Synthesis, Structure, and Crystallization Study of a Layered Lithium Thiophene-Dicarboxylate

A layered lithium carboxylate, Li₄[C₄H₂S­(CO₂)₂]₂[C₃H₇NO]₂, crystallizes under solvothermal conditions (160–180 °C) from lithium nitrate and the ligand 2,5-thiophenedicarboxylate in <i>N</i>,<i>N</i>-dimethylformamide as solvent. Single-crystal X-ray diffraction (<i>Pbca a</i> = 10.0216(18) Å, <i>b</i> = 18.327(4) Å, <i>c</i> = 24.871(5) Å) shows that the material is constructed from lithium-centered tetrahedral units linked by edge- and corner-sharing to give tetrameric clusters. These inorganic building units are linked in two dimensions by the bidentate ligand to give a layered structure in which additionally coordinated dimethylformamide projects into the interlayer region. A study of the crystallization of the material using time-resolved in situ energy-dispersive X-ray diffraction reveals that the material crystallizes directly from solution at the reaction temperature following an induction period. Analysis of the crystallization curves suggests that nucleation does not extend far into the crystallization period and that crystal growth is one-dimensional. These findings are corroborated by the observation of relatively large, anisotropic crystals by scanning electron microscopy