Cubic clusters of indium chalcogenides with 2,2-bipyridine ligand, a comprehensive view of [InQ(phen/bpy)Cl]4 (Q = S, Se) compounds

We have reported main group metal chalcogenido clusters of cubic [InQ(phen)Cl]4 (Q = S (1) and Se (2); phen = 1,10-phenanthroline). Herein two new cubic clusters with ligand of 2,2′-bipyridine (bpy) have been synthesized by solvothermal technique, [InSe(bpy)Cl]4 (3) and [InS(bpy)Cl]4·H2O (4). The molecular structures and electronic states of compounds 3 and 4 are presented by comparing with those of 1 and 2. Though the clusters of 1–4 are similar, their packing structures show diverse modes. Spectroscopic study and theoretical calculation indicate that introducing phen/bpy to chalcogenido clusters can decrease the energy gap of frontier orbitals from HOMO to LUMO due to the cluster to ligand charge-transfer (CLCT). Increasing the conjugated system of the organic ligand or using the heavier chalcogenido element might improve the photophysical absorption of the materials.