Kubicki, James D. and Blake, Geoffrey A. and Apitz, Sabine E. (1999) Molecular models of benzene and selected polycyclic aromatic hydrocarbons in the aqueous and adsorbed states. Environmental Toxicology and Chemistry, 18 (8). pp. 1656-1662. ISSN 1552-8618 http://resolver.caltech.edu/CaltechAUTHORS:20120914-103033501
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Energy gaps between the highest-occupied molecular orbital and lowest-unoccupied molecular orbital (ΔE_(HOMO-LUMO)) for a suite of common polycyclic aromatic hydrocarbons (PAHs) in the gas-phase were calculated with three different molecular modeling methods: semiempirical, ab initio Hartree-Fock, and density functional calculations. Results indicate that semiempirical, Hartree-Fock, and density functional calculations may provide useful relative HOMO-LUMO gap information, but these methods overestimate the actual ΔE_(HOMO-LUMO). Based on vibrational frequency analyses, density functional calculations reliably produce dynamically stable structures that can be used to predict model ΔE_(HOMO-LUMO) values. Both the semiempirical and ab initio Hartree-Fock methods were unreliable in predicting dynamically stable structures; hence prediction of ΔE_(HOMO-LUMO) values was not possible for several PAHs. Changes in the HOMO-LUMO gap of benzene and selected PAHs due to solvation effects were calculated using self-consistent reaction field methods and explicit solvation. Self-consistent isodensity polarized continuum model calculations modeling water and octanol solvation do not change calculated ΔEHOMO-LUMO values enough to affect predicted phototoxicities; thus, gas-phase values may be used for PAHs in solution and in vivo. Energetics of PAH bonding to mineral surface groups were also modeled. In some cases, interaction of PAHs with model aluminate surface defects suggests that ΔE_(HOMO-LUMO) values may be lowered significantly by adsorption that would lower chemical stabilities. Significant increases in calculated ΔE_(HOMO-LUMO) that would increase chemical stability of the compounds were not predicted.
|Additional Information:||© 1999 Society of Environmental Toxicology and Chemistry Press (SETAC). Issue published online: 2 November 2009; Article first published online: 2 November 2009; Manuscript Accepted: 15 June 1998; Manuscript Received: 14 April 1998. S.E. Apitz and J.D. Kubicki acknowledge the financial support of the Office of Naval Technology and the Office of Naval Research. Computer resources were supplied by the U.S. Department of Defense High Performance Computing initiative through the Space and Naval Warfare Systems Center, the Army Corps of Engineers Waterways Experimental Station, and the Aeronautical Systems Center.|
|Subject Keywords:||Polycyclic aromatic hydrocarbon; Phototoxicity; Adsorption; Infrared|
|Official Citation:||Kubicki, J. D., Blake, G. A. and Apitz, S. E. (1999), Molecular models of benzene and selected polycyclic aromatic hydrocarbons in the aqueous and adsorbed states. Environmental Toxicology and Chemistry, 18: 1656–1662. doi: 10.1002/etc.5620180807|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||14 Sep 2012 18:56|
|Last Modified:||14 Sep 2012 18:56|
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