Novel Cadmium(II) Phosphonatophenylsulfonate Cluster Compounds: Syntheses, Structures, and Luminescent Properties

Hydrothermal reactions of cadmium(II) salt with m-phosphonophenylsulfonic acid (H3L) and 1,10-phenanthroline
(phen) or 4,4‘-bipyridine (bipy) led to three novel cadmium(II) phosphonatephenylsulfonates, namely, [Cd4(L)2(phen)6(Cl)2(H2O)2]·14H2O (1), [Cd6(L)4(phen)8]·14H2O (2), and [Cd3(L)2(bipy)3(H2O)6]·4H2O (3). Compound 1 contains a tetranuclear cadmium(II)
cluster in which four cadmium(II) ions are bridged by two tetradentate phosphonate groups. Compound 2 features a hexanuclear
cadmium(II) cage in which six cadmium(II) ions are bridged by one tetradentate and three pentadentate phosphonate groups. The
structure of compound 3 features a novel 3D network based on 1D chains of [Cd3(L)2] cross-linked by 4,4‘-bipy ligands; its topological
structure is similar to that of CdSO4. Compounds 1−3 exhibit broad blue fluorescence emission bands at 408, 410, and 396 nm,
respectively.