A three-dimensional supramolecular framework based on the interlinkage of an interpenetrating diamondoid coordination network

In the development of coordination-driven crystalline materials, O-and N-atom donors from carboxylate and pyridyl-based ligands are widely used classes of multidentate bridging ligands composed of several terminal coordinating groups linked by either rigid or flexible spacers. The rigidity of the ligands can play a vital role in the determination of the structures formed. A new Cd-II supramolecular compound, namely poly[mu-adipato-kappa O-2(1):O-4-mu-adipato-kappa O-4(1), O-10:O-4, O-4'-diaquabis[mu-1,4-bis(pyridin-4-yl)-1,3-butadiene-kappa(2) N: N']dicadmium(II)], [Cd-2(C6H8O4)(2)(C14H12N2)(2)(H2O)(2)](n), (I), has been synthesized by the selfassembly of Cd(NO3)(2)center dot 4H(2)O, adipic acid (hexane-1,6-dioic acid; H2adp) and the dipyridyl ligand 1,4-bis(pyridin-4-yl) buta-1,3-diene (1,4-bpbd) under hydrothermal conditions. Single-crystal X-ray diffraction analysis reveals that each Cd II centre is located in a distorted octahedral coordination environment, coordinated by one water O atom, three carboxylate O atoms from two different adp(2) ligands and two N atoms from two different 1,4-bpbd ligands. The Cd(H2O) units are interconnected by the mu(2), kappa(2)-adp(2-), mu(2), kappa(4)-adp(2) and 1,4-bpbd ligands, which lie across centres of inversion, to give a 6 6 -dia network. Large cavities within a single diamondoid network permit the mutual threefold interpenetration of crystallographically equivalent frameworks. Hydrogenbonding interactions between the coordinated water molecules and adp(2) carboxylate O atoms anchor the interpenetrating networks into a unique three-dimensional supramolecular structure. Topologically, taking the coordinated water molecules and Cd II centres as nodes, the whole architecture can be simplified as a binodal (3,7)-connected supramolecular framework. The identity of (I) was further characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis and powder X-ray diffraction. The solid-state photoluminescence properties of (I) were also investigated.