'Naked-Eye' Detection of Histidine by Regulation of Cu~II Coordination Modes

摘要

The association of various alpha-amino acids with four new,coordina-tively unsaturated metal complexes([Cu(5)]~(2+),[Cu(6)]~(2+),[Cu(7)]~(2+),and[Zn(8)]~(2+))was examined.The receptors[Cu(5)]~(2+)and[Cu(7)]~(2+)were found to discriminate histidine(His)from other zwitterionic alpha-amino acids by means of indicator-displacement assays(IDAs)using 5(6)-carboxyfluor-escein as an indicator in buffered methanol/water(3:1)solvent.The colori-metric detection of His was achieved by using this IDA method,which appears to owe its selectivity to a unique process involving disruption of the host complex to form a 2:1 His/Cu~II complex rather than simple indicator displacement.The occurrence of distinct intermolecular coordination processes in response to the introduction of a different amino acid is observed.X-ray crystal structures of the host metal complexes were obtained and exhibit the adoption of a variety of coordination geometries about the metal center.