In-depth analysis of the photophysics of BOPAHY dyes in solution, glass and film

Aromatic-Ring-Fused BOPPY Fluorophores: Synthesis, Spectral, Redox Properties, and Bioimaging Application

“…Conformation-restricted 1e in toluene displayed two wellsplit absorbance with maxima at 502 and 537 nm, which might be ascribed to the vibrational fine structure of the same excited state rather than to the different excited states. 27,55 After the chloride atom of 1e is substituted by the amino groups, the resulting BOPPYs 1f and 1g exhibited slight changes in their absorption maxima in comparison with 1e. β-Benzothiophenefused BOPPYs 2a−c exhibit the maximum absorption peaks at 482, 492, and 486 nm in toluene, respectively, which exhibit 64−74 nm bathochromic shifts of the absorption maximum compared to that of the parent BOPHY.…”

Synthesis and photophysical properties of (post-)functionalized BOAHY dyes with strong aggregation-induced emission

“…45 Therefore, the shift in absorption wavelength maximum is larger upon substitution with thiophene (424 nm for 2e ) when compared to furan (416 nm for 2d ). Quite surprisingly and in contrast with similar compounds 11–13 the Stokes shift and FWHM of the emission band are not increased upon introduction of this substituent. This indicates very little electron–phonon coupling with rotation of this substituent or a difference in its coplanarity in ground and excited state.…”

“…The suppression of these rotations due to rigidification in the solid state cause the high fluorescence quantum yields of the solid powders compared to the solutions. When one compares spectra and fluorescence decay times of BOAHYs with the aryl substituted BOPAMs 57 or BOPAHYs 11 the generally much faster nonradiative decay of the BOAHYs is not reflected systematically in a significantly broader spectra or a significantly larger Stokes shift. This indicates that this pyrrole nucleus has a similar degree of coplanarity in the ground and excited state, perhaps related to H-bonding between the pyrrole NH and a nitrogen atom of the hydrazone moiety.…”

“…3,4 Furthermore, owing to its strong electron-withdrawing effect, the difluoroboron group can facilitate intramolecular charge transfer (ICT), leading to small bandgaps and long absorption and emission wavelengths. [4][5][6][7][8] The benefits of incorporating this difluoroboron moiety have fueled the development of a multitude of organoboron compounds, including BODIPY, 2,9,10 BOPAHY, [11][12][13] BOPHY 14,15 and BOPPY 16 derivatives (Fig. 1).…”

“…Applications such as light harvesting, optoelectronic devices, chemical sensing, biological imaging and medical theranostics have been reported for these dyes. 2,8,10–16…”