Evaluation of the acidic strengths on electronic ground and excited states of proton transfer dye using Excitation-Emission fluorescence matrix (EEM) and Multivariate Curve Resolution with Alternating Least Squares (MCR-ALS)

Abstract

Multivariate Curve Resolution with Alternating Least Squares (MCR-ALS) was for the first time successfully used to evaluate an intricate photophysical behavior, where deprotonation on the electronic ground state (S0), intra and intermolecular proton transfer processes (ESPT and ESIPT) on the electronic excited state (S1) can simultaneously be presented. In this sense, the organic dye 2-(2′-hydroxyphenyl)benzothiazole (HBT) was used as a proof-of-concept model, where MCR-ALS showed to be a powerful tool for discriminate chemical reactions that occur concomitantly on different potential energy surfaces, which include photochemical reactions. As a result, the chemometric method showed to be a straightforward approach for the determination of the acidic strengths of those equilibria were estimated as 8.61 and 1.11 to hydroxyl deprotonation on electronic ground and excited states, respectively.

Balancing the Push–Pull Effect on the Synthesis and Fluorescent Properties of New ESIPT Dyes for Thin Film Applications

“…Dark-green crystals, 87% yield. 1 3-((tert-Butoxycarbonyl)thio)propanoic Acid (2). The compound was prepared as described in the literature.…”

“…The E species is regenerated after a reverse proton transfer in the ground state. As a consequence of the proton transfer in the excited state, ESIPT dyes show low energy fluorescence emission (FL) characterized by large Stokes shifts (∼10,000 cm –1 ). , …”

“…As a consequence of the proton transfer in the excited state, ESIPT dyes show low energy fluorescence emission (FL) characterized by large Stokes shifts (∼10,000 cm −1 ). 1,2 Considering molecules that undergo ESIPT emission, 2-(2hydroxyphenyl)benzothiazole (HBT) derivatives have been studied extensively due to their facile, scalable, and straightforward synthesis in addition to the broad scope of applications. Benzothiazole is a strong electron-withdrawing group (EWG) which works as an acceptor, while the phenol ring plays the role of a donor in the ESIPT process.…”