Chiral complexes of copper(II), containing polyether podands and a quaternary ammonium group, as potential receptors and carriers of α-amino acid anions

Abstract

In an attempt to develop a viable metalloreceptor for the recognition of α-amino acid anions a detailed study of proline (Pro) complexation by {(R)-7,8,15,18-tetrahydro-5,10-bis(2′-methoxyethoxy-5′-methylphenyl)-7-(p-trimethylammoniophenyl)dibenzo[e, m]-[1,4,8,11]tetra-azacyclotetradecine-16,17-dionato(1–)-N⁶N⁹N¹⁵N¹⁸}copper(II) chloride (1) in D₂O at pD 11.0, using n.m.r. relaxation techniques, was undertaken. Structural information has been obtained, including the distances between hydrogen or carbon atoms of proline (Pro) and copper ion in the mixed complex where Pro occupies the apical position. Preliminary data on the ability of (1) to serve as a phase-transfer carrier for α-amino acid anions (Phe, Leu, Pro, or Hyp) are also reported. The extraction constants were correlated with those found using a routine phase-transfer agent, tetrapentylammonium iodide. Noticeable differences in phase-transfer properties were detected for these reagents.