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

A new iron(II) molecular complex {[W(CN) 8 ][Fe(bik*) 3 ] 2 }BF 4 ·7H 2 O·1.5CH 3 OH ( 1 .7H 2 O·1.5CH 3 OH) was synthesized using a versatile octacyanotungstate(V) building block and N-donor bidentate ligand (bik* = bis(1-ethyl-1 H -imidazol-2-yl)ketone) and detailed characterizations were carried out. The crystal structure of 1 .7H 2 O·1.5CH 3 OH is composed of an ionic salt from one anionic [W(CN) 8 ] 3- unit, two isolated cationic [Fe(bik*) 3 ] 2+ units, and one BF 4 - counteranion in the asymmetric unit. Magnetic studies of 1 .7H 2 O·1.5CH 3 OH display interesting two-step reversible thermo-induced spin-state switching and the partially desolvated form 1 .7H 2 O shows a photomagnetic effect at low temperatures. Additionally, the physical properties of 1 .7H 2 O·1.5CH 3 OH were compared with the monomeric unit of {[Fe(bik*) 3 ] 2 }·4ReO 4 ·H 2 O ( 2 .H 2 O) and detailed photophysical investigations were also performed to study the effect of a structural matrix {[W(CN) 8 ] 3- and ReO 4 - unit} on the spin-state switching properties of the [Fe(bik*) 3 ] 2+ unit in both systems ( 1 .7H 2 O·1.5CH 3 OH and 2 .H 2 O).