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Theoretical Study of Fluorescence Spectra Utilizing the p K a Values of Acids in Their Excited States
Author(s) -
Hiyama Miyabi,
Akiyama Hidefumi,
Yamada Kenta,
Koga Nobuaki
Publication year - 2013
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/php.12156
Subject(s) - excited state , fluorescence , chemistry , protonation , emission spectrum , analytical chemistry (journal) , spectral line , absorption (acoustics) , aqueous solution , photochemistry , atomic physics , physics , ion , organic chemistry , quantum mechanics , astronomy , chromatography , acoustics
Assignment of the fluorescence spectrum of firefly luciferin in aqueous solutions was achieved by utilizing not only emission energies but also theoretical absorption spectra and relative concentrations as estimated by p K a values. Calculated Gibbs free energies were utilized to estimate p K a values. These p K a values were then corrected by employing the experimental results. It was previously thought that the main peak near 550 nm observed in the experimental fluorescence spectra at all pH values corresponds to emission from the first excited state of the luciferin dianion [Ando et al . (2010) Jpn. J. Appl. Phys. 49, 117002–117008]. However, we found that the peak near 550 nm at low pH corresponds to emission from the first excited state of the phenolate monoanion of luciferin. Furthermore, we found that the causes of the red fluorescence at pH 1–2 are not only the emission from phenol monoanion but also the emission from the protonated species at nitrogen atom in the thiazoline ring of dianion.