Metal nuclearity modulated four-, six-, and eight-connected entangled frameworks based on mono-, Bi-, and trimetallic cores as nodes

To investigate the relationship between network connectivity and metal nuclearity, we designed and synthesized a series of three-dimensional (3D) entangled coordination frameworks based on different metal cores, namely [Zn-2(bdc)(2)(L)(2)]center dot 2H(2)O (1), [Zn(bdc)(L)(0.5)] (2), [Zn(oba)(L)(0.5)] (3) and [Cd-3(bdc)(3)(L)(2)(H2O)(2)] (4) by self-assembly of d(10) metal salts with the flexible long-chain ligand 1,4-bis(1,2,4-triazol-1-yl)butane (L), and with the rigid and nonrigid aromatic dicarboxylate ligands 1,4-benzenedicarboxylate (bdc) and 4,4'-oxybis(benzoate) (oba). Compound 1 exhibits a threefold interpenetrated diamondoid array typically based on a tetrahedral second building unit (SBU) at a single Zn center. Compound 2 adopts a threefold interpenetrated a-polonium-type network that is built from bimetallic cores as six-connected vertices. The structure of 3 also consists of dinuclear units; it comprises a novel (3,4)-connected threefold interpenetrated net with complex (4 center dot 6 center dot 10)(4 center dot 6(2)center dot 10(3)) topology when single zinc centers act as four-connected nodes (or the alpha-Po topology if dinuclear units are considered as six-connected nodes). Compound 4, derived from a crosslinked fivefold interpenetrated diamond-like substructure, is an unusual example of a self-penetrating coordination framework displaying an unprecedented eight-connected 4(20)6(8) topology with trinuclear cadmium clusters as eight-connected nodes which, to our knowledge, not only defines a new topology for eight-connected coordination networks, but also represents the highest connected topology presently known for self-penetrating systems. Detailed structural comparison of these complexes indicates that the increase in metal nuclearity induces the progressive increase in the connectivities of the ultimate nets: that is, the metal nuclearity plays a significant role in tuning the connectivity of a specific network. The thermal and luminescent properties of these compounds are discussed.