catena-Poly[[diaqua(nitrato-κO)(nitrato-κ2O,O′)(μ-2,5-bis[(pyridin-3-yl)ethynyl]thiophene-κN:κN′)cadmium(II)] hydrate]

The reaction of Cd(NO3)2·4H2O with the fluorescent ditopic N-donor ligand 2,5-bis[(pyridin-3-yl)ethynyl]thiophene (L) afforded the new coordination polymer {[Cd(L)(H2O)2(NO3)2]∙1.25H2O}n (1). Single-crystal X-ray diffraction analysis revealed that the CdII centre is heptacoordinated and adopts a distorted pentagonal-bipyramidal coordination geometry, with two bridging L ligands in the axial positions and water molecules and nitrate anions occupying the equatorial plane. The antiperiplanar conformation of L promotes the formation of zigzag polymeric chains, which are further assembled through O–H···O hydrogen bonds and π–π stacking interactions into a 3D supramolecular network containing solvent-accessible channels. Compound 1 was further characterised by FT-IR spectroscopy, melting point determination, and solid-state absorption and emission spectroscopy.