Theoretical study of the electronic structures and spectroscopic properties of [(4′-XC ≡ Ctrpy)PtCl]+ (trpy = 2,2′:6′,2″-terpyridine; X = H, Me and Ph)

Abstract

The electronic structures and spectroscopic properties of [(4′-XC≡Ctrpy)PtCl]+(trpy = 2,2′:6′,2″-terpyridine; X = H (1), methyl (Me) (2), and phenyl (Ph) (3) were studied by the ab initio method. The structures at the ground and excited state were optimized at the B3LYP and CIS levels, respectively. The absorption and emission spectra in the dichloromethane solution were obtained by using the TD-DFT (B3LYP) method associated with the PCM model. The molecular orbital energy of the HOMOs of 1–3 with the d(Pt), p(Cl), π(trpy), and π(XC≡C) character is sensitive to the substituents on the acetylide ligand, but that of the trpy-based LUMOs with the π*(trpy) character varies slightly. The lowest lying emission at 503 nm for 1 is mainly attributed to the 3ILCT perturbed by the 3MLCT and 3LLCT transitions, but that at 535 nm for 2, and that at 558 nm for 3 are mainly attributed to the 3LLCT perturbed by the 3ILCT and 3MLCT transitions. The different electron-donating ability of H, Me, and Ph is responsible for the differences in emission character. Moreover, the calculation results show that the phosphorescent color can be turned by adjusting the substituents. Both the lowest energy absorption and emission of 1–3 are red-shifted in the order of 1<2<3, consistent with the electron-donating of H<Me<Ph.