X-ray diffraction study of the crystal structure of the pi-molecular compound pyrene ... pyromellitic dianhydride at 19 K.

The crystal structure of the pyrene ... pyromellitic dianhydride (PMDA) pi-molecular compound [(C16H10:C10H2O6); PYRPMA] has been refined from intensities measured at 19 K using the low-temperature accessory designed by Samson, Goldish & Dick [J. Appl. Cryst. (1980), 13, 425-432] for a four-circle diffractometer. Earlier results for the ordered structure [Herbstein & Snyman (1969). Philos. Trans. R. Soc. London Ser. A, 264, 635-666] are confirmed and extended; at 19 K, a = 13.664 (3), b = 9.281 (2), c = 14.420 (3) A, beta = 91.80 (2) degrees, space group P2(1)/n, Z = 4, with two sets of pyrenes at independent centres of symmetry and the four PMDAs at general positions. The geometrical structures of the two components are in good agreement with quantum mechanical calculations. Analyses of thermal motion and packing show that one set of pyrenes is more tightly packed than the other; the principal interactions in the crystal are pi-pi* plane-to-plane interactions between pyrene and PMDA and > CH ... O = C <, between pyrene and PMDA, and between PMDAs.