Salting benzenes

Simple salt crystals, such as potassium sulfate or barium acetate, were gro wn in the presence of a variety of aromatic molecules, especially aniline d erivatives, bearing sulfonate or carboxylate substituents. We call this pro cess salting, borrowing the term from Michl and co-workers who coined it in ,2 related context (Kirkor, E.; Gebicki, J.; Phillips, D. R.; Michl, J. J. Am. Chem. Sec. 1986, 108, 7106-7107). Particular growth sectors of the resu ltant crystals were luminescent, and the emitted light was highly polarized indicating that the benzene derivatives were oriented inside of the salt l attices. These results are presented in the contest of a generalization of single crystal matrix isolation; isomorphous matching of hosts and guests n eed not be a constraint. We show by polarization spectroscopy and magnetic resonance that different faces of the crystals will entrap molecules in dif ferent conformations otherwise separated by small energies in solution. Met astable triplet states are remarkably long-lived at room temperature in sti lt matrixes. The mechanisms of benzene derivative incorporation depend high ly on secondary surface structures that are imaged by differential interfer ence contrast microscopy. Luminescent molecules identify these features by lighting-up particular substructures and as such serve as probes of crystal growth mechanisms. We show how patterns of light in crystals are used to a ssign absolute growth directions. We conclude by arguing that the results h erein can be extended to a limitless range of guests, while encouraging the use of salts as matrixes for the study of organic compounds.