Honda Akinori, Nozawa Ryo, Miyamura Kazuo
Department of Chemistry, Faculty of Science, Tokyo University of Science 1-3 Kagurazaka Shinjuku-ku Tokyo 162-8601 Japan
RSC Adv. 2024 Jan 25;14(6):3776-3781. doi: 10.1039/d3ra08293h. eCollection 2024 Jan 23.
The cold-crystallization behaviors of dodecyl-substituted nucleobases (adenine, uracil, and thymine) were analyzed. The dodecyl derivative from uracil alone did not exhibit cold crystallization; however, a mixture of adenine and uracil derivatives at a molar ratio of 1 : 1 exhibited cold crystallization. These results are similar to the thermal behavior of dodecyl derivatives of adenine and thymine alone and in mixtures reported in a previous study. Temperature-controlled infrared spectroscopy was used to observe the molecular assembly states of the liquid, supercooled state, and cold-crystallized compounds. Hydrogen-bonded molecular pairs in the high-temperature liquid state, multiple hydrogen-bonded networks in the supercooled state, and reverse Hoogsteen-type complementary hydrogen bonds in cold-crystallized compounds were observed using infrared spectroscopy. The heterogeneity of the system, due to multiple types of hydrogen bonding, retarded the crystallization rate, resulting in supercooling and cold crystallization. Infrared spectroscopy, which can be used to measure the aggregation state of molecules, including the liquid and supercooled states, is an effective analytical method for clarifying the process of cold crystallization.
分析了十二烷基取代的核碱基（腺嘌呤、尿嘧啶和胸腺嘧啶）的冷结晶行为。仅尿嘧啶的十二烷基衍生物未表现出冷结晶；然而，腺嘌呤和尿嘧啶衍生物以1∶1的摩尔比混合时表现出冷结晶。这些结果与先前研究报道的单独的腺嘌呤和胸腺嘧啶十二烷基衍生物及其混合物的热行为相似。采用控温红外光谱法观察液体、过冷状态和冷结晶化合物的分子组装状态。利用红外光谱观察到高温液态下的氢键分子对、过冷状态下的多重氢键网络以及冷结晶化合物中的反向Hoogsteen型互补氢键。由于多种类型的氢键导致体系的不均匀性，延缓了结晶速率，从而导致过冷和冷结晶。红外光谱可用于测量包括液态和过冷态在内的分子聚集状态，是阐明冷结晶过程的一种有效分析方法。
