Unveiling the Hidden, Dark, and Short Life of a Vibronic State in a Boron Difluoride Formazanate Dye.
Angew Chem Int Ed Engl
; 58(43): 15339-15343, 2019 Oct 21.
Article
em En
| MEDLINE
| ID: mdl-31419366
Boron difluoride (BF2 ) formazanate dyes are contenders for molecular species that exhibit a large Stokes shift and bright red emission. Excitation of 3-cyanoformazanate complexes with 10â
µs wide pulses of specific wavelengths resulted in strong luminescence at 663â
nm at both room temperature in solution and at 77â
K in a frozen solution. Analysis of the short-lived excitation spectrum from this luminescence shows that it arises from a vibronic manifold of a higher-lying excited state. This dark state relaxes to the emitting state over 10â
µs. TD-DFT calculations of the two lowest-energy excited states show that the relaxed geometries are planar for S1 but highly distorted in S2 . The specific time- and wavelength-dependence of the excitation profile provides a unique optical encryption capability through the comparison of emission intensities between adjacent vibronic bands only accessible in the 0-12â
µs time domain.
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MEDLINE
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En
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2019
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Article