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Journal of Structural Chemistry

2013 year, number 5


A. Moghimi1, H.R. Khavasi2, F. Dashtestani1, D. Kordestani3, E. Behboodi1, B. Maddah4
1Islamic Azad University, Tehran North Branch, Tehran, Iran
2Shahid Beheshti University, G. C, Tehran, Iran
3Razi University, Kermanshah, Iran
4Imam Hossein University, Tehran, Iran
Keywords: crystal chemistry, single crystal X-ray diffraction, proton transfer, hydrogen bonding, caffeine, dipicolinic acid


A reaction between caffeine (caff) and dipicolinic acid = 2,6-pyridine dicarboxylic acid (pydc.H 2) in water results in the formation of a cocrystal compound (pydc.H2.H2O)(caff) 1. The characterization of the resulting crystallohydrate is performed using 1H, 13C NMR and IR spectroscopy and X-ray crystallography. X-ray crystal structure analysis reveals the presence of both starting materials and water in the lattice. It also indicates intensive intermolecular H-bonding interactions between carboxylic acid, caffeine, and water as well as π—π stacking between the pydc.H2 and caff rings as constituents of the cocrystal. The hydrogen bonding and non-covalent interactions play roles in the formation of the cocrystal. The crystal system is triclinic with the space group P- 1 and two formula units per unit cell. The unit cell parameters are a = 6.906(2) Å, b = 8.451(3) Å, c = 14.68 (4) Å with α = 81.51(3°), β = 78.47(3°), and γ = 78.14(3°). The final R value is 0.0660 for 7943 measured reflections.