Syntheses, crystal structures and magnetic properties of manganese(ii)-hedp compounds involving alkylenediamine templates (hedp = 1-hydroxyethylidene-diphosphonate)

Abstract

Four new manganese(II) diphosphonates, [NH₃(CH₂)₄NH₃][Mn(hedpH₂)₂] (1) and [NH₃(CH₂)_nNH₃][Mn₂(hedpH)₂]·2H₂O [n = 4 (2), 5 (3), 6 (4)] (hedp = 1-hydroxyethylidenediphosphonate), have been synthesized under hydrothermal conditions and structurally determined by X-ray single crystal diffraction. Compound 1 consists of polymeric Mn(hedpH₂)₂ single chains built up from vertex-sharing MnO₆ octahedra and CPO₃ tetrahedra. The chains are cross-linked by very strong hydrogen bonds to form a three-dimensional network with large channels containing the diammoniumbutane cations. Compounds 2–4 can be considered as isomorphous from a chemical point of view, although 3 crystallizes in the non-centrosymmetric space group P2₁ while 2 and 4 are in the centrosymmetric space group P2₁/n. Each of the three compounds contains Mn₂(hedpH)₂ double chains. These double chains are held together by very strong hydrogen bonds, forming one-dimensional channels that host the diammonium alkane cations and lattice water. The effect of the alkane length of the templates on the channel size and the hydrogen bonding network is discussed. Magnetic measurements show that weak antiferromagnetic interactions are mediated between the manganese centers in all four compounds.