SYNTHESIS, STRUCTURE AND PROPERTIES OF VARIOUS MOLECULES BASED ON THE2-TRIOXA-4,8,12,12C-TETRAHYDRODIBENZO[CD,MN]PYRENE SYSTEM WITH AN EVALUATION OF THE EFFECT DIFFERING MOLECULAR SUBSTITUTION PATTERNS HAS ONTHE SPACE GROUP SYMMETRY

2-Trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrene (3), t-butyl-4,8,12 -trioxa-4,8,12,12c-tetrahydrodibenzo [cd,mn]pyrene (11) and tri-tert-b utyl-4,8,12-trioxa-12c-methyl-4,8,12,12c -tetrahydrodibenzo[cd,mn]pyre ne (12) have been synthesised and their crystal structures determined, The crystal structure of ophospha-4,8,12,12c-tetrahydrodibenzo[cd,mn] pyrene (13) has also been determined for comparison, Compounds 3 and 1 1 crystallise in non-centrosymmetric space groups, Compound 12 also cr ystallises in a non-centrosymmetric :space group but molecules of oppo site chirality are present within the unit cell, Finally compound 13 c rystallises in a centrosymmetric space group, The room temperature pyr oelectric coefficient of 3 has been determined, The spatial extent of the trioxatriangulene ground system has been perturbed by chemical sub stitution and the effect: of the substitutions upon the space group sy mmetry of the chemical derivative has been uncovered by X-ray structur al resolution, The non-centrosymmetric point group symmetry of the mol ecules is reflected in a non-centrosymmetric space group symmetry when ever the spatial perturbations do not prohibit the stacking of the mol ecules.