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

Abstract

The crystallization of 2,3-dihydro-thieno[3,4- b][1,4] dioxine-5,7-dicarboxylic acid (H 2tddc) 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(C 8H 4O 6S) · 3H 2O] ( 1), [Co(C 8H 4O 6)(1,10-phen)(H 2O)] · H 2O ( 2), [Ni(C 8H 4O 6S)(4,4′-bipy)(H 2O)] · 3H 2O ( 3) [Sm(C 8H 4O 6S)(NO 3)(H 2O) 4] · 2H 2O ( 4), [Zn(C 8H 4O 6S)(H 2O) 3] ( 5), and [Cd 2(C 8H 4O 6S) 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 4 66 38 nodes. The photoluminescent properties of the H 2tddc 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.