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

Abstract

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...

Electronic Structure of Face- and Edge-Shared Bioctahedral Systems: A Comparison of M2Cl93- and M2Cl104-, M = Cr, Mo, W

“…In the case of Mo 2 Cl 10 4-, the S ) 3 state lies lowest, and hence the global minimum in the broken-symmetry state is found at large rMo-Mo (4.1 Å), where all metal-based electrons are completely localized. The ground state is therefore distinctly different from that of the isovalent face-shared species, Mo 2 Cl 9 3 in which all metal-based electrons are delocalized, and the Mo-Mo separation is short.…”

“…In recent years the chemistry of systems containing two or more transition metal centers has expanded rapidly . Small clusters of metal atoms have obvious applications in the study of metal surfaces, electronic devices, and catalysts, as well as the relatively new discipline of bioinorganic chemistry . For example, the oxygen-transport proteins hemerythrin and hemocyanin feature diiron and dicopper sites, respectively, while manganese catalase contains two manganese ions .…”

Layer-by-Layer Growth of Electrostatically Assembled Multilayer Porphyrin Films

“…The interplanar distances in epitaxyally grown phthalocyanine films 4,20 and stacked unidimensional porphyrin crystals 40,41 were estimated to be approximately 3.2 and 3.5 Å, respectively. In the case of a rodlike nematic mesogenic porphyrin phase, Bard and co-workers reported that the value increases to about 4 Å.…”

The assignment and validation of metal oxidation states in the Cambridge Structural Database

“…These oxidation states were veri®ed by manual inspection, with reference to the CSD compound name ®eld. The oxidation state was calculated incorrectly for the bis(1,2,6,7 -tetracyano -3,5 -diimino-3,5 -dihydropyrrolizinido-N,N H ) Cu(2) complexes VAVKOS [Bonamico et al, 1989; BVS 1.13 using the R 0 value for Cu(1), 1.84 R 0 of Cu(2)], WEGDUH [Bonamico et al, 1993;1.12 R 0 of Cu(1), 1.82 R 0 of Cu(2)] and the 5,10,15,20-tetramethylporphyrinato Cu(2) complex JILGAM [McGhee et al, 1991; BVS for R 0 of Cu(1) 1.10, R 0 of Cu(2) 1.78], although the BVS with Cu(2) R 0 values are in acceptable agreement. Similar problems were encountered for Ni complexes using equation 4 (Naskar et al, 1997).…”