Light-Induced, Structural Matrix Guided Stepwise Spin-State Switching in 3d-5d Molecular Assembly

A new iron (II) molecular complex W (CN) 8Fe (bik*) 32BF4·7H2O·1. 5CH3OH (1. 7H2O·1. 5CH3OH) was synthesized using a versatile octacyanotungstate (V) building block and N-donor bidentate ligand (bik* = bis (1-ethyl-1H-imidazol-2-yl) ketone) and detailed characterizations were carried out. The crystal structure of 1. 7H2O·1. 5CH3OH is composed of an ionic salt from one anionic W (CN) 83– unit, two isolated cationic Fe (bik*) 32+ units, and one BF4– counteranion in the asymmetric unit. Magnetic studies of 1. 7H2O·1. 5CH3OH display interesting two-step reversible thermo-induced spin-state switching and the partially desolvated form 1. 7H2O shows a photomagnetic effect at low temperatures. Additionally, the physical properties of 1. 7H2O·1. 5CH3OH were compared with the monomeric unit of Fe (bik*) 32·4ReO4·H2O (2. H2O) and detailed photophysical investigations were also performed to study the effect of a structural matrix W (CN) 83– and ReO4– unit on the spin-state switching properties of the Fe (bik*) 32+ unit in both systems (1. 7H2O·1. 5CH3OH and 2. H2O).