Synthesis, crystal structures, and fluorescence properties of six complexes with thiophene derivative carboxylic acid ligand

The crystallization of 2,3-dihydro-thieno[3,4-b][1,4] dioxine-5,7-dicarboxylic acid (H2tddc) with divalent transitional metal (Co, Ni, Zn, Cd) or with tervalent lanthanide metal (Sm) and with mixed ligand 4,4′-bipyridine (4,4′-bipy) or 1,10-phenanthroline (1,10-phen) formed six new complexes: [Co(C8H4O6S) · 3H2O] (1), [Co(C8H4O6)(1,10-phen)(H2O)] · H2O (2), [Ni(C8H4O6S)(4,4′-bipy)(H2O)] · 3H2O (3) [Sm(C8H4O6S)(NO3)(H2O)4] · 2H2O (4), [Zn(C8H4O6S)(H2O)3] (5), and [Cd2(C8H4O6S)2(4,4′-bipy)2] (6). The structures of these six crystals have been characterized by single-crystal X-ray diffraction analyses, which revealed that complexes 1, 4, 5 are all one-dimensional chain structures and they self-assemble into three-dimensional super-molecules via the hydrogen bond interactions and π–π stacking interactions, 2 is also a one-dimensional chain structure but still self-assembles into one-dimensional double-chains, the complex 3 has two-dimensional undulating parallelogram grid structure extended along the bc-plane, the crystal of 6 is a 3D threefold interpenetration topology framework with 46638 nodes. The photoluminescent properties of the H2tddc ligand and the six compounds have been measured in the solid state at room temperature. Free ligand has no luminescence, while its complexes 1, 4, and 6 all exhibit intense photoluminescence which implies that these complexes may be excellent candidates for potential photoactive materials.

Graphical abstractThe six coordination polymers with H2tddc ligand have been synthesized. Their structures were determined by X-ray diffraction and fluorescent properties have been investigated.Figure optionsDownload full-size imageDownload as PowerPoint slide