Crystal structures and spectroscopic properties of copper(II) pseudohalide complexes with two sparteine epimers, having a CuN 4 chromophore

Abstract

Tetrahedrally distorted copper(II) sparteine pseudohalide complexes having a CuN 4 chromophore were prepared and characterized by various spectroscopic techniques and X-ray crystallography. Among them, the crystal structures of copper(II) isothiocyanate complexes with two sparteine epimers, (−)- l-sparteine (Sp) and (−)-α-isosparteine (α-Sp), were determined. The N Sp–Cu–N Sp plane in copper(II) (−)- l-sparteine isothiocyanate [Cu(Sp)(NCS) 2] and copper(II) (−)-α-isosparteine isothiocyanate [Cu(α-Sp)(NCS) 2] is twisted by 58.2(6)° and 52.2(9)°, respectively, from the N NCS–Cu–N NCS plane. Based on the values of the dihedral angles and tilted distances of these two complexes, the geometry around Cu(II) in Cu(α-Sp)(NCS) 2 is more distorted from the perfect tetrahedron than that in Cu(Sp)(NCS) 2. For copper(II) sparteine pseudohalide (NCS − and N 3 −) complexes having a CuN 4 chromophore, the EPR and the optical spectral data were collected. The results of X-ray crystallography and ESR spectroscopy are in a good agreement with the assumption that the degree of distortion from planarity to tetrahedron will reduce the A || value of four-coordinate copper(II) sparteine pseudohalide complexes.