Infrared and ultraviolet laser spectroscopy of jet-cooled substituted salicylic acids; substitution effects on the excited state intramolecular proton transfer in salicylic acid
Infrared and ultraviolet laser spectroscopy of jet-cooled substituted salicylic acids; substitution effects on the excited state intramolecular proton transfer in salicylic acid
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DOI：
10.1080/00267890500123543
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发表时间：
2005-06-10
影响因子：
1.7
通讯作者：
Mikami, N
中科院分区：
文献类型：
--
作者：
Abou El-Nasr, ABEH;Fujii, A;Mikami, N
采用电子和红外光谱研究了5-甲氧基水杨酸（5-MeOSA）、5-甲基水杨酸（5-MeSA）、5-氟水杨酸（5-FSA）、6-氟水杨酸（6-FSA）和水杨酸甲酯（MS）在水杨酸（SA）框架中激发态质子转移（ESIPT）的取代效应。在3 μ m区域测量了电子基态（S-0）和第一激发态（S-1）的红外光谱。5-MeSA和6-FSA的电子激发/发射光谱显示了典型的ESIPT光谱特征，这些特征在SA的光谱中已经发现。另一方面，5-MeOSA和5-FSA的激发和发射光谱呈镜像关系，这被认为是ESIPT抑制的结果。尽管电子光谱之间存在如此显著的差异，但红外光谱显示，在所有取代的sa的电子激发下，酚OH拉伸振动发生了剧烈变化，即所有sa的酚OH带在3mm区域消失，表明S-1中酚O-H键的伸长幅度很大（超过0.1埃）。这一结果表明，在所有取代的sa中，电子激发显著增强了分子内氢键强度。讨论了二聚体中ESIPT的取代效应。
Substitution effects on the excited state intramolecular proton transfer (ESIPT) in the salicylic acid ( SA) frame were studied by electronic and infrared spectroscopy of jet-cooled 5-methoxylsalicylic acid (5-MeOSA), 5-methylsalicylic acid (5-MeSA), 5-fluorosalicylic acid (5-FSA), 6-fluorosalicylic acid (6-FSA), and methyl salicylate ( MS). Infrared spectra were measured in the 3 mu m region for both the electronic ground (S-0) and first excited (S-1) states. The electronic excitation/emission spectra of 5-MeSA and 6-FSA showed the typical spectral features of ESIPT, which have been found in the spectra of SA. On the other hand, 5-MeOSA and 5-FSA exhibit a mirror-image relation between their excitation and emission spectra, which has been regarded as a result of the suppression of ESIPT. Despite such a remarkable difference among the electronic spectra, IR spectroscopy shows that a drastic change of the phenolic OH stretching vibration does occur upon electronic excitation of all substituted SAs, that is, the phenolic OH band of all the SAs disappears from the 3 mm region, indicating a large elongation of the phenolic O-H bond (over 0.1 angstrom) in S-1. This result means that the intramolecular hydrogen bond strength is remarkably enhanced by electronic excitation in all the substituted SAs. Substitution effects on ESIPT in dimers are also discussed.