Conductive molecular crystals, structural, magnetic, and charge-transport properties of (5,10,15,20-tetramethylporphyrinato)nickel(II) iodide
(5,10,15,20-Tetramethylporphyrinato)nickel(II), Ni(tmp), has been partially oxidized by reaction with iodine. We report structural, magnetic, and charge-transport properties of single crystals of the resulting compound, Ni(tmp)I. The compound crystallizes in space group D/sup 4//sub 4h/-P4/nnc of the tetragonal system with four formula units in a cell of dimensions a = 16.610 angstrom and c = 6.932 angstrom at 114 K. Full-matrix least-squares refinement of 69 variables gives gives a final value for the R index on F/sup 2/ of 0.079 for 1418 observations. The structure consists of S/sub 4/-ruffled Ni(tmp) molecules, stacked metal-over-metal, with a Ni-Ni spacing along the stack of 3,466 angstrom. Adjacent Ni(tmp) units in the unit cell are staggered by 37/sup 0/. Severely disordered chains of iodine are located in channels surrounding the Ni(tmp) stacks. The iodine is identified as I/sub 3//sup -/ from diffuse X-ray scattering and resonance Raman spectroscopy. Splitting of the I/sub 3//sup -/ bands in the resonance Raman spectrum becomes evident at low temperature. Single-crystal room-temperature conductivity along the needle axis averages 110 ..cap omega../sup -1/ cm/sup -1/, slightly less than that of large-ring porphyrinic conductors. The temperature dependence of the conductivity of Ni(tmp)I is metal-like above 115 K and activated at lower temperatures. Single-crystal EPR studies indicate that the oxidation of the Ni(tmp) moiety is ligand centered. The magnetic susceptibility is metal-like, being temperature independent above 28 K but anomalously high indicative of enhanced Coulomb correlations. This susceptibility enhancement may arise from the mixing in of a magnetic triplet state that is available because of the electronic structure of small porphyrinic macrocycles. The susceptibility decreases sharply as the temperature is lowered below 28K.
- Research Organization:
- Northwestern University, Evanston, IL
- OSTI ID:
- 5728514
- Journal Information:
- J. Am. Chem. Soc.; (United States), Vol. 105:9
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
NICKEL COMPLEXES
PHYSICAL PROPERTIES
ORGANOMETALLIC COMPOUNDS
PORPHYRINS
CHEMICAL PROPERTIES
ELECTRIC CONDUCTIVITY
IODINE
MAGNETIC SUSCEPTIBILITY
RAMAN SPECTRA
STRUCTURAL CHEMICAL ANALYSIS
TEMPERATURE DEPENDENCE
X-RAY DIFFRACTION
CARBOXYLIC ACIDS
COHERENT SCATTERING
COMPLEXES
DIFFRACTION
ELECTRICAL PROPERTIES
ELEMENTS
HALOGENS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
MAGNETIC PROPERTIES
NONMETALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
SCATTERING
SPECTRA
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties