Acta Crystallographica Section B

Volume 65, Part 5 (October 2009)

research papers

 

Weak interactions in chain polymers [M(-X)₂L₂] (M = Zn, Cd; X = Cl, Br; L = substituted pyridine) - an electron density study

R. Wang, C. W. Lehmann and U. Englert

Abstract: The experimental electron-density distributions in crystals of five chain polymers [M(-X)₂(py)₂] (M = Zn, Cd; X = Cl, Br; py = 3,5-substituted pyridine) have been obtained from high-resolution X-ray diffraction data sets (sin / > 1.1 Å^-1) at 100 K. Topological analyses following Bader's `Atoms in Molecules' approach not only confirmed the existence of (3, -1) critical points for the chemically reasonable and presumably strong covalent and coordinative bonds, but also for four different secondary interactions which are expected to play a role in stabilizing the polymeric structures which are unusual for Zn as the metal center. These weaker contacts comprise intra- and inter-strand C-HX-M hydrogen bonds on the one hand and C-XX-C interhalogen contacts on the other hand. According to the experimental electron-density studies, the non-classical hydrogen bonds are associated with higher electron density in the (3, -1) critical points than the halogen bonds and hence are the dominant interactions both with respect to intra- and inter-chain contacts.

Keywords: chain polymers; electron density distribution; topological analyses.

	Structure factor file (CIF format) (213.1 kbytes) [ doi:10.1107/S0108768109028626/so5025comp1iamsup2.hkl ] Contains datablock comp1iam
	Structure factor file (CIF format) (210.0 kbytes) [ doi:10.1107/S0108768109028626/so5025comp2iamsup3.hkl ] Contains datablock comp2iam
	Structure factor file (CIF format) (252.1 kbytes) [ doi:10.1107/S0108768109028626/so5025comp3iamsup4.hkl ] Contains datablock comp3iam
	Structure factor file (CIF format) (417.6 kbytes) [ doi:10.1107/S0108768109028626/so5025comp4iamsup5.hkl ] Contains datablock comp4iam
	Structure factor file (CIF format) (249.4 kbytes) [ doi:10.1107/S0108768109028626/so5025comp5iamsup6.hkl ] Contains datablock comp5iam

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