Two cadmium coordination polymers based on tris(p-carboxyphenyl) phosphane oxide with highly selective sensing of nitrobenzene derivatives and Hg2+ cations

Two coordination polymers (CPs), namely, [Cd-1/2(L) (1/3)(bib)(1/2)(H2O)](n) (1) and {[Cd-2(HL)(2)(bibp)(2)]center dot 3H(2)O}(n) (2), have been assembled from the tripodal ligand tris.p-carboxyphenyl) phosphane oxide (H3L) with the help of 1,4-bis(imidazol-1-yl) benzene (bib) or 4,4'-bis(imidazol-1-yl) biphenyl (bibp). Structural analyses revealed that complex 1 is an unprecedented (3,4)-connected {10(3)}(2){10(6)}(3) net with 2D [Cd-3(L)(2)](n) sheets arranged in an ABCA' B' C' A '' B '' C '' fashion. Complex 2 exhibits 3-fold interpenetrated sheets with a 4-connected {4(4).6(2)}sql sheet. Structural comparison reveals that the length of bis.imidazole) ancillary linkers plays a critical role in determining the structures and topologies. To our delight, fluorescence measurements show that the two Cd(II) CPs can selectively and sensitively detect Hg2+ cations and nitrobenzene derivatives (nitrobenzene, p-nitrotoluene, p-nitroaniline, and p-nitrophenol), which suggests that the two Cd(II) CPs are promising bifunctional luminescence sensor materials that could sense metal ions and small organic molecules.