Reversible proton-switchable fluorescence controlled by conjugation effect in an organically-functionalized polyoxometalate

Abstract

A novel monosubstituted organoimido hexamolybdate containing 6-nitroquinoline moiety has been successfully synthesized. This organically-functionalized polyoxometalate exhibits proton-induced switchable fluorescence property in aqueous acetonitrile solution at room temperature. Experimental and theoretical investigations of this reversible “on” and “off” switching mechanism have been carried out, and it is found that the protonation and deprotonation at the heterocyclic nitrogen atom within quinoline fragment leads to the breaking and reformation of the conjugation through strong d-π interaction between the hexamolybdate anionic cluster and the quinoline moiety, resulting in “on” and “off” luminescence signal.

Insights into organic–inorganic hybrid molecular materials: organoimido functionalized polyoxomolybdates

“…The organo functionalized polyoxometalates-based sensors have shown interesting proton-responsive switchable fluorescence activity. 90 The same group has also investigated the degradable organoimido derivative of hexamolybdate with cleavable organic group. This hybrid POM shows good pharmacodynamics in human malignant glioma cells (U251) as well as the ability to cross the blood–brain barrier and less toxic behaviour in rat pheochromocytoma (PC12) cells.…”

Two new transition metal–organic frameworks as multiresponsive fluorescence sensors for detecting Fe3+, Cr2O72− and TNP

“…Metal-organic frameworks (MOFs) are promising crystalline porous materials, which are self-assembled by metal ions or clusters and organic linkers containing binding sites. [16][17][18][19][20] Due to their structural diversity and designability, ultra-high specific surface area and chemical stability, [21][22][23] MOFs have been applied in many fields, such as magnetism, 24,25 catalysis, 26 fluorescence sensing, [27][28][29][30][31][32] gas adsorption and storage, [33][34][35][36] proton conduction, [37][38][39][40][41][42] etc. Among many applications, luminescent MOFs (LMOFs) based on transition metals have attracted wide attention due to their low cost and potential as a simple and effective fluorescent sensing material.…”

TiO2/CsPbBr3 Quantum Dots Coupled with Polyoxometalate Redox Clusters for Photoswitches

“…On–off fluorescence switching of inorganic, , organic, , and hybrid , materials has gained considerable attention because such photoswitches have potential applications in super-resolution imaging, , single particle/molecule memory, fluorescent patterning, , and biosensing . These applications rely on reversible fluorescence changes in the materials, which coincide with alterations of the optical and physicochemical properties in response to light stimulation.…”