Influence of ligand substituent conformation on the spin state of an iron(ii)/di(pyrazol-1-yl)pyridine complex

Abstract

The temperature of the solution-phase spin-crossover equilibrium in iron(II) complexes of 4-alkylsulfanyl-2,6-di{pyrazol-1-yl}pyridine (bpp^SR) complexes depends strongly on the alkylsulfanyl substituent. DFT calculations imply this reflects the conformation of the alkylsulfanyl groups, which lie perpendicular to the heterocyclic ligand donors in [Fe(bpp^StBu)₂]²⁺ but are oriented co-planar with the ligand core for smaller SR substituents.