Polymeric silver(i) complexes with pyridyl dithioether ligands: experimental and theoretical investigations on the coordination properties of the ligands

Abstract

The reactions of four flexible tetradentate ligands, 1,3-bis(2-pyridylthio)propane (L¹), 1,4-bis(2-pyridylthio)butane (L²), 1,5-bis(2-pyridylthio)pentane (L³) and 1,6-bis(2-pyridylthio)hexane (L⁴) with AgX (X = BF₄⁻, ClO₄⁻, PF₆⁻, or CF₃SO₃⁻) lead to the formation of seven new complexes: [AgL¹(BF₄)]₂ (1), {[AgL²](ClO₄)}_∞ (2), {[AgL²(CH₃CN)](PF₆)}_∞ (3), {[AgL³](BF₄)(CHCl₃)}₂ (4), {[AgL³(CF₃SO₃)](CH₃OH)_0.5}_∞ (5), {[Ag₂L⁴₂](BF₄)₂}_∞ (6), and {[AgL⁴](PF₆)}_∞ (7), which have been characterized by elemental analyses, IR spectroscopy, and X-ray crystallography. Single-crystal X-ray analyses show that complexes 1 and 4 possess dinuclear macrometallacyclic structures, and complexes 2, 3, and 5∼7 take chain structures. In all the complexes, the nitrogen atoms of ligands preferentially coordinate to silver atoms to form normal coordination bonds, while the sulfur atoms only show weak interactions with silver atoms and the intermolecular Ag⋯S weak contacts connect the low-dimensional complexes into high-dimensional supramolecular networks. Additional weak interactions, such as π–π stacking, F⋯F weak interactions, Ag⋯O contacts or C–H⋯O hydrogen bonds, also help to stabilize the crystal structures. It was found that the parity of the –(CH₂)_n– spacers (n = 3–6) affect the orientation of the two terminal pyridyl rings, thereby significantly influence the framework formations of these complexes. The coordination features of ligands and their conformation changes between free and coordination states have been investigated by DFT calculations.