Gossypol clathrates: Structure and thermal behavior of gossypol solvates with two picoline isomers |
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Authors: | S A Talipov M T Khonkeldieva L Yu Izotova Z G Tilyakov and B T Ibragimov |
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Institution: | (1) Southern Regional Research Center, ARS, USDA, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, USA;(2) Department of Chemistry, University of New Orleans, 2000 Lakefront Drive, New Orleans, LA 70148, USA |
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Abstract: | Gossypol forms stable solvates with 4- and 2-picolines at room temperature. The solvates are investigated by single crystal
X-ray diffraction and thermal analysis. Solvate crystals of gossypol with 4-picoline (1) have the 1:3 composition (gossypol:4-picoline) and crystallize in the P21/c space group. This substance is isostructural to a trisolvate of gossypol with pyridine. Solvate crystals of gossypol with
2-picoline (2) have the 1:4 composition (gossypol:2-picoline) and crystallize in the P-1 space group. The unit cell parameters for the investigated structures are as follows: 1 monoclinic crystals, C30H30O8·3C6H7N, a = 10.7530(1) ?, b = 20.7834(3) ?, c = 19.1166(2) ?, β = 95.537(1)°, V = 4252.32(9) ?3, M = 797.92, Z = 4, d
x = 1.246 g/cm3, and R = 0.0489 for 4102 reflections; 2 triclinic crystals, C30H30O8·4C6H7N, a = 11.467(1) ? b = 14.962(2) ?, c = 15.570(3) ?, α = 75.62(1)°, β = 69.83(1)°, γ = 79.58(1)°, V = 2414.6(7) ?3, M = 891.04, Z = 2, d
x = 1.226 g/cm3, and R = 0.0528 for 3779 reflections. The results of the single crystal XRD and thermal analysis confirm that gossypol with 4-picoline
forms a trisolvat, and a tetrasolvate with 2-picoline. The transition from 4-picoline to 2-picoline proves to change the type
of the host-guest association from one-dimensional to zero-dimensional, i.e., to lead to a new crystal structure. Desolvation
of compound 2 begins at a lower temperature than that for compound 1, which is explained by their different crystal structures. Keywords: gossypol, 4-picoline, 2-picoline, clathrate formation,
crystal structure. |
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