pH-dependent solvothermal formation of two different 3D multiple interpenetrating nets from the same components of Zn(NO3)2, 1,3-benzenedicarboxylate and 1,4-bis[2-(4-pyridyl)ethenyl]benzene

Abstract

Hydrothermal reactions of Zn(NO₃)₂·6H₂O with 1,3-benzenedicarboxylic acid (1,3-H₂BDC) and 1,4-bis[2-(4-pyridyl)ethenyl]benzene (1,4-bpeb) under pH = 2.5 or 8.0 gave rise to two coordination polymers {[Zn₆(μ-OH₂)(1,3-BDC)₆(1,4-bpeb)₄]·MeCN}_n (1) and {[Zn₈(1,3-BDC)₈(1,4-bpeb)₄]·2H₂O}_n (2). Both compounds were characterized by elemental analysis, IR, powder X-ray diffraction, and single-crystal X-ray diffraction. Compound 1 has two types of dinuclear zinc cores as nodes and displays an intriguing three-dimensional (3D) three-fold interpenetrating (4,6)-connected network with an unprecedented (3²6⁴)(3²4⁴6⁸7)₂ topology. Compound 2 exhibits an unusual 3D two-fold interpenetrating pcu net with a Schlafli symbol 4¹²6³. The formation of 1 and 2 provided an interesting insight into the effect of pH values on the construction of coordination polymers under solvothermal conditions. Thermal stability and photoluminescence properties of 1 and 2 were also investigated.