Synthesis, characterization, and luminescence properties of magnesium coordination networks using a thiophene-based linker

By varying the solvents and temperatures under solvothermal conditions, two new magnesium based coordination networks were synthesized using 2,5-thiophenedicarbxoylate as a linker. Mg₃(TDC)₃(DMF) ₃ [1; TDC = 2,5 thiophenedicarboxylate; space group P2₁/c, a = 17.747(4) , b = 9.805(2) , c = 21.359(4) , β = 103.13(3)°] is constructed by a combination of magnesium polyhedral trimers, which are connected by the TDC^2- linkers to form a 3-D network. Coordinated DMF molecules are present within the channels. Mg(TDC)(H₂O)₂ [2; space group Pnma, a = 7.296(4) , b = 17.760(4) , c = 6.6631(3) ] is formed by 1-D chains of magnesium octahedra connected by the TDC^2- linker. Water molecules are coordinated at the axial positions of the magnesium octahedra. Compound 1 is formed using DMF as the synthesis solvent at 180 °C, while compound 2 is formed using ethanol as the synthesis solvent at 100 °C. Both compounds show enhanced photoluminescence intensity when excited at 397 nm compared to the free TDC ligand, suggesting a charge transfer between the ligand and the magnesium metal center.