Zhu L, Becker HC, Henriksen L, Kilså K. A class of fluorescent heterocyclic dyes revisited: photophysics, structure, and solvent effects.
SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2009;
73:757-763. [PMID:
19457716 DOI:
10.1016/j.saa.2009.03.026]
[Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2008] [Revised: 02/09/2009] [Accepted: 03/30/2009] [Indexed: 05/27/2023]
Abstract
The photophysical behavior of a series of 2-methylthio-5-(Z-carbonyl)thieno-[3,4-e]-3,4-dihydro-1,2,3-triazine-4-ones was investigated by absorption and emission spectroscopy in a range of solvents representing a systematic variation in polarity, polarizability, as well as hydrogen bond donating and accepting capabilities. In all the investigated compounds, the heterocyclic 6-membered ring of the chromophore is involved in interactions between electron donor and acceptor substituents on the thiophene ring. Throughout the series, the charge-donating methylthio group is kept constant, while the acceptor (Z-carbonyl) is varied between amide, ester, and ketone functionalities. The fluorescent first electronically excited state is primarily of intramolecular HOMO-LUMO charge transfer character. All members of the series exhibit solvent-dependent photophysics, although the magnitude of the dependence varies with the nature of the acceptor group. In addition to the solvent-sensitive photophysics, the investigated class of compounds shows high thermal and chemical stability. Among this class of heterocyclic dyes, the amide-substituted compound is superior with respect to high quantum yield and lifetime, and also shows the largest change in emission lifetimes and fluorescence quantum yields upon solvent variation (about 5-fold).
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