Department of Chemistry and Biochemistry, University of Notre Dame, 251 Nieuwland Science Hall, Notre Dame, Indiana 46556, USA.
J Org Chem. 2012 Mar 16;77(6):2756-62. doi: 10.1021/jo2025527. Epub 2012 Mar 7.
The syntheses and photophysical/photochemical properties of two amide-tethered coumarin-labeled nicotinamides are described. Photochemical studies of 6-bromo-7-hydroxycoumarin-4-ylmethylnicotinamide (BHC-nicotinamide) revealed an unexpected solvent effect. This result is rationalized by computational studies of the different protonation states using TD-DFT with the M06L/6-311+G** method with implicit and explicit solvation models. Molecular orbital energies responsible for the λ(max) excitation show that the functionalization of the coumarin ring results in a strong red-shift from 330 to 370 nm when the pH of solution is increased from 3.06 to 8.07. From this MO analysis, a model for solvent interactions has been proposed. The BHC-nicotinamide proved to be photochemically stable, which is also interpreted in terms of NBO calculations. The results provide a set of principles for the rational design of either photostable labeling reagents or photolabile cage compounds.
描述了两种酰胺键合香豆素标记烟酰胺的合成及光物理/光化学性质。对 6-溴-7-羟基香豆素-4-基甲基烟酰胺（BHC-烟酰胺）的光化学研究揭示了一种意想不到的溶剂效应。使用 TD-DFT 与 M06L/6-311+G** 方法结合隐式和显式溶剂化模型对不同质子化态进行计算研究，对这一结果进行了合理化解释。负责 λ(max)激发的分子轨道能量表明，当溶液的 pH 值从 3.06 增加到 8.07 时，香豆素环的功能化导致从 330nm 到 370nm 的强红移。根据这种 MO 分析，提出了一种溶剂相互作用模型。BHC-烟酰胺被证明具有光化学稳定性，这也可以根据 NBO 计算来解释。这些结果为光稳定标记试剂或光解笼状化合物的合理设计提供了一组原则。
