How do substituent groups in the 5-position of 1,3-benzenedicarboxylate affect the construction of supramolecular frameworks?

Abstract

Four 1,3-benzenedicarboxylic acid derivatives, with substituted R (OH, COOH, NO2, Me) groups at the 5-position, were employed to explore their effect on the construction of supramolecular assemblies. Four coordination polymers, [Zn(OH2)(5-HO-1,3-BDC)(1,4-bpeb)]n (1), [Zn(1,3,5-HBTC)(1,4-bpeb)]n (2), {[Zn(5-NO2-1,3-BDC)(1,4-bpeb)]·2(H2O)0.5}n (3), and [Zn(5-Me-1,3-BDC)(1,4-bpeb)]n (4) (1,4-bpeb = 1,4-bis[2-(4-pyridyl)ethenyl]benzene, 5-HO-1,3-BDC = 5-hydroxy-1,3-benzenedicarboxylate, 1,3,5-H3BTC = 1,3,5-benzenetricarboxylate, 5-NO2-1,3-BDC = 5-nitro-1,3-benzenedicarboxylate, 5-Me-1,3-BDC = 5-methyl-1,3-benzenedicarboxylate) were prepared by the hydrothermal reactions of Zn(NO3)2·6H2O with 1,4-bpeb and 5-HO-1,3-H2BDC, 1,3,5-H3BTC, 5-NO2-1,3-H2BDC or 5-Me-1,3-H2BDC. All these compounds were characterized by elemental analysis, IR, powder X-ray diffraction, and single-crystal X-ray diffraction. The structure of 1 has a 3D H-bonded structure derived from linking 1D comb-like [Zn(OH2)(5-HO-1,3-BDC)(1,4-bpeb)]n chains via intermolecular H-bonding interactions between the coordinated H2O molecule and 1,4-bpeb or one COO− group and between the OH group and the other COO− group. 2 has a 3D H-bonded net based on holding 2D [{Zn2(1,3,5-HBTC)2}4]n layers through intermolecular H-bonding interactions between 1,4-bpeb and the uncoordinated COOH group. 3 could be considered as a 6-fold interpenetrating 3D H-bonded supramolecular framework constructed by linking 2D [Zn4(5-NO2-1,3-BDC)4(1,4-bpeb)4]n networks through intermolecular H-bonding interactions between the water solvent molecules and the NO2 group. 4 has a 3-fold interpenetrating 3D framework in which each 2D (4,4) [Zn4(5-Me-1,3-BDC)4(1,4-bpeb)4]n network is interpenetrated by two other equivalent nets. The Schlafli symbols for the four supramolecular frameworks are 41263, (4·62)2(426687), (63)(658) and 4462, respectively. The thermal stability and photoluminescent properties of 1–4 were also investigated.