Cofacial Assembly of Partially Oxidized Metallomacrocycles as an Approach to Controlling Lattice Architecture in Low-Dimensional Molecular Solids. Chemical and Architectural Properties of the “Face-to-Face” Polymers [M(phthalocyaninato)0], Where M = Si, Ge, and Sn

This contribution reports a detailed chemical, spectroscopic, and X-ray diffractometric study of the nature and structures of the cofacially joined metallomacrocyclic polymers [M(Pc)0], where M = Si, Ge, Sn and Pc = phthalocyaninato. These materials are precursors for a new class of electrically conductive polymers. Improved syntheses of the polymers are first reported. Optical spectra are assigned within the context of a porphyrinic “four orbital” model and related to those of the corresponding M(Pc)C12 and M(Pc)(OH)2 monomers. The vibrational spectra of the polymers are assigned, employing data from the aforementioned monomers and 180 substitution. Identification of the M-O stretching modes allows an estimation of the polymer molecular weights as a function of polymerization procedure via an end group analysis. Degrees of polymerization obtained for typical samples are n = 120 (30) (M = Si), 70 (40) (M = Ge), 100 (40) (M = Sn). A parallel, radiotracer determination employing labeled M(Pc)(03H)2 monomers yields results in favorable agreement. It is found that n can be substantially varied by controlling the polymerization conditions. X-ray diffraction measurements show the [M(Pc)G] polymers to be highly crystalline. An analysis of the powder X-ray diffraction data has been carried out with carefully selected model compounds and computer simulation techniques. The results are in good accord with the proposed structure consisting of parallel chains of cofacially arrayed metallomacrocycles. The simplest structures which fit the experimental data are as follows: [Si(Pc)0], orthorhombic space group Ibam, a = 13.80 (5) Á, b = 27.59 (5) Á, c = 6.66 (4) Á, Z = 4, interplanar spacing = 3.33 (2) A, intrastack phthalocyanine staggering angle = 39 (3)º, density (g cm) = 1.458 (21) (caled), 1.432 (10) (found); [Ge(Pc)0], tetragonal space group P4/m, a = 13.27 (5) k,c = 3.53 (2) Á, Z = 1, interplanar spacing = 3.53 (2) Á, intrastack phthalocyanine staggering angle = 0 (5)º, density (g cm) = 1.609 (28) (caled), 1.512 (10) (found), or tetragonal space group I4/m, a = 18.76 (7) Á, c = 3.57 (2) A, Z = 2, intrastack phthalocyanine staggering angle = 0 (5)º, density (g cm) = 1.589 (26) (caled), 1.512 (10) (found); [Sn(Pc)0], tetragonal space group P4/m, a = 12.82 (5) Á, c = 3.82 (2) A, Z = 1, intrastack phthalocyanine staggering angle = 0º, density (g cm″3) = 1.712 (25) (caled), 1.719 (10) (found). The data for the latter structure are best fit to a model where the larger size of the Sn(IV) ion induces buckling of the macrocycle skeleton. An approximate analysis of the diffraction line widths suggests that crystallite dimensions are on the order of several hundred angstroms and are not grossly anisotropic.