Electronic structure and reactivity analysis for a set of Zn-chelates with substituted 8-hydroxyquinoline ligands and their application in OLED

A set of four Zn organometallic complexes with aromatic substituents in the 5-position of quinoline skeleton connected through an amido linkage to the ligands were studied and compared, by using electronic descriptors such as the energy gap between the highest occupied molecular orbital (HOMO) and the energy of the lowest unoccupied molecular orbital (LUMO), molecular orbitals’ surfaces, atomic charges, global hardness, local softness, Fukui function, and global and local electrophilicity indexes. All the geometries were optimized in the scheme of density functional theory (DFT) with the hybrid functional B3LYP and the 6-31G(d) basis set. The results show that the geometries of the molecules were all distorted tetrahedral, which are unaffected by substitution when they are compared with the prototypical OLED material Znq2. The frontier molecular orbitals HOMO and LUMO are delocalized over both ligands and are confined within a specific region. The reactivity analysis shows that the specific atoms prone to receive electrons are those associated with the lowest unoccupied molecular orbital (LUMO).