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Title: Optical band gap of cross-linked, curved, and radical polyaromatic hydrocarbons
Authors: Menon, Angiras
Dreyer, Jochen A. H.
Martin, Jacob W.
Akroyd, Jethro
Robertson, John
Kraft, Markus
Keywords: Engineering::Chemical engineering
Issue Date: 2019
Source: Menon, A., Dreyer, J. A. H., Martin, J. W., Akroyd, J., Robertson, J. & Kraft, M. (2019). Optical band gap of cross-linked, curved, and radical polyaromatic hydrocarbons. Physical Chemistry Chemical Physics, 21(29), 16240-16251.
Journal: Physical Chemistry Chemical Physics
Abstract: n this work, the optical band gaps of polycyclic aromatic hydrocarbons (PAHs) crosslinked via an aliphatic bond, curved via pentagon integration and with radical character were computed using density functional theory. A variety of different functionals were benchmarked against optical band gaps (OBGs) measured by ultraviolet-visible spectroscopy with HSE06 being most accurate with a percentage error of 6% for a moderate basis set. Pericondensed aromatics with different symmetries were calculated with this improved functional providing new scaling relationships for the OBG versus size. Further calculations showed crosslinks cause a small decrease in the OBG of the monomers which saturates after 3–4 crosslinks. Curvature in PAHs was shown to increase the optical band gap due to the resulting change in hybridisation of the system, but this increase saturated at larger sizes. The increase in OBG between a flat PAH and a strained curved one was shown to be equivalent to a difference of several rings in size for pericondensed aromatic systems. The effect of σ-radicals on the optical band gap was also shown to be negligible, however, π-radicals were found to decrease the band gap by ∼0.5 eV. These findings have applications in understanding the molecular species involved in soot formation.
ISSN: 1463-9076
DOI: 10.1039/C9CP02363A
Schools: School of Chemical and Biomedical Engineering 
Organisations: Cambridge Centre for Advanced Research and Education in Singapore (CARES)
Rights: © 2019 The Owner Societies. All rights reserved. This paper was published by Royal Society of Chemistry in Physical Chemistry Chemical Physics and is made available with permission of The Owner Societies.
Fulltext Permission: open
Fulltext Availability: With Fulltext
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