Three copper complexes containing the sulfur-bridged bis-pyridine ligands, 2,2′-dithiodipyridine and di-2-pyridyl sulfide

<div><p>Three copper complexes constructed with sulfur-bridged bis-pyridine ligands 2,2′-dithiodipyridine (dtdp) and di-2-pyridyl sulfide (dps), [Cu₂(dps)₂(H₂O)₂(μ-SO₄)₂]·(H₂O)₂ (<b>1</b>), [Cu₂I₂(dps)₂] (<b>2</b>), and [Cu₄I₄(dtdp)₂] (<b>3</b>), have been synthesized by reaction of copper(I) iodide with dtdp under solvothermal and solution-diffusion conditions, and characterized by single crystal X-ray diffraction. The dps ligands were generated via <i>in situ</i> cleavage of S–S and S–C(py) bonds of dtdp. Cu ions are divalent in <b>1</b>, implying involvement of the starting Cu⁺ cations in a redox process, while the Cu ions remained univalent in <b>2</b> and <b>3</b>. In <b>1</b> and <b>2</b>, the dps adopted N,N-chelate coordination, in contrast to the N,S-chelation of the dtdp ligand in <b>3</b>. Complex <b>1</b> displays a 2-D framework linked by hydrogen bonds and was further connected into a 3-D supramolecular structure by <i>π–π</i> stacking interactions between adjacent layers. Complexes <b>2</b> and <b>3</b> exhibited 2-D layer structures through <i>π</i>–<i>π</i> stacking interactions. The luminescent properties of <b>2</b> and <b>3</b> were also studied in the solid state at room temperature.</p>