| Abstract: | The absorption spectra, luminescence spectra, excited-state lifetimes, and electrochemical behavior of the cyclometalated Rh(ppz)2bpy]+, Rh(3-Cl-ppz)2(bpy)]+, Rh(4-NO2-ppz)2(bpy)]+, Rh(ppz)2(biq)]+ and Rh(4-NO2-ppz)2(biq)]+ complexes (ppz?, 3-Cl-ppz?, and 4-NO2-ppz? are the ortho-C-deprotonated forms of 1-phenylpyrazole, l-(3-chlorophenyl)pyrazole and l-(4-nitrophenyl)pyrazole, respectively) have been investigated. The results obtained have been compared with those concerning the free protonated ligands and some previously studied mixed-ligand cyclometalated Rh(III) complexes. Luminescence originates from the lowest ligand-centered (LC) excited state, which involves the diimine ligands in all cases except for Rh(4-NO2-ppz)2(bpy)]+, where it involves the ortho-metalating ligand. s. In the absorption spectra, LC and metal-to-ligand charge-transfer (MLCT) bands, involving the diimine and/or the ortho-metalating ligands, have been assigned, and correlations between spectroscopic and electrochemical data are discussed. |
