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The synthesis, structure and photophysical properties of the complexes [Ru[(CO)(TFA) (PPh 3 ) 2 (L)][(L = ppy = 2-phenylpyridine, ( 1a ); L = 2–(p–tolyl)pyridine] ( 1b ), are reported. The complexes were characterized by UV-VIS, IR and NMR and by single-crystal X-ray diffraction techniques. We also report the synthesis, structure and photophysical properties of [Ru(CO)(L)(PPhMe 2 ) 2 (L′)] + [PF 6 ] − [L′ = bipyridine, L = TFA, ( 3a ); L = H, ( 3b ) and L = H, L′ = 4,4′-dimethlyl bipyridine ( 3c )]. These compounds were characterized by UV-VIS, IR and NMR techniques and by a single crystal X-ray diffraction in the case of 3a. The solid state structure of [Ru(Me 2 PhP) 2 (CO) 2 (TFA) 2 (2) which is the starting material for the synthesis 3a - 3c is also reported to verify the trans relationship of the less bulky PPhMe 2 and for comparison with the previously reported PPh 3 analogs. The purpose of this study was to determine the impact, if any, of replacing bpy with ppy in the case of 1a and alkylation of the benzene ring in the case of 1b on the photophysical and electrochemical properties compared to related Ru(bpy) complexes. In contrast to the bpy analogs 1a and 1b showed reversible 1e − oxidations and blue-shifted MLCT absorptions. In the case of 3a - 3c we were interested in the effect on the photophysical properties of substituting PPh 3 with the less bulky but more electron donating PPhMe 2 . There were only minor changes in the photophysical and electrochemical properties relative to the previously reported PPh 3 analogs. [ABSTRACT FROM AUTHOR]

The series of complexes [XRu(CO)(L–L)(L′)2][PF6] (X = H, TFA, Cl; L–L = 2,2′-bipyridyl, 1,10-phenanthroline, 5-amino-1,10-phenanthroline and 4,4′-dicarboxylic-2,2′-bipyridyl; L′2 = 2PPh3, Ph2PC2H4PPh2, Ph2PCH＝CHPPh2) have been synthesized from the starting complex K[Ru(CO)3(TFA)3] (TFA = CF3CO2) by first reacting with the phosphine ligand, followed by reaction with the L–L and anion exchange with NaPF6. In the case of L–L = phenanthroline and L′2 = 2PPh3, the neutral complex Ru(Ph3P)(CO)(1,10-phenanthroline)(TFA)2 is also obtained and its solid state structure is reported. Solid state structures are also reported for the cationic complexes where L–L = phenanthroline, L2 = 2PPh3 and X = Cl and for L–L = 2,2′-bipyridyl, L2 = 2PPh3 and X = H. All the complexes were characterized in solution by a combination of 1H and 31P NMR, IR, mass spectrometry and elemental analyses. The purpose of the project was to synthesize a series of complexes that exhibit a range of excited-state lifetimes and that have large Stokes shifts, high quantum yields and high intrinsic polarizations associated with their metal-to-ligand charge-transfer (MLCT) emissions. To a large degree these goals have been realized in that excited-state lifetimes in the range of 100 ns to over 1 μs are observed. The lifetimes are sensitive to both solvent and the presence of oxygen. The measured quantum yields and intrinsic anisotropies are higher than for previously reported Ru(II) complexes. Interestingly, the neutral complex with one phosphine ligand shows no MLCT emission. Under the conditions of synthesis some of the initially formed complexes with X = TFA are converted to the corresponding hydrides or in the presence of chlorinated solvents to the corresponding chlorides, testifying to the lability of the TFA Ligand. The compounds show multiple reduction potentials which are chemically and electrochemically reversible in a few cases as examined by cyclic voltammetry. The relationships between the observed photophysical properties of the complexes and the nature of the ligands on the Ru(II) is discussed. [Copyright &y& Elsevier]

Abstract: We report a combined experimental and computational study of new rhenium tricarbonyl complexes based on the bidentate heterocyclic N–N ligands 2-(4-methylpyridin-2-yl)benzo[d]-X-azole (X=N–CH3, O, or S) and 2-(benzo[d]-X-azol-2-yl)-4-methylquinoline (X=N–CH3, O, or S). Two sets of complexes are reported. Chloro complexes, described by the general formula Re(CO)3[2-(4-methylpyridin-2-yl)benzo[d]-X-azole]Cl (X=N–CH3, 1; X=O, 2; X=S, 3) and Re(CO)3[2-(benzo[d]-X-azol-2-yl)-4-methylquinoline]Cl (X=N–CH3, 4; X=O, 5; X=S, 6) were synthesized heating at reflux Re(CO)5Cl with the appropriate N–N ligand in toluene. The corresponding pyridine set {Re(CO)3[2-(4-methylpyridin-2-yl)benzo-X-azole]py}PF6 (X=N–CH3, 7; X=O, 8; X=S, 9) and {Re(CO)3[2-(benzo[d]-X-azol-2-yl)-4-methylquinoline]py}PF6 (X=N–CH3, 10; X=O, 11; X=S, 12) was synthesized by halide abstraction with silver nitrate of 1–6 followed by heating in pyridine and isolated as their hexafluorophosphate salts. All complexes have been fully characterized by IR, NMR, electrochemical techniques and luminescence. The crystal structures of 1 and 7 were obtained by X-ray diffraction. DFT and time-dependent (TD) DFT calculations were carried out for investigating the effect of the organic ligand on the optical properties and electronic structure of the reported complexes. [Copyright &y& Elsevier]

The synthesis and solution chemistry of the water soluble clusters [Os3(CO)9(μ-η2-Bz)(μ-H)L+] (HBz=quinoxaline, L+=[P(OCH2CH2NMe3)3I3], 1) along with its negatively charged analog [Os3(CO)9(μ-η2-Bz)(μ-H)L-] (L-=[P(C6H4SO3)3Na3], 2) are reported. In addition, we have examined the reduction potentials of the complexes [Os3(CO)9(μ-η2-Bz)(μ-H)L] (HBz=phenanthridine, L=L+ (3); HBz=5,6 benzoquinoline, L=L+ (4); HBz=3-amino quinoline, L=L+ (5); HBz=3-amino quinoline, L=L- (6). The neutral analog of 1 and 2 [Os3(CO)9(μ-η2-Bz)(μ-H) PPh3] (Bz=quinoxaline, 7) was also examined for comparison. Both compounds 1 and 2 show pH dependent NMR spectra that are interpreted in terms of the extent of protonation of the uncoordinated quinoxaline nitrogen which impacts the degree of aggregation of the clusters in aqueous solution. Compound 1 undergoes a reversible 1e- reduction in water while 2 undergoes a quasi-reversible 1e- reduction at more negative potentials as expected from the difference in charge on the phosphine ligand. Compound 7 undergoes a marginally reversible CV in methylene chloride at a potential intermediate between the positively and negatively charged clusters. The overall stability of the radical anions of 1, 2 and 7 is somewhat less than the corresponding decacarbonyl [Os3(CO)10(μ-η2-Bz)(μ-H)] (HBz=quinoxaline). While complexes 1 and 2 show reversible 1e- reductions, all the other complexes examined show 1e- and/or two 1e- irreversible reductions in aqueous and non-aqueous solvents. The potentials for these complexes follow expected trends relating to the charge on the phosphine and the pH of the aqueous solutions. The ligand dependent trends are compared with those of the previously reported corresponding decacarbonyls. The interactions of the positively and negatively charged clusters with albumin have been investigated using the transverse and longitudinal relaxation times of the hydride resonances as probes of binding to the protein. Evidence of binding is observed for both the positive and negative clusters but the positive and negative clusters exhibit distinctly different rotational correlation times. Two additional complexes [Os3(CO)9(μ-η2-Bz)(μ-H)L] (HBz=2-methylbenzimidazole, L=L+ (8); L=L- (10) and HBz=quinoline-4-carboxaldehyde, L=L+ (9); L=L- (11)) are reported in connection with these studies. [Copyright &y& Elsevier]