Light-stable and antimicrobial active silver(I) complexes composed of triphenylphosphine and amino acid ligands: Synthesis, crystal structure, and antimicrobial activity of silver(I) complexes constructed with hard and soft donor atoms ( n∞{[Ag(L)(PPh 3)] 2} with L = α-ala − or asn − and n = 1 or 2)

Abstract

Three novel silver(I) complexes consisting of both hard Lewis bases (O and N atoms) and one soft Lewis base (P atom) (( dl-α-alaninato)(triphenylphosphine)silver(I) ( 1), ( dl-asparaginato) (triphenylphosphine)silver(I) ( 2) and ( l-asparaginato) (triphenylphosphine)silver(I) ( 3)) were prepared from stoichiometric reactions of amino acid–silver(I) complexes with PPh 3 in a 1:1 molar ratio in a mixed organic solvent. These silver(I) complexes were soluble in organic solvents but insoluble in water; they are also more light-stable as compared to the corresponding precursors, amino acid–silver(I) complexes. Their solid-state and solution structures were unequivocally characterized using elemental analysis, TG/DTA, FTIR, X-ray structure analysis, solution ( 1H, 13C, and 31P) NMR and solid-state 31P CPMAS NMR spectroscopy. The X-ray structure analysis of complexes 1 and 2 revealed that these complexes were dimers with an inversion center. Each silver(I) atom was coordinated in a distorted four-coordinate environment containing an AgNO 2P core. Complexes 1 and 2 formed 1D and 2D networks in the crystal through intermolecular hydrogen bonding networks that can be described as ∞{[Ag( dl-α-ala)(PPh 3)] 2 · 2H 2O} and 2 ∞{[Ag( dl-asn)(PPh 3)] 2 · 2H 2O · 2EtOH}, respectively. Complexes 1– 3 showed moderate to modest antimicrobial activities against selected bacteria and yeasts in a water-suspension system.