Molecular and electronic structure of pyracylene

Freiermuth, B.; Gerber, Stefan; Riesen, Andreas; Wirz, Jakob; Zehnder, Margareta

doi:10.1021/ja00158a037

Cited by 57 publications

(56 citation statements)

References 5 publications

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“…The adiabatic S 0 -›S 1 (2A g ) transition was measured at 650 nm (44 kcal/mol) 103 in good agreement with our CASSCF result (47.3 kcal/mol). However, while the S 1 state is strongly stabilized at its minimum, the ground state is destabilized, resulting in a large decrease of the S 0 /S 1 energy gap to 24.4 kcal/mol.…”

Section: Resultssupporting

confidence: 89%

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CASSCF calculations for photoinduced processes in large molecules: Choosing when to use the RASSCF, ONIOM and MMVB approximations

Bearpark

Ogliaro

Vreven³

et al. 2007

Journal of Photochemistry and Photobiology A: Chemistry

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In this article, we compare and contrast the RASSCF, ONIOM and MMVB electronic structure methods for calculating relaxation paths on potential energy surfaces of the excited states of large molecules, and for locating any resulting conical intersections at which nonadiabatic decay can take place. Each method is treated here as an approximation to CASSCF, which we choose as our reference level of theory, but which becomes prohibitively expensive computationally for large molecules. Both MMVB and ONIOM are hybrid computational methods -combining different levels of theory in an energy plus derivatives calculation at a particular molecular geometry -but they differ fundamentally in that MMVB is a hybrid-atom method, whereas ONIOM is a hybrid-molecule method. We explain this distinction through four representative applications: the photostability of pyracylene (studied with CASSCF, RASSCF, MMVB); large geometry changes in the singlet excited states of triangulene (studied with MMVB); a model for interstitial nickel defects in a synthetic diamond lattice (studied with ONIOM CAS:UFF); and the photochemical [4+4] cycloaddition of cyclohexadiene to naphthalene (studied with ONIOM CAS:MMVB). We show that each method is more appropriate for a particular type of photochemical problem. This article is part perspective, part review, and contains new results for three multi-state or photoinduced processes in complex systems.

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Section: Resultssupporting

confidence: 89%

“…Pyracylene is a polycyclic aromatic hydrocarbon known experimentally 103 Figures 3 and 4) close to a minimum on S 1 , which leads to ultrafast internal conversion and explains the observed photostability. This conical intersection has a similar chemical origin to the crossing previously located for S 0 /S 1 in azulene 106 .…”

Section: Pyracylenementioning

confidence: 83%

CASSCF calculations for photoinduced processes in large molecules: Choosing when to use the RASSCF, ONIOM and MMVB approximations

Bearpark

Ogliaro

Vreven³

et al. 2007

Journal of Photochemistry and Photobiology A: Chemistry

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“…Since both semi-empirical [35] and ab initio [38][39][40][41] calculations as well as available single X-ray crystal structures [42,43] of CP-PAH show that the externally fused five-membered rings possess (localised) olefinic bonds, it is expected that these bonds will be most susceptible to undergo epoxidation by cytochrome P450 epoxidases present in the S9-mix (Fig. 7).…”

Section: Epoxidation Of Olefinic Bonds: Am1 Calculationsmentioning

confidence: 99%

Bacterial mutagenicity of the three isomeric dicyclopenta-fused pyrenes: the effects of dicyclopenta topology

Otero-Lobato

Jenneskens

Seinen

2004

Mutation Research/Genetic Toxicology and Environmental Mutagene

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Cyclopenta[cd]pyrene (1) and its congeners dicyclopenta [cd,mn]-(2), dicyclopenta [cd,fg]-(3), dicyclopenta [cd,jk]pyrene (4), which were all identified as constituents of combustion exhausts, as well as their partially hydrogenated derivatives 3,4-dihydrocyclopenta[cd]-(5), 1,2,4,5-tetrahydrodicyclopenta[cd,mn]-(6), 5,6,7,8-tetrahydrodicyclopenta[cd,fg]- (7) and 1,2,6,7-tetrahydrodicyclopenta[cd,jk]pyrene (8), were assayed for mutagenicity in the Salmonella typhimurium strain TA98 using different concentrations of microsomal protein in the metabolic activation system (S9-mix, with S9-fraction from liver of Aroclor-1254-treated rats: 2, 4 and 10% (v/v), respectively). Whereas a positive mutagenic response is found for 1-4 in the presence of S9-mix, 5-8 exert no mutagenicity either with or without S9-mix. Since for 1-4 the highest response is observed with S9-mix 2% (v/v) instead of the standard 4% (v/v), a one-step activation pathway, i.e. epoxidation of the five-membered ring olefinic bonds, appears to be operational. Surprisingly, 3 and, to a lesser extent, 2 (11.7 versus 4.2 His revertants/nmol) also give a positive response in the absence of S9-mix. Hence, 2 and 3 are expected to contribute to the direct-acting mutagenicity of the non-polar fraction of combustion exhausts. Presumably for the direct-acting mutagenicity one-electron transfer processes play a role in bioactivation. The experimental observations are supported by semi-empirical AM1 calculations on the possible ultimate metabolites, i.e. mono-epoxides (2a-4a), cis-di-epoxides (2b-4b) and trans-di-epoxides (2c-4c) and the related mono-hydroxy carbocations (2d-4d and 2e-4e), and the radical anions 1 •− -4 •− .

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“…It is well established that for most CP-PAHs, the double bond at the cyclopenta moiety possesses olefinic character: it represents the most localized double bond according to both theoretical (ab initio calculations) [50][51][52] and experimental data (single crystal X-ray structures) [53,54].…”

Section: Mutagenicity Assaysmentioning

confidence: 99%

CP-arene oxides: the ultimate, active mutagenic forms of cyclopenta-fused polycyclic aromatic hydrocarbons (CP-PAHs)

Otero-Lobato

Kaats-Richters

Koper

et al. 2005

Mutation Research/Genetic Toxicology and Environmental Mutagene

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The bacterial mutagenic response (Ames-assay, Salmonella typhimurium strain TA98 ± S9-mix) of a series of monocyclopentafused polycyclic aromatic hydrocarbons (CP-PAHs) identified in combustion exhausts, viz. cyclopenta[cd]pyrene (1), acephenanthrylene (2), aceanthrylene (3) and cyclopenta[hi]chrysene (4), is re-evaluated. The mutagenic effects are compared with those exerted by the corresponding partially hydrogenated derivatives, 3,4-dihydrocyclopenta[cd]pyrene (5), 4,5-dihydroacephenanthrylene (6), 1,2-dihydroaceanthrylene (7) and 4,5-dihydrocyclopenta[hi]chrysene (8). It is shown that the olefinic bond of the externally fused five-membered ring of 1, 3 and 4 is of importance for a positive mutagenic response. In contrast, whilst CP-PAH 2 is found inactive, its dihydro analogue (6) shows a weak metabolism-dependent response. The importance of epoxide formation at the external olefinic bond in the five-membered ring is substantiated by the bacterial mutagenic response of independently synthesized cyclopenta[cd]pyrene-3,4-epoxide (9), acephenanthrylene-4,5-epoxide (10), aceanthrylene-1,2-epoxide (11) and cyclopenta[hi]chrysene-4,5-epoxide (12). Their role as ultimate, active mutagenic forms, when CP-PAHs 1, 3 and 4 exhibit a positive mutagenic response, is confirmed. Semi-empirical Austin Model 1 (AM1) calculations on the formation of the CP-arene oxides (9-12) and their conversion into the monohydroxy-carbocations (9a-12a and 9b-12b) via epoxide-ring opening support our results. For 2 and 4, which also possess a bay-region besides an annelated cyclopenta moiety, the calculations rationalize that epoxidation at the olefinic bond of the cyclopenta moiety is favoured.

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Molecular and electronic structure of pyracylene

Cited by 57 publications

References 5 publications

CASSCF calculations for photoinduced processes in large molecules: Choosing when to use the RASSCF, ONIOM and MMVB approximations

CASSCF calculations for photoinduced processes in large molecules: Choosing when to use the RASSCF, ONIOM and MMVB approximations

Bacterial mutagenicity of the three isomeric dicyclopenta-fused pyrenes: the effects of dicyclopenta topology

CP-arene oxides: the ultimate, active mutagenic forms of cyclopenta-fused polycyclic aromatic hydrocarbons (CP-PAHs)

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