Nitro–Nitrito Photoisomerization of Platinum(II) Complexes with Pt(NO₂)₄^2– and (FSO₂)₂N^– Anions: Correlation between Isomerization Ratio and Reaction Cavity

Nitro–nitrito linkage isomerization is a well-known photochemical reaction of metal complexes in the solid state. To quantitatively elucidate the influence of the crystal environment on this reaction, we synthesized salts of a cationic platinum(II) nitrito complex with Pt(NO2)42– and (FSO2)2N– anions (1-Pt(NO2)4 and 1-FSA, respectively). Their thermal properties and photoreactivities were investigated, and the linkage isomerization of the cations and the Pt(NO2)4 anion upon ultraviolet photoirradiation at 180 K was observed by X-ray structural analysis. The isomerization levels for the cations in 1-Pt(NO2)4 and 1-FSA were 49% and 80%, respectively, and that for the Pt(NO2)4 anion was in the range of 0–65%. The conversion was correlated with the reaction cavity size surrounding the NO2 ligands.