Photoreduction of Methyl Viologen in Zeolite X

Abstract

The photoreduction of methyl viologen (MV2+) was examined in zeolite X. A series of alkali metal ion-exchanged zeolite X materials with ion-exchanged methyl viologen was photoionized with 320 nm light at room temperature in the absence of any reducing counteranion. Photoreduction of methyl viologen containing alkali metal ion-exchanged zeolite X results in the formation of methyl viologen cation radicals (MV•+). The radicals were identified by electron spin resonance (ESR). Upon irradiation at room temperature the samples turn light blue in color and a single line ESR spectrum characteristic of the methyl viologen radical cation is observed. The photoyield depends on the nature of the alkali metal ion-exchanged into the zeolite framework. The photoyield increases in the order Li−X/MV2+ < Na−X/MV2+ < K−X/MV2+ < Rb−X/MV2+ < Cs−X/MV2+. The donor strength of the zeolite framework increases in the order Li−X < Na−X < K−X < Rb−X < Cs−X. Thus, the electron donor is suggested to be the anionic aluminosilicate framework of the host zeolite. This is supported by a linear correlation of the photoyields of alkali metal ions exchanged into zeolite X with Sanderson's partial charges on the framework oxygens.

Dissipation of charge on MALDI‐TOF polymeric chips using an electron‐acceptor: analysis of proteins

“…The observed color changes are in accordance with previously observed color changes of MV 2+ upon irradiation with UV or visible light 19, 20. MV photochemical reactions have been described in zeolite X19 and in silica‐gel matrix20; however, no such photoreduction of MV 2+ has been described in crystalline organic acids (a matrix in this study) with a UV abs. maximum close to the UV light wavelength.…”

Laser flash photolysis study of anthracene/viologen charge transfer complex in non-polar, dealuminated zeolites

“…[1][2][3][4][5][6][7][8][9][10][11] The current accepted rationalization assumes that the zeolite is playing a '' passive '' role, merely defining a reaction space with considerable polarity. However, sufficient examples have been more recently reported in which the zeolite lattice is able to intervene in photoinduced electron transfer (ET), either as electron acceptor or donor [12][13][14][15][16][17]22 Particularly, it has been established that methyl viologen (MV þþ ) in its excited state can abstract one electron from alkali-exchanged faujasites given MV þ decaying in the ms time scale. [13][14][15][16]18 On the other hand, biphenyl, anthracene (AN) and other aromatics adsorbed on faujasites also generate radical cations upon laser excitation.…”

“…However, sufficient examples have been more recently reported in which the zeolite lattice is able to intervene in photoinduced electron transfer (ET), either as electron acceptor or donor [12][13][14][15][16][17]22 Particularly, it has been established that methyl viologen (MV þþ ) in its excited state can abstract one electron from alkali-exchanged faujasites given MV þ decaying in the ms time scale. [13][14][15][16]18 On the other hand, biphenyl, anthracene (AN) and other aromatics adsorbed on faujasites also generate radical cations upon laser excitation. 19,20 Importantly, AN and MV þþ are among the CT complexes whose charge separated state was observed to decay in the ms timescale.…”

Layer‐by‐layer films based on charge transfer interaction of ϕ‐conjugated poly(dithiafulvene) and incorporation of gold nanoparticles into the films

“…A sharp signal (g ¼ 2.005) was assigned to the anion radical of the viologen unit. 20 A broad singlet line (g ¼ 2.011) is almost the same as that of the ESR signal of the TTF-TCNQ complex.…”