Oxovanadium(iv) complexes of salicyl-l-aspartic acid and salicylglycyl-l-aspartic acid

Abstract

The dipeptide and tripeptide analogues salicyl-L-aspartic acid (Sal-L-Asp) and salicylglycyl-L-aspartic acid (SalGly-L-Asp) were synthesized and their protonation and complex formation with V(IV)O2+ were studied in aqueous solution through the use of pH-potentiometry and spectroscopic (UV-Vis, CD and EPR) techniques. The phenolate terminus proved to be a good anchoring site to promote (i) the metal ion-induced deprotonation and subsequent coordination of the peptide amide group(s) in the pH range 4-5 for the dipeptide analogue, (ii) and in the pH range 5-6 in a very cooperative way for the tripeptide analogue. The results suggest that the presence of good anchoring donors on both sides of the amide groups is responsible for the cooperative deprotonation of the two amide-NH groups.

Thirty years through vanadium chemistry

“…Taking into account their much higher intrinsic stability and much lower susceptibility toward hydrolysis, several publications were released either with characterization of metal complexes [153,[160][161][162][163][164] or using these very versatile ligands to prepare suitable complexes to prepare metal-based catalytic systems [163,[165][166][167][168][169][170][171][172].…”

Metal complexes of amino acids and amino acid side chain groups. Structures and properties

“…For example, the Asp moiety of salicylaspartate binds with VO(II) through the deprotonated amide nitrogen and the two carboxylate groups at neutral-basic pH. 43 Met binds with intermediate metal ions by N,O-chelation and with soft metal ions by N,S-chelation 4,44 as seen in the structures of [PdCl 2 (DL-Met)] (2) 45 and [PtCl 2 (L-Met)] (3) 46 The structures of the stereoisomers arising from the side chain group coordination of Met to Pt(II) were studied by X-ray analysis, NMR spectroscopy, etc. 47 The thioether sulfur of Met is well established as a donor atom in blue copper proteins with a distorted tetrahedral coordination geometry, 48 and methionylglycine binds with Pt(II) through the amino nitrogen and thioether sulfur atoms, 49 while glycylmethionine binds with Pt(II) through the amine and peptide nitrogen atoms and the sulfur atom.…”

Vanadium, niobium and tantalum

“…14 Schiff bases and their reduced analogues continue to play a prominent role in the coordination chemistry of vanadium, 15 and similar methodology in the preparation of the ligand has enabled salicyl-L-aspartic acid and salicylglycyl-L-aspartic acid to be prepared. 16 These di-and tri-peptide compounds were reacted with [VO] 21 sources in aqueous solution, and studied under various pH regimes. Related hydrazone-based ligands also featured prominently in the coordination chemistry of vanadium, [17][18][19][20] in which they predominantly form dianionic tridentate O,N,Oligands.…”