Five New Pseudopolymorphs of sym-Trinitrobenzene.
In: Crystal Growth & Design, Jg. 3 (2003) ; Nr. 6, S. 1033-1040
Zeitschriftenaufsatz / Fach: Chemie
1,3,5-Trinitrobenzene (TNB) was recrystd. from about 30 solvents and five mixed solvents in around 50 expts. to yield five new solvates. All the solvates lose their solvent readily, and special precautions were required to det. their crystal structures. In all cases, the solvents that gave solvates are electron-rich aroms. leading to the conjecture that p...p donor-acceptor stacking interactions are important. This was confirmed from the crystal structures. Addnl., these structures are composed of hexagonal sheets in which TNB and solvent mols. are linked with weak C-H...O hydrogen bonds. The benzene solvate contains an unusual finite TNB motif not hitherto seen. The toluene and chlorobenzene solvates are not isostructural, and C-H...Cl interactions in the latter are unusually short and linear, accounting thereby for the failure of chloro-Me structural exchange. The m-xylene and mesitylene solvates are similar to the toluene solvate. This study indicates that the use of terms such as solvate, pseudopolymorph, donor-acceptor complex, and mol. complex is a subjective matter, and also that a better definition for the term pseudopolymorph may be needed, esp. because it occurs frequently in the pharmaceutical literature.