Excited state dynamics of 3,6-diaryl-1,2,4,5-tetrazines. Experimental and theoretical studies

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• 作者：Marcel Plugge^a ; Valé ; rie Alain-Rizzo^b ; Pierre Audebert^b ; Albert M. Brouwer^a ; ^{a.m.brouwer@uva.nl}
• 关键词：Fluorescence ; Nonradiative decay ; Femtosecond transient absorption ; Time-dependent density functional theory
• 刊名：Journal of Photochemistry and Photobiology A ; Chemistry
• 出版年：2012
• 期刊代码：66_10106030
• 类别：ch
• 出版时间：15 April, 2012
• 卷：234
• 期：Complete
• 页码：12-20
• 文件大小：1307 K

摘要

The photophysical behavior was studied of three symmetrical 1,2,4,5-tetrazine derivatives substituted with two aromatic substituents (phenyl: DPT; p-methoxyphenyl: DAT; thiophen-2-yl: DTT). The UV-visible absorption spectra of these compounds in cyclohexane and acetonitrile show two absorption maxima at 500-550 nm and 290-330 nm, as well as a shoulder at lower energies on the latter absorption band. The electronic transitions were assigned on the basis of TD-DFT calculations. In contrast with some other tetrazine derivatives, these compounds exhibit only weak fluorescence (桅_f 鈮?#xA0;10^鈭? to 10^鈭?) from the S₁ (n蟺*) state. When the molecules are excited to a higher energy 蟺蟺* state, fluorescence from the nth excited state (n = 6 for DPT, n = 5 for DAT and n = 4 for DTT) is detected. Time-correlated single photon counting (TC-SPC) and femtosecond transient absorption (fs-TA) measurements showed that internal conversion from the S_n state to the S₁ state is unusually slow, of the order of 30 ps for DTT and 20 ps for DAT.