Acta Phys. -Chim. Sin. ›› 2015, Vol. 31 ›› Issue (2): 221-226.doi: 10.3866/PKU.WHXB201412232


Terahertz Spectroscopic Analysis of Adenine and Fumaric Acid Cocrystals

FANG Hong-Xia, ZHANG Qi, ZHANG Hui-Li, DU Yong, HONG Zhi   

  1. Centre for Terahertz Research, China Jiliang University, Hangzhou 310018
  • Received:2014-11-05 Revised:2014-12-22 Published:2015-01-26
  • Contact: DU Yong
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21205110).


The absorption spectra of adenine, fumaric acid, and their cocrystal were measured using terahertz time-domain spectroscopy (THz-TDS) at room temperature. Experimental results show that they all have distinct fingerprint spectra in the terahertz region. The absorption peaks observed in the terahertz spectra of the cocrystal were at 0.92, 1.24, and 1.52 THz. These are very different from the corresponding reagents. Based on the characteristic hydrogen donor and/or acceptor behavior of adenine, density functional theory (DFT) was used to simulate three possible theoretical cocrystal structures with a focus on hydrogen bond formation between adenine and fumaric acid. The theoretical result shows that one of three possible simulated cocrystal structures had absorption peaks at 0.89, 1.16, and 1.41 THz, which is in agreement with the terahertz experimental result. Therefore, the structure of the cocrystal was confirmed wherein the first hydrogen bond is formed between the amino group of adenine and the hydroxyl group of fumaric acid. The second hydrogen bond is formed between the nitrogen atom of the nitrogen ring in adenine and the carbonyl group of fumaric acid. The characteristic absorption bands of the cocrystal between adenine and fumaric acid are also assigned based on the simulation results from the DFT calculation.

Key words: Adenine, Fumaric acid, Cocrystal, Hydrogen bond, Terahertz time-domain spectroscopy, Density functional theory


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