Ultrafast processes triggered by one- and two-photon excitation of a photochromic and luminescent hydrazone

Year: 2019

Authors: Iagatti Alessandro; Shao Baihao; Credi Alberto; Ventura Barbara; Aprahamian Ivan; Di Donato Mariangela

Autors Affiliation: LENS European Lab Nonlinear Spect, Via N Carrara 1, I-50019 Sesto Fiorentino, FI, Italy; Dartmouth Coll, Dept Chem, Hanover, NH 03755 USA; Univ Bologna, Dipartimento Sci & Tecnol Agroalimentari, CLAN, Viale Fanin 50, I-40127 Bologna, Italy; CNR, Ist Sintesi Organ & Fotoreatt, Via Gobetti 101, I-40129 Bologna, Italy; INO, Largo Enrico Fermi 6, I-50125 Florence, Italy.

Abstract: In this work we apply a combination of steady state and time resolved luminescence and absorption spectroscopies to investigate the excited-state dynamics of a recently developed molecular photoswitch, belonging to the hydrazone family. The outstanding properties of this molecule, involving fluorescence toggling, bistability, high isomerization quantum yield and non-negligible twophoton absorption cross section, make it very promising for numerous applications. Here we show that the light induced Z/E isomerization occurs on a fast <1 ps timescale in both toluene and acetonitrile, while the excited state lifetime of the Z-form depends on solvent polarity, suggesting a partial charge transfer nature of its low lying excited state. Time-resolved luminescence measurements evidence the presence of a main emission component in the 500-520 nm spectral range, attributed to the Z-isomer, and a very short living blue-shifted emission, attributed to the E-isomer. Finally, transient absorption measurements performed upon farred excitation are employed as an alternative method to determine the two-photon absorption cross-section of the molecule. Journal/Review: BEILSTEIN JOURNAL OF ORGANIC CHEMISTRY

Volume: 15      Pages from: 2438  to: 2446

More Information: This work was supported by the European Union, through the Horizon 2020 Research and Innovation Program (RIA “Laserlab-Europe”, n. 654148 and ERC AdG “Leaps” n. 692981 to A. C.). I. A. acknowledges the generous support of the National Science Foundation (DMR-1506170). Support from Italian CNR (Project ´PHEEL´) is also acknowledged.
KeyWords: hydrazone; molecular switch; pump-probe spectroscopy; time-resolved fluorescence
DOI: 10.3762/bjoc.15.236

Citations: 8
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