title: Femtosecond spectroscopy on the photochemistry of ortho-nitrotoluene.
abstract: The photo tautomerisations of ortho-nitrotoluene (oNT) and its methylated derivative ortho-ethylnitrobenzene (oENB) have been studied by means of femtosecond spectroscopy and (TD)-DFT computations. In UV/Vis transient absorption spectroscopy a band peaking at 400 nm is seen to rise in a bi-modal manner with time constants of 1-10 ps and 1500 ps. Femtosecond stimulated Raman experiments clearly identify aci-nitro forms as the spectroscopic carriers of the 400 nm band. The assignment of the Raman spectra is based on TD-DFT computations. The quantum yields of the aci-nitro forms after 3 ns are 0.08 (oNT) and 0.3 (oENB). The aci-nitro forms are formed via a singlet channel (1-10 ps) and a triplet channel (1500 ps). There are indications that the triplet channel involves a bi-radical intermediate. In between 3 ns and 1 ms the spectrum of the aci-nitro form shifts from 400 to 390 nm. This could indicate a tautomerisation from Z-aci-nitro to an E form.
authors.affiliation: Fakultät für Physik, Ludwig-Maximilians-Universität, Oettingenstr. 67, D-80538 München, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Schmierer
authors.forename: S
authors.initials: S
authors.lastname: Laimgruber
authors.forename: K
authors.initials: K
authors.lastname: Haiser
authors.forename: K
authors.initials: K
authors.lastname: Kiewisch
authors.forename: J
authors.initials: J
authors.lastname: Neugebauer
authors.forename: P
authors.initials: P
authors.lastname: Gilch
mesh_terms: D000042:Absorption; D001547:Benzaldehydes / Q000737:chemistry; D005663:Furans / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D009578:Nitrobenzenes / Q000737:chemistry / Q000528:radiation effects; D055668:Photochemical Processes; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet; D013057:Spectrum Analysis / Q000379:methods*; D013059:Spectrum Analysis, Raman; D014050:Toluene / Q000031:analogs & derivatives* / Q000737:chemistry / Q000528:radiation effects
chemical_list: D001547:Benzaldehydes; D005663:Furans; D009578:Nitrobenzenes; D014050:Toluene; C018674:tetrahydrofuran; C043850:2-nitrobenzaldehyde; C029955:2-nitrotoluene