Quantum chemical study of the chelate effect in the complex formation of alkali and alkaline earth metal ions with biuret

Abstract

The 1:1 complexes of biuret with the ions of Li, Na, K, Be, Mg, Ca and Zn have been investigated by means of ab initio MO SCF calculations with minimal GLO basis sets. The relative stablities of the cis- and trans-isomers have been calculated and compared with the chelate complexes, which proved to be the most stable conformation.

The energetic effect of chelate formation has been determined and its dependence on ion radius and atomic number discussed. Finally, the effect of the binding of a second biuret ligand is studied by means of calculations on the 1:2 complexes of Li, Na, Be and Mg ions with biuret.