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

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 (1), [Cu2I2(dps)2] (2), and [Cu4I4(dtdp)2] (3), 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 in situ cleavage of S–S and S–C(py) bonds of dtdp. Cu ions are divalent in 1, implying involvement of the starting Cu+ cations in a redox process, while the Cu ions remained univalent in 2 and 3. In 1 and 2, the dps adopted N,N-chelate coordination, in contrast to the N,S-chelation of the dtdp ligand in 3. Complex 1 displays a 2-D framework linked by hydrogen bonds and was further connected into a 3-D supramolecular structure by π–π stacking interactions between adjacent layers. Complexes 2 and 3 exhibited 2-D layer structures through ππ stacking interactions. The luminescent properties of 2 and 3 were also studied in the solid state at room temperature.