The character of the photo-induced metastable state is investigated via molecular-orbital calculation. The anisotropic g-factor and the hyperfine coupling constants are simulated based on the extended-Hückel calculation. The most plausible environment around the metastable PtIIIis found to be a spin-soliton like state, whose spin-orbital mainly comprises one platinum and one chlorine atoms. The vibration mode of the elemental unit of the complex is calculated for both high- and low-temperature structures employing a density-functional method.