Wolpert Daniel, Schade Marco, Brixner Tobias
Physikalisches Institut, Universitat Wurzburg, Am Hubland, 97074 Wurzburg, Germany.
J Chem Phys. 2008 Sep 7;129(9):094504. doi: 10.1063/1.2971037.
Time-resolved vibrational femtosecond spectroscopy is employed to investigate the photoinduced Wolff rearrangement reaction of diazonaphthoquinone (DNQ) dissolved in different solvents (methanol and water). DNQ is an important compound in commercial Novolak photoresists. Upon photoexcitation the ketene intermediate appears within 300 fs, indicating that the ketene is formed in a very fast concerted process involving N(2) loss and rearrangement. The strong shift of the vibrational band, assigned to the ketene by density functional theory calculations and experimental infrared spectra, toward higher wavenumbers is attributed to vibrational cooling. The relaxation time depends on the solvent (10 ps in methanol and 3 ps in water). However, the spectroscopic data show that the indirect ketene formation via a carbene intermediate might also be involved in the reaction process contributing to the ketene formation on the 10 ps time scale.
采用时间分辨飞秒振动光谱研究了溶解在不同溶剂（甲醇和水）中的重氮萘醌（DNQ）的光诱导沃尔夫重排反应。DNQ是商用酚醛清漆光刻胶中的一种重要化合物。光激发后，乙烯酮中间体在300飞秒内出现，这表明乙烯酮是通过涉及氮气损失和重排的非常快速的协同过程形成的。通过密度泛函理论计算和实验红外光谱确定为乙烯酮的振动带向更高波数的强烈位移归因于振动冷却。弛豫时间取决于溶剂（甲醇中为10皮秒，水中为3皮秒）。然而，光谱数据表明，通过卡宾中间体的间接乙烯酮形成也可能参与反应过程，在10皮秒时间尺度上对乙烯酮的形成有贡献。
