Ligand geometry-driven formation of different coordination polymers from Zn(NO3)2, 1,4-bpeb and phenylenediacetic acids

Abstract

The hydrothermal reactions of Zn(NO₃)₂·6H₂O with 1,4-bis[2-(4-pyridyl)ethenyl]benzene (1,4-bpeb), NaOH, and 1,4-phenylenediacetic acid (1,4-H₂PDA), 1,3-phenylenediacetic acid (1,3-H₂PDA) or 1,2-phenylenediacetic acid (1,2-H₂PDA) afforded three coordination polymers {[Zn(1,4-PDA)(1,4-bpeb)]·2H₂O}_n (1), [Zn(1,3-PDA)(1,4-bpeb)]_n (2) and [Zn₄(μ-OH)₂(1,2-PDA)₃(1,4-bpeb)₂]_n (3), respectively. All these compounds were characterized by elemental analysis, IR, powder X-ray diffraction, and single-crystal X-ray diffraction. 1 exhibits a five-fold interpenetrating 3D diamondoid framework constructed by linking Zn atoms with trans-1,4-PDA and trans-trans-trans-1,4-bpeb ligands. 2 has a 2D (4,4) network formed by connecting dinuclear [Zn₂(1,3-PDA)₂] (1,3-PDA serving as a trans conformation) units with trans-cis-trans-1,4-bpeb ligands. 3 could be considered as a 2D 5-connected network derived from linking tetranuclear [Zn₄(μ-OH)₂(1,2-PDA)₃] (1,2-PDA acting as cis and trans conformations) units via trans-cis-trans-1,4-bpeb bridges. The results provided some insight into the ligand geometry-driven assembly of coordination polymers. Thermal stability and photoluminescent properties of 1–3 were also investigated.