Solvent-dependent steady-state fluorescence spectroscopy for searching ESPT-dyes: solvatochromism of HPTS revisited

Abstract

We reinvestigated the solvatochromism of 8-hydroxypyrene-1,3,6-trisulfonate (pyranine) in conjunction with that of 8-methoxypyrene-1,3,6-trisulfonate and of 1-hydroxypyrene (pyrenol) by use of 25 different solvents. Conclusions for the prediction of ESPT behaviour of synthetic dyes were drawn by comparison with the solvatochromism of p-hydroxystyryl Bodipy dyes. Solvents were chosen according to their Kamlet-Taft parameters alpha and beta for elucidating the acidicity of the dyes and the basicity of their conjugated bases in the ground and excited state. Comparison of the spectra of pyranine and pyrenol in solvents with varying beta-values revealed that the acidity of both dyes is similar therein. The well-known ESPT behaviour of pyranine in water is assigned to a change of the electronic state at alpha-values approximately 0.7 to 0.8. The high acidity of this excited state also appears in the vanishing solvatochromism of the photoproduct fluorescence. However, prediction of an ESPT tendency of synthetic dyes might fail when only fluorescence emission data are considered. We propose to refer instead to the energetic difference of the 0-0 transition in absorption together with the solvatochromism of the acidic form in aprotic solvents of similar polarity.

Wagging motion of hydrogen-bonded wire in the excited-state multiple proton transfer process of 7-hydroxyquinoline·(NH3)3 cluster

“…Proton transfer is one of the most important reactions in acidbase chemical and biological dynamics caused by the site-specific interaction such as hydrogen bonding [24][25][26][27][28][29]. The skeletal mechanistic picture proposed by Grotthuss is still a guide for our understanding of the proton hopping in hydrogen-bonded systems [30,31].…”

Excited-State Proton Transfer via Hydrogen-Bonded Acetic Acid (AcOH) Wire for 6-Hydroxyquinoline

“…[1][2][3][4] As the important role of hydrogen bonds playing in physics, chemistry, and biology has been recognized, [5][6][7][8][9][10][11][12][13][14][15][16][17][18] the proton transfer along hydrogen bonding has been given more and more attention in recent years. [19][20][21][22][23][24][25] This is especially true for photoacids, where a well-defined zero-point of time for the proton-transfer reaction due to the acidity of photoacids can be switched by optical excitation. 24,25 Thus, monitoring the hydrogen release of photoacids is the fashionable method to study proton transfer.…”

Quantitative Structure‐Fluorescence Property Relationship Analysis of a Large BODIPY Library

“…[60] ICT has been discussed with BODIPY-linked phenol and anisole, as well, where the oxygen is the electron donating group. [61,[64][65][66] However, the emission maximum of these compounds was found to be solvent independent. Fluorescence emission intensities decreased with increasing pH suggesting a non-emissive excited state of the phenoxide anion due to very efficient ICT.…”

“…[61] Jung et al reported an extreme Stokes shift of 137 nm of a deprotonated phenoxide BODIPY derivative. [66] Increased Stokes shifts of 1H-pyrrole and furan-linked BODIPYs have not yet been reported. We speculate that an intramolecular charge transfer is the cause for extended Stokes shifts of some BD 288 compounds.…”