COPPER(II) COMPLEXES OF THE IMIDAZOLINONE HERBICIDE IMAZAPYR

The copper(II) complexes formed by the imidazolinone herbicide imazapy r opropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid] were studie d in aqueous solution by potentiometric and spectroscopic techniques. Imazapyr acts as a chelating molecule and is effective over a wide pH range. The chelating set active in acidic media involves rather weak d onors, namely the pyridine and imidazole nitrogens. In neutral media, the lactam site of the imidazolinone ring deprotonates and the ligand takes advantage of a rather basic nitrogen atom, which, assisted by th e pyridine donor, yields stable complexes with five-coordination at th e metal ion.