Construction of a three‐dimensional supramolecular framework based on an anionic cadmium(II) coordination network and protonated dipyridine organic cations

摘要

As a class of multifunctional materials, crystalline supramolecular complexes have attracted much attention because of their unique architectures, intriguing topologies and potential applications. In this article, a new supramolecular compound, namely catena ‐poly[4,4′‐(buta‐1,3‐diene‐1,4‐diyl)dipyridin‐1‐ium [(μ 4 ‐benzene‐1,2,4,5‐tetracarboxylato‐κ 6 O 1 , O 1′ : O 2 : O 4 , O 4′ : O 5 )cadmium(II)]], {(C 14 H 14 N 2 )[Cd(C 10 H 2 O 8 )]} n or {(1,4‐H 2 bpbd)[Cd(1,2,4,5‐btc)]} n , has been prepared by the self‐assembly of Cd(NO 3 ) 2 ·4H 2 O, benzene‐1,2,4,5‐tetracarboxylic acid (1,2,4,5‐H 4 btc) and 1,4‐bis(pyridin‐4‐yl)buta‐1,3‐diene (1,4‐bpbd) under hydrothermal conditions. The title compound has been structurally characterized by IR spectroscopy, elemental analysis, powder X‐ray diffraction and single‐crystal X‐ray diffraction analysis. Each Cd II centre is coordinated by six O atoms from four different (1,2,4,5‐btc) 4? tetraanions. Each Cd II cation, located on a site of twofold symmetry, binds to four carboxylate groups belonging to four separate (1,2,4,5‐btc) 4? ligands. Each (1,2,4,5‐btc) 4? anion, situated on a position of symmetry, binds to four crystallographically equivalent Cd II centres. Neighbouring Cd II cations interconnect bridging (1,2,4,5‐btc) 4? anions to form a three‐dimensional {[Cd(1,2,4,5‐btc)] 2? } n anionic coordination network with infinite tubular channels. The channels are visible in both the [10] and the [001] direction. Such a coordination network can be simplified as a (4,4)‐connected framework with the point symbol (4 2 8 4 )(4 2 8 4 ). To balance the negative charge of the metal–carboxylate coordination network, the cavities of the network are occupied by protonated (1,4‐H 2 bpbd) 2+ cations that are located on sites of twofold symmetry. In the crystal, there are strong hydrogen‐bonding interactions between the anionic coordination network and the (1,4‐H 2 bpbd) 2+ cations. Considering the hydrogen‐bonding interactions, the structure can be further regarded as a three‐dimensional (4,6)‐connected supramolecular architecture with the point symbol (4 2 6 4 )(4 2 6 8 7·8 4 ). The thermal stability and photoluminescence properties of the title compound have been investigated.