Synthesis and crystal structure of three silver(I) complexes with (S)-(+)-5-oxo-2-tetrahydrofurancarboxylic acid (S-Hothf) and its isomeric forms (R-Hothf and R,S-Hothf) showing wide spectra of effective antibacterial and antifungal activities. Chiral helical polymers in the solid state formed by self-assembly of the dimeric [Ag(othf)]2 cores

Abstract

Three water-soluble silver(I) complexes, i.e., {[Ag(S-othf)]₂}_n1, {[Ag(R-othf)]₂}_n2 and {[Ag₂(R-othf)(S-othf)]}_n3 (S- and R-Hothf = (S)-(+)- and (R)-(−)-5-oxo-2-tetrahydrofurancarboxylic acid, respectively), showing effective antibacterial and antifungal activities, have been synthesized and their crystal structures determined. Single-crystal X-ray analysis revealed that 1 and 2 in the solid state are a left- and a right-handed chiral helical polymer, respectively, formed by self-assembly of non-centrosymmetric, bis-carboxylato-bridged bis(carboxylato-O,O′)disilver dimers (Ag–Ag distances 2.822(1) Å for 1 and 2.823(2) Å for 2; O–Ag–O angles 164.0(2), 155.2(2)° for 1 and 163.8(3), 154.5(3)° for 2). The helicity of 1 and 2 in the solid state is accomplished with a connection of one oxo group in one dimeric core to one of the silver(I) centers of the adjacent dimeric unit and also with simultaneous connection of one of the carboxylato oxygens to the silver(I) center of a different dimer. These bonding modes are quite different from those of the stair-like polymer 3 formed by self-assembly of the dimeric core (Ag–Ag 2.781(1) Å; O–Ag–O angle 164.8(1)°). Crystals of 3 with achiral polymer structure were identical with those of 4 obtained from an aqueous solution containing equal amounts of 1 and 2, evidencing the presence of a ligand replacement between 1 and 2 in aqueous solution. The complexes 1–3 have also been characterized by elemental analysis, TG/DTA, FT-IR, and ¹H and ¹³C NMR spectroscopies. The wide spectra of effective antibacterial and antifungal activities observed in 1–3 suggested that the weaker silver(I)–O bonding properties play a key role in the antimicrobial activities.