Single crystals of the lactone form of rhodamine b were hydrothermally synthesized in a sol-gel system encapsulating rhodamine B. The obtained product was identified with ^1H NMR. The single crystal structure was determined. The cell of lactone contains two independent rhodamine B molecules with virtually identical geometry. Both molecules contain a central planar section and planar groups bonded to C(7) and C(35), and the two major planes of the molecules are perpendicular to each other (89.77° and 92.73° respectively).

Key words: SOL-GEL PROCESS, CRYSTAL GROWTH, CRYSTAL STRUCTURE