Two- and three-dimensional coordination polymers based on zinc(II) and furan-2,5-dicarboxylic acid: structure variation due to metal-to-linker ratio.

Two ZnII-based coordination polymers (CPs) were synthesized by the hydrothermal method, using Zn(NO3)2·6H2O and furan-2,5-dicarboxylic acid (FDCA) in dimethylformamide (DMF) solvent, at 95 °C. Poly[tetrakis(dimethylazanium) [tetrakis(μ2-furan-2,5-dicarboxylato-κ2O2:O5)dizinc(II)]], {(C2H8N)4[Zn2(C6H2O5)4]}n or {[DMA]4[ZnII2(FDC)4]}n (DMA = dimethylazanium and FDC = furan-2,5-dicarboxylate), (1), was obtained with a 1:1 molar ratio of ZnII and FDCA. It crystallized in the monoclinic space group C2/c. Coordinated by ZnII ions, FDC2- ligands form 21 double-stranded helices propagating along the b axis. The helices are interconnected and extend laterally in the a direction, forming a two-dimensional (2D) sheet-like network. The 2D sheets are stacked along the c direction without interconnections. DMA cations are cocrystallized in (1) and are hydrogen bonded with carboxylate O atoms of the FDC2- ligands. The hydrogen-bonding pattern consists of R22(4) and R22(10) motifs alternating in a chain. Poly[bis(dimethylazanium) [bis(μ4-furan-2,5-dicarboxylato-κO2:κO2':κO5:κO5)bis(μ3-furan-2,5-dicarboxylato-κO2:κO2':κO5)dizinc(II)] dimethylformamide 3.08-solvate], {(C2H8N)2[Zn2(C6H2O5)4]·3.08C3H7NO}n or {[DMA]2[ZnII3(FDC)4]·3.08DMF}n, (2), was obtained with a 1:2 molar ratio of ZnII and FDCA. It crystallized in the monoclinic space group P21/c, forming a three-dimensional network. The pores are filled with DMA cations and DMF solvent molecules.