Structural chemistry of phthalocyaninato-cobalt(II) and -manganese(II)

Abstract

The crystal and molecular structures of the β-polymorphic forms of phthalocyaninatomanganese(II), [Mn(pc)], and phthalocyaninatocobalt(II), [Co(pc)], have been determined by single-crystal X-ray diffraction methods at 295 K, and also at 116 K in the case of [Mn(pc)]. Crystals are of the monoclinic β-polymorph type, space group P2₁/c, Z= 2; for [Mn(pc)](116 K), a= 14.590(3), b= 4.741(1), c= 19.301(5)Å, β= 120.79(1)°; (295 K), a= 14.576(5), b= 4.755(1), c= 19.362(7)Å, β= 120.70(2)°; [Co(pc)](295 K), a= 14.542(2), b= 4.773 1(5), c= 19.352(2)Å, β= 120.824(7)°. Automatic diffractometry has provided significant Bragg intensities for 1 608 {[Mn(pc)], 116 K}, 1 525 (295 K), and 1 930 {[Co(pc)]} independent reflections and the structures have been refined by full-matrix least-squares methods to R 0.038 {[Mn(pc)], 116 K}, 0.072 (295 K), and 0.039 {[Co(pc)]}. The metal atoms co-ordinate within the central cavity of the macrocyclic phthalocyaninate ligand to a precisely planar array of nitrogen atoms, with mean bond lengths Mn–N = 1.941(3)Å at 116 K, 1.933(5)Å at 295 K, and Co–N 1.908(2)Å. The intermolecular packing is of the typical herringbone arrangement, with angles of 47.9 {[Mn(pc)], 116 K} and 47.3°{[Co(pc)]} between the normals to the MN₄ co-ordination planes and the crystallographic b axes. Each molecule has close contacts with two neighbours related by translations of ±b, resulting in pseudo-octahedral metal environments with axial Mn–N contacts of 3.150(3)(116), 3.169(6)Å(295 K), and a Co–N contact of 3.219(3)Å. The importance of these intermolecular contacts in establishing a ferromagnetic exchange path in [Mn(pc)] is discussed, as are deviations within the macrocyclic ligand from D_4h symmetry.