Two cadmium coordination polymers based on tris(p-carboxyphenyl) phosphane oxide with highly selective sensing of nitrobenzene derivatives and Hg2+ cations†
Abstract
Two coordination polymers (CPs), namely, [Cd1/2(L)1/3(bib)1/2(H2O)]n (1) and {[Cd2(HL)2(bibp)2]·3H2O}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 {103}2{106}3 net with 2D [Cd3(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 {44·62}-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.