Photochemistry and photophysics of 1,4-dewarnaphthalene

Carr, Richard V. C.; Kim, Bongsub; McVey, Jeffrey K.; Yang, N. C.; Gerhartz, Wolfgang; Michl, Josef

doi:10.1016/0009-2614(76)85195-0

Cited by 23 publications

(14 citation statements)

References 12 publications

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“…The fact that only the latter occurs in detectable yield is consistent with previous results that indicate that the efficiency of photochemical cyclobutene ring opening depends to some extent on the strength of the cyclobutenyl C3-C4 bond (12,20). The possibility that the overall nonstereoselectivity of photochemical ring opening might be explained by a mechanism in which purely disrotatory ring opening occurs adiabatically is suggested by the experimental results of Michl, Yang, and co-workers (37,38), which demonstrated that direct irradiation of Dewar naphthalene (38) and Dewar anthracene (37) affords the corresponding aromatic hydrocarbons in the lowest excited singlet states. This was evidenced by the observation of the characteristic fluorescence of the aromatic hydrocarbons upon excitation of the corresponding Dewar isomers in solution.…”

Section: Resultssupporting

confidence: 88%

Cyclobutene photochemistry. Adiabatic photochemical ring opening of alkylcyclobutenes

Leigh¹,

Postigo²,

Zheng³

1996

Can. J. Chem.

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The photochemistry of the cis and trans isomers of a series of dimethylbicyclo[n.2.O]alk-(n+2)-enes (n = 2-5) (bicyclic cyclobutene derivatives in which the C=C bond is shared by the two rings) in pentane solution is described. Irradiation of these compounds using monochromatic 193-or 214-nm light sources results in ring opening to yield the corresponding 1,2-bis(l-ethylidene)cycloalkanes (C,-C,) in high chemical and quantum yields. In all cases, the reaction proceeds with a high (70-90%) degree of disrotatory stereoselectivity. Quantum yields for direct cis,trans photoisomerization of the isomeric E,Eand E,Z-1,2-bis(l-ethylidene)cycloalkanes have also been determined. The product distributions from irradiation of the cyclobutenes are wavelength dependent, but for 214-nm excitation the isomeric diene distributions obtained from cyclobutene ring opening agree fairly closely with those calculated from the quantum yields for cis,trans photoisomerization of the isomeric dienes on the assumption that the process involves purely disrotatory ring opening to yield a single diene isomer in the lowest excited singlet state. The results are consistent with an orbital-symmetry-controlled, adiabatic mechanism for ring opening.Key words: photochemistry, cyclobutene, electrocyclic, adiabatic, conical intersection, orbital symmetry.Resume : On dCcrit la photochimie des isomkres cis et trans d'une sCrie de dimCthylbicyclo[n.2.0]alc-(n+2)-knes (n = 2-5) (dCrivts cyclobutknes bicycliques dans lesquels la liaison C% est partagCe entre deux cycles) en solution dans le pentane. L'irradiation de ces composCs utilisant des sources de lumikre monochromatique (193 ou 214 nm) provoque une ouverture de cycle qui conduit aux 1,2-bis(1-Cthylidbne)cycloalcanes (C,-C,) correspondants avec des rendements chimiques et quantiques tlevCs. Dans tous les cas, la reaction se produit avec un degrC ClevC (70-90%) de stCrCosClectivitt disrotatoire. On a determink les rendements quantiques pour la photoisomtrisation cis/trans des E,E-and E,Z-1,2-bis(1-Cthy1idkne)cycloaIcanes. Les distributions des produits dtrivant de l'irradiation des cyclobutknes dependent de la longueur d'onde, mais, pour l'excitation B 214 nm, les distributions des diknes isomkres obtenues pour l'ouverture de cycle du cyclobutkne sont en assez bon accord avec ceux calculCs ii partir des rendements quantiques pour la photoisomCrisation cis/trans des diknes isomkres en supposant que le processus implique une ouverture de cycle strictement disrotatoire pour conduire B un seul dikne isomkre dans 1'Ctat singulet excitC le plus bas. Les rtsultats sont en accord avec un mCcanisme, pour l'ouverture de cycle, qui serait adiabatique et sous contr6le d'une symCtrie des orbitales.

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Section: Resultssupporting

confidence: 88%

Cyclobutene photochemistry. Adiabatic photochemical ring opening of alkylcyclobutenes

Leigh¹,

Postigo²,

Zheng³

1996

Can. J. Chem.

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“…1 sented as hybrids of ionic structures (3, 4). A more complete analysis Gerhartz et al, 1976), outlined briefly below, shows that in some instances D can be substantially less ionic than S and lies below it in energy.…”

Section: Electronic States At Biradicaloid Geometriesmentioning

confidence: 99%

“…The conclusion to be drawn is that return from a "stretched o-bond minimum" in the TI surface to So is likely to occur at a loose geometry at which the bond is very long and completely broken, while return from an analogous minimum in the S1 surface is likely to occur at a tight geometry at which the bond is only stretched but not completely destroyed. Figure 3 is based on the results of approximate calculations (Gerhartz et al, 1976) at geometries corresponding to the hypothetical best ground-state rectangular path for H2 + D2 isotopic exchange reaction (no experimental data are available since the thermal reaction does not actually proceed along this path and photochemical reactions have not been studied, but qualitative features of the results are undoubtedly correct). The S and D states drop in energy at the biradicaloid square geometries while the G state rises, to become the expected trio of low-energy singlet states.…”

Section: (B) the Upper Two Statesmentioning

confidence: 99%

“…in photocycloaddition reactions, it is of interest to relate these states to the electronic states of the two reacting fragments, in our model case, both equal to H2. It then turns out that, in the limit of infinite intermolecular separations, the G state corresponds to a combination of two ground-state fragments H2 + H2, the S state to a combination of a ground state fragment (H2) with a singlet excited fragment Ht, and the D state to an overall singlet coupling of two triplet excited fragments H: + H: Gerhartz et al, 1976).…”

Section: (B) the Upper Two Statesmentioning

confidence: 99%

“…It is interesting to investigate the difference between the order of states at the biradicaloid geometry of H2 (S below D) vs H4 (D below S) (Michl, 1975a;Gerhartz et al, 1976). The simple 3 x 3 CI description mentioned at the outset predicts that both S and D states are ionic and predicts the order S below D. As more CI is introduced, the S state is little affected, but the D state gradually becomes less ionic and decreases in energy.…”

Section: (B) the Upper Two Statesmentioning

confidence: 99%

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The Role of Biradicaloid Geometries in Organic Photochemistry

Michl

1977

Photochem & Photobiology

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Abstract-Excited molecules tend to return to the ground state at biradicaloid geometries, i.e. those for which the simple MO description yields two non-bonding orbitals occupied by only two electrons in the ground state. The nature of electronic states at these geometries and the consequences for the course of photochemical reactions are summarized, using the cases of Hz and H4 as simple models. Several aspects of classification schemes for photochemical reactions are discussed.Detailed mechanisms of photocycloaddition, of adiabatic photochemical rearrangement of Dewar aromatics, and of luminol chemiluminescence are considered as examples.

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Adiabatische Photoreaktionen organischer Moleküle

et al. 1979

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Eine adiabatische Photoreaktion ist ein chemischer Vorgang, der auf einer einzigen Potentialhyperflache (,,Potentialflache") eines elektronischen Anregungszustandes ablauft. Die rneisten Photoreaktionen organischer Molekule beginnen zwar auf der Potentialhyperflache eines elektronischen Anregungszustandes, ,,springen" aber irgendwo entlang der Reaktionskoordinate auf eine niedriger liegende Potentialhyperflache. Ausnahmen von dieser allgemeinen Regel sind zum Beispiel Photoreaktionen, die nur zu geringfiigigen Strukturanderungen oder kleineren Veranderungen an den kovalenten Bindungen fuhren (z. B. Protonen-Transfer und Komplexbildung). Diese Reaktionen verlaufen im allgemeinen adiabatisch. Der Zweck dieses Aufsatzes ist die Behandlung komplizierterer Beispiele adiabatischer Photoreaktionen wie Fragmentierungen, elektrocyclischer Reaktionen und geornetrischer Isomerisierungen. Die angewendeten Konzepte werden einleitend besprochen.

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Photochemistry and photophysics of 1,4-dewarnaphthalene

Cited by 23 publications

References 12 publications

Cyclobutene photochemistry. Adiabatic photochemical ring opening of alkylcyclobutenes

Cyclobutene photochemistry. Adiabatic photochemical ring opening of alkylcyclobutenes

The Role of Biradicaloid Geometries in Organic Photochemistry

Adiabatische Photoreaktionen organischer Moleküle

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