Five metal–organic frameworks based on isomeric chloro-functionalized azobenzenedicarboxylic acids

Abstract

Chloro-functionalized azobenzenedicarboxylic acids were prepared and their 2D and 3D metal–organic frameworks (MOFs), namely {[Co(4,4′-Cl2abdc)(DMA)]·H2O}n (1), {[Cu(4,4′-Cl2abdc)(DMA)]·G}n (2), {[Zn(4,4′-Cl2abdc)(DMSO)]·H2O}n (3), {[Mn(3,3′-Cl2abdc)(DMA)]·0.5DMA}n (4) and {[Cu(3,3′-Cl2abdc)(DMA)]·0.5DMA}n (5), (4,4′-H2Cl2abdc: 3,3′-dichloro-4,4′-azobenzenedicarboxylic acid, 3,3′-H2Cl2abdc: 4,4′-dichloro-3,3′-azobenzenedicarboxylic acid), were systematically synthesized to investigate the positional isomer effect on the structures and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. The X-ray results demonstrate that 1 and 3 possess a 2-fold interpenetrated 3D + 3D → 3D framework with the seh-4,6-Imma topology, while 2, 4 and 5 display 2D layers. In 1 and 3, infinite [M2O(COO)2] rod units occur, whilst well-known binuclear [M2(COO)4] units are observed in the other compounds. Compounds 4 and 5 display a lower dimension due to the cis-position of the carboxylate groups of 3,3′-Cl2abdc as compared to compounds 1–3, prepared with 4,4′-Cl2abdc. Moreover, the thermal, photoluminescence and optical properties of the compounds were also examined.