Crystallographic characterisation of a possible model for photosystem II

Abstract

An X-ray crystal study of [Mn(3,5,Cl-salen)(H₂O)₂]₂(ClO₄)₂[3,5,Cl-salen =N,N′-3,5-dichloro(salicylidene)-1,2-diaminoethane] reveals it to be a hydrogen-bonded di-aquabridged dimer; a combination of the steric bulk of the ligand and a hydrogen bonding system creates a coordination cleft which can allow the approach of p-benzoquinone and water photolysis to occur on irradiation with visible light (no such photolysis occurs when sterically bulky 2,5-tert-butyl-p-benzoquinone is employed).