Ir(III) Complexes for Photochemical Energy Conversion and Optoelectronics

The exponential growth in published studies on phosphorescent metal complexes has been triggered by their utilization in optoelectronics, solar energy conversion, and biological labeling applications. Very recent breakthroughs in organic photoredox transformations have further increased the research efforts dedicated to discerning the inner workings and structure-property relationships of these chromophores. Initially, the principal focus was on the Ru(II)-tris-diimine complex family. However, the limited photostability and lack of luminescence tunability discovered in these complexes prompted a broadening of the research to include 5d transition metal ions. The resulting increase in ligand field splitting prevents the population of antibonding eg* orbitals and widens the energy range available for color tuning. Particular attention was given to Ir(III), and its cyclometalated, cationic complexes have now replaced Ru(II) in the vast majority of applications. At the start, this Account documents the initial efforts dedicated to the color tuning of these complexes for their application in light emitting electrochemical cells, an easy to fabricate single-layer organic light emitting device (OLED). Systematic modifications of the ligand sphere of [Ir(ppy)2bpy]+ (ppy: 2-phenylpyridine, bpy: 2,2'-bipyridine) with electron withdrawing and donating substituents allowed access to complexes with luminescence emission maxima throughout the visible spectrum exhibiting room temperature excited state lifetimes ranging from nanoseconds to dozens of microseconds and quantum yields up to 15 times that of [Ru(bpy)3]2+. The diverse photophysical properties were also beneficial when using these Ir(III) complexes for driving solar fuel-producing reactions. For instance, photocatalytic water-reduction systems were explored to gain access to efficient water splitting systems. For this purpose, a variety of water reduction catalysts were paired with libraries of Ir(III) photosensitizers in high-throughput photoreactors. This parallelized approach allowed exploration of the interplay between the diverse photophysical properties of the Ir compounds and the electron-accepting catalysts. Further work enhanced and simplified the critical electron transfer processes between these two species through the use of bridging functional groups installed on the photosensitizer. Later, a novel approach summarized in this Account explores the possibility of using Zn metal as a solar fuel. Structure-activity relationships of the light-driven reduction of Zn2+ to Zn metal are described. DFT calculations along with cyclic voltammetry were utilized to gain clear insights into the complexes' electronic structures responsible for the effective photochemical properties observed in these dyes. While [Ir(ppy)2bpy]+ and its derivatives were found to be much more photostable than the Ru(II)-tris-diimine complex family, mass spectrometry indicated that the bpy ligand still photodissociated under extensive illumination. An interesting new approach involved the substitution of the bidentate 2,2'-bipyridine with a stronger chelating terpyridine ligand. This approach leaves room for one 2-phenylpyridine ligand and a third, anionic ligand, either Cl- or CN-. This Account reviews the effect of structural modifications on the photophysical properties of these [Ir(tpy)(ppy)X]+ complexes and corroborates the findings with the results obtained through DFT modeling. These complexes found application in photocatalytic CO2 reductions as well as a solvent tolerant light-absorber for the photogeneration of hydrogen. It was also documented that the robustness of these dyes in photoredox processes supersedes those of the commercially available [Ir(ppy)2(dtbbpy)]PF6 and [Ir(dF(CF3)ppy)2(dtbbpy)]PF6 complexes pioneered in the Bernhard laboratory.

Synthesis of three series of ruthenium tris-diimine complexes containing acridine-based π-extended ligands using an efficient "chemistry on the complex" approach.

The preparation and characterization of three series of novel ruthenium(ii) complexes are reported, each series differing by the nature of the ancillary ligands (2,2'-bipyridine - bpy, 1,10-phenanthroline - phen or 1,4,5,8-tetraazaphenanthrene - TAP). The third ligand was either the heptacyclic heterocycle dipyrido[3,2-a:2',3'-c]quinolino[3,2-h]phenazine (dpqp) substituted at position 12 by an hydroxyl (oxo), 2,2-dimethoxyethylamine (DMEA) or halogeno (Cl or Br) substituent, or the octacyclic dipyrido[3,2-a:2',3'-c]pyrido[2,3,4-de]quinolino[3,2-h]phenazine (dppqp), prepared by a multi-step "chemistry on the complex" strategy from [RuL2(oxo-dpqp)](PF6)2. The three steps, halogenation, substitution by a dimethoxyethylamino group and cyclization in trifluoroacetic acid, were performed in reasonable to high yields depending on the nature of the ancillary ligands. Isolation and purification processes were facilitated by the ability to switch the solubility of the complex from aqueous to organic solvents, depending on the counter-ion. All new complexes were fully characterized; in particular their absorption properties were compared by UV-vis spectroscopy. Finally, π-stacking properties induced by these extended ligands were studied by 1H NMR studies and quantum chemical calculations.

Efficient light harvesting via sequential two-step energy accumulation using a Ru–Re5 multinuclear complex incorporated into periodic mesoporous organosilica

An efficient artificial light harvesting (LH) system was developed via sequential two-step energy accumulation. A periodic mesoporous organosilica with bridging biphenyl groups in the framework (Bp–PMO) was used as an LH antenna. The center of a linear-shaped Re(I) pentanuclear complex was connected to a Ru(II) trisdiimine complex through a covalent bond, these served as the first and second energy acceptors, respectively, (Ru–Re5). Hybridization was achieved with the non-ionic surfactant C12H25(OCH2CH2)4OH in an acetonitrile solution, and in the hybrid (Ru–Re5–Bp–PMO), the Ru–Re5 molecules were adsorbed in an orderly fashion in the mesopores of the Bp–PMO. Photons absorbed by 437 ± 43 of the Bp units were first accumulated in the five Re units in Ru–Re5 and then transferred to only one Ru unit, which emitted the light strongly.

Ruthenium Bis-diimine Complexes with a Chelating Thioether Ligand: Delineating 1,10-Phenanthrolinyl and 2,2′-Bipyridyl Ligand Substituent Effects

Despite the high π-acidity of thioether donors, ruthenium(II) complexes with a bidentate 1,2-bis(phenylthio)ethane (dpte) ligand and two chelating diimine ligands (i.e., Ru(diimine)2(dpte)(2+)) exhibit room-temperature fluid solution emission originating from a lowest MLCT excited state (diimine = 2,2'-bipyridine, 5,5'-dimethyl-2,2'-bipyridine 4,4'-di-tert-butyl-2,2'-bipyridine, 1,10-phenanthroline, 5-methyl-1,10-phenanthroline, 5-chloro-1,10-phenanthroline, 5-bromo-1,10-phenanthroline, 5-nitro-1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline, and 3,4,7,8-tetramethyl-1,10-phenanthroline). Crystal structures show that the complexes form 2 of the 12 possible conformational/configurational isomers, as well as nonstatistical distributions of geometric isomers; there also are short intramolecular π-π interactions between the diimine ligands and dpte phenyl groups. The photoinduced solvolysis product, [Ru(diimine)2(CH3CN)2](PF6)2, for one complex in acetonitrile also was characterized by single-crystal X-ray diffraction. Variations in the MLCT energies and Ru(III/II) redox couple, E°'(Ru(3+/2+)), can be understood in terms of the influence of the donor properties of the ligands on the mainly metal-based HOMO and mainly diimine ligand-based LUMO. E°'(Ru(3+/2+)) also is quantitatively described using a summative Hammett parameter (σT), as well as using Lever's electrochemical parameters (EL). Recommended parametrizations for substituted 2,2'-bipyridyl and 1,10-phenanthrolinyl ligands were derived from analysis of correlations of E°'(Ru(3+/2+)) for 99 homo- and heteroleptic ruthenium(II) tris-diimine complexes. This analysis reveals that variations in E°'(Ru(3+/2+)) due to substituents at the 4- and 4'-positions of bipyridyl ligands and 4- and 7-positions of phenanthrolinyl ligands are significantly more strongly correlated with σp(+) than either σm or σp. Substituents at the 5- and 6-positions of phenanthrolinyl ligands are best described by σm and have effects comparable to those of substituents at the 3- and 8-positions. Correlations of EL with σT for 1,10-phenanthrolinyl and 2,2'-bipyridyl ligands show similar results, except that σp and σp(+) are almost equally effective in describing the influence of substituents at the 4- and 4'-positions of bipyridyl ligands. MLCT energies and d(5)/d(6)-electron redox couples of the complexes with 5-substituted 1,10-phenanthroline exhibit correlations with values for other d(6)-electron metal complexes that can be rationalized in terms of the relative number of diimine ligands and substituents.

Novel DNA photocleavage properties of [Cr(NN)3]3+ complexes

Abstract The aim of this study was to investigate the ability of chromium(III) tris-diimine complexes, [Cr(NN)3]3+, to induce DNA photodamage and to examine its capability to impair the survival of irradiated bacteria with the purpose of using these compounds as photocleavage reagents. [Cr(NN)3]3+ complexes, where NN stands for the ligands: phen (1,10-phenanthroline), 5-Mephen, 4,7-diMephen, 3,4,7,8-tetraMephen, 5-Phphen and 5-Clphen were used for this purpose. Their properties of DNA photocleavage were investigated by electrophoretic studies and assays of the photosensitization of transformed bacteria. The results clearly indicate that [Cr(NN)3]3+ complexes promote the photocleavage of plasmid DNA with varied degrees of efficiency after 12 h of irradiation. The combination of DNA, [Cr(NN)3]3+ and light proved to be required to induce the breakdown of DNA. Irradiated plasmid DNA-[Cr(NN)3]3+ association is also capable of impairing the transforming capacity of bacteria. These results provide evidence which confirms the responsibility and essential role of the excited state of [Cr(NN)3]3+ for inducing damage. Moreover, assays of the photosensitization of transformed bacterial suspensions suggest that Escherichia coli may be photoinactivated by irradiation in the presence of [Cr(NN)3]3+ complexes.

Development of New LC Chiral Stationary Phases Based on Ruthenium Tris(diimine) Complexes

Enantiopure ruthenium(II) tris(diimine) complexes have been covalently bonded to silica and evaluated as chiral stationary phases for LC. Three binding chemistries were tested and the CSP synthesized by reductive amination of the aldehyde-functionalized silica provided the largest enantioselectivity. The Ru complex bonded CSP showed selectivity toward a variety of racemic compounds. Circular dichroism (CD) detection was used to confirm the enantiomeric separations. This CSP worked especially well for the enantiomeric separation of binaphthyl type compounds in the normal phase mode and appeared to be selective for acidic compounds in the polar organic mode. Effects of mobile phase composition on the enantioseparations were also studied.

Enantioselective host–guest complexation of Ru(II) trisdiimine complexes using neutral and anionic derivatized cyclodextrins

Enantioselective host–guest complexation between five racemic Ru(II) trisdiimine complexes and eight derivatized cyclodextrins (CDs) has been examined by NMR techniques. The appearance of non-equivalent complexation-induced shifts of between the Δ and Λ-enantionomers of the Ru(II) trisdiimine complexes and derivatized CDs is readily observed by NMR. In particular, sulfobutyl ether-β-cyclodextrin sodium salt (SBE-β-CD), R-naphtylethyl carbamate β-cyclodextrin (RN-β-CD), and S-naphtylethyl carbamate β-cyclodextrin (SN-β-CD) showed good enantiodiscrimination for all five Ru complexes examined, which indicates that aromatic and anionic derivatizing groups are beneficial for chiral recognition. The complexation stoichiometry between SBE-β-CD and [Ru(phen) 3] 2+ was found to be 1:1 and binding constants reveal that Λ-[Ru(phen) 3] 2+ binds more strongly to SBE-β-CD than the Δ-enantiomer. Correlations between this NMR method and separative techniques based on CDs as chiral discriminating agents (i.e., selectors) are discussed in detail.

Sugar derived hexacoordinated phosphates: Chiral anionic auxiliaries with general asymmetric efficiency

Mannose-derived hexacoordinated phosphate anions, prepared in as few as two steps from methyl-alpha-D-mannopyranoside and tris(dimethylamino)phosphine, are chiral anionic auxiliaries with broad asymmetric efficiency. These chemically robust anions are effective NMR chiral solvating agents and efficient asymmetry-inducers, able to control the configuration of conformationally labile C2-symmetric monomethinium cations (organic, helical, charge 1+, P or M enantiomers) and D3-symmetric iron(II) trisdiimine complexes (metallo-organic, octahedral, charge 2+, Delta or Lambda enantiomers). Diastereomeric control with often unmatched selective levels was achieved with the help of mannopyranoside backbone of the anions and the substituents on the [1,3]dioxane ring that play a key role in the recognition process, something not obvious at first sight.

Synthesis and characterization of tris(heteroleptic) diimine complexes of chromium(III)

A preparative procedure of potentially wide applicability is described for the synthesis of previously unreported tris(heteroleptic) [Cr(diimine) 3] 3+ complexes. The synthetic scheme involves the sequential addition of three different diimine ligands, and employs CrCl 3 · 6H 2O as the initial Cr(III) reagent. The synthesis and characterization of the complexes [Cr(TMP)(phen)(diimine′)] 3+ are reported (where TMP = 3,4,7,8-tetramethyl-1,10-phenanthroline, phen = 1,10-phenanthroline; and diimine′ is either bpy = 2,2′-bipyridine, Me 2bpy = 4,4′-dimethyl-2,2′-bipyridine, 5-Clphen = 5-chloro-1,10-phenanthroline, or DPPZ = dipyridophenazine). Chiral capillary electrophoresis and electrospray mass spectrometry were essential aids in determining the presence or absence of diimine ligand scrambling. Utilizing emission and electrochemical data obtained on these compounds, the oxidizing power of the lowest lying excited state ( 2E g(O h)) was calculated, and was found to vary in a systematic fashion with diimine ligand type.

Stereoselectivity in the formation of tris-diimine complexes of Fe(ii), Ru(ii), and Os(ii) with a C2-symmetric chiral derivative of 2,2′-bipyridine

A C2-symmetric enantiopure 4,5-bis(pinene)-2,2'-bipyridine ligand (-)-L was used to investigate the diastereoselectivity in the formation of [ML3]2+ coordination species (M = Fe(II), Ru(II), Os(II), Zn(II), Cd(II), Cu(II), Ni(II)), and [ML2Cl2] (M = Ru(II), Os(II)). The X-ray structures of the [ML3]2+ complexes were determined for Delta-[FeL3](PF6)2, Delta-[RuL3](PF6)2, Lambda-[RuL3](PF6)2, Delta-[OsL3](PF6)2, and Lambda-[OsL3](TfO)2. All of these compounds were also characterized by NMR, CD and UV/VIS absorption spectroscopy. The [FeL3]2+ diastereoisomers were studied in equilibrated solutions at various temperatures and in several solvents. The [RuL3]2+ complexes, which are thermally stable up to 200 degrees C, were photochemically equilibrated.

Capillary electrophoresis as a probe of enantiospecific interactions between photoactive transition metal complexes and DNA.

Recently, we have demonstrated the capacity to separate chiral transition metal (TM) complexes of the type [M(diimine)(3)](n+) using CE buffers containing chiral tartrate salts. In separate work, several chromium(III)-tris-diimine complexes in particular have been shown to bind enantioselectively with calf-thymus (CT) DNA, and a qualitative assessment of the relative strength and enantiospecificity of this interaction is of significant interest in the characterization of these complexes as potential DNA photocleavage agents. Here, we describe two convenient approaches to investigate such binding behavior using chiral CE. For complexes with lower DNA affinities exhibiting primarily surface binding, DNA itself is used as the chiral resolving agent in the electrophoretic buffer. In this approach, resolution of the TM complexes into their Lambda and Delta isomers is achieved with the isomer eluting later exhibiting superior binding affinity toward DNA. For more strongly bound TM complexes containing ligands known to intercalate with DNA, the [Cr(diimine)(3)](3+) complexes are preincubated with oligonucleotide and subsequently enantiomerically resolved in a dibenzoyl-L-tartrate buffer system that facilitates analysis of the unbound TM species only. Differences in isomer binding affinity are distinguished by the relative peak areas of the Lambda- and Delta-isomers, and relative binding strengths of different complexes can be inferred from comparison of the total amount of unbound complex at equivalent DNA/TM ratios.

Capillary electrophoresis with laser-induced fluorescence detection for chiral analysis and DNA binding studies of ruthenium(II) Tris–diimine complexes

The separation of Ru(II)) tris-diimine enantiomers was performed by chiral capillary electrophoresis (CE). A highly sensitive laser-induced fluorescence (LIF) detection system was employed for detection of transition metal complexes present in solution at the low micromolar range. An argon ion laser (457.9 nm, 0.15 mW) was used as an excitation source. The enantiomers of the [Ru(diimine) 3] 2+ complexes were separated using either potassium antimonyl- d-tartrate or dibenzoyl- l-tartrate ( l-DBT) as chiral resolving agents. The concentration limit of detection (LOD) for the tris(1,10-phenanthroline) Ru(II) complex was 12.5 μM and the LOD for the tris(2,2′-bipyridine) ruthenium(II) complex was 1.0 μM. These limits represent an improvement in the overall LOD by three-orders of magnitude relative to that obtained via UV–VIS detection. The CE–LIF system was also used to assess the stereoselective interactions between tris(1,10-phenanthroline) Ru(II) complexes and B-form deoxyribonucleic acid (B-DNA).

A bis 1,10-phenanthroline ligand leading to octahedral Ru(II) complexes containing a well-defined axis

A bis-chelating ligand (1), made of two 1,10-phenanthroline subunits connected with a p-(CH2)2C6H4(CH2)2- spacer through their 4 positions, has been prepared, using Skraup syntheses and reaction of the anion of 4-methyl-7-anisyl-1,10-phenanthroline with α,α’-dibromo-p-xylene. Complexation of 1 with Ru(CH3CN)4Cl2 and subsequent reaction with 4,4’-dimethyl-2,2’-bipyridine afforded an octahedral Ru(II) tris-diimine complex, in which a well-defined axis running through the terminal anisyl substituents and the central metal has been created, as shown by an X-ray molecular structure analysis. Un ligand (1), constitué de deux sous-unités de type 1,10-phénanthroline, connectées à leurs positions 4 par l’espaceur p-(CH2)2C6H4(CH2)2- et portant le substituant anisyle sur leurs positions 7 a été synthétisé. Le précurseur 4-méthyl-7-anisyl-1,10-phénanthroline a d’abord été préparé par double réaction de Skraup. L’anion correspondant a ensuite été engendré par réaction avec le LDA, puis traité par le α,α’-dibromo-p-xylène, pour fournir dans cette dernière étape le double chélate 1, avec un rendement de 88 %. La complexation de 1 avec le ruthénium(II) a été réalisée par réaction de ce ligand avec Ru(CH3CN)4Cl2, puis les ligands chlorure ont été remplacés par la 4,4’-diméthyl-2,2’-bipyridine. Le complexe tris-diimine octaédrique obtenu (3) a été notamment caractérisé par radiocristallographie aux rayons X. Sa structure moléculaire montre un enroulement du ligand 1 autour de l’ion Ru2+, plaçant les substituants anisyles aux extrémités d’un axe traversant le métal central. Le bis-chélate 1 a donc permis de définir de manière originale une direction privilégiée dans un complexe de type Rubipy2+3, permettant, dans une étape ultérieure, la construction de triades pour la séparation photoinduite des charges.

Automated Solid-Phase DNA Synthesis and Photophysical Properties of Oligonucleotides Labeled at the 5‘-Terminus with Ru(bpy)32+

A facile procedure for the incorporation of Ru(bpy)32+ in an oligonucleotide is reported. A Ru(bpy)32+ phosphoramidite is synthesized, and then attached to the 5‘-terminus of DNA using a standard protocol on an automated DNA solid-phase synthesizer. Photophysical studies of the Ru(II) tris-diimine complex as well as the corresponding labeled oligonucleotides demonstrate that the excited-state electron is localized on one specific bipyridine with the dipole directed toward the linkage to DNA, and that the Ru(II) excited state is long-lived when attached to the DNA.

Spin chemistry of Ru(II)-trisdiimine complex photooxidation in magnetic fields up to 17.5 tesla

The magnetic field dependence of the efficiency of cage escape η ce , which is due to the magnetic field and spin control of the effective rate of electron backtransfer in geminate pairs of photogenerated Ru(III) complexes and electron acceptor radicals, has been measured for Ru(bpy) 3 2+ and Ru(phen) 3 2+ over the entire field range from 0 to 17.5 T. These magnetic field dependent data on η ce , together with the experimental values of the g-tensor components of the Ru(III) complex, allow us to evaluate unambiguously and without recourse to supplementary information, the absolute values of the rate constants of cage escape (κ ce ), (spin-conserving) backward electron transfer (κ bet ) and electron spin relaxation time τ s of the Ru(III) complex.

ChemInform Abstract: A Model for the Interpretation of the Absorption and Circular Dichroism Spectra of Tris(diimine) Complexes of Iron(II) and Ruthenium(II)

ChemInform Abstract: A Model for the Interpretation of the Absorption and Circular Dichroism Spectra of Tris(diimine) Complexes of Iron(II) and Ruthenium(II)