ANYL 50 |
| Crystal polymorphism, the formation of different crystal structures from the same molecules, is a major unsolved problem in solid-state chemistry and pharmaceutical manufacturing. Meta-substituted diphenyl ureas (MXPU) with X=Cl, Br, I, CN, NO2, CH3, and OH can adopt different conformations in different solid state packing arrangements, a phenomena called conformational polymorphism. We have recently determined the single crystal growth conditions and X-ray structure solutions of many of these meta-substituted compounds. Ab initio calculations were also performed for a series of symmetrical and unsymmetrical MXPUs. Potential energy scans for the rotation of either one or both phenyl rings show some regions of low conformational energy which correspond to anti-anti < anti-syn < syn-syn in all of the compounds except when X= CH3 or OH. In these cases syn isomers are more stable. Comparisons are made between the calculated torsion angles and those observed in the crystalline solid state. |
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General Papers
7:00 PM-9:00 PM, Sunday, 10 September 2006 Moscone Center -- Hall D, Poster
Division of Analytical Chemistry |