Solvatochromism and Prototropism in 2-(Aminophenyl)benzothiazoles.

スポンサーリンク

概要

• 論文の詳細を見る

• The absorption and fluorescence spectra of 2-(2-aminophenyl)-, 2-(3-aminophenyl)-, and 2-(4-aminophenyl)benzothiazoles (<I>o</I>-APBT, <I>m</I>-APBT, and <I>p</I>-APBT, respectively) have been studied in different solvents and at various acid/base concentrations. The ultraviolet and fluorescence spectra and the low p<I>K</I><SUB>a</SUB> value for the monocation–neutral equilibrium have indicated the presence of an intramolecular hydrogen bond (IHB) in <I>o</I>-APBT in the S<SUB>0</SUB> state. Excited state intra-molecular proton transfer (ESIPT) in <I>o</I>-APBT, gives rise to a non-fluorescent phototautomer. Large solvatochromic shifts in polar solvents have indicated the increase in the dipolemoment of <I>m</I>-APBT in S<SUB>1</SUB> state. It has been observed that in protic solvents, <I>m</I>-APBT forms a complex with solvent molecule in the S<SUB>1</SUB> state. The equilibrium constants for different prototropic equilibria of the molecules have been determined in both S<SUB>0</SUB> and S<SUB>1</SUB> states. The absorption and fluorescence spectra of the prototropic species have been explained and compared with those of 2-phenylbenzothiazole (2-PBT). The monocation (<B>2</B>) of p-APBT, formed by protonation at the –NH<SUB>2</SUB> group is found to undergo structural reorganization leading to a quinonoid structure (<B>2</B>′). The absorption and fluorescence excitation spectra (recorded at 390 nm and 460 nm fluorescence bands) indicate the simultaneous presence of species (<B>2</B>) and (<B>2</B>′), the former being more favorable in protic and the latter in nonpolar solvents. The molecular orbital calculation (PPP) has been used to calculate the absorption spectra and the charge densities at the basic centers of the neutral molecules.

著者

• Dogra Sneh

  Department Of Chemistry I. I. T.

• Dey Joy

  Department of Chemistry, Indian Institute of Technology

関連論文

• Excited State Intramolecular Proton Transfer Reactions in 2-(2-Hydroxyphenyl)benzimidazole in Micellar Solutions
• Solvatochromism and Prototropism in 2-(Aminophenyl)benzothiazoles.
• Electronic spectra of 9,10-phenanthrenediamine: Effects of solvents and acid concentrations.
• Excited-state and ground-state proton-transfer reactions in 5-aminoindole.
• Effects of solvents and pH on the spectral behavior of 2-(p-aminophenyl)benzimidazole.

スポンサーリンク