Charge transfer phase transition with reversed thermal hysteresis loop in the mixed-valence Fe9[W(CN)8]6·xMeOH cluster

Abstract

A bimetallic pentadecanuclear cyanido-bridged {Fe₉[W(CN)₈]₆ (MeOH)₂₄}·xMeOH cluster of an Fe^II/III–W^IV/V mixed valence nature, reveals a reversible single-crystal-to-single-crystal transformation, concomitant with metal-to-metal charge transfer between Fe and W ions. The dominance of ^HSFe^II–NC–W^V units at a high temperature, and ^HSFe^III–NC–W^IV units at a low temperature, leads to an unprecedented reversed thermal hysteresis loop in magnetic measurements.