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Solvent mediated reversible solid state photochromism of {Mo72Fe30} Keplerate
Kesar Tandekar1, Neeraj Kumar Mishra1, Sabbani Supriya1
1School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067, India. ssabbani@mail.jnu.ac.in sabban07@gmail.com.
Sunlight irradiation of Keplerate crystals in N,N-dimethylformamide (DMF) induces reversible photochromism. This solvent-driven process involves the reduction of MoVI to MoV, changing crystals from yellow to green.
Area of Science:
- Inorganic Chemistry
- Materials Science
- Photochemistry
Background:
- Keplerate polyoxometalates are complex nanoscale inorganic clusters with unique structural and electronic properties.
- Photochromism, the reversible change of color upon light irradiation, is a phenomenon of interest for advanced materials.
- Solvent-mediated activation of solid-state reactions offers novel pathways for material functionalization.
Purpose of the Study:
- To investigate the photochromic behavior of a specific Keplerate compound, [Mo72Fe30O252(CH3COO)12{Mo2O7(H2O)}2{H2Mo2O8(H2O)}(H2O)91]·150H2O (1).
- To determine the role of N,N-dimethylformamide (DMF) solvent in the photochromic process.
- To elucidate the underlying mechanism of the observed color change.
Main Methods:
- Synthesis and characterization of the Keplerate compound (1).
- Irradiation of the compound with sunlight in the presence of DMF.
- Visual observation and spectroscopic analysis of color changes.
Main Results:
- Yellow rhombohedral crystals of compound 1 exhibited reversible photochromism upon wetting with DMF and subsequent sunlight irradiation.
- The formation of green-colored crystals (1red) was observed, indicating a significant color change.
- The photochromic activity was exclusively dependent on the presence of DMF, highlighting a solvent-driven effect.
Conclusions:
- The observed photochromism is attributed to the reduction of molybdenum centers from Mo(VI) to Mo(V) states.
- Compound 1 demonstrates sunlight-activated, solvent-driven photoactivity, a unique characteristic for Keplerate materials.
- This study presents a novel example of reversible solid-state photochromism in polyoxometalates activated by external stimuli.
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