Photochemical splitting

Because anhydrous nitric acid is of low thermal stability even at room temperature, very few photochemical and radiolytic studies have been carried out with it. A flash photolytic study of nitric acid vapour by Husain and Norrish250 has provided evidence for a primary photochemical split into OH and N02, viz. 

An improvement in the efficiency of photochemical splitting of water was the incentive for Morris [49]. A parallel optical screening method was developed to select photocatalytically active catalysts by their adsorption spectra (UV and visible light). 

Molecular mechanisms in nucleic acid photochemistry I. Sensitized photochemical splitting of thymine dimer. J. Amer. chem. Soc. 88, 813 (1966). 

Osterloh FE. Inorganic materials as catalysts for photochemical splitting of water. Chem Mater 2008 20 35-54. 

Photochemical splitting of water achieved by combining two photocatalytic reactions on suspended Ti02 particles namely, the reduction of water to H2 using bromide ions and the oxidation of water using Fe(III) species. High efficiency also observed for the photoassisted OER on TiCte in the presence of Fe(III) ions. 326, 327... 

This reaction proceeds also photochemically as indicated by the concomitant spectral changes that are identical in both cases. When the irradiation is carried out in acidic solution (L = H20) comparable spectral variations are observed. Since the photolysis products are apparently stable under these conditions and interfering inner-filter effects are absent the photolysis can be performed to completion. The Os(III) dimer disappears with 4> = 8xl0 at lirr = 436nm. Disproportionations of this kind that take place as a consequence of the photochemical splitting of a metal-metal bond are an important reaction type in organo-metallic chemistry (17,18). 

At this point a few comments about the mechanism of the photochemical splitting of carbonate are appropriate. We suggest that in agreement with the excited state properties of Tp complexes in general (46,47) the photoexcitation of Cu Tp leads to the population of an IL excited state followed by electron transfer to the carbonate. A radical anion is thus formed as an intermediate which is subsequently reduced by a second Cu Tp complex forming CO. Simultaneously, two Cu Tp fragments are generated as oxidation products. Under these conditions... 

Water photochemical splitting cyclic process, 353 Fe OFe moiety, 348 osmocene, 349-353... 

An interesting proof has recently been given of photochemical splitting of free radical NO2 from nitroalkane Marciniak and Paszyc [62] irradiated nitro-methane dissolved in cyclohexane and received nitrosocyclohexane dimer ... 

However, by 3.5 billion years ago photochemical splitting of water, or photosynthesis was happening. 

Scheme 1.2 Mechanism of the ozone formation in the stratosphere [26]. Dioxygen is photochemically split into atomic oxygen, which adds to another dioxygen molecule. The excess energy from the recombination is carried away by a collision partner (M).

Osterloh, F. E., Inorganic Materials as Catalysts for Photochemical Splitting of Water, Chem. Mater. 2008, 20, 35 54. 

Gaseous Evolution of Molecular Hydrogen and Oxygen in Photochemical Splitting of Water by Platinized Chlorophyll a Dihydrate Polycrystals... 

Only metal compounds with d° ions (Ti, Zr, Nb, and Ta) and d ° ions (Ga, In, Ge, Sn, and Sb) have activity for overall photochemical splitting of water. Oxides are dominant, bnt nitrides and oxynitrides (GaN ZnO and Ge3N4) are also known to catalyze the reaction. 

---