100655-02-5Relevant academic research and scientific papers
Isolation and characterization of the principal kinetic products in the Rothemund synthesis of sterically hindered tetraarylporphyrins. Crystal and molecular structures of [tetrakis(2,6-dichlorophenyl)porphinato]zinc(II) and bis[(meso-2,6-dichlorophenyl)-5-(o,o′-dichlorobenzyl)dipyrromethene] zinc(II) complexes
Williamson, Michael M.,Prosser-McCartha, Christina M.,Mukundan Jr., Srinivasan,Hill, Craig L.
, p. 1061 - 1068 (2008/10/08)
The Rothemund condensation reaction, the most useful route to hindered 5,10,15,20-tetraarylporphyrins, has been examined in detail in context with the production of tetrakis(2,6-dichlorophenyl)porphyrin, TDCPP, a porphyrin used extensively at present in homogeneous oxygenation and biomimetic heme studies. The principal products from the reaction of pyrrole, 2,6-dichlorobenzaldehyde, and zinc acetate in refluxing 2,4,6-collidine are the bis(dipyrromethene) complex bis[(meso-2,6-dichlorophenyl)-5-(o,o′-dichlorobenzyl)dipyrromethene] zinc(II) (2), produced in ca. 40% yield, and the Zn porphyrin [tetrakis(2,6-dichlorophenyl)porphinato]zinc(II), ZnIITDCPP (1), produced in ca. 10% yield. In contrast to a previous report, there is no evidence that meso,5,5′-trisubstituted dipyrromethenes are formed. Furthermore, no zinc complexes of pyrromethenes nor dipyrromethanes build up to observable levels under the conditions of this aerobic high-temperature condensation reaction. The X-ray crystal structure of 2 coupled with 1H NMR, 13C NMR, infrared, UV-visible, and mass spectral data confirms the formulation of the compound as a Zn2+ ion coordinated by two planar bidentate disubstituted dipyrromethene ligands. Although the data indicate that carbon-carbon bond formation and cyclization in 2 to form the metalloporphyrin, 1, should not be a difficult process, 2 does not produce 1 in appreciable yield under the Rothemund conditions examined in this work. The metalloporphyrin, 1, isolated from the reaction, crystallizes as its five-coordinate N-methylpyrrolidinone (NMP) complex in triclinic space group P1: a = 11.470 (9) ?, b = 13.155 (7) ?, c = 19.894 (10) ?, α = 84.25 (4)°, β = 79.00 (5)°, γ = 75.59 (6)°; V = 2849.3 (3.3) ?3, Z = 2. The zwitterionic canonical form of the O-bound axial NMP is considerably enhanced upon ligation to the zinc, and the pocket depth defined by the eight phenyl o-chloro substituents in 1 is ca. 2.6 ?. Although the spectroscopic data indicate that free-radical bromination of 2 followed by treatment of the product under Rothemund condensation conditions yields some porphyrin, the principal products are brominated derivatives of 1 and 2.
Isolation and Characterization of the Principal Kinetic Product in the Preparation of a Sterically Hindered Tetra-arylphorphyrin: X-Ray Structure of a Bis(dipyrromethene) Complex of Zinc, ZnII(C22H13Cl4N2)2*toluene
Hill, Craig L.,Williamson, Michael M.
, p. 1228 - 1229 (2007/10/02)
The principal kinetic product in the Rothemund template synthesis of sterically hindered tetra-arylphorphyrins is not the metalloporphyrin complex but the bis(dipyrromethene) complex; the latter has been isolated from a typical porphyrin preparation, that of tetrakis(2,6-dichlorophenyl)porphyrin, and characterized by u.v.-visible, i.r., and n.m.r. spectroscopy, and X-ray crystallography.
