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.

Graphical abstractNew bridging ligand, 1,3-dibutyl-2,3-dihydro-1H-imidazo[4,5-f][1,10]phenanthroline-2-yl (IL) has been prepared and various complexes, [RuII-(IL)–MI(COD)Cl and RuII-(IL)–MI(CO)2Cl] (M = Ir and Rh) have been synthesized. These complexes have shown luminescent properties depending upon the ligand attached to Ir and/or Rh metal. Thus, these complexes have been studied as luminescent CO detectors.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► New bridging ligand based on 1,10-phenanthroline and NHC has been prepared. ► Ru(II), Ru(II)–Ir(I), and Ru(II)–Rh(I) have been synthesized using new bridging ligand. ► Luminescent properties can be tuned by COD or CO ligand at second metal. ► Bimetallic complexes have been used for a detector of carbon monoxide.