title: Glycine zinc sulfate penta-hydrate: redetermination at 10 K from time-of-flight neutron Laue diffraction.
abstract: Single crystals of glycine zinc sulfate penta-hydrate [systematic name: hexa-aqua-zinc tetra-aquadiglycinezinc bis-(sulfate)], [Zn(H2O)6][Zn(C2H5NO2)2(H2O)4](SO4)2, have been grown by isothermal evaporation from aqueous solution at room temperature and characterized by single-crystal neutron diffraction. The unit cell contains two unique ZnO6octa-hedra on sites of symmetry -1 and two SO4tetra-hedra with site symmetry 1; the octa-hedra comprise one [tetra-aqua-diglycine zinc]2+ion (centred on one Zn atom) and one [hexa-aqua-zinc]2+ion (centred on the other Zn atom); the glycine zwitterion, NH3+CH2COO-, adopts a monodentate coordination to the first Zn atom. All other atoms sit on general positions of site symmetry 1. Glycine forms centrosymmetric closed cyclic dimers due to N-H⋯O hydrogen bonds between the amine and carboxyl-ate groups of adjacent zwitterions and exhibits torsion angles varying from ideal planarity by no more than 1.2°, the smallest values for any known glycine zwitterion not otherwise constrained by a mirror plane. This work confirms the H-atom locations estimated in three earlier single-crystal X-ray diffraction studies with the addition of independently refined fractional coordinates andUijparameters, which provide accurate inter-nuclearX-H (X= N, O) bond lengths and consequently a more accurate and precise depiction of the hydrogen-bond framework.
authors.affiliation: ISIS Facility, Rutherford Appleton Laboratory, Harwell Science and Innovation, Campus, Didcot, Oxfordshire OX11 0QX, England.
authors.forename: A Dominic
authors.initials: AD
authors.lastname: Fortes
authors.affiliation: Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, England.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Howard
authors.affiliation: Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, England.
authors.forename: Ian G
authors.initials: IG
authors.lastname: Wood
authors.affiliation: ISIS Facility, Rutherford Appleton Laboratory, Harwell Science and Innovation, Campus, Didcot, Oxfordshire OX11 0QX, England.
authors.forename: Matthias J
authors.initials: MJ
authors.lastname: Gutmann
keywords: crystal structure; dimer; glycine; neutron diffraction; zinc sulfate; zwitterion