A series of Wells-Dawson and Keggin-based compounds with uncoordinated S donors as fluorescence sensors to Hg2+

Abstract

Through using a S-containing ligand 2,2’-dimethyl-4,4’-bithiazole (dbt), a series of Wells-Dawson and Keggin-based compounds, {Zn(dbt)3}{Zn(dbt)2(H2O)}2{HP2WVWVI17O62}·4H2O (1), {Cd(dbt)2(H2O) (HP2WVWVI17O62)}{Cd(dbt)3}{Cd(dbt)2(H2O)}·13H2O (2), {Cd2(dbt)4Cl} {PW12O40} (3) and {Cd2(dbt)4}{SiW12O40} (4), were synthesized under hydrothermal conditions and structurally characterized. In 1, there are three dissociated subunits: Wells-Dawson anion, {Zn(dbt)3}2+ and {Zn(dbt)2(H2O)}2+. In 2, the mono-supporting Wells-Dawson anions exhibit abundant hydrogen bonding interactions with discrete {Cd(dbt)3}2+ and {Cd(dbt)2(H2O)}2+ mononuclear coordination complexes, constructing a supramolecular layer. Compound 3 has a binuclear Cd cluster {Cd2(dbt)4Cl}4+ with a Cl as a bridging atom. The Keggin anions link these binuclear Cd clusters alternately to build a 1D chain. In 4, a pair of {Cd(dbt)2}2+ subunits connect adjacent Keggin anions and a 1D chain is formed. In these four compounds, only the N donors coordinate with Zn or Cd and the S atoms are uncoordinated. These compounds show good fluorescence sensing performance to Hg2+. We also studied the electrochemical and photocatalytic properties of 1–4. These compounds also can act as electrochemical sensors for the detection of nitrite.