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A polyazine ligand, 5,5′-di(1-butyl-1,2,3-triazol-4-yl)-2,2′-bipyridine(Bu-dtabpyH), has been prepared by a “click” reaction.The treatment of Bu-dtabpyH with [Ru(bpy)2Cl2] affords complex [Ru(bpy)2(Bu-dtabpyH)]2+(bpy= 2,2′-bipyridine), which has been characterized by single-crystalX-ray analysis. The reaction of [Ru(bpy)2(Bu-dtabpyH)]2+with another equivalent of [Ru(bpy)2Cl2] in the presence of AgOTf gives a redox-asymmetric bisrutheniumcomplex, [Ru(bpy)2(Bu-dtabpy)Ru(bpy)2]3+(Bu-dtabpy is the 4-deprotonated form of Bu-dtabpyH), with one rutheniumatom binding to the pyridin-4-yl bridge with a Ru–N bond andthe other with a Ru–C bond. This complex displays two Ru(II/III)redox couples at +0.79 and +1.28 V vs Ag/AgCl. After being transformedinto a mixed-valence species, [Ru(bpy)2(Bu-dtabpy)Ru(bpy)2]4+, by one-electron oxidation, it exhibits a moderatemetal-to-metal charge-transfer band around 1300 nm. Density functionaltheory and time-dependent density functional theory calculations havebeen carried out for the model complex [Ru(bpy)2(Me-dtabpy)Ru(bpy)2]3+and the mixed-valence state [Ru(bpy)2(Me-dtabpy)Ru(bpy)2]4+to complement theseexperimental results, where Me-dtabpy is the 4-deprotonated form of5,5′-di(1-methyl-1,2,3-triazol-4-yl)-2,2′-bipyridine. [ABSTRACT FROM AUTHOR]

The linear bis-cyclometalated Ru(II) complex [(ttpy)Ru(ttabp)Ru(ttpy)]2+was prepared from the oxidative coupling of the monometalliccomplex [(ttpy)Ru(dtab)]+in good yield, where ttpy is4′-tolyl-2,2′:6′,2″-terpyridine, ttabpis 3,3′,5,5′-tetrakis(1-butyl-1H-1,2,3-triazol-4-yl)biphenyl,and dtab is 1,3-bis(1-butyl-1H-1,2,3-triazol-4-yl)benzene.The electronic properties of these two complexes were studied andcompared by electrochemical and spectroscopic methods and DFT/TDDFTcalculations. The complex [(ttpy)Ru(ttabp)Ru(ttpy)]2+showedtwo consecutive RuII/IIIredox waves at +0.34 and +0.51V vs Ag/AgCl with a comproportionation constant Kcof 760. One-electron oxidation of [(ttpy)Ru(ttabp)Ru(ttpy)]2+by electrochemical methods produced the mixed-valent complex[(ttpy)Ru(ttabp)Ru(ttpy)]3+, which exhibited a symmetricintervalence charge transfer band at 1800 nm (νmax= 5550 cm–1, εmax= 5100 M–1cm–1, Δν1/2= 3580 cm–1). The energy and shape of this bandare very similar in the different solvents studied (CH3CN, DMF, CH2Cl2). [(ttpy)Ru(ttabp)Ru(ttpy)]3+was determined to be a class II/III borderline system withthe electronic coupling parameter Hab=530 cm–1. It displayed a metal-centered rhombicEPR signal at 77 K with an isotropic gfactor of2.109 and total ganisotropy of 0.256, which pointsto an appreciable spin distribution on the bridging ligand in additionto the metal centers. [ABSTRACT FROM AUTHOR]

We examine the correlations of the dipole moment and conformational stability to the self-assembly and solar cell performance within a series of isomorphic, solution-processable molecules. These charge-transfer chromophores are described by a D1-A-D-A-D1 structure comprising electron-rich 2-hexylbithiophene and 3,3′-di-2-ethylhexylsilylene-2,2′-bithiophene moieties as the donor units D1 and D, respectively. The building blocks 2,1,3-benzothiadiazole (BT) and [1,2,5]thiadiazolo[3,4-c]pyridine (PT) were used as the electron-deficient acceptor units A. Using a combination of UV-visible spectroscopy, field-effect transistors, solar cell devices, grazing incident wide-angle X-ray scattering, and transmission electron microscopy, three PT-containing compounds (1-3) with varying regiochemistry and symmetry, together with the BT-based compound 5,5′-bis{(4-(7-hexylthiophen-2-yl)thiophen-2-yl)-[1,2,5]thiadiazolobenzene}-3,3′-di-2-ethylhexylsilylene-2,2′-bithiophene (4), are compared and contrasted in solution, in thin films, and as blends with the electron acceptor [6,6]-phenyl-C70-butyric acid methyl ester. The molecules with symmetric orientations of the PT acceptor, 1 and 2, yield highly ordered blended thin films. The best films, processed with the solvent additive 1,8-diiodooctane, show donor "crystallite" length scales on the order of 15-35 nm and photovoltaic power conversion efficiencies (PCEs) of 7.0 and 5.6%, respectively. Compound 3, with an unsymmetrical orientation of PT heterocycles, shows subtle differences in the crystallization behavior and a best PCE of 3.2%. In contrast, blends of the BT-containing donor 4 are highly disordered and give PCEs below 0.2%. We speculate that the differences in self-assembly arise from the strong influence of the BT acceptor and its orientation on the net dipole moment and geometric description of the chromophore. [ABSTRACT FROM AUTHOR]