Interrelations between Linkage Isomers of an Efficient Square‐planar Nickel(II) Nitrite Photoswitch in the Solid State

Abstract

AbstractAn efficient nitrite nickel(II) photoswitch, with the 1‐phenyl‐2‐hydroxyimino‐3‐[(2’‐dimethylamino)ethyl]imino‐1‐propanone moiety used as the ancillary ligand, is reported. In the ground‐state (‘dark’) crystal structure, the studied compound exists predominantly as the nitro‐(η1‐N(O)2) isomer, however, traces of the exo‐ and endo‐nitrito‐(η1‐ONO) forms are detected both at 100 K (4–5 % each) and under ambient conditions (~9 % each). When excited with the 405–530 nm LED light, the nitro‐to‐nitrito isomerization takes place. The total conversion exceeds 90 %. The exo‐nitrito linkage isomer constitutes the dominant photo‐generated form, whereas the relative population of both nitrito species depends on temperature. The reaction is fully reversible and reproducible. The photo‐products are stable up to 200 K. The system constitutes a good model case for the reaction mechanism studies. Thus, experimental and theoretical investigations on the photo‐isomerism were conducted and are presented in detail. Eventually, the nitro→exo‐nitrito→endo‐nitrito reaction pathway is proposed.