Crystal and molecular structure of 1,6:8,13-propane-1,3-diylidene[14]-annulene

Abstract

Initial positional parameters for the crystal structure of 1,6:8,13-propane-1,3-diylidene[14]annulene (orthorhombic, space group Fdd2, a= 19·455, b= 36·358, c= 6·572 Å, Z= 16) were obtained by two methods, and the structure refined by least-squares techniques to R 0·062 for 826 observed reflextions. The geometry is compared with that of the isolated molecule calculated by molecular mechanics, and that suggested from consideration of the u.v. spectrum. The molecular symmetry in the crystal is close to mm2 within experimental error. In spite of the distortion imposed by the propane bridge, the annulene ring maintains aromatic behaviour.