A molecular orbital treatment of the electronic spectra of some tryptamines

The electronic absorption spectra of tryptamine, 5‐methoxytryptamine, 6‐fluorotryptamine, N‐acetyl‐5‐hydroxytryptamine, gramine, and melatonin were investigated. The observed transitions were π–π*, and the values of band maxima and intensity reflected an extent of interaction between the indole ring and the alkylamine side chain. Molecular orbital calculations at the level of INDO/S–CI were performed on all the studied molecules. State functions and transition energies were calculated. The correspondence between the experimental and theoretical results was satisfactory. © 1992 John Wiley & Sons, Inc.