Photochemical reduction of carbonate

Kuwabata S, Nishida K, Tsuda R, Inoue H, Yoneyama H (1994) Photochemical reduction of carbon dioxide to methanol using ZnS microcrystaUite as a photocatalyst in the presence of methanol dehydrogenase. J Electrochem Soc 141 1498-1503... 

The challenging photochemical reduction of carbon dioxide to formate is catalyzed by Ru" [111] (cf. Section 3.3.4). For example, with the 2,2 -bipyridine-ruthenium(II) complex the active species is formed by photolabilization. Water renders the system more efficient with quantum yields up to 15%. Methanol is the photoproduct when CO2 is reduced with Ti02 in propene carbonate/2-propanol... 

Trimethylene-2,2 -bi-l,8-naphthyridine with [Re(CO)5Br] in heptane gives the bidentately coordinated complex 27 (960M3463). Compounds of the same composition, [Re(CO)3(LL)Cl] (LL = 3,3,-dimethylene-2,2,-biquinoline) can be prepared similarly (94IC2341). / -(2,6-di-2-pyridyl-4-pyridyl)phenol reacts with [Re(CO)5Cl] and forms complex 28 with bidentate coordination of the ligand (92JPP(A)259). The product is active in the electro- and photochemical reduction of carbon dioxide. Species [Re(CO)3(2,7-bis(2,-pyridyl)-l,8-naphthyridine)Br] is known (83ICA(76)L29). 

SCHEME 6.19 Tetraazamacrocyclic complexes for catalytic electrochemical and photochemical reduction of carbon dioxide. 

Fig. (13). Photochemical reduction of carbon dioxide into formic acid using tricyclic tertiary amine as a sacrificial donor (a) Plant photosynthesis (b) amine radical cation formed from tricyclic amine (c) regeneration of amine by hydrogenation using Pd catalyst. Reproduced with permission from Ref. [58, 59]. 2011 McMillan Publishers Ltd.

Richardson, R.D. Carpenter, B.K. A Computational Study of Remote C—H Activation by Amine Radical Cations Implications for the Photochemical Reduction of Carbon Dioxide. J. Am. Chem. fee., 2008, 730,3169-3180. 

Khenkm AM, Elfemenko I, Weiner L et al (2010) Photochemical reduction of carbon dioxide catalyzed by a ruthenium substituted polyoxometalate. Chem A Eur J 16 1356-1364... 

GranL J.L., K. Goswami, L.O. Spreer, J.W. Otvos, and M. Calvin (1987). Photochemical reduction of carbon dioxide to carbon monoxide in water using nickel(II) telra-azamacrocycle complex as catalyst, J. Chem. Soc. Dalton Trans. 9, 2105-2109. 

I. Taniguchi (1989) Electrochemical and photochemical reduction of carbon dioxide , in J. M. Bockris, R. E. White and B. E. Conway (eds). Modern Aspects of Electrochemistry, Plenum Publishing Corporation, New York, pp. 327-400. 

Electrochemical reduction of carbon dioxide has found no extensive application so far, yet it is of great interest for scientists in the fields of theoretical and applied electrochemistry. To a certain extent, it is analogous to the photochemical carbon dioxide reduction, but it involves no chlorophyll and yields simpler products. In recent years some books and reviews on this topic have been published (e.g., Taniguchi, 1989 Sullivan et al., 1993 Bagotsky and Osetrova, 1995). 

Lehn and Ziessel166 have also developed systems for the photochemical reduction of C02. These systems are similar to those represented by Fig. 18. Visible-light irradiation of C02-saturated aqueous acetonitrile solutions containing Ru(bpy)2+ as a photosensitizer, cobalt(II) chloride as an electron acceptor, and triethyl-amine as a sacrificial electron donor gave carbon monoxide and... 

The photochemical reduction of particulate and of dissolved iron(III) is coupled to the oxidation of a reductant, i.e., of dissolved organic carbon. 

For a fuel, an electron source is needed. Water is the ultimate electron source from an economical point of view. Water photolysis is the simplest among the chemical conversion systems of solar energy. Photochemical reduction of nitrogen or carbon dioxide to produce ammonia or hydrocarbons with the electrons from water is also an attractive system of conversion. 

These products are the most important components of the living matter of plants, e.g. cellulose. In these simple terms photosynthesis is the photochemical oxidation of water, and reduction of carbon dioxide, by means of a photoactivated catalyst which in green plants is the molecule chlorophyll. 

The end result of the photochemical part of photosynthesis is the formation of 02, NADPH, and ATP. Much of the oxygen is released to the atmosphere, but the NADPH and ATP are utilized in a series of dark reactions that achieve the reduction of carbon dioxide to the level of a carbohydrate (fructose). A balanced equation is... 

Photochemical, Electrochemical, and Photoelectrochemical Reduction of Carbon Dioxide... 

Ishitani O, Inoue C, Suzuki Y, Ibusuki T. Photocatalytic reduction of carbon dioxide to methane and acetic acid by an aqueous suspension of metal-deposited Ti02. J Photochem Photobiol A Chem 1993 72 269-71. 

From the point of view of organic synthesis, the overall process consists of the formation of carbohydrates (CH20) by the reduction of carbon dioxide. The essence of the process is the use of photochemical energy to split water and concomitantly to reduce C02. Many proteins and small molecules are involved in photosynthetic machinery. Inorganic species are in the centre of photosynthesis as pigments in light harvesting, substrates, products, catalysts, and electron transfer mediators. 

Photochemical reduction of C02 was also achieved in the presence of the p-type semiconductor (copper oxide) or silicon carbide electrodes [97]. Irradiation of this system generates methanol and methane as the main products in the case of CuO electrode whereas hydrogen (with efficiency about 80%), methanol (16%), methane, and carbon monoxide in the case of SiC electrode. Also Ti02/CuO systems appeared relatively efficient (up to 19.2% quantum yield) in photocatalytic C02 to CH3OH reduction [98]. 

Khan MMT, Rao NN, Chatterjee D. A novel photosynthetic mimic reaction catalysed by K[Ru(H-EDTA)C1]-2H20 reduction of carbon dioxide to formate and formaldehyde in the presence of an aqueous suspension of Pt-CdS-Ru02. / Photochem Photobiol A Chem 1991 60 311-18. 

The Mehler reaction is a photochemical reduction of O2 to H2O2 or H2O in photosystem I (Box 35.2). Mehler activity is thought to be a mechanism for energy dissipation under high tight intensities or when carbon frxation is limited by supply... 

The electrochemical or photochemical reduction of CO2, when catalyzed by ruthenium complexes, also produces formic acid derivatives. Furthermore, ruthenium-catalyzed electrochemical reduction of CO2 can provide carbon-carbon bond-forming reactions. Although at present the efihciency of such electrochemical and photochemical reactions does not appear to be satisfactory for use as a new tool in large-scale organic synthesis, the chemistry suggests that these methodologies may someday be useful in organic synthesis. 

The reduction of carbon dioxide to formate in the presence of FDH represents a photochemical C02-fixation process. In addition to MV+, the enzyme recognizes other electron carriers such as 2,2 -bipyridinium radical cations [184]. Reduction of nitrate (N03 ) to nitrite (NO2 ) and subsequently the reduction of nitrite to ammonia in the presence of NitraR and NitriR, respectively, allows the sequential 8e ... 

Natural photosynthesis is the most important of the many interesting photochemical processes known in biology. Not only was the evolution of the Earth s atmosphere dependent on it, but it is also the main route by which the free energy of the environment is made available to the living world. Green plants, algae and cyanobacteria make use of sunlight to drive a thermodynamically uphill reaction, the reduction of carbon dioxide to carbohydrates by water ... 

The essence of natural photosynthesis is the use of photochemical energy to split water and reduce CO2. Molecular oxygen is evolved in the reaction, although it appears at an earlier stage in the sequence of reactions than the reduction of carbon dioxide. Photochemical processes produce compounds of high chemical potential, which can drive a multistep synthetic sequence from CO2 to carbohydrate in a cyclic way. Reaction (16) is quite endoergic and thus thermodynamically very improbable in the dark (AG° = 522 kJ per mole of CO2 converted). Production of one molecule of oxygen and concomitant conversion of one molecule of carbon dioxide require the transfer of four electrons ... 

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