Acridines, Deazaflavins, Andtris(2,2'‐bipyridine)ruthenium as Catalysts for Photoproduction of Hydrogen From Organic Compounds

Abstract

Abstract— The previously reported (Krasna, 1979) photoproduction of hydrogen from organic compounds in the presence of methyl viologen and platinum, catalyzed by proflavin, has now been accomplished with other photocatalysts. The acridine derivatives acriflavin, acridine yellow and acridine orange were active catalysts, whereas 9‐aminoacridine was not. The reaction was similar to the proflavin catalyzed reaction with respect to electron donor specificity and mechanism. Tris(2,2'‐bipyridine)ruthenium (II) also replaced proflavin and the reaction was similar in most respects to that catalyzed by proflavin except that rris(2,2'‐bipyridine)ruthenium catalysis was most effective at alkaline pH values. The deazaflavins, deazaribofiavin and 3,10‐dimethyl‐5‐deazaisoalloxazine, were more active than proflavin, particularly at alkaline pH values. Deazaflavins catalyzed photoproduction of hydrogen from a variety of compounds that were inactive with acridines and fra(2,2'‐bipyridine)ruthenium. This includes carboxylic acids, amines, sugars and amino acids. This system may have potential for hydrogen production as a means of solar energy conversion.

In situ observation of the initial adsorption process of heptylviologen cation radicals by slab optical waveguide spectroscopy synchronized with electrode potential modulation methods

“…Recent studies have been performed for the application of viologens to herbicides, electron mediators and catalysts [18][19][20]. 1,1 0 -Diheptyl-4,4 0 -bipyridinium (heptylviologen; HV) is usually studied for electrochromic applications because its one-electron reduction of the dication HV 2+ to the mono-cation radical salt HV +AE in aqueous solutions can form a violet colored precipitate on electrode surfaces [21][22][23].…”

On the One and Two-Electron Oxidations of Water-Soluble Zinc Porphyrins in Aqueous Media

“…Earlier, we have demonstrated [4 a] that water-soluble zinc porphyrins serve very well as photosensitizers for H2-evolution from water via reactions (1) and (2). Towards further exploration of their utility in reaction (3), herein, we de-scribe our studies on one and two-electron oxidation of these porphyrins in water. Data are presented on the half-wave potentials, their spectra and electrochemical reversibility for one and two-electron oxidations of one cationic (ZnTMPyP) and two anionic (ZnTPPS and ZnTPPC) porphyrin systems.…”

“…4D+ + 2H20 >*4D + 02+4H+ (3) is receiving scrutiny [1][2][3][4][5] all over the world. Partial success has been achieved with photosensitizers such as Ru(bpy)3 2+ [2], acridine dyes [3] and porphyrins [4].…”

Spectroscopy and Photochemistry of 8‐substituted 5‐deazaflavins

“…7990 filter for several hours prior to irradiation and during irradiation. The light source for the photoreactions was a 20-W blue fluorescent lamp [Sylvania F20T12-B; for the spectral output see Krasna (1980)l. Due to the instability of the photoreduction products during purification procedures we were not able to achieve accurate yields, melting points and elemental analysis.…”