Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea.
J Phys Chem A. 2013 Jan 17;117(2):370-7. doi: 10.1021/jp310842z. Epub 2013 Jan 3.
Intramolecular charge transfer (ICT) of DMABN has been the subject of extensive investigations. Through the measurements of highly time-resolved fluorescence spectra (TRFS) over the whole emission region, we have examined the ICT dynamics of DMABN in acetonitrile free from the solvation dynamics and vibronic relaxation. The ICT dynamics was found to be characterized by a broad range of time scales; nearly instantaneous (<30 fs), 160 fs, and 3.3 ps. TRFS revealed that an ICT state with partially twisted geometry, ICT(P), is formed within a few hundred femtoseconds either directly from the initial photoexcited state or via the locally excited (LE) state. The ICT(P) state undergoes further relaxation along the intramolecular nuclear coordinate to reach the twisted ICT (TICT) state with the time constant of 4.8 ps. A conformational diversity along the rotation of the dimethylamino group was speculated to account for the observed diffusive dynamics.
二甲氨基芴（DMABN）的分子内电荷转移（ICT）一直是广泛研究的课题。通过在整个发射区域内进行高时间分辨荧光光谱（TRFS）的测量，我们研究了DMABN 在不含溶剂动力学和振子松弛的乙腈中的 ICT 动力学。发现 ICT 动力学的特征是具有广泛的时间尺度；几乎瞬时（<30 fs）、160 fs 和 3.3 ps。TRFS 表明，具有部分扭曲几何形状的 ICT 态（ICT(P)）在几百飞秒内直接从初始光激发态或通过局部激发（LE）态形成。ICT(P) 态沿着分子内核坐标进一步松弛，以 4.8 ps 的时间常数达到扭曲 ICT（TICT）态。推测沿二甲氨基基团旋转的构象多样性可以解释观察到的扩散动力学。
