For some time it had been tacitly assumed that the low thermal stability of organic molecules precluded their incorporation into inorganic matrices. This view did not survive the invention of sol-gel glasses whose relatively cold processing temperatures enabled the entrapment of dyes as well as other organic molecules.' These doped aluminosilicate glasses have shown a wide range of optical properties? including laser a~t i o n .~ We have been studying not glasses but single crystals of simple salts that contain oriented inclusions of organic dyes? These materials have a longer history5 than doped sol-gel glasses, although their uses as optical materials have not been previously considered. Herein, we describe a simple preparation of single K2S04 crystals doped with pyrene and rhodamine derivatives and their operation as blue, green, and red solid state dyeWe recently described a procedure for choosing organic guests for simple salts which involved the matching of anionic functionalities on chromophores with the anion spacings in simple salt lattices such as K2S04.4a The structures of several doped K2SO4 crystals, containing triarylmethyl (1) or pyrene (2) dyes, were determined through absorption studies with polarized light. For example, crystals containing pyranine (2a, 8-hydroxy-1,3,6-pyrenetris~lfonate)~ were typically grown by evaporating water solutions (5 x M 2a, 0.5 M K2S04). Crystals in excess of 1 cm3 were grown from seeds suspended (1) Avnir, D.; Levy, D.; Reisfeld, R. 1: A-H 0rCk 3 I Figure 1. Idealized habit of KzS04 crystal. Boundaries between "inner nucleus" and out polyhedron delineate growth sectors. This drawing indicates that 1 and 3 color the { 110) growth sectors, while 2 principally colors the (010) growth sectors.in aqueous solutions. The yellow dye was principally adsorbed in the (010) growth sectors (Figure l).9 The green luminescence was polarized parallel to [Ool]. This is consistent with OUT model in which the sulfonate groups substitute for sulfates in the lattice that are related to one another by the a and c lattice translations.The 1,3,6-trisulfonated pyrene moeity can tolerate a variety of substituents in the 8-position without interrupting the (9) Miller indices refer to ratios determined by classical goniometry where b > c ' a . (10) Dyes 2a,d were purchased from Eastman. The following dyes were prepared as described previously. 2c: Kondo, H.; Miwa, I.; Sunamoto, J. J. Phys. Chem. 1982, 86, 4826-4831. 2g: Whitaker, J. E.; Haugland, R. P.; Moore, P. L.; Hewitt, P. C.; Reese, M.;Anal. Biochem. 1991,198, 119-130. The syntheses of 2e,f,h-j were modeled after the general sulfonation procedure reported in the following. Huntress, E. H.; Carten, F. H. J. Am.(20: A solution of finely powdered 1-aminopyrene (869 mg, 4 mmol) in 10 mL of chlorosulfonic acid was stirred under argon atmosphere for 10 h at room temperature. The solution was poured on 30 g of crushed ice, and the crude product was collected by filtration, washed with 20 mL of cold water, and dried under argon to give 1.4 g of 8...