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The intermolecular complexes formed between imidazol-2-ylidene and its heavy-atom analogues C2H4N2X: (X = C, Si, Ge, Sn, Pb) and YH3F (Y = Si, Ge, Sn, Pb) have been optimized at the MP2/aug-cc-pVTZ level. C2H4N2X: have two electron-rich moieties, one of which is the lone pair on the X atom and the other is the 6π-electron system. Three types of binding modes (type-A, type-B and type-C) can be distinguished for C2H4N2X: according to the locations of YH3F. The type-A and type-B complexes can be located for C2H4N2C:···YH3F system, and the Eint values of the type-A complexes are much larger than those of the type-B complexes. The type-A, type-B and type-C complexes can be located for the other four systems, and the Eint values of these complexes go in the order type-B > type-C > type-A. The binding strength of the type-A complexes becomes weaker, and that of the type-B and type-C complexes becomes stronger with the increase of the X atomic number for C2H4N2X:···YH3F system, which can be clarified by the MEP maps of C2H4N2X:. The NBO, AIM and SAPT analysis was employed to explore the nature of the interactions in these complexes. [ABSTRACT FROM AUTHOR]

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]