New Insight into the Origin of the Red/Near-Infrared Intense Fluorescence of a Crystalline 2-Hydroxychalcone Derivative: A Comprehensive Picture from the Excited-State Femtosecond Dynamics

Zahid, N.I. and Mahmood, M.S. and Subramanian, B. and Said, S.M. and Abou-Zied, O.K. (2017) New Insight into the Origin of the Red/Near-Infrared Intense Fluorescence of a Crystalline 2-Hydroxychalcone Derivative: A Comprehensive Picture from the Excited-State Femtosecond Dynamics. Journal of Physical Chemistry Letters, 8 (22). pp. 5603-5608. ISSN 1948-7185

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Official URL: http://dx.doi.org/10.1021/acs.jpclett.7b02601

Abstract

Fluorescence upconversion and transient absorption techniques are used to explain the source of the intense red/near-infrared emission of crystalline 4-dimethylamino-2′-hydroxychalcone. We found that the initially excited enol form undergoes tautomerization in 3 ps to form the keto tautomer. The latter is stable in the ground state as a consequence of J-type aggregation in the crystal packing and is manifested in an absorption peak at 550 nm that spectrally overlaps with the short-lived enol emission, leading to self-reabsorption and adding a factor to the complete depletion of the enol emission. Relaxation of the keto tautomer takes place in the form of intense fluorescence (600-750 nm) with 1.7 ns lifetime. The different spectroscopy in solution is due to vibrational cooling (300 fs), followed by solvation dynamics (5 ps in methanol) and twisting of the hydroxyphenyl ring (16 ps), before relaxation of the enol tautomer in the form of weak green fluorescence with 350 ps lifetime.

Item Type: Article
Uncontrolled Keywords: Crystalline materials; Fluorescence; Ground state
Subjects: Q Science > QD Chemistry
T Technology > TK Electrical engineering. Electronics Nuclear engineering
Divisions: Faculty of Engineering
Faculty of Science > Dept of Chemistry
Depositing User: Ms. Juhaida Abd Rahim
Date Deposited: 08 Jun 2018 07:11
Last Modified: 08 Jun 2018 07:11
URI: http://eprints.um.edu.my/id/eprint/18861

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