Experimental and theoretical studies on the electronic spectra of indole-3-acetic acid and its anionic and protonated species

• Published in: Journal of molecular structure 1991-06, Vol.246 (3), p.203-215
• Main Authors: Tomas-Vert, F., Ponce, C.A., Estrada, M.R., Silber, J., Singh, J., Anunciatta, J.
• Format: Article
• Language: English
• Subjects: Atomic and molecular physics; Exact sciences and technology; Intensities and shapes of molecular spectral lines and bands; Molecular properties and interactions with photons; Physics
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/0022-2860(91)80127-P

The geometrical and electronic structure of indole-3-acetic acid (IAH) have been investigated using the MINDO/3 molecular orbital method, the geometries being optimized by Rinaldi's method. The UV spectrum of IAH has been recorded in different solvents. The corresponding spectra of IAH + 2 and IA − were also respectively obtained, from IAH in different H 2SO 4/water mixtures and NaOH solutions. The agreement of experimental spectra with the ones theoretically calculated by the CNDO/M-Cl method after optimization of the κ parameter, is discussed. The p K a values of IAH have also been determined from the IAH + 2 spectra and are compared with literature data.