Crystal structure and magnetic properties of the single-μ-chloro copper(II) chain [Cu(bipy)Cl2] (bipy = 2,2′-bipyridine)

The crystal and molecular structure of the copper(II) chain [Cu(bipy)Cl-2] (1) (bipy = 2,2'-bipyridine) has been determined by X-ray diffraction methods. The crystal structure of 1 consists of neutral single chloro-bridged copper(II) chains with alternating shea and long Cu-Cl distances through a screw axis parallel to a. The copper surrounding is best described as distorted square pyramidal, the equatorial plane being built by the two nitrogen atoms of the chelating bipy and two chlorine atoms tone terminal and the other bridging), whereas the apical position is filled by the bridging chlorine atom from the symmetry-related adjacent unit. The equatorial Cu-Cl bonds (2.291(3) and 2.259(3) Angstrom) are shorter than the axial one (2.674(3) Angstrom). The intrachain copper-copper separation is 4.010(3) Angstrom whereas the shortest interchain copper-copper distance is 8.381(3) Angstrom. The magnetic properties of 1 have been investigated in the temperature range 1.8-300 K. They reveal the occurrence of a weak intrachain antiferromagnetic coupling, J = -2.3 cm(-1) (uniformly-spaced linear chain of local spin S = 1/2). This value is compared to those of related mono- and di-chloro-bridged copper(II) polymers and the available magneto-structural data are discussed in the framework of a simple orbital model. (C) 1999 Elsevier Science S.A. All rights reserved.