4-Substituted 1-Acyloxypyridine-2(1H)-thiones: Experimental and Computational Studies of the Substituent Effect on Electronic Absorption Spectra

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• 作者：Aleksandra Jankowiak ; Piotr Kaszynski
• 刊名：Journal of Organic Chemistry
• 出版年：2009
• 出版时间：October 2, 2009
• 年：2009
• 卷：74
• 期：19
• 页码：7441-7448
• 全文大小：926K
• 年卷期：v.74,no.19(October 2, 2009)
• ISSN：1520-6904

文摘

A series of eight 4-substituted 1-(adamantane-1-carbonyloxy)pyridine-2(1H)-thiones (1, X = H, OC₇H₁₅, Me, CF₃, SC₃H₇, CN, COOMe, and Cl) was prepared and characterized by UV−vis spectroscopy in MeCN and cyclohexane. The observed lowest energy transition, designated as π_CS → π*_ring, exhibits a substantial substituent effect and λ_max ranges from 333 (X = OC₇H₁₅) to 415 nm (X = CN). Experimental λ_max values for all esters except for 1b (X = OC₇H₁₅) correlate with the σ_p⁻ parameter (ρ = 0.41 ± 0.03, r² = 0.95). In contrast, the energy of the absorption band at about 295 nm, designated as π_CS → π*_CS, is practically substituent independent. Both absorption bands exhibit a modest negative solvatochromic effect. The experimental absorption energies correlate better with excitation energies calculated for N-acetyloxy analogues 2 with the ZINDO//DFT than with the TD-DFT//DFT method. Calculations for a series of 12 N-acetates 2 predict the most blue-shifted π → π* transition for the alkoxy substituent and most red-shifted for the NO₂ group relative to the parent 2a (X = H).