Preparation and characterization of complexes of the antitumour copper(II) 2-formylpyridine thiosemicarbazone (HL) system and the single-crystal X-ray structures of [{Cu(HL)(CF3CO2)}2][CF3CO2]2and [Cu(HL)(H2O)(CLO4)2]·2H2O

Abstract

The complexes [{Cu(HL)X₂·nH₂O (HL = 2-formylpyridine thiosemicarbazone, X = CF₃CO₂, F or I, n= 0; X = Br, n= 2) and [Cu(HL)(H₂O)X₂]·nH₂O (X = ClO₄, n= 2; X = NO₃, n= 0) have been prepared from the reaction of [{CuL(MeCO₂)}₂] with the appropriate acid, HX. Also prepared were the deprotonated ligand complexes [(CuLX)₂]·nH₂O from the reaction of NaL with the appropriate copper(II) salt (X = F, n= 5.5; X =½SO₄, n= 3) or by the reaction of [{CuL(MeCO₂)}₂] with the appropriate sodium salt, NaX (X = N₃, n= 1; X = CN, n= 2). The complexes have been characterized by a variety of physicochemical techniques and the crystal and molecular structures of [{Cu(HL)(CF₃CO₂)}₂][CF₃CO₂]₂ and [Cu(HL)(H₂O)(ClO₄)₂]·2H₂O determined by single-crystal X-ray diffraction studies. Crystals of [{Cu(HL)(CF₃CO₂)}₂][CF₃CO₂]₂ are triclinic, space group P, with a= 9.6015(7), b= 10.837(1), c= 8.811(2)Å, α= 100.71(1), β= 117.06(1), γ= 80.877(7)°, and Z= 1. The complex cation is a centrosymmetric dimer, the monomeric units being bridged by two CF₃CO₂ ^– anions. The copper atoms have a distorted square-pyramidal co-ordination geometry with three donor atoms (NNS) coming from HL and the fourth donor (an oxygen) from the bridging anion. The fifth position is occupied by a less strongly bound oxygen from the second bridging anion. Crystals of [Cu(HL)(H₂O)(ClO₄)₂]·2H₂O are monoclinic, space group P2₁/c, with a= 12.9615(5), b= 9.7638(4), c= 14.9964(8)Å, β= 111.580(4)°, and Z= 4. The complex is monomeric with a distorted tetragonal co-ordination around the copper atom. The four in-plane donor atoms are provided by HL (NNS) and an oxygen from a co-ordinated water molecule. Two weakly bound ClO₄ ^– ions occupy the fifth and sixth positions. In both complexes hydrogen-bonding schemes appear to be important in stabilizing them in the solid state. The differences in the bonding parameters for the Cu(HL)²⁺ and CuL⁺ systems are discussed and related to the fact that the S→Cu^II ligand-to-metal charge-transfer absorption (at ca. 400 nm) is always observed at higher energies for the HL complexes.