UCL Discovery

Abstract

All measurements with Mo K-alpha radiation (lambda = 0.71073 angstrom). (I) p-Phenylenebis(2,5-dimethyl-pyrrole), C18H20N2, M(r) = 264.40, orthorhombic, Ccmb, a = 7.273 (2), b = 12.463 (4), c = 16.559 (4) angstrom, V = 1501.1 angstrom 3, Z = 4, D(x) = 1.17 Mg m-3, F(000) = 568, T = 295 K, molecular symmetry 2/m. R = 0.056 (wR = 0.053) for 454 reflections having I greater-than-or-equal-to 3-sigma(I) with the coordinates of all atoms refined, anisotropic thermal parameters for C and N atoms, and a fixed value of U(iso) for H atoms. (II) 2,2',5,5'-Tetramethyl-1,1'-bipyrrole, C12H16N2, M(r) = 188.27, orthorhombic, Cc2a, a = 11.773 (3), b = 25.154 (6), c = 11.841 (3) angstrom, V = 3507 (1) angstrom 3, Z = 12, D(x) = 1.07 Mg m-3, F(000) = 1224, T = 292 K, molecular symmetry 2 for three independent molecules. R = 0.078 (wR = 0.080) for 605 reflections having I greater-than-or-equal-to 3-sigma(I) with isotropic refinement for C, N and H atoms in calculated positions. (III) 13,14-Diazatetracyclo[8.2.1(1,10).-1(4,7).0(13,14)]tetradeca-4,6,10,12-tetraene, C12H12N2, M(r) = 182.6, monoclinic, P2(1)/a, a = 7.667 (2), b = 8.191 (2), c = 8.231 (2) angstrom, beta = 112.04 (2)-degrees, V = 479.1 (2) angstrom 3, Z = 2, D(x) = 1.26 Mg m-3, F(000) = 196, T = 292 K, molecular symmetry 1BAR. R = 0.087 for 354 reflections having I greater-than-or-equal-to 3-sigma(I) with C and N atoms refined anisotropically and H atoms in calculated positions. There is disorder in the -CH2-CH2-groups. In all three compounds, each 2,5-substituted pyrrole group is planar with unexceptional bond lengths and angles. In (I) the two pyrroles are strictly orthogonal to the benzene ring, in (II) they are orthogonal to each other, while in (III) they are coplanar. The crystal structures correlate well with the results of electron spin resonance measurements made on the corresponding radical cations in solution.