A New Inorganic−Organic Hybrid Zinc Phosphate Prepared with l-Histidine with an Unusual Stability in Water

Abstract

A new layered zinc phosphate (Mu-39) has been synthesized by hydrothermal treatment with biomolecules as original templates. It was synthesized with the l-histidine amino acid (C6H9N3O2). The structure was determined by a single crystal X-ray diffraction study combined with exhaustive solid-state NMR experiments. These last ones [1H → 13C HETCOR, 1H single quantum/double quantum (DQ), 31P, 1H → 31P CPMAS, 1H → 31P HETCOR] ascertained the formulation of Mu-39 as {[C6H10N3O2+][Zn2(HPO4)(PO4)−]·H2O}n with a hydrogen phosphate and phosphate ligands, and ruled out partial protonation such as (H1−xPO4)(HxPO4). A 31P magic angle spinning (MAS) NMR study supported the almost complete racemization of l-histidine during the hydrothermal synthesis with only a small enantiomeric excess of 25% remaining. The compound crystallizes in the triclinic symmetry (space group P1) with a = 8.6109(6) A, b = 9.0319(6) A, c = 9.9523(7) A, and α = 84.481(2)°, β = 83.279(2)°, γ = 74.652(2)°, V = 739.56(9) A3, Z = 2. The inorganic ...