Heinrich-Heine-Universität, Institut für Physikalische Chemie I, 40225 Düsseldorf, Germany.
Chemphyschem. 2011 Jul 11;12(10):2035-41. doi: 10.1002/cphc.201000576. Epub 2011 Jan 14.
We measured the rotationally resolved electronic spectra of the origin and of three vibronic bands of 1,4-benzodioxan. From comparison to various ab-initio-calculated structures of 1,4-benzodioxan, the twisted C(2) symmetric 1,4-benzodioxan was shown to be responsible for all the observed spectral features. We analyzed the inertial defects in both electronic states as sensitive indicators of the non-planarity of the system. The molecule was found to be more planar in the electronic ground state than in the electronically excited singlet state. This effect can be traced back to an increased puckering of the dioxan ring, which also comprises the oxygen atoms, in the excited state. This observation is discussed in terms of natural bond orbitals.
我们测量了 1,4-苯并二恶烷的起源和三个振子带的旋转分辨电子光谱。通过与 1,4-苯并二恶烷的各种从头计算结构的比较，显示扭曲的 C(2)对称 1,4-苯并二恶烷是所有观察到的光谱特征的原因。我们分析了两个电子态的惯性缺陷，作为系统非平面性的敏感指标。结果发现，分子在电子基态比在电子激发单重态更平面。这种效应可以追溯到在激发态中，氧原子也包括在内的二恶烷环的凸起增加。这一观察结果将根据自然键轨道进行讨论。
