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Intramolecular energy transfer in compounds with two 1-pyrenoate groups separated by methylene spacers (1996)

Bravo, Julio ; Mendicuti, Francisco ; Saiz, Enrique ; [et al.]

Springer

Journal of fluorescence 6 (1996), S. 41-50

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ISSN: 1573-4994

Keywords: Intramolecular energy transfer ; 1-pyrenoate ; methylene spacers ; fluorescence anisotropy ; fluorescence lifetime

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract Steady-state fluorescence anisotropy (r) and fluorescence lifetime (τ) measurements have been used to study the efficiency of nonradiative singlet energy transfer as a function of alkane size in 1-pyrenecarboxylic acid alkanediyl esters (as a function ofm in Py-COO-(CH2) m -OOC-Py, where Py denotes pyrene substituted in the 1-position, andm=2–6). Experiments were performed in media of different viscosity, η, obtained by changing the temperature (from −20 to 40°C) of dilute solutions in ethylene glycol and by examination of the compounds in a solid matrix of poly(methyl methacrylate) (PMMA) at ambient temperature. The Py-COO-(CH2)m-OOC-Py exhibit intramolecular excimer emission in ethylene glycol at these temperatures, but the intensity of this emission is much lower than when these compounds are placed in common solvents of lower η. The values of τ indicate that excitation hopping or intramolecular energy transfer takes place between the chromophores attached to the ends of the alkane bridges. Values ofr obtained by the extrapolationsT/η→0 orτT/η→0 in ethylene glycol, as well as the values obtained in the rigid matrix of PMMA, show very little dependence onm. A theoretical conformational analysis, using the rotational isomeric state (RIS) model, was also performed. The combination of the experimental results forr in the media of high η with the theoretical (RIS) analysis produces an estimated value of 21 ±2 Å for the Förster radius in Py-COO-(CH2)m-OOC-Py.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00726725

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Conformation of the ground-state dimer in poly(ethylene terephthalate) (1993)

Dodge, Robert W. ; Mattice, Wayne L.

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 207-212

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ISSN: 0887-6266

Keywords: dimer ; fluorescence ; PET ; poly(ethylene terephthalate) ; Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: Absorbance, excitation, and emission measurements have been performed with methyl benzoate and five model compounds, C6H5COO (CH2)xOOCC6H5, x = 2-6. Under appropriate conditions, three of the model compounds (those with x = 3, 4, 5) show evidence for the formation of intramolecular ground-state dimers. The model compound with x = 5 can form two types of dimers which emit with different energies. The model compound with x = 3 forms one of these dimers, and the model compound with x = 4 prefers the other ground-state dimer. Molecular modeling of the dimers suggests that the two conformations of the ground-state dimers differ in the orientation of the two C=O bonds. In the one dimer these two bonds are nearly parallel, but in the other they make an angle of about 120°. © 1993 John Wiley & Sons, Inc.

Additional Material: 7 Ill.