Three Novel Zinc(II) Sulfonate−Phosphonates with Tetranuclear or Hexanuclear Cluster Units

Hydrothermal reactions of zinc(II) carbonate with m-sulfophenylphosphonic acid (m-HO3S-Ph-PO3H2) and 1,10-phenanthroline (phen) or 4,4'-bipyridine (bipy) lead to three novel zinc(II) sulfonate-phosphonates, namely, [Zn(phen)3]2[Zn4(m-O3S-Ph-PO3)4(phen)4].20H2O (1), [Zn6(m-O3S-Ph-PO3)4(phen)8].11H2O (2), and [Zn6(m-O3S-Ph-PO3)4(bipy)6(H2O)4].18H2O (3). Compound 1 contains a tetranuclear zinc(II) cluster anion in which four Zn(II) ions are bridged by two tetradentate and two bidentate phosphonate groups, and the four negative charges of the cluster are compensated by two [Zn(phen)3]2+ cations. Compound 2 features a hexanuclear zinc(II) cluster in which the same tetranuclear cluster of 1 is bridged with two additional Zn(II) ions. The structure of 3 features a porous 3D network based on hexanuclear zinc(II) units of [Zn6(m-O3S-Ph-PO3)4] interconnected by 4,4'-bipy ligands. The hexanuclear cluster in 3 is different from that in 2 in that all four phosphonate groups in 3 are tridentate bridging. Compounds 1, 2, and 3 exhibit broad blue fluorescent emission bands at 378, 409, and 381 nm, respectively.