Reduction of Nitrogen-containing Compounds

An examination of the photoelectron transfer in covalently -(CH2)io- linked eosin-butylviologen has shown that the intramolecular process is more efficient 

Irradiation (X 300 nm) of solutions of the Schiff bases N-benzylidenebenzyl-amine and N-benzylideneaniline in propan-2-ol in the presence of either platinised titanium(IV) oxide or platinised CdS induces transfer hydrogenation to give the corresponding secondary amines, dibenzylamine and N-benzylaniline respectively. Donor-acceptor compounds of the type N,N -dicyanobenzo[b]-naphtho[2,3-e][l, 4]dithiin-6,11 -quinonediimine, N,N -dicyanobenzo[b]naphtho 

Irradiation of 1,4,8,11,15,18,22,25-octabutoxyphthalocyanine or its copper derivatives in degassed ethanol containing triethanolamine causes its reduction by a mechanism which involves a higher excited state of the substrate,and a plot of the log of the rate constants for the photoinduced intramolecular electron transfer in a supramolecular assembly of Zn and Au porphyrins bridged by diphenylphenanthroline has been found to decrease linearly with diminishing energy difference between the HOMO and LUMO of the participating orbitals.  

Photoelectron transfer from the excited singlet state of zinc(II) tetraphenylpor-phyrin (ZnTPP) to MV in a compartmentalised system in which the ZnTPP moieties are covalently attached to amphiphilic sodium polysulfonates carrying lauryl 2-(naphthyl)methyl, or cyclododecyl groups, is reported to be much slower 

The fluorescence quenching dynamics of excited state electron donors by various pyrimidine and 5,6-dihydropyrimidine substrates have been examined and found to obey the Rehm-Weller relationship. In addition, an unexpected difference was observed between the reduction potentials for the trans-syn and cis-syn diastereoisomers of dimethylthymine cyclobutane dimers, and this has been ascribed to a stereoelectronic effect in the cis-syn dimer anion radical resulting from an unfavourable charge-dipole interaction between the added electron and the O carbonyl group of the pyrimidine ring 

Irradiation of acidic aqueous solutions of Fe(III) tetrakis(2-N-methylpyridyl)-porphyrin in the presence of mono- or dibasic amino acids or the corresponding 

N-acetylated derivatives leads to the formation of Fe(II) porphyrins together with the acyloxy radical which undergoes decarboxylation to give ammonio-alkyl or amidoalkyl radicals. Large differences in the observed rates of Fe(II) porphyrin formation can be accounted for in terms of two factors, the binding affinity of the carboxyl to form a photoactive complex, and competitive reactions of acyloxy radicals following photolysis. 

The (nn ) state of the azo chromophore present in azoalkanes such as 2,3-diazobicyclo[2.2.1]heptene (36 R, = CH3, Ph) is efficiently quenched by 

Numerous papers dealing with the photoreduction of viologens have appeared. Rate constants for electron transfer between aromatic hydrocarbon triplets and bipyridinium and pyridinium salts have been measured. The results suggest that the process is both facile and efficient. All the rate constants necessary for the determination of the quantum yield of formation of the viologen cation-radical in the methyl viologen-Eosin-EDTA system are also now available. The high activity of dihydroxytin(rv) uroporphyrin in the photoreduction of methyl viologen has been ascribed to the failure of a photochemi-cally inactive tt—tt complex to be formed between substrate and sensitizer. 

Harriman, G. Porter, and A. Wilowska, J. Chem. Soc., Faraday Trans. 2, 1983, 79, 807. S. Hashimoto and H. Mnramoto, Nippon Kagaku Kaishi, 1983, 1052. 

Photoreduction of the excited state of phenazine by THF occurs via the (n, TT ) and (rr, rr ) states of phenazine. The photodimerization of deazaflavin has been investigated, in particular its excitation in the presence of oxalate anion, which causes photodimerization with quantum yield Both electrochemical reduction and photochemical reaction of some i-(2- 

Kusunoki, fnorg. Chim. Acta, 1983, 71, 77. 

Vakul skaya, V. A. Lopyrev, and M. G. Voronkov. Dokl. Akad. Nauk SSSR, 1983, 272, 387. 

3 Reduction of Nitrogen-containing Compounds Dinitrogen has been reduced to ammonia in aqueous solutions containing colloidal transition metal catalysts, both radiolytically and photochemically.46 A study of photoinduced electron-transfer and its reversal 

In the absence of alcohol, the pathway in reaction (21) is not available. To explain reduction, Wubbels therefore proposes that the protonated ion pair [PhN02H bl] couples at the para-position of the aromatic ring forming (22), followed by elimination to yield 4-chloronitrosobenzene (23),48 as shown in 

4 x 10-2 when [HQ] lmoll-1. These results have been interpreted in terms of a previously proposed mechanism47 of electron transfer from chloride ion to the triplet state of the nitro-compound, although Cu and Testa49 prefer an hydroxylamino- rather than a nitroso-intermediate. 

Intramolecular hydrogen abstraction by excited nitrobenzene derivatives may lead to the introduction of an oxidized functional group in a remote part of the molecule, as previously reported by Scholl and Van De Mark.63 Japanese workers have now extended this reaction to the preparation of some oxidized derivatives of the triterpene dammaranediol.64 

Reduction of nitrogen-containing heterocyclic compounds continues to receive attention. Hoshino and Koizumi65 have postulated two mechanisms, one 

Shinzo, O. Tanaka, and K. Kawai, Chem. and Pharm. Bull. (Japan), 1974, 22 1213. 

The first results have been reported of the synthesis of l,T-bis[3-(trimethoxysilyl)propyl]-4,4 -bipyridinium bromide and of its use in the de-rivatization of Pt or p-type Si electrodes. In the dark, p-type Si is blocking to reduction but illumination with light of greater energy than the band gap results in reduction of the surface-confined reagent. This surface will reduce a variety of species such as Fe(f/ -CjH5)2 in MeCN, or [Ru(NH3)g] in water, and is 

Kobayashi, and T. Morita, Koen Yoshishu Bunshi Kozo Sogo Toronkai, 1979, 230. 

Aoyama, S. Suzuki, T. Hasegawa, and Y. Omote, J. Chem. Soc., Chem. Commun., 1979, 899. 

Aliphatic amines have been found to quench the fluorescence of acridine efficiently and a linear relationship has been demonstrated between the logarithms of the Stern-Volmer quenching constants and the ionization potentials of the amines. The photoreduction of the acridine occurs in 20% MejCOH-MeCN via an exciplex formed between the ground state of the amine and the acridine (ti, n ) state and in 20% McaCOH-CgHg via the (n,n ) state of the acridine. A quantitative study has been reported of the photoreactivity of 2-nitrophenazine with tertiary amines. Excitation to the state leads via a non-emitting 

A review of the phototochemistry of A-oxides has appeared and this includes a section on the photo-induced deoxygenation of heterocyclic A-oxides. A second review deals with the mechanistic aspects of the photochemistry of bicyclic azoalkanes and considers their photo-reduction by hydrogen donors, a process for which hydrogen-atom transfer and CT mechanisms have been suggested. 

There continues to be an interest in the development of novel reaction environments for photochemical reactions. The potential of quasi-solids , which are obtained from polysaccharides and contain a lot of water, has been ex-plored using the ET quenching of photoexcited Ru(bpy)3 by In 

Photoinduced charge separation processes in the supramolecular triad systems D -A-A, D -A -A and D -A-A have been investigated using three potential energy surfaces and two reaction coordinates by the stochastic Liouville equation to describe their time evolution. A comparison has l n made between the predictions of this model and results involving charge separation obtained experimentally from bacterial photosynthetic reaction centres. Nitrite anion has been photoreduced to ammonia in aqueous media using [Ni(teta)] and [Ru(bpy)3] adsorbed on a Nafion membrane. 

The irradiation of the phenoxazin-3-one dye, resazurin (21), in the presence of tertiary amines results in its efficient deoxygenation via the triplet state, forming the dye resorufin (22). The radiolysis/photolysis of aqueous solutions of pyrimidines produces radicals which are the result, in general, of 1-electron reduction involving hydrated electrons. The structures of the radicals were assigned on the basis of their by EPR spectra. The study included 2-hydroxypyrimidine 

A tetrathiafulvalene (TTF)-porphyrin dyad (47) has been synthesized in which efficient PET occurs between the pendant TTF and the porphyrin, quenching the fluorescence of the latter and giving the system potential as a 

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The Reduction of Nitrogen-containing Compounds with Sml2... 

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