Laser spectroscopic research on unconventional hydrogen bonds involving borane

1.用激光光谱技术研究了水杨酸(水杨酸和5-甲氧基水杨酸)与水或甲醇分子簇的几何结构和激发态质子位错。研究了这些团簇在超音速喷流中的电子基态和第一激发态的荧光激发、色散荧光和红外光谱。通过量子化学计算，根据OH伸展区的红外光谱确定了团簇的几何结构。团簇中的水或甲醇部分的羟基形成了涉及水杨酸部分的羧基的环。在团簇形成过程中，水杨酸部分中的分子内氢键仍然存在。分析了电子激发态中令人费解的红外光谱，并结合部分氢化研究进行了分析。激发态红外光谱和色散荧光…更多的光谱表明，分子内激发态的质子位错几乎不受水或甲醇的微溶剂化的影响，相反，自救过程中位错受到强烈的抑制。2.用电子和红外光谱研究了5-甲氧基水杨酸(5-McOSA)、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)对水杨酸(SA)框架中激发态分子内质子转移(ESIPT)的取代作用。在3 mm范围内测量了电子基态(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/发射光谱显示出典型的ESIPT光谱特征，这也是SA的光谱特征。另一方面，5-MeOSA和5-FSA的激发光谱和发射光谱之间呈现镜像关系，这被认为是ESIPT被抑制的结果。尽管电子光谱之间存在明显的差异，但红外光谱显示，所有取代SA的电子激发确实发生了一个剧烈的变化，即所有SA的酚羟基伸缩振动从3 mm区域消失，这表明S_1中的酚醛O-H键有很大的伸长(超过0.1Å)。这一结果表明，所有取代SA的分子内氢键强度都在电子激发后显著增强。还讨论了取代对二聚体ESIPT的影响。较少

1.Geometric structures and the excited-state proton-dislocation in size-selected clusters of salicylic acids (salicylic acid and 5-methoxysalicylic acid) with water or methanol were studied by using laser spectroscopic techniques. Fluorescence excitation, dispersed fluorescence, and infrared (IR) spectra of those clusters in supersonic jets were examined for both the electronic ground and first excited states. The geometric structures of the clusters were determined on the basis of the IR spectra of the OH stretch region with a help of quantum chemical calculations. The hydroxyl group of the water or methanol moiety in the clusters forms a ring involving the carboxylic group of the salicylic acid moiety. The intramolecular hydrogen bond in the salicylic acid moiety is still held upon the cluster formation. The puzzling IR spectra in the electronic excited state were analyzed in combination with a partial deuteration study. The IR spectra in the excited state and dispersed fluorescence … More spectra indicated that the intramolecular excited state proton dislocation is hardly affected by the microsolvation with water or methanol, in contrast with the strong suppression of the dislocation in the self-salvation. A drastic reduction of the acidity of the carboxylic OH upon the electronic excitation was also found.2.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-McOSA), 5-methylsalicylic acid (5-MeSA), 5-fluorosalicylic acid (5-FSA), 6-fluorosalicylie acid (6-FSA), and methyl salicylate (MS). Infrared spectra were measured in the 3 mm 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 of such a remarkable difference among the electronic spectra, IR spectroscopy exhibits that a drastic change of the phenolic OH stretching vibration does occur upon the electronic excitation of all the 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 Å) in S_1. This result represents that the intramolecular hydrogen-bond strength is remarkably enhanced upon the electronic excitation in all the substituted SAs. Substitution effects on ESIPT in dimers are also discussed. Less