Structural and charge transport properties of bis[(5,10,15,20-tetramethylporphyrinato)nickel(II)] perrhenate, [Ni(tmp)]2[ReO4]

Newcomb, Timothy P.; Godfrey, Martin R.; Hoffman, Brian M.; Ibers, James A.

doi:10.1021/ic00327a015

Cited by 22 publications

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“…d NiTMeP 7,7,8,8-tetracyanoquinodimethane, ref . e bis(NiTMeP) perrhenate, ref . f This conformation is not stable in our harmonic force field approach.…”

Section: Resultsmentioning

confidence: 95%

A New Method for Evaluating the Conformations and Normal Modes of Macromolecule Vibrations with a Reduced Force Field. 2. Application to Nonplanar Distorted Metal Porphyrins

et al. 1999

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We have developed a novel method for molecular mechanics calculations and normal-mode analysis. It is based on symmetry of local units that constitutes the given molecule. Compared with general valence force field calculations, the number of free parameters is reduced by 40-80% in our procedure. It was found to reproduce very well the vibrational frequencies and mode compositions of aromatic compounds and porphyrins, as shown by comparison with DFT calculations. A slightly altered force field obtained from Ni(II) porphin was then used to calculate the structure and the normal modes of several meso-substituted Ni(II) porphyrins which are known to be subject to significant ruffling and/or saddling distortions. This method satisfactorily reproduces their nonplanar structure and Raman band frequencies in the natural abundance and isotopic derivative spectra. The polarization properties of bands from out-of-plane modes are in accordance with the predicted nonplanar distortions. Moreover, we found that some of the modes below 800 cm -1 which appear intense in the Raman spectra contain considerable contributions from both in-plane and out-of-plane vibrations, so that the conventional mode assignments become questionable. We also demonstrate that the intensity and polarization of some low-frequency Raman bands can be used as a (quantitative) marker to elucidate type and magnitude of out-of-plane distortions. These were recently shown to affect heme groups of hemoglobin, myoglobin, and, in particular, of cytochrome c.

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“…d NiTMeP 7,7,8,8-tetracyanoquinodimethane, ref . e bis(NiTMeP) perrhenate, ref . f This conformation is not stable in our harmonic force field approach.…”

Section: Resultsmentioning

confidence: 95%

A New Method for Evaluating the Conformations and Normal Modes of Macromolecule Vibrations with a Reduced Force Field. 2. Application to Nonplanar Distorted Metal Porphyrins

et al. 1999

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“…We have extensively studied quasi one-dimensional molecular metals based on porphyrin molecules. − When the central metals and ligands are changed, the electrical, magnetic, and spectral properties are significantly modified. For example, negative thermoelectric power for Co(pc)I (pc = phthalocyanine) suggests that Co(pc)I is a metal-centered conductor where the Co d z 2 orbital is the path for conduction electrons .…”

Section: Introductionmentioning

confidence: 99%

Structural, Electrical, Magnetic, and Spectroscopic Properties of Ring-Oxidized Molecular Metals Produced by Iodination of Metal-Free and Nickel Tetrabenzporphyrins

et al. 1997

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Detailed studies of the structure, conductivitity, magnetoresistance, optical spectra, and magnetic properties (susceptibility, EPR) for the new molecular metal tetrabenzporphyrin iodide (H(2)(tbp)I) and the electrical, spectral, and magnetic properties of Ni(tbp)I are reported. Paramagnetic transition-ion impurities were carefully excluded during the synthesis of H(2)(tbp)I and Ni(tbp)I, and both materials show much higher, metal-like conductivites than previously seen for less-pure Ni(tbp)I. Comparison of the specular reflectance data for Ni(tbp)I and H(2)(tbp)I allows a distinction between purely ring pi-transitions and metal-involved charge-transfer transitions, and the spectra fix the energy levels of the pi orbitals involved in conduction. Transport, magnetic, and optical properties show that both H(2)(tbp)I and Ni(tbp)I are ring-based conductors that have metal-like conductivities, varying as approximately 1/T, down to ca. 30-40 K. However, the remaining level of defects is higher in the tbp conductors than in H(2)(pc)I, and whereas the latter is metallic down to the mK temperature range, the defects in the (tbp) compounds localize the conduction electrons at approximately 10 K (Ni(tbp)I) and approximately 30 K (H(2)(tbp)I), leading to transport through one-dimensional variable-range hopping. EPR g-values for H(2)(tbp)I and Ni(tbp)I are close to that for the free electron and are nearly temperature-independent. The line widths for both samples are extremely narrow and also are nearly temperature-independent. These results show that Ni(tbp)I does not display doubly-mixed valence, as thought earlier: Paramagnetic impurities significantly altered the EPR signals of the prior samples. H(2)(tbp)I crystallizes in the space group P4/mcc with cell constants of a = 14.173(10) Å and c = 6.463(4) Å. Full-matrix least-squares refinement of 63 variables gave an R index of 0.061 on F(o)(2).

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“…Single crystals of [Cu(tmp)]2[Re04] exhibit an axial line-width tensor. The room-temperature line width at g( is 50 (2) G and at g± is 21 (1) G. The angular dependence of the line width can be fit to the functional form ( ) = ](3 cos2 -l)2 + 0 (6) with a dipolar component , = 7.6 (5) G and an isotropic component 0 = 17.4 (5) G at room temperature (Figure 8). The functional form of eq 6 can arise in two cases.4b First, it will occur in the weak-exchange limit, where the exchange frequency 6 = J/h for coupling between adjacent dipoles is considerably smaller than the Larmor frequency, toe « 0, or second, it will occur if the exchange is strongly one-dimensional.…”

Section: Resultsmentioning

confidence: 99%

Thermally activated magnetic interactions in a one-dimensional semiconductor. Structural, charge-transport, and magnetic studies of bis[(tetramethylporphyrinato)copper] perrhenate

McGhee¹,

Godfrey²,

Hoffman³

et al. 1991

Inorg. Chem.

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Electrochemical oxidation of (5, IO, I5,20-tetramethylporphyrinato)copper(II), Cu(tmp), in the presence of the perrhenate ion affords the new molecular conductor [Cu(tmp)12 [Re04]. The compound is composed of partially oxidized Cu(tmp) cations stacked metal-over-metal and surrounded by chains of Reo, anions. Single-crystal, room-temperature conductivity along the needle (crystallographic c) axis averages 40 Q-' cm-I, lower than the values previously reported for Ni(tmp)-based conductors. The conductivity is thermally activated and may be fit to an expression that describes a semiconductor with temperature-dependent carrier mobility: u = a , , F exp(-AE/kBr) (AE = 0.126 (2) eV, a = 3.8 (2)). Magnetic studies show that the local Cu(l1) moments and thc itincrant T-carrier electrons participate in strong spin exchange. This intramolecular Cu-T coupling is shown to mediate Cu-Cu spin cxchange along the linear chains of Cu(l1) ions found in this compound. These magnetic interactions depend on the thermally activated carrier concentration. The angular variation of the line width indicates that exchange is highly one-dimensional. Thc compound crystallizes in space group C&-P4/n of the tetragonal system with two formula units in a cell of dimensions a = 16.774 (9) 8, and c = 6.746 (4) 8, ( V = 1898 A3) at 1 I O K. Full-matrix least-squares refinement of 144 variables gives a final valuc of 0.069 for the R index on for 4695 unique observations and a value of 0.043 for the R index on F for the 2582 observations having Fo2 > 3u(F:). IntroductionPartial oxidation of metalloporphyrins yields a variety of electronically conductive solids.'-I2 Many of these exhibit the same basic structural motif chains of anions surrounding metal-over-metal stacks of metal lo macro cycle^.^^ One such conductor may be prepared by chemical oxidation of Ni(pc) (pc = phthalocyaninato) with molecular iodine and has the composition Ni(pc)l.' The phthalocyaninato ligand is partially oxidized in this compound, and the iodine is present as linear chains of 1,anions. Ni(pc)I is a highly conductive molecular metal (uRT = (a) Schramm, C. J.; Scaringe, R. P.: Stojakovic, D. R.; Hoffman, B. M.; Ibers, J. A.; Marks, T. J. J. Am. Chem. Soc. 1980,102,6702-6713. (b) Martinsen. J.; Greene, R. L.; Palmer, S. M.; Hoffman, B. M.; Ibers, J. A. J . Am. Chem. SOC. 1983, 105, 677-678. (c) Martinsen, J.; Palmer, S. M.; Tanaka, J.; Greene, R. L.; Hoffman, B. M. Phys. Reo. B 1984, (a) Ogawa, M. Y.; Martinsen, J.; Palmer, S. M.: Stanton, J. L.: Tanaka, J.; Greene, R. L.: Hoffman, B. M.; Ibers, J. A. J. Am. Chem. Sot. 1987, 109, 1 1 15-1 121. (b) Ogawa, M. Y.; Hoffman, B. M.: Lee, S.: Yudkowsky. M.: Halperin, W. P. Phys. Rev. Lett. 1986, 57, 1177-1180. Tatbp = triazatetrabenzoporphyrinato dianion. (a) Liou, K. K.; Ogawa, M. Y.: Newcomb, T. P.; Quirion, G.; Lee, M.; Poirier, M.: Halperin, W. P.; Hoffman, B. M.; Ibers, J. A. Inorg. Chem. 1989,28,3889-3896. (b) Quirion, G.; Poirier, M.; Ogawa, M. Y.: Hoffman, B. M. Solid State Commun. 1987,64,613-616. ( e ) Quirion, G.; Poirier...

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Structural and charge transport properties of bis[(5,10,15,20-tetramethylporphyrinato)nickel(II)] perrhenate, [Ni(tmp)]2[ReO4]

Cited by 22 publications

References 0 publications

A New Method for Evaluating the Conformations and Normal Modes of Macromolecule Vibrations with a Reduced Force Field. 2. Application to Nonplanar Distorted Metal Porphyrins

A New Method for Evaluating the Conformations and Normal Modes of Macromolecule Vibrations with a Reduced Force Field. 2. Application to Nonplanar Distorted Metal Porphyrins

Structural, Electrical, Magnetic, and Spectroscopic Properties of Ring-Oxidized Molecular Metals Produced by Iodination of Metal-Free and Nickel Tetrabenzporphyrins

Thermally activated magnetic interactions in a one-dimensional semiconductor. Structural, charge-transport, and magnetic studies of bis[(tetramethylporphyrinato)copper] perrhenate

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