Departamento de Química Física, Sección de Químicas, Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, Avda. Carlos III, S.N., 45071 Toledo, Spain.
Phys Chem Chem Phys. 2010 Mar 7;12(9):2107-15. doi: 10.1039/b920951d. Epub 2010 Jan 15.
The normal and anion structures of salicylaldehyde azine (SAA) in solvents of different viscosities and polarities have been studied by means of femto- to nanosecond time-resolved emission techniques. In the normal form, an excited-state intramolecular proton-transfer (ESIPT) reaction takes place with a time constant shorter than 80 fs to produce an excited keto-type tautomer in which intramolecular-vibrational energy redistribution and vibrational cooling occur in 100 fs to 2 ps. The viscosity-dependent emission decay in the red part of the spectrum with 5-11 ps reflects a twisting motion leading to rotamers of these keto-type structures, most probably of (n,pi*) nature. For the anion type, the viscosity dependent rise-times (3 to 400 ps) at the red part of the emission, and the wavelength-dependent fluorescence lifetimes (20 to 1100 ps) indicate a stepwise formation of different conformers of the anions. The results reported here should be relevant to a better understanding of the photobehaviour of photochromic compounds and charged chromophores in biological systems.
通过飞秒至纳秒时间分辨发射技术研究了水杨醛嗪（SAA）在不同粘度和极性溶剂中的正常和阴离子结构。在正常形式中，发生激发态分子内质子转移（ESIPT）反应，其时间常数短于 80 fs，以产生激发的酮式互变异构体，其中分子内振动能量再分配和振动冷却发生在 100 fs 至 2 ps 内。光谱红色部分的粘度相关发射衰减（5-11 ps）反映了导致这些酮式结构的旋转体的扭曲运动，很可能是（n，pi*）性质。对于阴离子型，发射红色部分的粘度相关上升时间（3 至 400 ps）和波长相关荧光寿命（20 至 1100 ps）表明阴离子的不同构象依次形成。这里报道的结果应该与更好地理解光致变色化合物和生物系统中带电生色团的光行为有关。
