Application of Overlapping Spheres Method for Low-energy Conformation Search to Coordination Compounds: Conformational Analysis of Copper(II) Complexes with 1 -[N-(tert-Butoxycarbonyl)amino]-2-hydroxymethylcyclopropane-1-carboxylic Acids

Sa？etak The overlapping spheres (OS) method, based on minimization of the overlapping volume of the Central sphere and the van der Waals volumes of neighbouring atoms, was applied to copper(II) mono-and bis-complexes with 1 -[N-(tertbutoxycarbonyl)amino]-2-hydroxy-methylcyclopropane-1-carboxylic acid, N-Boc-ACC-OH, in the quest for low-energy conformations. The Central sphere was situated in the geometrical centre of one kind of molecular fragments in the case of mono-complexes, and three kinds of molecular fragments in the case of bis-complexes; the radius of the sphere varied from 0.3 to 0.6 nm. Altogether 168 and 112 conformations of (SS)-and (SR)-isomers of mono-complex were obtained, respectively. The conformation with the lowest energy, obtained by the OS method, had the energy only 0.8 kJ mol-1 higher than the global minimum. By applying the OS method to bis-complexes of N-Boc-ACC-OH, a drop in the conformational energy up to 60 kJ mol-1 was achieved in one cycle of optimization