Vibrationally hot fluorescence in chlorophyll-a

Menzel, E. R.; Polles, J. S.

doi:10.1016/0009-2614(74)80176-4

Cited by 13 publications

(4 citation statements)

References 7 publications

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“…Such fluorescence would occur from excited (unrelaxed) vibrational components of the excited electronic state. Hot-band fluorescence was previously reported on the basis of measurements at 77 K of fluorescence emission spectra of Chl a in two glass-forming solvent mixtures: EPA (diethyl ether/isopentane/ethanol) and PM (isopentane/methyl cyclohexane) . Although it was subsequently shown that this report of hot-band fluorescence probably owed itself to the presence of impurities, nevertheless the presence of hot-band fluorescence is a straightforward way of accounting for the behavior that we find for BChl a in the ITR.…”

Section: Discussionsupporting

confidence: 64%

“…Hot-band fluorescence was previously reported on the basis of measurements at 77 K of fluorescence emission spectra of Chl a in two glass-forming solvent mixtures: EPA (diethyl ether/isopentane/ethanol) and PM (isopentane/methyl cyclohexane). 38 Although it was subsequently shown that this report of hot-band fluorescence probably owed itself to the presence of impurities, 39 nevertheless the presence of hot-band fluorescence is a straightforward way of accounting for the behavior that we find for BChl a in the ITR. The blue shift of the new emission feature, the absence of any corresponding mirror-image absorption, and the lack of correlation with the Q x absorption changes are all readily understandable if the new fluorescence originates in higher-energy vibronic components of the Q y emission manifold.…”

Section: Discussionmentioning

confidence: 62%

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Temperature Dependence of Optical Spectra of Bacteriochlorophyll a in Solution and in Low-Temperature Glasses

Bellacchio

Sauer

1999

J. Phys. Chem. B

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Absorption, fluorescence emission, and fluorescence excitation spectra of bacteriochlorophyll a [BChl a] are examined throughout the temperature range from 298 to 79 K in several glass-forming solvents. Changes in the absorption spectra that occur continuously throughout this range may reflect increased extent of coordination of the central Mg, changes in solvent dielectric, and/or altered hydrogen bonding. Fluorescence emission spectra exhibit a new feature that grows steadily, beginning at temperatures below about 250 K in solvents that are hydrogen-bond donors: 1-propanol and 2-propanol. The emerging fluorescence band, located about 300 cm-1 to the blue of the fluorescence band seen at higher temperatures, achieves nearly equal amplitude at 163 K and below. It is noteworthy that no corresponding feature appears in the absorption on the blue side of the Q y absorption band. The Kennard−Stepanov relation between absorption and fluorescence, which holds with somewhat elevated T* values in the high-temperature region, is seen to fail dramatically at lower temperatures as the short-wavelength fluorescence feature grows. The short-wavelength feature is interpreted as fluorescence resulting from an excited electronic state that is conformationally unrelaxed. At temperatures below 178 K evidence for additional spectroscopic features appears, especially in conjunction with measurements of emission spectra using different excitation wavelengths and of excitation spectra of fluorescence measured at different emission wavelengths. This is in the region of matrix glass formation, and the new BChl a components may reflect site inhomogeneity. Similar spectroscopic studies of BChl a in non-hydrogen-bonding solvents do not provide evidence of new blue-shifted fluorescence in the 298−79 K temperature range. They do, however, exhibit evidence of site inhomogeneity in the low-temperature glass matrices. Implications are discussed regarding the interpretation of low-temperature spectral features that have been reported for photosynthetic membranes and isolated pigment−proteins.

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Section: Discussionsupporting

confidence: 64%

Section: Discussionmentioning

confidence: 62%

Temperature Dependence of Optical Spectra of Bacteriochlorophyll a in Solution and in Low-Temperature Glasses

Bellacchio

Sauer

1999

J. Phys. Chem. B

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“…The uppermost trace is that for stock Chl diluted in t-butyl methyl ether solution, with detection at 628 nm. There is no band at this wavelength in the fluorescence spectrum, but a sort of low plateau that might be anti-Stokes fluorescence (Menzel and Polles, 1974), or perhaps just leakage of normal fluorescence, extending to the blue of the main fluorescence band. The excitation spectrum is appropriate for Chl, and qualitatively the same as that for excitation of 670 nm fluorescence (not shown) in the same solution, which confirms the contention that there was no protochlorophyll in the stock solution.…”

Section: Introductionmentioning

confidence: 99%

ON THE ORIGIN OF 628 nm FLUORESCENCE IN CERTAIN CHLOROPHYLL PREPARATIONS

Seely¹

1992

Photochem & Photobiology

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A fluorescence band at 628 nm seen in certain preparations of chlorophyll on polyethylene particles swollen with tetradecane comes not from an impurity of protochlorophyll in the original chlorophyll, but from a substance like protochlorophyll formed upon adsorption of chlorophyll to the particles. Much of the chlorophyll is grafted to polyethylene in the same particles by a process that does not affect the chromophore. These and other properties peculiar to the particles are tentatively ascribed to a prior free radical oxidation process in the swollen particles.

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“…The intensity varies with temperature which is explained by an exciton trapping model. A new report on the fluorescence of chl a in EPA [88] attributes earlier reports [89,751 of hot fluorescence due to impurities and that of chl dimers due to self-absorption. Apparently, there are no dimers in solution up to M from 77-298 K…”

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confidence: 99%

Excited States of Biomolecules—iv

Fugate

Song

1976

Photochem & Photobiology

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The electronic excited states of biomolecules are selectively reviewed from approximately mid 1975 through mid 1976. The inclusion of all papers has not been attempted and exclusion does not necessarily reflect the pertinence of a paper. We urge authors to send us their reprints for future series of this Yearly Review. Porphyrins and chlorophyllsThe CND0/2 calculations have been performed for chlorophyll a (chl a), chlorophyll b (chl b) and their Be analogs [65]. Results indicate that the 3d atomic orbitals of the metal contribute significantly to the CJ and n bonding energies. The molecule is stabilized by 167 kJ . mol-' (40 kcal mol-I) when MgZf is replaced by Be2+. Shipman et al. [ 12 11 have discussed

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Vibrationally hot fluorescence in chlorophyll-a

Cited by 13 publications

References 7 publications

Temperature Dependence of Optical Spectra of Bacteriochlorophyll a in Solution and in Low-Temperature Glasses

Temperature Dependence of Optical Spectra of Bacteriochlorophyll a in Solution and in Low-Temperature Glasses

ON THE ORIGIN OF 628 nm FLUORESCENCE IN CERTAIN CHLOROPHYLL PREPARATIONS

Excited States of Biomolecules—iv

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