“Reversible” photochromism of polyoxomolybdate–viologen hybrids without the need for proton transfer

Abstract

The “reversible” photochromism of polyoxomolybdate–viologen hybrids can be achieved without proton transfer, and the weak electron-withdrawing ability of viologen favors photoreduction of Mo(vi).

Printable UV-Light Sensor for Human Eye Protection

“…Therefore, it can be concluded that the observed electron transfer is due to the intermolecular effect. However, both Bpy-Ethyl-Cl and Bpy-SO 3 have a long flexible carbon chain attached to the bipyridinium, and the molecular arrangement is more complicated and results in a weak donor–acceptor charge transfer. , Unfortunately, crystal cultivation of Bpy-Urea-Cl and Bpy-Urea-SO 3 was failed due to their poor solubility. The chemical structures of these compounds were further studied by X-ray powder diffraction (XRD), FTIR, and electron-spin resonance (ESR) measurements.…”

“…Among the photochromic compounds investigated, viologen ( N , N ′-disubstituted 4,4′-bipyridinium) derivatives have received particular attention, due to their smart and reversible color switching in different forms. The accepted mechanism for photochromic viologen is a light-induced stimulation through intermolecular electron transfer (ET) between electron-rich species (donor) and viologen (acceptor). ,− As the core factor of the photochromic rate, intermolecular forces including van der Waals forces, electrostatic forces, and conjugate effects have been widely studied. For example, phenyl-substituted bipyridine is the most extensively reported organic photochromes. − In theory, the introduction of a benzene ring reduces molecular spacing through π–π conjugation, thus promoting the ET effect.…”

“…The accepted mechanism for photochromic viologen is a light-induced stimulation through intermolecular electron transfer (ET) between electron-rich species (donor) and viologen (acceptor). ,− As the core factor of the photochromic rate, intermolecular forces including van der Waals forces, electrostatic forces, and conjugate effects have been widely studied. For example, phenyl-substituted bipyridine is the most extensively reported organic photochromes. − In theory, the introduction of a benzene ring reduces molecular spacing through π–π conjugation, thus promoting the ET effect. However, due to the larger steric hindrance between the benzene ring and bipyridine, the benzene ring is twisted by a dihedral angle with respect to the bipyridine plane and limits intermolecular π overlap and ET. , Therefore, a more reasonable structure is desired to promote ET, which will enhance the sensitivity of photochromism.…”

Optically actuating ultra-stable radicals in a large π-conjugated ligand constructed photochromic complex

“…In this respect, the electron-transfer photochromic complexes undoubtedly can be served as an ideal medium, in which naked-eye detectible color changes are easily observed and relatively stable radicals can be effectively regulated through direct light irradiation. Hitherto, lots of photochromic complexes have been prepared by using the donor-acceptor strategy, exemplified by some inorganicorganic hybrid photochromic frameworks, in which electronrich inorganic motifs like metallophosphates, polyoxomolybdates and halometallates [20][21][22] may offer electrons while electron-deficient organic groups [23][24][25] may be prone to accepting and stabilizing generated radicals. However, it is still a pivotal research challenge for extremely improving the stability of the photogenerated radicals under ambient conditions, which could greatly enhance the catalysis, luminescence and conductivity of the radical-based functional properties.…”

A Series of Polyoxometalate‐Viologen Photochromic Materials for UV Probing, Amine Detecting and Inkless and Erasable Printing

“…Up to now, only a few reports on this series were reported. [19][20][21] The POM and viologen are easier to transfer electrons due to their respective structural characteristics, which not only enhances the photochromic effect of these compounds, but also adds a member to the photochromic materials. Thus, systematic syntheses of photochromic compounds based on both POMs and viologen will expand a new progress in developing the applications of POMs.…”