Density functional study of platinum polyyne monomer, oligomer, and polymer: Ground state geometrical and electronic structures

摘要

Geometries of monomers and oligomers of a platinum polyyne and its free ligands were optimized using density functional theory with B3LYP hybrid functional. The LANL2DZ basis set was used for Pt and the 6-31G* for other atoms in geometry optimizations. The electronic structures of these compounds were analyzed using Stuttgart/Dresden ECPs (SDD) basis set for metal atoms and 6-311G* for others. The polymerization has very little effect on the bond lengths and by introducing the metal, the acetylide bond length increases slightly. The strong overlap between metal sp_x orbitals and σp_x orbitals of acetylides results in localized σ bonding. The hybridization between the ligand pπ orbitals and the platinum dπ orbital resulted in the π-conjugation enhancement. This conjugation enhancement causes some effects such as the highest-occupied molecular orbital-lowest-unoccupied molecular orbital gap reduction and charge transfer characteristic of low-energy vertical transitions.