Crystal structure and magnetic properties of 1 -aqua-µ-hydroxo-1,2,2- tris(perchlorato)-1,2-bis(2,2′;6′,2″-terpyridine)dicopper(II)

Abstract

The crystal and molecular structure of [Cu₂(terpy)₂(OH)(OH₂)(CIO₄)₃](terpy = 2,2′;6′,2″-terpyridine) has been determined by X-ray diffraction methods. It crystallizes in the triclinic space group P with two formula units in a cell of dimensions a= 8.825(5), b= 10.391(10), c= 19.258(8)Å, α= 88.24(2), β= 99.27(3), γ= 96.63(4)°. Least-squares refinement of 3 590 reflections with I > 2.5σ(I) and 353 parameters gave a final R′= 0.052. The structure consists of discrete dimeric molecules where the two copper(II) ions are bridged by only a single hydroxide anion with a Cu–O–Cu angle of 145.7(3)°, the resulting copper–copper distance being 3.642(1)Å. No crystallographic symmetry is imposed on the binuclear entities. The co-ordination geometry around each copper ion is approximately elongated tetragonal octahedral with the bridging hydroxide ion occupying an equatorial site. The apical sites are occupied by a perchlorate oxygen atom and a water oxygen atom for Cu(1), and by two perchlorate oxygen atoms for Cu(2). The tetragonal distortion is greater for Cu(2) due to the longer Cu–O apical distances. Magnetic susceptibility measurements performed from 295 to 5 K show relatively strong antiferromagnetic exchange interaction between the copper(II) ions (2J=–303 cm^–1, g= 2.07, and ρ= 0.019). The strength of the exchange interaction is discussed on the basis of the structural features and correlated with published magneto-structural data on similar single hydroxide-bridged copper(II) complexes.