Manifestation of copper coordination sphere plasticity in [Cu2(2-bromopropionato)4]n and [Cu2(3-bromopropionato)4(H2O)2]

The crystal structure of [Cu-2(CH3BrCHCOO)(4)](n) (I) is composed of polymeric chains. Within each chain the shortest Cu...Cu distances are 2.583(6) A long. The structure of [Cu-2(CH2BrCH2COO)(4)(H2O)(2)] (II) is composed of asymmetric complex units mutually connected by hydrogen bonds. The crystal structures of both compounds have been communicated in this work. Cu atoms are coordinated by four O atoms of bridging 2- and 3-bromopropionates. The Cu...Cu distances in the compound II are 2.609(1) and 2.6580(9) A. The structures differ in the geometry of their inner copper coordination sphere and the bonding of carboxylic ligands. Using the bond-valence sum model, the interdependence of apical Cu-O bond length vs. copper atom displacement from the basal plane of coordination polyhedron for copper carboxylate complexes with CuO4O chromophore was developed. The limits of apical Cu...O distance and copper displacement for plastic deformations of inner copper atom coordination sphere were predicted. The partial atomic charges of copper atoms and the optical transitions were investigated using the time-dependent density functional theory for the geometries selected from the crystal structures. (C) 2018 Elsevier B.V. All rights reserved.