Binding ability of N-Para-amino-phenylsulfonyl derivatives of amino acids. Potentiometric and spectroscopic studies of Cu(II) complexes
Abstract N-Para-amino-phenylsulfonyl derivatives of amino acids are very effective ligands for Cu(II) ions. Potentiometric and spectroscopic results have shown that Cu(II) ions are able to deprotonate and bind to sulfonamide nitrogen below pH 5 to form stable mono- and bis-[N − , COO − ] chelates. The basicity of sulfonamide nitrogen is lower than peptide amide nitrogen and no distinct anchoring site is necessary to promote the amide nitrogen deprotonation.
N-p-Amino- and N-p-nitro-phenylsulfonyl derivatives of dipeptides, a new family of ligands for copper(II). Potentiometric and spectroscopic studies
The co-ordination ability of four dipeptide analogues substituted on the N-terminal amino group with p-nitrophenylsulfonyl (nps-Ala-Ala and nps-Ala-His) and p-aminophenylsulfonyl (aps-Ala-Ala and aps-Ala-His) groups was studied by potentiometric and spectroscopic (UV/VIS absorption, CD and EPR) techniques. The N-terminal sulfonyl substituent drastically changes the acidity of the sulfonamide proton making nitrogen very efficient in binding to CuII. The sulfonamide nitrogen having pK between 9 and 11 does not need any anchoring binding group to form complexes with CuII. The para substituent on the phenyl ring (amino or nitro) influences very strongly the acidity of the sulfonamide proton. Th…