The crystal and molecular structure of quaterrylene: a redetermination

Abstract

The crystal structure of quaterrylene, C 40 H 20 -first studied with limited two dimensional X-ray data in 1960 - has been redetermined with three dimensional data. Some 2816 independent reflexions have been measured. Fullmatrix least-squares refinement with large matrices of up to 200 parameters has reduced Rto 4.00 % for the 1162 reflexions with intensities significantly above background and 11.04% for the total data set. Carbon atom positions were refined anisotropically and C-C distances have been determined with an estimated standard deviation of ±0.004 A. The average length of the six pen-bonds is 1.465(5) Å . These can be divided into two chemically equivalent sets with an average length of 1.467(3) Å for the four outer bonds and 1.462(6) Å for the central pair. The crystal contains dimers consisting of two centro-symmetrically related molecules separated by a mean perpendicular distance of 3.41 Å . This is smaller than the corresponding separation in a-perylene, and approaches the interlayer spacing in graphite. There are small, significant deviations from planarity in the quaterrylene molecule at least some of which seem to be related to the interactions between the two molecules of the dimer.