研究目的
Determination of the structures of TB species related to the color change, which is investigated by multivariate analysis of electronic absorption spectra and quantum chemical calculations.
研究成果
The pH dependent structures of TB, a long-standing controversial issue, have been determined by the analytical method of quantum chemistry and multivariate analysis of electronic absorption spectra cooperatively. TB takes the neutral biprotonated form with open-sulton ring showing red in strong acid solution, the monovalent anion of the pure quinoid form showing yellow in acid to neutral solution and the quinoid-phenolate form showing blue in alkaline solution.
研究不足
The study focuses on the pH-dependent structural changes of TB in solution, and the conclusions are based on the specific conditions and methods used. The applicability of the findings to other sulfonphthalein dyes or under different conditions may require further investigation.
1：Experimental Design and Method Selection:
The study employs quantum chemistry and multivariate analysis of electronic absorption spectra to determine the pH-dependent structures of thymol blue (TB).
2：Sample Selection and Data Sources:
TB solutions with varying pH values were prepared, and their electronic absorption spectra were measured.
3：List of Experimental Equipment and Materials:
Powdered TB, hydrochloric acid, UV-Visible/NIR spectrometer, quartz cell, pH meter, MATLAB for multivariate analysis, Gaussian 16 for quantum chemical calculations.
4：Experimental Procedures and Operational Workflow:
Preparation of TB solutions with varying pH, measurement of electronic absorption spectra, multivariate analysis (PCA and ALS), quantum chemical calculations for structural optimization and simulation of electronic absorption spectra.
5：Data Analysis Methods:
Principal component analysis (PCA) and alternative least-squares (ALS) regression analysis of the electronic absorption spectra, quantum chemical calculations using DFT and TD-DFT methods.
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