Scorpion-shaped carboxylate ligand tailored molecular square, bilayer, self-threading and (3,6)-connected nets

A novel designed scorpion-shaped 5-oxyacetateisophthalic acid ( H(3)OABDC) was used to construct a series of luminescent metal-organic frameworks, namely [Zn-2( HOABDC)(2)( phen)(2)( H2O)(2)](n)center dot nH(2)O (1), [Zn-2(OABDC)(4,4'- bipy)(mu(2)- OH)(H2O)](n)center dot 4/3nH(2)O ( 2), [Cd-3( OABDC)(2)( 4,4'- bipy)(4)(H2O)(4)](n) center dot 2nH(2)O (3), [Cd-2(OABDC)(phen)(2)(mu(3)- OH)](n)center dot 1/3nH(2)O (4), and [Zn-8( OABDC)(4)( 2,2'- bipy)(4)(mu(2)-OH)(4)](n)center dot 2nH(2)O (5) ( bipy = bipyridine, phen = 1,10-phenanthroline). Complex 1 features a discrete molecular square and pi - pi and C-H center dot center dot center dot pi interactions between molecular squares give rise to a 2D sheet. Complex 2 shows an unusual 2D bilayer architecture with ( 3,5)- connected topology. A prominent structural feature in 3 is the self-threading 2D layered structure. Both 4 and 5 exhibit ( 3,6)- connected topology. In 4, an extraordinary folded four-step-ladder Cd-4(OH)(2) unit acts as 6-connected node and the framework is 2D ( 3,6)- connected net. While in 5, the Zn2( OH) unit adopts octahedral geometry and the whole framework features a 3D ( 3,6)- connected rutile (rtl) topology. Photoluminescence studies revealed that these complexes are interesting blue, green and orange luminescent materials. The thermal stabilities of these complexes are also discussed.