LAUSR

The standard redox potentials of the Fe3+/Fe2+ (+0.77 V) and H3AsO4/H3AsO3 (+0.56 V) stabilize the easy crystallization of ferric arsenates. However, activating solvothermal reactions with a reducing agent such as hydrazine or ethanol may destabilize the solid compounds towards ferric, ferrous or mixed Fe2+/3+ arsenites. Few of them have been reported and in this work we have prepared four new members with various counter cations (Ba2+) or anions (OH−, Cl−) and various iron valence. The versatile condensation of ortho-arsenites (AsO32−) into pyro–(As2O54−), rings or meta-arsenites favours the creation of efficient spacers, able to tune the magnetic dimensionality of the iron-based framework. These four new members cover from 0D (paramagnetic Ba2FeII(As3+3O6)2·H2O), 1D (S = 5/2 ladders in BaFeIII2(As2O5)(AsO3)(OH)), 2D (layers of S = 5/2 dimers in Ba2FeIII2O(As2O5)2, up to 3D (TN = 97 K in Fe32.66+(As2O5)(AsO3)Cl with charge ordering) topologies. Their magnetic properties are analysed by means of combined structural, experimental results and ab initio calculations.