Importance of spin-orbit coupling effect and solvent effect in electronic transition assignments of Pt~(II) complexes: In the case of cis/trans-[Pt~(II)Cl_2(NH_3)_2]

摘要

Electronic excitation spectra of cis-platin (cis-[Pt~(II)Cl _2(NH_3)_2]), which is a well-known antitumor drug, and trans-platin (trans-[Pt~(II)Cl_2(NH _3))2]) were experimentally observed and theoretically analyzed using ab initio spin-orbit CASPT2 (SO-CASPT2) calculations. Cis-platin showed two series of absorption bands in the wavelength regions of 250-350 nm and 350-450 nm. On the other hand, trans-platin showed three series of absorption bands in the wavelength regions of 260-280 nm, 300-340 nm and 360-400 nm. Comparing SO-CASPT2 calculations at the optimum structures in gas-phase conditions with those in DMF solvent, which were obtained by PCM implicit solvation model, it was clarified that both spin-orbit effect and solvent effect cannot be negligible even for quantitative assignments of electronic excitation spectra of cis/trans-platin.