Ru(II)–M(I) (M = Rh and Ir) bimetallic complexes based on a bridging ligand composed of 1,10-phenanthroline and N-heterocyclic carbene: Coordination chemistry and detection property of carbon monoxide

A series of mono-RuII and di-nuclear complexes, [RuII–MI(COD)Cl and RuII–MI(CO)2Cl] (M = Ir, Rh), have been prepared by using a bridging ligand, 1,3-dibutyl-2,3-dihydro-1H-imidazo[4,5-f][1,10]phenanthroline-2-yl (IL). This bridging ligand consists of 1,10-phenanthroline and N-heterocyclic carbene (NHC) and has two coordinating sites which can bind two different metals. The complexes synthesized have been fully characterized by 1H NMR, 13C NMR, high resolution mass spectrometry (HRMS), elemental analysis, and X-ray crystallography in one case. These complexes exhibited typical π–π∗ and metal-to-ligand charge transfer (MLCT) bands in the UV and visible regions, respectively. Compounds RuII–IrI(CO)2Cl and RuII–RhI(CO)2Cl have the stronger emission intensities and the longer luminescence lifetimes (τ) than those of RuII–IrI(COD)Cl and RuII–RhI(COD)Cl, respectively. Complex RuII–IrI(COD)Cl was applied to detect carbon monoxide.