Direct Observation of Photodissociation Products from Phenylperoxyl Radicals Isolated in the Gas Phase

摘要: Gas phase peroxyl radicals are central to our chemical understanding of combustion and atmospheric processes typically characterized by strong absorption in the UV (lambda(max) approximate 240 nm). The analogous maximum feature for arylperoxyl is predicted shift visible but has not previously been nor have any photoproducts arising from this transition identified. Here we describe controlled synthesis isolation vacuo an array charge-substituted phenylperoxyl at room temperature, including 4-(N,N,N-trimethylammonium)methyl radical cation (4-Me3N[+]CH2-C6H4OO center dot), using linear ion-trap mass spectrometry. Photodissociation spectra obtained wavelengths ranging 310 500 nm reveal two major photoproduct channels corresponding homolysis aryl-OO arylO-O bonds resulting loss O-2 O, respectively. Combining photodissociation yields across spectral window produces a broad (FWHM 60 nm) clearly resolved centered lambda(max) = 403 (3.08 eV). influence charge-tag identity its proximity site investigated demonstrate no effect on dominant channels. Electronic structure calculations located vertical (B) over tilde <- (X) these substituted within experimental uncertainty further predict unsubstituted (C6H5OO dot) be 457 (2.71 eV), nearly 45 shorter than previous estimates good agreement with recent computational values.