Photophysical and spectroscopic manifestations of the low-lying pi sigma* state of 4-(dimethylamino)benzethyne: solvent-polarity dependence of fluorescence and excited-state absorptions

From National Research Council Canada

DOI	Resolve DOI: https://doi.org/10.1039/B820371G
Author	Search for: Fujiwara, Takashige; Search for: Lee, Jae-Kwang; Search for: Zgierski, Marek Z.¹; Search for: Lim, Edward C.
Affiliation	National Research Council of Canada. NRC Steacie Institute for Molecular Sciences
Format	Text, Article
Subject	photophysics; spectrospopic manifestations; polar environments; computational study; nanosecond
Abstract	concerted experimental and computational study of 4-(dimethylamino)benzethyne, DMABE, has been carried out to probe the low-lying pisigma* state and the role it plays in the photophysics of the molecule. The subpicosecond transient absorption spectra reveal the presence of a strong excited-state absorption at about 700 nm and a weaker absorption at about 520 nm. The observed absorption maxima are in excellent agreement with the TDDFT calculations that place a strongly allowed pisigma* <--pisigma* transition at 750 nm, and a weaker pipi* <--pipi* (LE) transition at 528 nm. This agreement combined with the differing decay times, and differing solvent shifts of the two transients, allow assignments of the 700 nm absorption to the pisigma* state and the 520 nm absorption to the LE (pipi) state. The bifurcation of the initially excited L(a) (pipi) state into the pisigma* state and the LE state, as probed by transient absorption, is strongly influenced by solvent polarity, with polar environments favoring the L(a)-->pisigma* decay channel over the competing L(a)--> LE decay channel. The nanosecond radiationless decay of the LE state to the dark pisigma* state is also strongly enhanced in polar environments, thus accounting for the dramatic quenching of fluorescence in solvents of high polarity.
Publication date	2009-05-01
In	Physical Chemistry Chemical Physics 11, no. 14: 2475–2479.
Language	English
Peer reviewed	Yes
NRC publication	This is a non-NRC publication "Non-NRC publications" are publications authored by NRC employees prior to their employment by NRC.
NPARC number	16751241
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Record identifier	ac509da6-df09-465a-8088-526c7b6b847b
Record created	2011-02-09
Record modified	2020-04-16

Date modified:: 2024-04-26