Solvatochromism, prototropism and complexation of para-aminobenzoic acid

Photoinduced intramolecular charge-transfer reactions in 4-amino-3-methyl benzoic acid methyl ester: A fluorescence study in condensed-phase and jet-cooled molecular beams

“…The increase in Stokes shift of the low-energy emission indicates that this band arises from the CT state as was observed in other related molecules. [10][11][12][31][32][33] It is to be noted that a distinct dual emission is observed in β CD (4 mM) solution which confirm the presence of both the LE and CT states ( figure 1b). The excitation spectra of both the emission bands are found to be independent of emission wavelength and agree reasonably well with the absorption spectrum.…”

“…This absorption band is basically the π-π* type of transition as was observed in case of benzene-like systems. [10][11][12] As seen in figure 1a, polarity of the solvent has very little effect on the absorption peak position, indicating the weak polar character of the system in the ground state. Comparing the absorption spectra with other related systems, this broad band indicates a possible overlap of S 1 and S 2 states in AMBME.…”

“…Similar Stokes-shifted emission bands for the CT state are also observed in 4-amino benzoic acid, 3-amino benzoic acid and 2-amino benzoic acid. [10][11][12] However, the Stokes shift of the emission band in AMBME is less than that of 2-and 3-amino benzoic acids indicating the lower polar character of AMBME compared to 2-and 3-amino benzoic acids. With increasing polarity of the solvent, i.e., going from cyclohexane to acetonitrile, a clear Stokes shift is observed in the emission band maximum.…”

“…There are very few examples where a primary amino group is used as the charge donor. Zachariasse and his group 9 demonstrated ICT in some fluoro-substituted amino benzonitrile derivative and very recently Stalin et al [10][11][12] reported charge-transfer reaction in p-amino benzoic acid, 3-amino benzoic acid and 2-amino benzoic acid in the solution phase. There have been several attempts to investigate the same photo-induced CT process of bare molecules or their size-selected solvated clusters in jet-cooled molecular beams to obtain better understanding of the process.…”

High‐Resolution Electronic Spectroscopy Studies of meta‐Aminobenzoic Acid in the Gas Phase Reveal the Origins of its Solvatochromic Behavior

“…[8] The different ABA isomers are postulated to have varying degrees of charge transfer (CT) character in both electronic states in the condensed phase. [9][10][11][12][13] Here, we aim to compare the electron-donor strength of ÀNH 2 with the electron-acceptor strength of ÀCOOH as a function of their relative position. Our tool is high resolution S 1 -S 0 electronic spectroscopy both in the absence and presence of an applied electric field.…”