Complexes of copper(II) acetate with nicotinamide:: preparation, characterization and fungicidal activity;: crystal structures of [Cu2(O2CCH3)4(nia)] and [Cu2(O2CCH3)4(nia)2]

Three new copper(II) acetate complexes with nicotinamide (nia) were synthesized, analyzed and characterized by standard chemical and physical methods and tested for fungicidal activity. The crystal and molecular structures of the compounds [Cu-2(O2CCH3)(4)(nia)] (1B) and [Cu-2(O2CCH3)(4)(nia)(2)] (2) were determined by X-ray diffraction. Both consist of binuclear units of bridging tetracarboxylate type, however they differ in the bonding mode of nicotinamide molecules. They are bonded at the apical positions of the dimers and connect them in an infinite chain in 1B. On the other hand the dimers remain isolated in the structure of the compound 2. It seems that compound 1B is the first example where a nicotinamide molecule acts as a bidentate bridging ligand. The results of EPR spectra agree with the dimeric nature of the complexes. Dissolved in water or DMSO, the compounds completely stop mycelial growth at a concentration of 5.0 x 10(-3) moll(-1). Less concentrated solutions (up to 1.0 x 10(-3) moll(-1)) show weaker fungicidal activity. (C) 1999 Elsevier Science Ltd. All rights reserved.