Structurally diverse copper(II) herbicide complexes: mono- and bi-nuclear neutral or cationic complexes

Abstract

Copper complexes with the commerical auxin herbicides 2,3-dichlorophenoxyacetic acid and 2-(2,4-dichlorophenoxy)propanoic acid and 2,2′-bipyridine(bipy) were prepared and characterized: [Cu₂(Cl₂C₆H₃OCH₂CO₂)₄(MeOH)₂]1, [Cu{Cl₂C₆H₃OCH(Me)CO₂}₂(bipy)(H₂O)]2 and [Cu{Cl₂C₆H₃OCH(Me)CO₂}(bipy)₂]Cl 3. The available evidence supports a dimeric structure for complexes 1 while the presence of bipy leads to monomeric forms. In dimethylformamide solution the binuclear complex is converted into a monomeric complexe upon addition of a > 1:2 ratio of bipy. The ESR powder spectrum of compound 2 exhibits features characteristic of the presence of a S= 1 triplet state which may be assigned to a hydrogen-bond network. The crystal structures of the three complexes have been determined.