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Paper | Special issue | Vol 73, No. 1, 2007, pp.275-287
Published online, 12th June, 2007
DOI: 10.3987/COM-07-S(U)2
Substituent Effects on Ultraviolet Absorption Spectra of 5-Substituted Nb-Acetyl-1-methoxytryptamines Studied by Density Functional Theory Calculations

Kunihiro Tokumura,* Kenta Imai, Akio Hayashi, Tomonori Ida, and Masanori Somei*

*Division of Pharmaceutical Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan

Abstract

Density functional theory (DFT) calculations were performed for twelve 5-substituted Nb-acetyl-1-methoxytryptamines (5-X: NO2, SO2CH3, CN, CF3, Cl, H, CH3, OH, OCH3, NHCOCH3, NH2, N(CH3)2) in methanol. The respective HOMO→LUMO and HOMO-1→LUMO singly excited configurations are mainly responsible for the lowest and the second singlet excited states (S1 and S2). Observed UV absorption spectra of 5-H, 5-NHAc, and 5-CH3 derivatives are well predicted by simple time-dependent DFT calculations. Distinct substituent effects are found with respect to the energies of MOs responsible for S1←S0 and S2←S0 transitions. Both HOMO-1 and HOMO are destabilized by electron-donating groups, and stabilized by electron-withdrawing groups. LUMO+1 of 5-NO2 derivative should be classified into normal LUMO, which are found for eleven other derivatives as well as indole. Normal LUMO is not significantly affected in energy by electron-donating groups, but stabilized by electron-withdrawing groups.