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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]

A tridentate cyclometalating ligand, 1,3-di(1,2,3-triazol-4-yl)benzene (dtab), has been prepared and used for the syntheses of a number of cyclometalated RuIIcomplexes. A comparison of the electrochemical and spectroscopic properties of cyclometalated complexes made from dtab or 1,3-di(2-pyridyl)benzene is presented as well. [ABSTRACT FROM AUTHOR]