Semidirected versus holodirected coordination and single-component white light luminescence in Pb(ii) complexes

Abstract

2-Methyl-8-hydroxyquinoline (HMq) and the tripodal ligands 4,4′,4′′-(2,2′,2′′-nitrilotris (methylene)tris(1H-benzo[d]imidazole-2,1-diyl)tris(methylene))tribenzonitrile (triBZ-NTB) and 4,4′,4′′-(2,2′,2′′-nitrilotris(methylene)tris(1H-benzo[d]imidazole-2,1-diyl)tris(methylene))tribenzoic acid (H₃triCB-NTB) were used individually to assemble a hetero-nuclear, a tetra-nuclear and two mono-nuclear Pb(II) complexes. The Pb(II) coordination centers in two of these complexes were observed to display semidirected coordination with the ligands and counter anions (small solvent molecules), whereas the other two complexes showed holodirected coordination, together leading to varied coordination geometries. The combination of ligand-to-metal charge-transfer (LMCT) and metal-centered (MC) emissions in the semidirected Pb(II) complexes resulted in single-component white light luminescence.