Influence of ligand backbones and counter ions on structures of helical silver(I) complexes with di-Schiff bases derived from phthalaldehydes and diamine

Abstract

Five silver(I) complexes of Schiff bases, [Ag₂L₂][ClO₄]₂1, [Ag₂L₂][PF₆]₂·H₂O 2, [Ag₂L₂][NO₃]₂3, ¹_∞[(AgL′)(dnb)(H₂O)_0.25] (dnb = 3,5-dinitrobenzoate) 4 and ¹_∞[(AgL′)(NO₃)] 5 were synthesized, where L and L′ are derived from the [1 + 2] condensation of 2-(aminoethylamino)ethanol with isophthalaldehyde or terephthalaldehyde. Complexes 1, 2, 4 and 5 have been structurally characterised by X-ray crystallography, which shows that the cations in 1 and 2 have similar double helical structures, and 4 has a single-stranded helical structure. However, complex 5 exhibits a one-dimensional staircase-like structure. Each Ag atom in 1, 2 and 4 adopts a highly distorted tetrahedral geometry, while that in 5 features a T-shaped geometry. In solution, 1–3 have virtually identical ¹H NMR spectra, similar FAB mass spectra and electrochemical properties.