CRYSTAL-STRUCTURE OF 2 ISOSTRUCTURAL TETRAMETHYLDIOXAPYRENE SALTS

The crystal structures of two organic conductors di(3,5,8,10-tetrameth yl-1,6-dioxapyrenium) tetrafluoroborate, (C18H16O2)2+ BF4-, and di(3,5 ,8,10-tetramethyl-1,6-dioxapyrenium) hexafluorophosphate, (C18H16O2)2 PF6-, have been studied with single crystal X-ray diffraction methods . The two salts are isostructural and crystallize in the space group P mna, Z = 2, with the unit cell parameters a = 6.772(1), b = 9.762(1) a nd c = 21.825(2) angstrom for the BF4- salt and a = 6.792(l), b = 9.76 9(l) and c 22.096(3) angstrom for the PF6- salt. The models were refin ed to R-values of 0.082 (BF4-) and 0.069 (PF6-) using 860 and 979 refl ections, respectively, with I > 2sigma(I). The tetramethyldioxapyrene molecules lie on mirror planes stacked along the a-axis with an interp lanar distance of exactly a/2 (3.386 and 3.396 angstrom for the BF4- a nd PF6- structure, respectively). The BF4- anion exhibits considerable disorder whereas the PF6- anion is ordered, which is reflected in the higher R-value for the BF4- structure. Both salts are semiconductors.