Layered supramolecular compounds with 3-nitrophthalic acid assembled via hydrogen bonding

Layered supramolecular compounds containing different patterns of hydrogen bonds, [C₄H₁₂N₂]-(HL)₂ (I) and [YL(HL)(H₂O)₃]·2H₂O (II) (H₂L=O₂NC₆H₃ (CO₂H)₂, 3-nitrophthalic acid) have been synthesized and characterized by elemental analysis, IR spectra and X-ray single crystal diffraction. Compound I consists of one diprotonated piperazine cation and two 2-carboxy-6-nitrobenzoate anions. The anions are linked by the strong O-H⋯O hydrogen bonds into infinite chains, which further extend to sheets by the N-H⋯O interactions between the anion chains and cations. The 2D layers are assembled into 3D supramolecular network via the weak forces from the adjacent layers. Complex II also has a layered supramolecular architecture packed by the 2D layers, which are constructed by the dinuclear rare-earth complexes with 3-nitrophthalate via intermolecular hydrogen bonds. There are two crystallization water molecules filling up each of the rhombic pores of the network. Compound I crystallizes in the monoclinic system, space group P2_1/c with parameters a=1.3176(3) nm, b=1.1096(2) nm, c=0.75950(15) nm, β=97.14(3)°, V=1.1017(4) nm₃, Z=4, μ=0.129 mm^-1, D_c=1.533 Mg/m₃. Complex II crystallizes in triclinic system, space group P-1 with a=0.81262(16) nm, b=0.86942(18) nm, c=1.5011(3) nm, α=99.84(3)°, β=91.26(3)°, γ=104.55(3)°, V=1.0091(4) nm₃, Z=1, μ=2.983 mm^-1, D_c=1.910 Mg/m₃.