Organic photochemistry. XII. Further studies on the mechanism of coumarin photodimerization, observation of an unusual "heavy atom" effect

Hoffman, Richard; Wells, Paula P.; Morrison, Harry

doi:10.1021/jo00800a022

Cited by 98 publications

(70 citation statements)

References 2 publications

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“…The smaller singlet concentration increases the relative concentration of excited triplet state coumarins, thus pushing the dimer equilibrium toward the anti products. 72,73,77 Belfield and co-workers recently studied the two-photon dimerization of 5,7-dimethoxycoumarin as a model for psoralen enone photochemistry. 79 They found that ratios of the dimer formed, via two-photon excitation at 650 nm, were similar to the ratios achieved with the traditional single-photon UV exposure.…”

Section: Photodimerization and Photocleavagementioning

confidence: 99%

Coumarins in Polymers: From Light Harvesting to Photo-Cross-Linkable Tissue Scaffolds

et al. 2004

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Section: Photodimerization and Photocleavagementioning

confidence: 99%

Coumarins in Polymers: From Light Harvesting to Photo-Cross-Linkable Tissue Scaffolds

et al. 2004

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“…320 8C, although most coumarin dimers melt between 170 and 200 8C depending on configuration. [12][13][14][15][16] Although Ciamician and Silber first discovered photodimerization reactions involving coumarin in 1902, the photocleavage reaction was not discovered until the 1960's when Schenck and coworkers further studied the photodimerization reaction. [14,15] It is important to note that neither the photodimerization nor the photocleavage reactions are thermally allowed.…”

Section: Introductionmentioning

confidence: 99%

Photoreversible Chain Extension of Poly(ethylene glycol)

Trenor

Long

Love

2004

Macro Chemistry & Physics

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Summary: Coumarin containing poly(ethylene glycol) monols and diols were prepared in a telechelic fashion using quantitative end group esterification. The coumarin modified poly(ethylene glycol) monols and diols were solution cast into films (1 to 15 μm) and chain extended via the dimerization of the coumarin derivatives with UVA (>300 nm) light irradiation. The coumarin‐modified PEG diol doubled in molecular weight, and the molecular weight distribution increased from 1.17 to 2.75 upon exposure to 110 J · cm−2 of UVA light. The chain extended poly(ethylene glycol)s were subsequently converted to their original molecular weight via the photocleavage reaction of the coumarin dimer at 254 nm with less than 2 J · cm−2. The photoreversible chain length modulation was monitored utilizing GPC, DSC and UV‐Vis spectroscopy.Molecular weight modulation of COU‐PEG‐COU.magnified imageMolecular weight modulation of COU‐PEG‐COU.

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“…The reaction proceeds by a [2p ? 2p] cycloaddition of the ethylenic groups (Hoffman et al 1971). Additionally to the photodimerization, a light induced photocleavage allows dimers to revert to their original structure (Krauch et al 1966).…”

Section: Photochemical Behaviormentioning

confidence: 99%

Water soluble photoactive cellulose derivatives: synthesis and characterization of mixed 2-[(4-methyl-2-oxo-2H-chromen-7-yl)oxy]acetic acid–(3-carboxypropyl)trimethylammonium chloride esters of cellulose

2012

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Photoactive derivatives of cellulose were prepared by a mild esterification of the biopolymer with 2-[(4-methyl-2-oxo-2H-chromen-7-yl)oxy]acetic acid via the activation of the carboxylic acid with N,N 0 -carbonyldiimidazole. Subsequently, modification with the cationic carboxylic acid (3-carboxypropyl)trimethylammonium chloride was carried out. Thus, water soluble polyelectrolytes decorated with high amounts of photochemically active chromene moieties were obtained. The structures of the novel polysaccharide esters and the polyelectrolytes were evaluated by means of NMR and IR spectroscopy. Moreover, the light triggered photodimerization of the chromene moieties of the photoactive polyelectrolytes was studied by means of UV-Vis spectroscopy in the dissolved state. The photochemistry observed may be used to control the properties of the new polysaccharide derivatives and are thus of interest in the design of smart materials.

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Organic photochemistry. XII. Further studies on the mechanism of coumarin photodimerization, observation of an unusual "heavy atom" effect

Cited by 98 publications

References 2 publications

Coumarins in Polymers: From Light Harvesting to Photo-Cross-Linkable Tissue Scaffolds

Coumarins in Polymers: From Light Harvesting to Photo-Cross-Linkable Tissue Scaffolds

Photoreversible Chain Extension of Poly(ethylene glycol)

Water soluble photoactive cellulose derivatives: synthesis and characterization of mixed 2-[(4-methyl-2-oxo-2H-chromen-7-yl)oxy]acetic acid–(3-carboxypropyl)trimethylammonium chloride esters of cellulose

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