Mixed cobalt(III) complexes with aromatic amino acids and diamine. Part IV. Influence of noncovalent intraand interligand interactions on rotamer population of the S-phenylalaninato and S-tyrosinato side groups in (1,2-diaminoethane)bis(S-aminocarboxylato)cobalt(III) complexes

Abstract

Rotamer population of S -tyrosinato and S -phenylalaninato ligands side groups in diastereomers of (1,2-diaminoethane) bis ( S -aminocarboxylato)cobalt(III) complexes is calculated by vicinal and proton coupling constant analysis. The effect of noncovalent intra- and interligand interactions on the population of rotamers in D 2 O solution is discussed. It has been established that in all the complexes investigated the most abundant is rotamer t , in which aromatic voluminous moiety and carboxylic group are in an anti position. In almost all complexes the lowest content is of rotamer g , in which these two groups are in the nearest position. Relatively high population of rotamer h in complex 5 tyr , in spite of high steric hindrances, is due to intra- and interligand NH interactions.