99458-45-4Relevant academic research and scientific papers
Charge-Transfer Photochemistry from the Donor-Acceptor Complexes of Anthracenes with Tetranitromethane
Masnovi, J. M.,Kochi, J. K.
, p. 5245 - 5255 (1985)
The formation of electron donor-acceptor or EDA complexes of a series of 9-substituted and 9,10-disubstituted anthracenes with tetranitromethane (TNM) can be visually observed in dichloromethane solutions.The colors arise from charge-transfer (CT) transitions from the aromatic donor (An) to the tetranitromethane acceptor.Specific irradiation of the CT absorption band at λ > 500 nm leads to the rapid bleaching of the solution, and high yields of photoadducts 1 can be isolated especially from those anthracenes bearing electron-withdrawing substituents.X-ray crystallography establishes the photoadducts 1 to derive from an overall anti addition of the TNM fragments, C(NO2)3 and NO2, across the meso positions of 9-bromo- and 9-phenylanthracene.The high quantum yields are associated with the efficient dissociative electron transfer accompanying the charge-transfer excitation of the 1:1 EDA complex.The subsequent multistep pathway by which the geminate species -, NO2> combine regiospecifically and stereospecifically to form the photoadduct 1 is described.The structural elucidation of the byproducts underscores the efficiency of ion-pair and radical-pair interactions following the CT excitation of EDA complexes.
REACTIVE ION PAIRS FROM THE CHARGE-TRANSFER EXCITATION OF ELECTRON DONOR-ACCEPTOR COMPLEXES
Masnovi, J. M.,Kochi, J. K.,Hilinski, E. F.,Rentzepis, P. M.
, p. 1126 - 1135 (2007/10/02)
Excitation within the charge-transfer (CT) band of the electron donor-acceptor or EDA complexes of tetranitromethane (TNM) with a series of 9-substituted and 9,10-disubstituted anthracenes (An) leads to photochemistry in high quantum yields (Φ ca. 1).The combined use of time-resolved picosecond spectroscopy, product isolation, and structure elucidation allows for the detailed mapping of the temporal evolution of the CT excited state to the photoproduct I via series of discrete reactive intermediates.Thus electron transfer within the EDA complex occurs effectively (+. and TNM-..The latter is not observed directly owing to its spontaneous fragmentation to C(NO2)3- and NO2 within 10 ps.The geminate ionic intermediates An+. and C(NO2)3-. undergo cage combination to produce hydranthryl radicals II within an interval of /= 1 ns and the trans stereochemistry required for the free radical coupling to occur.This detailed study is the basis for a generalized formulation (summarized in Scheme I) to be developed for CT photochemistry via reactive ion pairs.In particular, the comparison with the related EDA complexes of the anthracenes and tetracyanoethylene serves to emphasize the importance of back electron transfer from the geminate ion pair, i.e., +., A-.> -> .
