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{HP₂W^VW^VI₁₇O₆₂}·4H₂O (1), {Cd(dbt)₂(H₂O) (HP₂W^VW^VI₁₇O₆₂)}{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.

Graphical Abstract

Keywords:

• POMs
• S-containing ligand
• hydrothermal syntheses
• electrochemical properties
• fluorescence sensors to Hg²⁺

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Financial support of this research by the National Natural Science Foundation of China (Nos. 21571023 and 21101015).