NEUTRON-DIFFRACTION AT 115-K TO 1.09-A-1 FROM COBALT PHTHALOCYANINE

[Co(C32H16N8)], M(r) = 571.47, monoclinic, P2(1)/c, a = 14.489 (9), b = 4.763 (4), c = 19.156 (16) angstrom, beta = 120.76 (4)-degrees, V = 1136 (3) angstrom 3, Z = 2, D(n) = 1.67 Mg m-3, neutron lambda = 0.753 (1) angstrom, mu = 0.0879 mm-1, F(000) = 46.05 x 10(-14) m, T = 115.0 (1) K, R(F) = 0.018, R(F2) = 0.030, S = 1.08 for 2789 reflections, 1008 at wavevectors above 0.7 angstrom-1, with anharmonic Gram-Charlier expansion refinement and thermal diffuse-scattering (TDS) correction derived from theoretical intermolecular potentials. The introduction of 715 cubic and quartic anharmonic parameters reduces R(F2) by 0.011 and S by 0.11 from the values obtained in a harmonic refinement. Use of the local molecular approximate symmetry is not helpful in describing anharmonicity. Quartic parameters are more significant than cubic ones. Much of the anharmonic correction seems to result from intermolecular interaction affecting the relatively soft motion along b, resulting in one-particle potential wells with flat bottoms along b, but relatively harmonic potential in the ac plane. Agreement of positional parameters with the 115 K X-ray charge-density results is good, if similar refinements are made. But the neutron thermal parameters are significantly lower than X-ray, 8% on average, probably reflecting a difference in the TDS correction in the two experiments. The molecule is significantly distorted from planarity.