Segregated aromatic π–π stacking interactions involving fluorinated and non-fluorinated benzene rings: Cu(py)2(pfb)2 and Cu(py)2(pfb)2(H2O) (py = pyridine and pfb = pentafluorobenzoate)

The syntheses, physical characterization and crystal structures of two new molecular copper(II) complexes of composition [Cu(C5H5N)(2)(C7F5O2)(2)] (1) and [Cu(C5H5N)(2)(C7E5O2)(2)(H2O)] (2) (C5H5N = Py = pyridine and C7F5O2- = pfb = pentafluorobenzoate) are reported. Single-crystal X-ray structure determinations revealed that in 1, the Cu2+ ion, which lies on a crystallographic inversion centre, is coordinated to two py molecules and two oxygen atoms from two monodentate pfb anions, resulting in a trans-CuN2O2 square planar geometry. In 2, the Cu2+ ion is also coordinated to two py and two pfb species in addition to a water molecule in the apical site of a distorted CuN2O3 square pyramid. In the crystal packing, both 1 and 2 show segregated aromatic pi-pi stacking interactions in which (py + py) and (pfb + pfb) ring-pairings are seen, but no (py + pfb) pairings occur. Crystal data: 1: C24H10CuF10N2O4, M-r = 643.88, space group P (1) over bar, a = 8.0777 (3) angstrom, b = 8.0937 (3) angstrom, c = 10.5045 (5) angstrom, alpha = 90.916 (3)degrees, beta = 93.189 (2)degrees, gamma = 118.245 (3)degrees, V = 603.36 (4) angstrom(3), Z = 1.2: C24H12CuF10N2O5, M-r = 661.90, space group P (1) over bar, a = 7.5913 (5) angstrom, b = 15.6517 (6) angstrom, c = 21.1820 (14) angstrom, alpha = 95.697 (4)degrees, beta = 94.506 (2)degrees, gamma = 91.492 (4)degrees, V = 2495.2 (3) angstrom(3), Z = 4. (C) 2009 Elsevier B.V. All rights reserved.