The affinity of copper(ii) ions towards l-amino acids in the solid-state: a simple route towards mixed complexes

Abstract

Competitive milling was successfully employed to determine the relative affinity of copper(II) ions towards selected L-amino acids (Asn, Gln, His, Phe, Pro, and Trp). Although Cu(II) ions readily form complexes with all the investigated acids, only L-Trp is selectively bound from its solid (binary) mixtures [in the form of Cu(Trp)₂]. For the investigated reactions, solid-state milling proved to be superior to solution-based methods as it avoids unwanted competition and solubility problems while opening a simple route towards ternary coordination compounds (otherwise hard to obtain from solution).