Ab initio study of luminescent substituted 8-hydroxyquinoline metal complexes with application in organic light emitting diodes

The geometry, electronic structure and reactivity sites of a set of HQ-M (M = Be, Zn, Cd) with application in OLED's were computed and compared through computational calculations of both electronic and DFT-based chemical reactivity descriptors. All the structures were optimized at B3LYP level of theory and 6-31G(d) basis set for C, N, O, H and 3-21G(d) for Be, Zn and Cd. All the geometries were distorted tetrahedral, where both angles and bond length increase in the order Be+2 < Zn+2 < Cd+2. The molecular orbital analysis reveals that the frontier orbitals are delocalized and preserve largely the electronic structure of the individual 8-hydroxyquinoline ligand, being practically unaffected by both the amidopyridine group and the metal cation. The more reactive sites were found atoms belonging to the lowest unoccupied molecular orbital, which are in para-position to the quinoline nitrogen.