Advanced Science (Aug 2024)

Reversible Optical Switching of Polyoxovanadates and Their Communication via Photoexcited States

  • Eric Vogelsberg,
  • Jan Griebel,
  • Iryna Engelmann,
  • Jens Bauer,
  • Florian Taube,
  • Björn Corzilius,
  • Stefan Zahn,
  • Axel Kahnt,
  • Kirill Yu. Monakhov

DOI
https://doi.org/10.1002/advs.202401595
Journal volume & issue
Vol. 11, no. 30
pp. n/a – n/a

Abstract

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Abstract The 2‐bit Lindqvist‐type polyoxometalate (POM) [V6O13((OCH2)3CCH2N3)2]2– with a diamagnetic {V6O19} core and azide termini shows six fully oxidized VV centers in solution as well as the solid state, according to 51V NMR spectroscopy. Under UV irradiation, it exhibits reversible switching between its ground S0 state and the energetically higher lying states in acetonitrile and water solutions. TD‐DFT calculations demonstrate that this process is mainly initialized by excitation from the S0 to S9 state. Pulse radiolysis transient absorption spectroscopy experiments with a solvated electron point out photochemically induced charge disproportionation of VV into VIV and electron communication between the POM molecules via their excited states. The existence of this unique POM‐to‐POM electron communication is also indicated by X‐ray photoelectron spectroscopy (XPS) studies on gold‐metalized silicon wafers (Au//SiO2//Si) under ambient conditions. The amount of reduced vanadium centers in the “confined” environment increases substantially after beam irradiation with soft X‐rays compared to non‐irradiated samples. The excited state of one POM anion seems to give rise to subsequent electron transfer from another POM anion. However, this reaction is prohibited as soon as the relaxed T1 state of the POM is reached.

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