Influence of alkali and alkaline earth salts on the internal rotational barriers in N,N-dimethylbiuret. Experimental and theoretical studies

Abstract

The effect of alkali and alkaline earth salts on the barriers to internal rotation about the CNR 2 (R = H, CH 3) bonds in N,N-dimethylbiuret has been studied by means of 1H n.m.r. line shape and analysis. The 1:1 complexes of the ligand with the ions of Li, Na, K, Be, Mg and Ca have been investigated by ab initio MOSCF calculations with minimal GLO basis sets. The changes of the activation energies for the rotational barriers, the influence of methyl N-substitution on complex stability, and the geometry of the complexes are discussed on the basis of the theoretical results.