2- pyridine, photoinduced proton transfer

Frank, 1., Grimme, S., and Peyerimhoff, S. D. Quantum chemical investigations of the thermal and photoinduced proton-transfer reactions of 2-(2 , 4 -dinitrobenzyl)pyridine. J. Physical Chem., 100, 16187-16194(1996). 

Somewhat less investigated process is the photoinduced proton transfer in nitrobenzylpyridines. When excited with ultraviolet light, solutions of 2-(2, 4 -dinitrobenzyl)pyridine and similar ortho-nitrobenzyl compounds are known to display photochromism in solution whereby they change from colorless to dark blue (for a comprehensive review on the literature published prior to 2006, see [18]) (Scheme 8.5). Some of these compounds in some of their polymorphs [19,... 

R., and Corval, A., Multistep photoinduced proton transfer in crystalline 2-(2, 4 -dinitroben-zyl)pyridine, Chem. Phys., 250, 199, 1999 Zhao, J., Zhao, B., Liu, J., Xu, W, and Wang, Z., Spectroscopy study on the photochromism of Schiff bases N,N -bis(salicylidene)-l,2-diaminoet-hane and N,N -bis(saHcyHdene)-l,6-hexanediamine, Spectrochim. Acta, 57, 149, 2001. 

A related question is proton transfer, where two aspects are relevant, viz. proton transfer from a heterocyclic radical cation after an ET step (e.g. after photoinduced ET from indole to anthracenes or pyrene) [38] and the possible role of ET in proton transfer from aromatic radical cations and heterocyclic nucleophiles, in particular to pyridine derivatives [37b, 39]. 

Frutos LM, Markmann A, Sobolewski AL, Domcke W Photoinduced electron and proton transfer in the hydrogen-bonded pyridine-pyrrole system. J Phys Chem B 2007, lll(22) 6l 10-6112. 

Scheme 8.5 Photoinduced nitro-assisted proton transfer in 2-(2, 4 -dinitrobenzyl)pyridine.

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