Differing substituent effects on rates and regioselectivities in the di-π-methane rearrangement. New photochemical theory: excitation distribution (the ΔP matrix), reaction inhibition by vertical excited state stabilisation, ground Vs. excited state control

Zimmerman, Howard E.; Gruenbaum, W. T.; Klun, Robert T.; Steinmetz, Mark G.; Welter, Thomas R.

doi:10.1039/c39780000228

Cited by 10 publications

(3 citation statements)

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“…To understand better the electronic interaction of bridgehead groups with the bicyclooctane units, we carried out ab initio computations of the rods of interest. For this we employed the delta-density matrix approach which gives the distribution of excitation. The method takes the difference between the excited state and ground-state density matrixes obtained for a reactant by ab initio computation.…”

Section: Resultsmentioning

confidence: 99%

Rodlike Molecules and Singlet Energy Transfer¹^,²

2000

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In continuing our investigations on rodlike molecules composed of bicyclo[2.2.2]octane units, we studied the effect of interposing a single aromatic ring in the rod. Thus, two [3]-rods were synthesized with the two outer units being bicyclooctyls, the central unit being benzenoid, and with one terminal unit bearing an alpha-naphthyl moiety and the other terminus bearing an acetyl or benzoyl group. Excitation of the alpha-naphthyl group led to fluorescence emission by both the naphthyl and the acetyl units. However, compared to the [1]- and [2]-rods previously studied, transmission of singlet excitation proved to be less efficient as determined by the fluorescence emission and also by the singlet lifetimes obtained from single photon counting measurement. Transmission to the benzoyl group proved more rapid than to the acetyl moiety. In assessing the factors controlling energy transmission, Delta-density determinations were employed to describe the distribution of electronic excitation in such systems. It was observed that despite most of the energy being located in the terminal chromophores, some is distributed in the bicyclooctyl units. The extent of this distribution provides a guide to the facility of through-bond energy transfer. Evidence is presented that energy transfer in the short rods is mainly through-bond while in the longer rods Forster through-space transfer is involved.

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Section: Resultsmentioning

confidence: 99%

Rodlike Molecules and Singlet Energy Transfer¹^,²

2000

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“…A third method, which has been applied primarily to the consideration of the intramolecular rearrangements, was proposed by Malrieu and others,43-44 and recently has been applied extensively by Muszkat.45 Zimmerman et al have recently proposed a similar method. 46 First, one considers the bonding in the ground-state complex to two alkenes. On a one-electron level, where the presence or absence of electrons in an orbital does not influence how the orbital interacts with a second orbital, the changes in orbital energies are exactly those calculated in Figure 12.…”

Section: Photoelectron Spectramentioning

confidence: 99%

Photoelectron spectra of ortho- and meta-substituted benzonorbornadienes. Relationships to regioselectivities in triplet di-.pi.-methane rearrangements

Santiago¹,

McAlduff²,

Houk³

et al. 1978

J. Am. Chem. Soc.

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“…With a near HOMO-LUMO degeneracy in such an array (16), excitation flow in this direction does, indeed, become exothermic and favorable. Thus the AP elements (14,15) become small for that part of the system which is most diradicaloid and has a local near degeneracy. This general point is discussed further below in connection with reaction multiplicity.…”

Section: Gross Rearraizgement Mechanismsmentioning

confidence: 99%

The photochemistry of phenanthrene-substituted molecules

Zimmerman¹,

Wu²

1983

Can. J. Chem.

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7'11i.y 1)[1per is cledicoted to PI-ofessor Harry E. G L~I I~I~I~S 0 1 1 file occcr.sio11 of his 65th birtt~rlrlyHOWARD E. ZIMMERMAN and GUO-SHENG WU. Can. J. Chcm. 61, 866 (1983).The photochemistry of 3-methyl-3-(9-phcnanthry1)-1-butene was examined as part of 'an investigation into the effects of having two n chromophores of widely different energies participating in a di-n-methane rearrangement. Wc observed both direct and sensitized reactivity with quantum yiclds = 0.043 and 0.053. Thc primary reaction product from both direct and sensitized photolyses was I, 1-dimethyl-2-(9-phenanthryl)cyclopropan. However, in practice this product was obtained only from sensitized irradiations where it was almost completely unreactive. The triplet reactivity is unusual in that the typical free rotor decay exhibited by triplets does not lead to inhibition of di-n-methane reactivity in this case. This point is discussed. The intersystcm crossing efficiency of the phcnanthryl vinyl mcthanc reactant was obtained from the scnsitization of biacetyl phosphorescence by the phenanthrene derivative at varying biacetyl concentrations. This was +, , , = 0.86. This result and the bracketing relationships signify that essentially all of the direct irradiation rearrangement utilizes T I . In addition, from these experiments, 'k,,,,,,, was determined as 5.8 X 10' s-I. Similarly, 'k, = 250 s-I which is the slowest di-n-methane rearrangement encountered thus far. The rearrangement of the cyclopropane product to form 2-methyl-4-(9-phenanthry1)-I-butene was also investigated. 'I$ was determined to be 0.091 and '41 was determined as 0.00072. Thus the interesting contrast was encountered in which thc di-n-methane rearrangement proceeds from the triplet while the rearrangement of the cyclopropane product proceeds most efficiently from the singlet. HOWARD E. ZIMMERMAN et GUO-SHENG WU. Can. J. Chcm. 61, 866 (1983).On a CtudiC la photochimie du mCthyl-3-(phenanthryl-9-)-3 butene-I comme un aspcct dc la rechcrchc portant sur les effets de la presence de dcux chromophores n d'inergies tres differentes participant h la transposition di-n-mkthane. Nous avons observC les deux rCactivitCs directe et scnsibilisCc avec des rendemcnts quantiqucs +"IK = 0,043 et +SEN" 0,535. Le dimethyl-1, l (phinanthryl-9)-2 cyclopropane et le produit primaire de rCaction h partir de la photolyse directe et de la photolyse sensibiliske. Cependant, en fait, on obtient ce produit uniquement h partir des irradiations faites en presence de photosensibilisateurs oh il est presque complktement inactif. La reactivitk du triplet est inhabituelle en ce sens quc la dksintegration par centrifiguration libre typique exhibee par les triplets ne conduit pas h une inhibition de la r6activitC du di-n-methane dans ce cas. On discute de ce point. On retrouve I'efficacitC du croisement intersystkme du rCactif phCnanthrylvinyl methane h partir de la sensibilisation de la phosphorescence du biacCtyle par le derive du phknanthrene h des concentrations variables de biacCtyle. Cette efficacitk est...

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Differing substituent effects on rates and regioselectivities in the di-π-methane rearrangement. New photochemical theory: excitation distribution (the ΔP matrix), reaction inhibition by vertical excited state stabilisation, ground Vs. excited state control

Cited by 10 publications

References 0 publications

Rodlike Molecules and Singlet Energy Transfer¹^,²

Rodlike Molecules and Singlet Energy Transfer¹^,²

Photoelectron spectra of ortho- and meta-substituted benzonorbornadienes. Relationships to regioselectivities in triplet di-.pi.-methane rearrangements

The photochemistry of phenanthrene-substituted molecules

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Differing substituent effects on rates and regioselectivities in the di-π-methane rearrangement. New photochemical theory: excitation distribution (the ΔP matrix), reaction inhibition by vertical excited state stabilisation, ground Vs. excited state control

Cited by 10 publications

References 0 publications

Rodlike Molecules and Singlet Energy Transfer1,2

Rodlike Molecules and Singlet Energy Transfer1,2

Photoelectron spectra of ortho- and meta-substituted benzonorbornadienes. Relationships to regioselectivities in triplet di-.pi.-methane rearrangements

The photochemistry of phenanthrene-substituted molecules

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Rodlike Molecules and Singlet Energy Transfer¹^,²

Rodlike Molecules and Singlet Energy Transfer¹^,²