Structure and Thermal Vibrations of Spermine Phosphate Hexahydrate from Neutron Diffraction Data at 125K

Abstract

Spermine phosphate hexahydrate crystallizes in space group P2(1)/a with unit-cell dimensions a = 7.931 (1), b = 23.158 (5), c = 6.856 (2) A, and beta = 113.44 (2) degrees at 125 K with unit-cell contents [(C10H30N4)2(4+)(HPO4)4(2-).12H2O]. The packing of spermines and monohydrogen phosphates in this crystal structure has features which may be relevant to the binding of spermine to DNA. Another important structural feature is the presence of channels containing water that is hydrogen bonded as in ice-Ih with disordered protons. The channels occur between sheets of spermine long chains and are also bordered by hydrogen-bonded monohydrogen phosphate chains. The hydrogen-bonding scheme of these water chains proposed on the basis of an earlier X-ray study is now confirmed. Nuclear positions, anisotropic mean-square (m.s.) displacements, an overall scale factor and two extinction parameters (rho and g) were refined using full-matrix least-squares giving values of R(F0(2)) = 0.09, Rw(F0(2)) = 0.11 and S = 1.02. Thermal vibrational analysis revealed that the backbone of the spermine cation can be described as a single rigid segment with a substantial libration of 27 deg2 around the spermine molecular long axis.

The azide anion as a building block in crystal engineering from a charge density point of view

“…24,25 Before each step of the refinement, C-H and N-H bond distances were normalized to the values obtained from the neutron data (1.08 and 1.05 A, respectively). 20 The refinement was carried out against F (7551 merged reflections with I > 3s(I)) and converged to R ¼ 0.0299, R w ¼ 0.0300 and GOF ¼ 1.2107. The refinement of atomic coordinates and anisotropic displacement parameters was performed against high-angle data (sin q/l > 0.7), and the refinement of all other parameters was performed against all data.…”

Insights into supramolecular design 2: Analysis of anion coordination geometry of oxoanions in a protonated polyamine matrixPart 1: ref. 1. Electronic supplementary information (ESI) available: Hydrogen bonds for new compounds. See http://www.rsc.org/suppdata/ce/b1/b109449a/

“…The latter of these two salts has been previously analysed at room temperature 57 and a neutron study at 125 K has been reported recently. 58 However, it has been redetermined for the same reason as for 2c to greater precision. In both 2f and 2g salts the ligands adopt the all-anti conformation.…”