Abstract
Quinoxaline-bridged bidentate bis-imidazolium dicarbene ligand 1,1′-(quinoxaline-2,3-diyl)bis(3-methyl-1H-imidazol-3-ium) hexafluorophosphate salt H2L·2PF6 (3) was prepared by a two-step reaction based on 2,3-bis(imidazol-1-yl)quinoxaline (1). First, the 2,3-bis(imidazol-1-yl)quinoxaline reacted with CH3I resulting in the 1,1′-(quinoxaline-2,3-diyl)bis(3-methyl-1H-imidazol-3-ium) iodide salt H2L·2I (2), then through anion exchange reactions with NH4PF6 in water produced the desired bis-imidazolium bidentate ligand H2L·2PF6 (3). Reaction of the bidentate bis-imidazolium ligands H2L·2PF6 (3) with Ag2O in acetonitrile gave the macrocyclic binuclear silver(I) carbene complex [Ag2(L)2]·2PF6·CH3CN (4). Nickel carbene complex [Ni(L)PPh3Cl]·PF6·2DMSO (5) was obtained via transmetalation of 4 with Ni(PPh3)2Cl2 in DMSO. The bidentate carbene ligand is a chelating ligand in 5, while bridging in 4. The imidazolium ligand H2L·2PF6 (3) and transition metal carbene complexes 4 and 5 have been fully characterized by elemental analysis, NMR, ESI-MS spectroscopy, and X-ray diffraction analyses. Furthermore, the UV and luminescent properties of 3–5 were also studied.
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