The crystal structure of the pyrene···pyromellitic dianhydride (PMDA) π-molecular compound [(C _(16)H_(10):C_(10)-H_2O_6); 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) Å, β = 91.80 (2)°, space group P2_1/n = 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 π-π* plane-to-plane interactions between
pyrene and PMDA and >CH···O=C<, between pyrene
and PMDA, and between PMDAs
