Crystal structure and Hirshfeld surface analysis of an erbium(III) coordination polymer based on a 2,3,5,6-tetra-bromo-benzene-1,4-di-carboxyl-ate ligand.

Abstract

The title polymeric compound, poly[[tri-aqua-(μ3-2,3,5,6-tetra-bromo-benzene-1,4-di-carboxyl-ato)hemi(μ2-2,3,5,6-tetra-bromo-benzene-1,4-di-carboxyl-ato)erbium(III)] trihydrate], {[Er(C8Br4O4)1.5(H2O)3]·3H2O} n or {[Er(Br4bdc)1.5(H2O)3]·3H2O} n (1), was hydro-thermally synthesized and structurally characterized. The asymmetric unit contains one ErIII cation, one and a half Br4bdc2- dianions, three coordinated H2O mol-ecules, and three uncoordinated solvent H2O mol-ecules. The central ErIII cation is seven-coordinated within a distorted capped trigonal-prismatic geometry. The coordination sphere is defined by four carboxyl-ate oxygen atoms from four Br4bdc2- ligands and three aqua oxygen atoms. The Br4bdc2- ligand occupies a general position, and acts as a μ3-bridge linking three symmetry-related ErIII cations. It coordinates via μ3-κO:κO':κO'' mode, using its carboxyl-ate oxygen atoms to extend into a two-dimensional polymeric sheet parallel to the bc plane. Meanwhile, the remaining Br4bdc2- ligand is situated on a crystallographic inversion centre and adopts a μ2-κO:κO' coordination mode linking the sheets into a three-dimensional network. The cohesion of the three-dimensional supra-molecular framework is enhanced by classical O-H⋯O hydrogen bonds. The crystal packing is further consolidated by inter-molecular Br⋯Br and Br⋯O halogen bonding inter-actions. The analysis of the Hirshfeld surface reveals that the primary contributions arise from Br⋯Br (23.5%) and O⋯H/H⋯O (20.8%) contacts. Additional contributions include Br⋯H/H⋯Br (13.2%), H⋯C/C⋯H (12.5%), Br⋯C/C⋯Br (8.4%), Br⋯O/O⋯Br (7.0%), and O⋯O (5.3%) inter-actions.>.

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