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 Schläfli 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.