γ-氨基丁酸和苯甲酸共晶体及其形成条件的振动光谱分析

Vibrational Spectroscopic Characterization of the Co-Crystal and the Forming Condition between γ-Aminobutyric Acid and Benzoic Acid

使用太赫兹时域光谱(THz-TDS)、傅里叶红外光谱(FTIR)和傅里叶拉曼光谱(FT-Raman)技术在室温下对γ-氨基丁酸(GABA)、苯甲酸(BA)及其研磨和溶剂共晶体进行表征分析。FTIR,FT-Raman及THz光谱都能够分辨原料物质及GABA-BA共晶体。其中THz实验结果显示了GABA-BA研磨和溶剂共晶体位于0.93,1.33,1.57THz的吸收峰明显区别于原料物质,这体现了不同物质在THz波段具有明显的指纹特征。为确认GABA-BA共晶体的晶型结构,分别采用FTIR和FT-Raman光谱进行光谱归属。通过FTIR的光谱归属推断GABA-BA共晶体由GABA中的氨基H_23和BA中的羰基O1构成第一个氢键,氨基中的N18结合BA中的羟基H15形成第二个氢键。FT-Raman光谱中,原料物质GABA中位于576,886,1 250,1 283,1 337,1 423和1 470cm^(-1)处归属于—CH_2,—NH_2弯曲振动的Raman散射峰在GABA-BA共晶体内消失,判定GABA中的氮原子N18亦可作为氢键受体,从而验证了GABA-BA共晶体的晶型结构。此外,为了进一步说明溶剂pH值对GABA-BA共晶体的形成条件的影响,利用THz-TDS,FT-Raman光谱确认了该共晶体在溶剂条件2.00≤pH≤7.20可稳定地生成。这一研究结果同时也为利用THz-TDS,FTRaman光谱技术辨别固体物质晶型结构、晶型形成条件提供了实验及理论依据。

Terahertz time-domain spectroscopy （THz-TDS） ,Fourier transform infrared （FTIR） and Fourier transform Raman （FT-Raman） spectroscopic techniques were utilized for the characterization and analysis of γ-aminobutyric acid （GABA） ,benzoic acid （BA） ,and their solvent/grinding co-crystals .All experimental results demonstrated that GABA-BA co-crystal possessed unique spectroscopical characteristic compared with that of starting materials in THz-TDS ,FTIR ,FT-Raman spectra .THz-TDS results showed that similar absorption peaks of solvent and grinding co-crystals which formed between GABA and BA at 0.93 ,1.33 and 1.57 THz can be observed .The result demonstrated that THz-TDS technique could effectively identify and char-acterize GABA ,BA and its co-crystal ,which was also a presentation of various substance that had different fingerprint charac-teristic features in T Hz range .To identify and affirm the crystal structure of GABA-BA co-crystal ,FT-Raman and FTIR spec-troscopic techniques were also employed by spectral assignment .Through the assignment of FTIR spectrum ,it was confirmed that the first hydrogen bond of GABA-BA co-crystal was formed at place between amino H23 of GABA and carbonyl O1 of BA , while the second one was constituted by amino group N18 of GABA and hydroxyl group H15 of BA .Some Raman scattered peaked ,such as 576 ,886 ,1250 ,1283 ,1337 ,1423 and 1470 cm-1 which belonged to bending vibrations of —CH2 ,—NH2 in GABA ,disappeared upon the formation of GABA-BA co-crystal ,demonstrating the atom nitrogen （N18） in GABA can be served as hydrogen bond acceptor .So the Raman result verified the validity of above FTIR deduction ,which confirmed the crys-tal structure of GABA-BA co-crystal ,Furthermore ,formation of co-crystal was impacted by pH value of solvent .With the sol-vent condition of 2.00≤pH≤7.20 ,the GABA-BA co-crystal can be stably formed .This work provides experimental and theo-retical benchmark to discriminate and identify the crystal structure of co-crystal formed between active ingredients and co-crystal formers and crystalline formation conditions in the solid state with T Hz-TDS and FT-Raman techniques .