Title:	Transient Raman Snapshots of the Twisted Intramolecular Charge Transfer State in a Stilbazolium Dye
Authors:	Karmakar, Shreetama Ambastha, Abhinandan Dharmadhikari, J.A. +4 Co-Authors
Issue Date:	Jun-2020
Publisher:	American Chemical Society
Citation:	The Journal of Physical Chemistry Letters, 2020, Vol.11, p4842−4848
Abstract:	Optically triggered twisted intramolecular charge transfer (TICT) states in donor–acceptor chromophores form the molecular basis for designing bioimaging probes that sense polarity, microviscosity, and pH in vivo. However, a lack of predictive understanding of the “twist” localization precludes a rational design of TICT-based dyes. Here, using femtosecond stimulated Raman spectroscopy, we reveal a distinct Raman signature of the TICT state for a stilbazolium-class mitochondrial staining dye. Resonance-selective probing of 4-N,N-diethylamino-4″-N′-methyl-stilbazolium tosylate (DEST) tracks the excited-state structure of the dye as it relaxes to a TICT state on a picosecond time scale. The appearance of a remarkably blue-shifted C=C stretching mode at 1650 cm–1 in the TICT state is attributed to the “twist” of a single bond adjacent to the ethylenic π-bridge in the DEST backbone based on detailed electronic structure calculations and vibrational mode analysis. Our work demonstrates that the π-bridge, connecting the donor and acceptor moieties, influences the spatial location of the “twist” and offers a new perspective for designing organelle-specific probes through cogent tuning of backbone dynamics.
Description:	Restricted Access
URI:	http://hdl.handle.net/2289/7491
ISSN:	1948-7185
Alternative Location:	https://doi.org/10.1021/acs.jpclett.0c01124
Copyright:	2020 American Chemical Society
Additional information:	Supporting Information Available
Appears in Collections:	Research Papers (LAMP)

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