Anion-directed synthesis of copper(I/II) complexes with a Schiff base derived from 2-(diphenylphosphino)benzaldehyde and aminoguanidine

Condensation of aminoguanidine hydrochloride and 2-(diphenylphosphino)benzaldehyde yielded a new Schiff base derivative with the formula (HL)Cl & sdot;H2O. In addition to the usual methods for identification and characterization, such as spectroscopic and thermal analyses, as well as crystal structure determination, its coordination properties were thoroughly investigated. The reaction of methanolic solutions of copper(II) salts (chloride, bromide, and nitrate) with the ligand resulted in the formation of diverse products. In the reaction of copper(II) chloride and the ligand, two complexes were formed, viz. (HLO)2[CuIICl4] (1) and [CuI(HL)Cl2] (2). During the formation of 1, the diphenylphosphino residue of the ligand underwent oxidation. The reaction between the bromide salt and the ligand led to the formation of a mixture of two complexes with [CuI(HL)(Br/Cl)Br] (3) as the dominant product and only a few crystals of [{CuI(HL)(mu -Br/Cl)(Br/Cl)}2] (4). An interesting feature of these compounds is the substitutional disorder of two halide anions in different coordination sites. A similar phenomenon occurs in [CuI2(HL)2(mu -Cl)(mu -NO3)ClX], where X = Cl, NO3 (5), which is formed under the same reaction conditions when the nitrate salt is used. All the complexes were characterized by elemental analysis, FTIR, UVVis, SC-XRD, PXRD, and TG-MS, except for complex 4 due to its low yield. Additionally, the antioxidant capacity of 1, 2, 3 and 5 was investigated in vitro, with the copper(I) complexes exhibiting greater activity.