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Optical spectroscopic studies of mononitrated benzo[a]pyrenes.

Vyas-S; Onchoke-KK; Rajesh-CS; Hadad-CM; Dutta-PK

J Phys Chem A 2009 Nov; 113(45):12558-12565

http://dx.doi.org/10.1021/jp904234q

20036069

Spectroscopic properties, including absorption, emission spectra, and excited-state lifetimes of the mononitrated benzo[a]pyrenes (NBaPs), specifically 1-, 3-, and 6-nitrobenzo[a]pyrenes (1-, 3-, and 6-NBaP), are reported, and correlations with structure are developed. With 1- and 3-NBaP, bathochromic shifts are observed in the absorption spectra. The quantum yields of emission display the following trend: BaP >> 6-NBaP > 1-NBaP approximately 3-NBaP. Fluorescence lifetimes for nitrated BaPs were approximately 6 to 7 times shorter than that of BaP. With the help of time-dependent density functional theory (TD-DFT), assignments of the electronic transitions are proposed and are in good agreement with the electronic spectra for the NBaPs in methanol. On the basis of optimization of the triplet states, different photochemical consequences are discussed, and the observed fluorescence quenching is explained. Changes in the electron density distributions in the ground and excited states calculated at the second-order coupled-cluster level using the resolution-of-the-identity approximation (RI-CC2) provide information about the possible mechanism of photochemical reactions of NBaPs. Correlations between the orientation of the nitro group relative to the aromatic plane and the observed properties of the NBaP are discussed.

Aerosol-particles; Chemical-properties; Chemical-structure; Chemical-synthesis; Fluorescence-spectrometry; Particulates; Photochemical-reactions

Christopher M. Hadad and Prabir K. Dutta, Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210

JPCAFH

20091112

Journal Article

hadad.1@osu.edu

Grant

2010

Grant-Number-R01-OH-009141

45

1089-5639

Journal of Physical Chemistry A

OH; TX

The Ohio State University