Structures, electrochemical and spectral properties of a series of [MnN(CN)3(diimine)]^- complexes

The structures and the electrochemical and spectral properties of a series of discrete [PPh4][MnN(CN)3(diimine)] complexes {diimine = 2,2′-bipyridine [1(bpy)], 4,4′-dimethyl-2,2′-bipyridine [1(4-dmbpy)], 5,5′-dimethyl-2,2′-bipyridine [1(5-dmbpy)], 1,10-phenanthroline [1(phen)] and bipyrimidine [1(bpym)]} have been assessed. These complexes represent potential building blocks for the construction of coordination frameworks. The incorporation of diimine ligands with different π-accepting capacities allows the systematic tuning of the metal-to-ligand charge-transfer (MLCT) band as well as the MnV/MnVI redox potential. The complexes exhibit solvatochromism, and the marked sensitivity of λmax of the MLCT band to polar solvents leads the way towards their potential application in chemical sensing. The crystal structures, redox activities and spectral properties of five discrete [PPh4][MnN(CN)3(diimine)] complexes are reported. Through the modulation of the metal-to-ligand charge-transfer (MLCT) band by variation of the π-accepting capacity of the diimine ligand, the MnV/MnVI redox potential and solvatochromism can be tuned systematically.