CONTROL OF SUCCESSIVELY SWITCHING FROM LLCT TO ILCT AND MLCT EXCITED STATES IN PLATINUM(II) TERPYRIDYL ACETYLIDE COMPLEXES BY SEQUENTIAL PROTONATIONS

Abstract

Visualized theoretical evidence for successively switching from ligand-to-ligand charge transfer (LLCT) to intraligand charge transfer (ILCT) and then to metal-to-ligand charge transfer (MLCT) excited states in platinum(II) terpyridyl acetylide (PTA) complexes in low-energy absorption by sequential protonations has been given with charge transfer density, based on recently experimental report (Han X. et al., Chem Eur J13:1231, 2007). The sequential protonations have shown significant influence on the molecular geometries, ionization potential, affinity potential, and band gap of PTA. The protonations on the amino group of the ligands result in the shift of the molecular orbital energy levels of PTA. The physical mechanism of switching from LLCT to ILCT and then to MLCT excited states by sequential protonations is interpreted with the theory of molecular orbital transitions.