Synthesis and Crystal Structure of C 60 Complex with a Symmetrical Donor of 2, 3, 6, 7, 10, 11-Hexamethoxytriphenylene (
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LONG Y. CHIANG* Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan JOHN W. SWIRCZEWSKI AND KENG S. LIANG Corporate Research Laboratory, Exxon Research and Engineering Company, Annandale, New Jersey 08801
ABSTRACT We have successfully synthesized single crystals of C60 fullerene complex with a symmetrical triplet donor of 2,3,6,7,10,11-hexamethoxytriphenylene (HMT). All spectroscopic data and analyses support the chemical composition of this complex as C60 (HMT) 2 . Single crystals of C 60 (HMT) 2 are, at 20+1 °C, cubic, space group Fd3c-Oh8 (No. 228) with a = 30.251(9) A, a = 90.000, V = 27682(30) )k, Z = 16 (dcaled = 1.476 gcm- 3 ), and Ru (unweighted) = 0.098. INTRODUCTION Fullerene C60 molecule exhibits versatile multiple reductive electronic states1 -7 that make it suitable for use as a molecular acceptor in the synthesis of new solid state materials with electronic donors. Examples of charge transfer complexes comprised of C60 include
superconducting alkali metal doped fullerides, 8 ,9 C60 (TDAE), 10 ,11 and C60 -chromium(II) porphyrin. 12 Here we report the synthesis of the first example of C6 0 complex with a symmetrical organic triplet donor, 2,3,6,7,10,11-hexamethoxytriphenylene (1, HMT). 13,14 This complex of C60 (HMT) 2 (2) crystallized in a cubic unit cell structure with dimensions larger than those found in the crystal of superconducting K 3C60 .15 , 16 Individually, each C60 fullerene sphere is found to be surrounded by four HMT molecules in distinctive tetrahedral arrangement. The closest distance from one C60 centroid to the next C60 centroid in the adjacent chain is
13.099 H3CO
A. H3CO. 3
H3CO
OCH 3 OCH3
OCH3
1 (HMT)
C 60
85 Mat. Res. Soc. Symp. Proc. Vol. 328. ©1994 Materials Research Society
Since it has not been possible to isolate the discrete complex of C60 fullerene with triphenylene, perylene, or relatively stronger donors such as the fulvalene analogue TTF, TMTSF, or BEDT-TTF used in the study of organic electronic conductivity and superconductivity, 17 the facile complexation of C60 with the relatively poor donor HMT (with the first half-wave oxidation potential of 0.92 V vs SCE in acetonitrile) will be of interest theoretically.
RESULTS AND DISCUSSION Synthesis of 2,3,6,7,10, 11-hexamethoxytriphenylene was carried out by a trimerization of veratrole in the presence of sulfuric acid. 18 Complexation of HMT and C60 fullerene was prepared by the treatment of 2,3,6,7,10,1 l-hexamethoxytriphenylene (2 equiv.) in chloroform or 1,1,2-trichloroethane solution with C60 molecules (1 equiv.) dissolved in toluene solution. The mixture was stirred at 80 °C for 30 min and then maintained at that temperature for a period of 4h without stirring. During this heating period, the octahedral purple-blue crystals were grown from the solution mixture. After cooling the solution to ambient temperature, the crystals were collected and washed repeatedly with chloroform and toluene to afford higher than 90% yield of complex. The elemental analysis of this octahedral purpl
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