Heat of Formation and the Structure of Pyrene–<i>N</i>, <i>N</i>-Dimethylaniline Heteroexcimer

Okada, Tadashi; Matsui, Hirofumi; Oohari, Hiroo; Matsumoto, Hisato; Mataga, Noboru

doi:10.1063/1.1669938

Cited by 20 publications

(11 citation statements)

References 9 publications

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“…Such interference did not exist with other substrates. While tributylamine most likely interacted with singlet excited 2-NpC02CH3 by electron transfer (26), methyl iodide did so by promoting its intersystem crossing (27). The latter was confirmed by the observation of proportionately enhanced phosphorescence spectra at 77 K for a solution containing increasing concentrations of methyl iodide (see Fig.…”

Section: Naphthoatejiuorescence Studiesmentioning

confidence: 49%

“…Assuming that the unimolecular reactions of singlet excited 2-NpC02CH3 involving electron demotion were not affected significantly in this temperature range, TO could be taken as approximately constant. Therefore the rate constant of the acacH interaction with singlet excited 2-NpC02CH3 decreases with increasing temperature; such a negative temperature effect in fluorescence quenching suggests the presence of an exciplex (27,28), i.e., *(2-NpC02CH3.. . acacH).…”

Section: Naphthoatejiuorescence Studiesmentioning

confidence: 99%

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The photocycloaddition of naphthoates with acetylacetone; dramatic acid promotions of product quantum yields

Chow¹,

Liu²

1991

Can. J. Chem.

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. Can. J. Chem. 69, 1261Chem. 69, (1991. In acetonitrile and methanol, methyl 1-and methyl 2-naphthoate (1-and 2-NpC02CH3) underwent [2+2] photocycloaddition with acetylacetone (acacH) from a reactive species derived from the lowest spectroscopic singlet excited state to give cyclobutane derivatives such as 9 that ring-opened to afford addition products of acetyl and acetonyl moieties at the 7,8-position for 1-NpC02CH3 (2 and 3) and the 1,2-position for 2-NpC02CH3 (7). Further irradiation of 3 and 7 caused a deep-seated rearrangement of 3 to give 4 and an intramolecular addition of 7 to give the caged product 8. The photocycloaddition quantum yields were increased remarkably in the presence of a trace amount (<0.001 M) of protic acids. For example, the limiting quantum yield of 2 and 3 with Qadducrs = 0.033 (in the absence) increased to Qudducts >0.5 under comparable conditions in the presence of [H2S04] = 0.001 M, approaching the maximum asymptotically at about this concentration; the increases of the quantum yield could not be correlated with H2SO4 concentrations. The acid promotion of the product formation elevated the photocycloaddition to a significantly useful preparative reaction. The photocycloaddition of 2-NpC02CH3 was quenched by tributylamine, dimethylaniline, and methyl iodide, and could not be initiated by typical triplet sensitization. Strong fluorescence of 2-NpC02CH3 at 358 nm in CH3CN was quenched by acetylacetone, tributylamine, dimethylaniline, and methyl iodide, the last of which concurrently enhanced the phosphorescence intensity of 2-NpC02CH3. In the presence of [H2S04] >0.005 M the fluorescence intensity at 358 nm was quenched and a new fluorescence at 470 nm corresponding to protonated '~-N P C O~C H~ appeared. However, in the [H2S04] <0.002 M region, the new fluorescence was not observed, indicating that the protonation scarcely occurred. The Stem-Volmer constant, obtained by the quantum yield monitor, of the 2-NpC02CH3 photocycloaddition with acacH was more than an order of magnitude smaller than that obtained by the quenching of 2-NpC02CH3 fluorescence by acacH. The discrepancies outlined above clearly demonstrate that the reactive intermediate of the photocycloaddition is not the exciplex of the spectroscopic singlet excited species of '~-N~C O~C H~ and acacH, but one that is derived from the exciplex. It is speculated that this unknown reactive intermediate interacts with a proton to promote the photocycloaddition.Key worcls: photocycloaddition of naphthoates, photorearrangement of styryl ketones, acid catalysis of quantum yields, fluorescence of protonated naphthoates, acid enhancement of singlet quenching. 0,001 M) avec une croissance asymptotique qui atteint son maximum autour de cette valeur; on n'a pas pu Ctablir de correlation entre le rendement quantique et la concentration en H2SO4. La catalyse acide de la formation des produits a transform6 la photocycloaddition en une reaction preparative d'une grande utilitt. La photocyloaddition du 2-NpC02CH3 est dtsactivee par la tribu...

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Section: Naphthoatejiuorescence Studiesmentioning

confidence: 49%

Section: Naphthoatejiuorescence Studiesmentioning

confidence: 99%

The photocycloaddition of naphthoates with acetylacetone; dramatic acid promotions of product quantum yields

Chow¹,

Liu²

1991

Can. J. Chem.

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“…There are a number of reasons for doubting whether the values of AH°r eported by Okada et al 20 and by Murata et al21 are valid. First, Stevens-Ban plots38 were used to calculate AH°.…”

Section: Discussionmentioning

confidence: 97%

“…Such plots frequently yield inaccurate results,17 particularly when used with the results of measurements in polar solvents, in which kn is small. McDonald and Selinger39 have argued that, at the temperatures used by Okada et al 20 for their experiments with the pyrene-DMA system in DEE, £4 is not sufficiently greater than kp to justify the use of a Stevens-Ban plot in the calculation of AH°. Although it has been denied57 that Stevens-Ban plots were misinterpreted by Okada et al,20 the arguments of McDonald and Selinger probably have some validity.…”

Section: Discussionmentioning

confidence: 99%

“…McDonald and Selinger39 have argued that, at the temperatures used by Okada et al 20 for their experiments with the pyrene-DMA system in DEE, £4 is not sufficiently greater than kp to justify the use of a Stevens-Ban plot in the calculation of AH°. Although it has been denied57 that Stevens-Ban plots were misinterpreted by Okada et al,20 the arguments of McDonald and Selinger probably have some validity. Secondly, if the AH°value for the pyrene-DMA system in pyridine is combined with free-energy data, a AS0 value of +18 eu is calculated; a positive entropy of formation for the exciplex seems unlikely.…”

Section: Discussionmentioning

confidence: 99%

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Exciplex photophysics. 6. Quenching of .alpha.-cyanonaphthalene by 1,2-dimethylcyclopentene in slightly polar solvents

O’Connor¹,

Ware²

1979

J. Am. Chem. Soc.

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Excimere

Förster¹

1969

Angewandte Chemie

165

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Heat of Formation and the Structure of Pyrene–N, N-Dimethylaniline Heteroexcimer

Abstract: Articles you may be interested inElectric field effects on photoinduced electron transfer processes of methylene-linked compounds of pyrene and N,N -dimethylaniline in a polymer film

Cited by 20 publications

References 9 publications

The photocycloaddition of naphthoates with acetylacetone; dramatic acid promotions of product quantum yields

The photocycloaddition of naphthoates with acetylacetone; dramatic acid promotions of product quantum yields

Exciplex photophysics. 6. Quenching of .alpha.-cyanonaphthalene by 1,2-dimethylcyclopentene in slightly polar solvents

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