Intramolecular excimer formation in bichromophoric molecules linked by a short flexible chain

Schryver, F. C. De; Collart, P.; Vandendriessche, J.; Goedeweeck, R.; Swinnen, A. M.; Auweraer, Mark Van der

doi:10.1021/ar00137a001

Cited by 190 publications

(127 citation statements)

References 60 publications

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“…It is well known that in bisA C H T U N G T R E N N U N G (pyrenil) compounds the extent of excimer emission was limited by the probability of a molecule reaching, within the lifetime of the excited state, a conformation suitable for excimer formation and by the stabilization of the excimer. [17] The observed ratio between the excimer and monomeric fluorescence quantum yield F F EXC /F F MON was plotted in Figure 1 as a function of the viscosity of the solvent. Despite the different molecular nature, the ratio decreased sharply as the h value increased [18] and became zero at high viscosity.…”

Section: Resultsmentioning

confidence: 99%

Pyrene‐Excimers‐Based Antenna Systems

Cicchi

Fabbrizzi

Ghini

et al. 2008

Chemistry A European J

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A series of dendrimeric compounds bearing pyrene units were synthesized to afford light-harvesting antennae based on the formation of intramolecular excimers. The synthetic plan profited from the efficiency of the Huisgen reaction, the 1,3-dipolar cycloaddition of azides and terminal alkynes, which allowed ready assembly of the different building blocks. The three molecular antennae obtained, of increasing generation, revealed efficient energy transfer both in solution and in the solid state.

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Section: Resultsmentioning

confidence: 99%

Pyrene‐Excimers‐Based Antenna Systems

Cicchi

Fabbrizzi

Ghini

et al. 2008

Chemistry A European J

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“…There are many examples of intramolecular exciplexes of this type and many, though not all, are emissive (14). We have looked carefully for excimer emission and have not been able to observe any in either methanol or cyclohexane solvent.…”

Section: Discussionmentioning

confidence: 99%

Photolysis of the 1-naphthylmethyl ester of substituted phenylacetic acids: intramolecular charge transfer and rates of decarboxylation of arylacyloxy radicals

Hilborn¹,

Pincock²

1992

Can. J. Chem.

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. 70, 992 (1992). The photolysis of esters 6 and 8 in methanol leads to products resulting from both naphthylmethyl cations and radicals. The product distribution is nearly independent of X for the esters 6 except when X equals methoxy. A mechanism involving initial homolytic cleavage of the carbon-oxygen bond in the excited singlet state of the ester is proposed. Competition between electron transfer in the radical pair to form the ion pair and decarboxylation of the arylacyloxy radical allows calculations of the rates for this decarboxylation process. The p value versus u is close to zero. When X equals methoxy, intramolecular electron transfer occurs with the naphthalene ring serving as the acceptor and the methoxyaromatic as the donor. This exciplex fragments to carbon dioxide and 1-(I-naphthy1)-2-arylethane.Key words: acyloxy radical, decarboxylation, photolysis of benzylic esters.JAMES W. HILBORN et JAMES A. PINCOCK. Can. J. Chem. 70, 992 (1992). La photolyse des esters 6 et 8 dans le methanol conduit ii la formation de produits resultant ii la fois de cations et de radicaux naphtylmethyles. Pour les esters 6, la distribution des produits est independante de la nature de X, except6 lorsque X est un groupe methoxyle. On propose un mecanisme impliquant un clivage initial homolytique de la liaison carboneoxygkne dans 1'Ctat singulet excite de l'ester. Une competition entre le transfert d'electrons dans la paire de radicaux pour former la paire d'ions et la dtcarboxylation du radical arylacyloxy permet de calculer les vitesses de ce processus de decarboxylation. La valeur de p versus a s'approche de zero. Lorsque X est un groupe methoxyle, il se produit un transfert intramolCculaire d'tlectrons avec le noyau naphtalenique servant de accepteur et le fragment methoxyaromatique agissant comme donneur. Cet exciplexe se fragmente en dioxyde de carbone et I-(I-naphty1)-2-arylethane.

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“…A reasonable suggestion for these observations was that the excited singlet state was being quenched by intramolecular electron transfer, as is well documented for bichromophoric systems where the chromophores are separated by a three-carbon saturated chain (7,8). T o investigate this possibility the set of substituted benzoates 5a-g was synthesized and their excited-state behaviour examined.…”

Section: Introductionmentioning

confidence: 73%

Intramolecular electron transfer in the photochemistry of substituted 1-naphthylmethyl esters of benzoic acids

DeCosta¹,

Pincock²

1992

Can. J. Chem.

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Direct excitation of the esters 5 in methanol solvent leads to rapid intramolecular exciplex formation (kc, = 1 0 '~s -' for X = CH30, Y = CN) with electron transfer from the naphthalene to the benzoate ring. This process dominates the usual fluorescence and reaction of the excited singlet state. The rate of this process can be varied over lo3 by suitable change in the substituents X and Y. The electron-transfer rates can be correlated with the two-parameter Hammett equation: log kc, = 8.48 -l .5u+ + 0.775. For cases where the rate of exciplex formation is slow, the usual homolytic carbon-oxygen bond cleavage occurs from the excited singlet state. The eventual products result from the ion pair since the rate of electron transfer in the radical pair to form the ion pair is considerably faster than the rate of decarboxylation of the benzoyloxy radical. IntroductionThe photochemistry of benzylic compounds with leaving groups (ArCH2-LG) is well known (1) to give products that result from both arylmethyl cations and radicals. The partitioning between these two intermediates is controlled by a variety of factors such as the leaving group, the structure of the aromatic ring including substituent effects, the nature of the excited state (singlet or triplet), and the solvent. In general, these factors are still so poorly understood that a reliable prediction about the products for any new system is impossible.

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Intramolecular excimer formation in bichromophoric molecules linked by a short flexible chain

Cited by 190 publications

References 60 publications

Pyrene‐Excimers‐Based Antenna Systems

Pyrene‐Excimers‐Based Antenna Systems

Photolysis of the 1-naphthylmethyl ester of substituted phenylacetic acids: intramolecular charge transfer and rates of decarboxylation of arylacyloxy radicals

Intramolecular electron transfer in the photochemistry of substituted 1-naphthylmethyl esters of benzoic acids

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