Cofacial Assembly of Partially Oxidized Metallomacrocycles as an Approach To Controlling Lattice Architecture in Low-Dimensional Molecular “Metals”. Probing Band Structure-Counterion Interactions in Conductive [M(phthalocyaninato)O]n Macromolecules Using Nitrosonium Oxidants

Tamotsu Inabe, John G. Gaudiello, Michael K. Moguel, Tobin J. Marks, Joseph W. Lyding, Robert L. Burton, William J. McCarthy, Carl R. Kannewurf

Research output: Contribution to journalArticle

Abstract

This contribution reports an integrated chemical and physicochemical investigation of the consequences of doping the cofacially joined metallomacrocyclic polymers [M(Pc)O]n, M = Si and Ge, with the nitrosonium salts NO+X-, X-= BF4-, PF6-, and SbF6-. In the case of [Si(Pc)0]„, doped products {[Si(Pc)O]Xy}nare obtained with a limiting stoichiometry y ≈ 0.36 (essentially identical with band-fillings obtained with halogen oxidants). In contrast, NO+X-doping results in decomposition of [Ge(Pc)O]n. Upon incremental NO+X-doping of [Si(Pc)O]n, transmission infrared spectra reveal the progressive growth of electronic absorption, and transmission optical spectra reveal the formation of Pc ir radical cation species. Studies of the NO+X-doping process by X-ray diffractometry suggest that it is largely inhomogeneous. Computer-assisted analysis of the {[Si(Pc)O]Xy}npowder diffraction data (aided by judiciously chosen model compounds) indicates crystal structures closely analogous to those of {[Si(Pc)O] (I3)0.37}n, {[Si(Pc)O](Br3)0.37}n, Ni(Pc)(ClO4)0.40, and Ni(Pc)(BF4)0.35. The data can be indexed in the tetragonal space group P4/mcc, Z = 2, with a = 13.70 (7) A, c = 6.58 (4) A, phthalocyanine staggering angle = 40 (2)° (X-= BF4-); a = 13.98 (6) A, c = 6.58 (4) A; phthalocyanine staggering angle = 40 (2)° (X-= PF6-); a = 14.31 (4) A, c = 6.58 (4) A, phthalocyanine staggering angle = 40 (2)° (X-= SbF6-). It appears that the X-ions are disordered along c. ESR spectra reveal nearly free electron g values, in accord with the ligand-centered π Radical character of the oxidation. As a consequence of the pronounced unidimensionality and minimal interaction of the carriers with heavy atoms, X-band powder ESR line widths are rather narrow (2.9-0.36 G) and decrease in the order I3-> SbF6-> PF6-> BF4-. For {[Si(Pc)O](BF4)0.36)n, the line width is virtually temperature-independent from 4 to 300 K. Variable temperature (4–300 K) static magnetic susceptibility studies of the {[Si(Pc)O]Xy}nmaterials reveal a small, sample-dependent Curie-like component and a Pauli-like, weakly temperature dependent contribution. Within experimental error, the Pauli-like susceptibility is independent of X-. Optical reflectivity studies of these materials reveal a plasma edge in the infrared. A Drude analysis of the data yields plasma frequency and tight-binding bandwidth parameters which are essentially independent of X-. Four-probe electrical conductivity studies of polycrystalline {[Si(Pc)O]Xy}nsamples reveal a sharp increase of conductivity with increasing y. The temperature dependence of the data can be most convincingly fit to a transport model involving fluctuation-induced carrier tunneling through parabolic potential barriers that separate the high conductivity regions. As for the other collective properties, the charge transport properties are relatively insensitive to X-. A thermochemical analysis (Born-Haber cycle) indicates that the energetics of [Si(Pc)O]ndoping with Br2,I2, and NO+X-are surprisingly similar. The small magnitude of the band structure-counterion interactions in the {[Si(Pc)O]Xy}nmaterials is attributed both to the local electronic and molecular structure of the phthalocyanine subunits as well as the overall stacking rigidity imposed by the -(Si-O-)nchains.

Original languageEnglish (US)
Pages (from-to)7595-7608
Number of pages14
JournalJournal of the American Chemical Society
Volume108
Issue number24
DOIs
StatePublished - 1986
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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