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Three heterotopic ligands L1, L2, and L3have been prepared by the reaction of 4,4′-bis(bromomethyl)-2,2′-bipyridine with 4,5-diazafluoren-9-oxime, 9-(2-hydroxy)phenylimino-4,5-diazafluorene, and 9-(4-hydroxy)phenylimino-4,5-diazafluorene, respectively, in DMF. The three ligands consist of two 4,5-diazafluorene units and one 2,2′-bipyridine unit. Ru(II) complexes [{Ru(bpy)2}3(μ3-L1−3)](PF6)6(bpy = 2,2′-bipyridine) were prepared by refluxing Ru(bpy)2Cl2·2H2O and the ligands in 2-methoxyethanol. The three Ru(II) complexes display metal-to-ligand charge-transfer absorption at 445–450 nm and one Ru(II)-centered oxidation at 1.32 V in CH3CN solution at room temperature. Upon excitation into the metal-to-ligand charge-transfer band, the emission intensities of [{Ru(bpy)2}3(μ3-L2)]6+and [{Ru(bpy)2}3(μ3-L3)]6+are almost equal to that of [{Ru(bpy)2}3(μ3-L1)]6+in CH3CN solution at room temperature, but weaker than that of [{Ru(bpy)2}3(μ3-L1)]6+in EtOH–MeOH (4 : 1, v/v) glassy matrix at 77 K. [ABSTRACT FROM PUBLISHER]

Abstract: Three bridging ligands 5,5′-bis[(4,5-diazafluoren-9-ylimino)methyl]-2,2′-bipyridine (L1), 5,5′-bis[2-(4,5-diazafluoren-9-ylimino)phenoxymethyl]-2,2′-bipyridine (L2), 5,5′-bis[4-(4,5-diazafluoren-9-ylimino)phenoxymethyl]-2,2′-bipyridine (L3), and corresponding Ru(II) complexes [(bpy)6Ru3(L1–3)](PF6)6 (bpy=2,2′-bipyridine) have been synthesized. The three ligands have two kinds of nonequivalent chelating sites: one involving the 2,2′-bipyridine moiety, and the other involving the 4,5-diazafluorene moiety. The emission intensities of complexes [(bpy)6Ru3(L2)]6+ and [(bpy)6Ru3(L3)]6+ are almost equal to that of complex [(bpy)6Ru3(L1)]6+ in CH3CN solution at room temperature, but weaker than that of complex [(bpy)6Ru3(L1)]6+ in EtOH–MeOH (4:1, v/v) glassy matrix at 77K. Cyclic voltammetry and differential pulse voltammetry studies of the three complexes show one Ru(II)-centered oxidation at around 1.33V for the RuII/III couple. [Copyright &y& Elsevier]

Abstract: Uniform and monodispersed TiO2 hollow spheres with nanoporous titania shell are prepared successfully by using carboxyl-functionalized polystyrene spheres as templates. The results show that TiO2 hollow spheres pose a stable reversible capacity of 230 mAhg−1 at 33.5 mAg−1 and 120 mAhg−1 at 1675 mAg−1, which are higher than that of bulk TiO2 with coarse grain. The discharge process of TiO2 hollow spheres are suggested containing three consecutive stages: the formation of tetragonal Li x TiO2 solid solution, coexistence of two-phase mixture of Li0.05TiO2 and Li0.5TiO2 at 1.75 V and additional lithium storage in the surface. The superior high rate and high capacity performance of prepared TiO2 hollow spheres are due to its highly reversible additional surface capacities and accommodation of phase transformation within nanostructure. [Copyright &y& Elsevier]