Spin-Equilibrium Behavior in Solution of an Iron(III) Complex [Bis[3-(3-methoxysalicylideneamine)propyl]amino-O,N,N′,N″,O′](pyridine)iron(III) Tetraphenylborate

The title iron(III) complex with a spin equilibrium between high-spin(S=5/2) and low-spin(S=1/2) has been investigated by means of the temperature dependences of the magnetic susceptibilities (the Evans 1H NMR technique), the electronic spectra, and the cyclic voltammetry. The pure electronic spectra for high-spin and low-spin species were evaluated from the observed electronic spectra and the equilibrium constants obtained from the magnetic data. The electron-transfer entropy for the Fe3++e→Fe2+ process(ΔSet) was obtained as 205 JK−1 mol−1 from the temperature dependence of the cyclic voltammogram.