Chemistry Department, University of Virginia, Charlottesville, Virginia 22904, USA.
J Chem Phys. 2012 Sep 7;137(9):091101. doi: 10.1063/1.4752246.
Infrared-ultraviolet double resonance spectroscopy has been applied to study the infrared spectra of the supersonically cooled gas phase complexes of formic acid, acetic acid, propionic acid, formamide, and water with 9-hydroxy-9-fluorenecarboxylic acid (9HFCA), an analog of glycolic acid. In these complexes each binding partner to 9HFCA can function as both proton donor and acceptor. Relative to its frequency in free 9HFCA, the 9-hydroxy (9OH) stretch is blue shifted in complexes with formic, acetic, and propionic acids, but is red shifted in the complexes with formamide and water. Density functional calculations on complexes of 9HFCA to a variety of H bonding partners with differing proton donor and acceptor abilities reveal that the quantitative frequency shift of the 9OH can be attributed to the balance struck between two competing intermolecular H bonds. More extensive calculations on complexes of glycolic acid show excellent consistency with the experimental frequency shifts.
红外-紫外双共振光谱已被应用于研究甲酸、乙酸、丙酸、甲酰胺和水与 9-羟基-9-芴羧酸（9HFCA，乙醇酸的类似物）在超音速冷却气相配合物中的红外光谱。在这些配合物中，9HFCA 的每个配体可以同时作为质子供体和受体。与游离 9HFCA 的频率相比，9-羟基（9OH）伸缩在与甲酸、乙酸和丙酸的配合物中蓝移，但在与甲酰胺和水的配合物中红移。对 9HFCA 与各种具有不同质子供体和受体能力的氢键配体的配合物的密度泛函计算表明，9OH 的定量频率位移可归因于两种竞争的分子间氢键之间的平衡。对乙醇酸配合物的更广泛计算显示出与实验频率位移的极好一致性。
