Water-soluble silver(I) complexes of (R)-(+)- and (S)-(−)-2-pyrrolidone-5-carboxylic acid and their antimicrobial activities. Chiral helical polymer and polymer sheet structures in the solid-state formed by self-assembly of dimeric [Ag(Hpyrrld)]2 cores

Abstract

The synthesis and characterization of two water-soluble silver(I) complexes {[Ag(R-Hpyrrld)]₂}_n1 and {[Ag₂(R-Hpyrrld)(S-Hpyrrld)]}_n2 [R- and S-H₂pyrrld = (R)-(+)- and (S)-(−)-2-pyrrolidone-5-carboxylic acid, respectively] showing wide ranging effective antimicrobial activity are described and their crystal structures determined. Single-crystal X-ray analysis reveals that 1 and 2 in the solid state are a right-handed chiral helical polymer and an achiral polymer sheet, respectively, formed by self-assembly of the Ag₂(carboxylato-O,O′)₂ units [Ag–Ag 2.899(2) Å for 1 and 2.875(2) Å for 2; O–Ag–O 160.3(5), 163.2(5)° for 1 and 163.1(2)° for 2]. The helicity of 1 in the solid state was accomplished by connection of only one oxo group in one dimeric core to one of the silver(I) centers of the adjacent dimeric unit. It is elucidated that the chiral helical polymer 1 is a mirror image of the recently characterized enantiomer {[Ag(S-Hpyrrld)]₂}_n3. The bonding modes of 1 and 3 are quite different from those of the achiral polymer sheet 2. Complexes 1 and 2 have been also characterized by elemental analysis, TG/DTA, FT-IR, and solution (¹H and ¹³C) and solid-state ¹³C NMR spectroscopies. The wide ranging effective antimicrobial activities observed in the complexes suggest that weak silver(I)–oxygen bonding properties play a key role.