Browsing by Author "Lin, ShengHien"

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Localized Emitting State and Energy Transfer Properties of Quadrupolar Chromophores and (Multi)Branched Derivatives
(1970-01-01)
Yan, Linyin
;
Chen, Xudong
;
He, Qingguo
;
Wang, Yingying
;
Wang, Xuefei
"In order to better understand the nature of intramolecular charge and energy transfer in multibranched molecules, we have synthesized and studied the photophysical properties of a monomer quadrupolar chromophore with donor-acceptor-donor (D-A-D) electronic push-pull structure, together with its V-shaped dimer and star-shaped trimers. The comparison of steady-state absorption spectra and fluorescence excitation anisotropy spectra of these chromophores show evidence of weak interaction (such as charge and energy transfer) among the branches. Moreover, similar fluorescence and solvation behavior of monomer and branched chromophores (dimer and trimer) implies that the interaction among the branches is not strong enough to make a significant distinction between these molecules, due to the weak interaction and intrinsic structural disorder in branched molecules. Furthermore, the interaction between the branches can be enhanced by inserting pi bridge spacers (-C=C- or -C C-) between the core donor and the acceptor. This improvement leads to a remarkable enhancement of two photon cross sections, indicating that the interbranch interaction results in the amplification of transition dipole moments between ground states and excited states. The interpretations of the observed photophysical properties are further supported by theoretical investigation, which reveal that the changes of the transition dipole moments of the branched quadrupolar chromophores play a critical role in observed the two-photon absorption (2PA) cross-section for an intramolecular charge transfer (ICT) state interaction in the multibranched quadrupolar chromophores."
The molecular structures and spectroscopic properties of the ground state and the first excited state of pVP
(2017-10-01)
Wu, Lidan
;
Yan, Linyin
;
Xia, Andong
;
Lin, ShengHien
;
應用化學系
P-vinylphenol (pVP) is a common building block of a large number of fluorescent protein chromophores. Theoretical investigation employed TD-DFT calculation has been carried out on pVP molecule to reveal the structural properties that influence the absorption and fluorescence. The molecular structures of the first excited state (S-1) as well as the ground state (S-0) have been optimized. Based on these structures, the absorption spectra are simulated using the Franck-Condon factors and displaced-distorted harmonic oscillator model. The result agrees well with the reported experiment data. It's also found that the S-0 -> S-1 transition is a significant pi -> pi* transition. Besides the pi electrons on the benzene ring, the pi electron together with the lone pair electron on hydroxyl group takes parts in the transition. Therefore the absorption of pVP would be modulated not only by the isomerization but also by the intermolecular hydrogen bond. (C) 2017 Elsevier B.V. All rights reserved.