Changes in carbon-carbon and carbon-nitrogen stretching force constants in the macrocycles of bacteriochlorophyll a and bacteriopheophytin a upon triplet singlet excitation: Resonance-Raman spectroscopy and normal-coordinate analysis of the unlabeled and totally (super 15)N-, (super 13)C-, and (super 2)H-labeled species

Article Abstract:

The normal-coordinate analyses of the S0, T1, and S1 Raman spectra of unlabeled and (super 15)N-, (super 13)C-, and (super 2)H-labeled BChl a and BPhe a were performed to determine the stretching force constants of the carbon-carbon and the carbon-nitrogen bonds within the bacteriochlorin macrocycle. Changes in bond order upon triplet and singlet excitation were characterized in both BChl a and BPhe a, by the use of the stretching force constants as a scale.

Science & research, Chemical properties

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Changes in the carbon-carbon and carbon-nitrogen bond orders in the macrocycle of chlorophyll a upon singlet and triplet excitation as probed by resonance Raman spectroscopy of natural-abundance and singly and doubly labeled species with 15N, 13C, and 2H isotopes

Article Abstract:

A study was conducted to analyze alterations in the carbon-carbon and carbon-nitrogen bond orders associated with the macrocycle of chlorophyll a upon singlet and triplet excitation. Raman spectra was obtained in ethanol solution using the CW 457.9 nm line while 14N and 13C-Chl were determined from the cells of Chlamydomonas reinhardtii C-9. Results indicated that inversion of bond orders correlated with triplet excitation as averaged values.

Nitrogen (Chemical element), Nitrogen, Chlorophyll

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The 1Bu+, 1Bu-, and 2Ag- energies of crystalline lycopene, beta-carotene, and mini-9-beta-carotene as determined by resonance-Raman excitation profiles: dependence of the 1Bu- state energy on the conjugation length

Article Abstract:

Research into the energies of the optically forbidden 2Ag- and 1Bu- states of crystalline carotenoids is presented. It is suggested that the 1Bu- state plays a significant role in mediating the 1Bu+-to-2Ag- internal conversion.

Raman effect, Carotenoid metabolism

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