Pyrazole-type complexes with Ni(II) and Cu(II) Solvent exchange reactions in coordination compounds

Abstract

New nickel(II) and copper(II) coordination compounds were synthesized by the reaction of N-(benzyloxycarbonyl)-1H-pyrazole-1-carboxamidine ligand (HL) with Ni(II) and Cu(II) acetate in methanolic solution. The crystal and molecular structures of the complexes as well as those of the ligand were determined by single-crystal X-ray structure analysis. The octahedral surrounding around the metal centers in the isostructural complexes [ML2(MeOH)(2)], M = Ni(II), Cu(II), MeOH = methanol, is established by the bidentate coordination of two ligand molecules through the pyrazole nitrogen and the deprotonated nitrogen atom of the carboxamidine group along with the oxygen atoms from two MeOH molecules. Despite that the molecular structure of the complexes was determined by X-ray structure analysis, in the FT-IR spectra of the compounds the characteristic bands for MeOH were missing. By coupled TG-MS measurements, it was found that compounds during the transport and storage exchanged MeOH by water molecules. The amount of the water was calculated on the basis of thermogravimetric data. The antifungal activity of the compounds was tested against fungi Ph. viticola and B. dothidea and compared to that of a commercial fungicide. Depending on the fungi and on the structure, the compounds showed different, but somewhat lower activity than the commercial fungicide.