Synthesis, structure and properties of a new layered gadolinium benzenedicarboxylate with piperazine

A hydrothermal reaction of a mixture of Gd(NO3)3, 1,2-benzenedicarboxylic acid (1,2-BDC), piperazine, NaOH and water at 180 °C for three days under autogeneous pressure gave rise to a new compound of the formula [C4N2H12][Gd2(H2O)2(C6H4(COO)2)2] (I). The connectivity between GdO8 distorted dodecahedra and 1,2-BDC units gives rise to a two-dimensional structure with large apertures. The fully protonated piperazine molecule occupies the middle of these apertures. The compound has favorable CH⋯π interactions between the benzene rings of adjacent layers and shows photoluminescence at room temperature. Crystal data: monoclinic, space group = P21/c (No. 14), a = 13.1671(3) Å, b = 13.7336(3) Å, c = 11.3100(1) Å, β = 115.411(1)°, v = 1847.34(6) Å3, Z = 4, R1 = 0.0238 for 2658 reflections [I > 2σ(I)].