The structural and electrical properties of a metal-halide cubic perovskite, CH₃NH₃SnI₃, have been examined. The band structure, obtained using first-principles calculation, reveals a well-defined band gap at the Fermi level. However, the temperature dependence of the single-crystal electrical conductivity shows metallic behavior down to low temperatures. The temperature dependence of the thermoelectric power is also metallic over the whole temperature range, and the large positive value indicates that charge transport occurs with a low concentration of hole carriers. The metallic properties of this as-grown crystal are thus suggested to result from spontaneous hole-doping in the crystallization process, rather than the semi-metal electronic structure. The present study shows that artificial hole doping indeed enhances the conductivity.

A conducting partially oxidized salt of TPP[Fe(Pc)(CN)₂]₂, which contains paramagnetic iron(III), has been obtained by electrocrystallization of TPP[Fe(Pc)(CN)₂]. The crystal is composed of one-dimensional TPP arrays surrounded by slipped-stacked one-dimensional Fe(Pc)(CN)₂ chains. This structure is isomorphous with TPP[Co(Pc)(CN)₂]₂, in which the central metal is non-magnetic cobalt(III). The electrical conductivity at room temperature, ca. 10 Ω⁻¹ cm⁻¹, is about one order of magnitude lower than that of the Co analogue. On lowering the temperature, the conductivity shows a much steeper decline compared with the temperature dependence of the conductivity of TPP[Co(Pc)(CN)₂]₂. The band width, estimated from both thermoelectric power measurements (which show apparent metallic behavior at high temperatures) and an extended Hückel calculation, is found to be the same as that obtained for TPP[Co(Pc)(CN)₂]₂. This is consistent with observations from the single-crystal reflectance spectra, in which both partially oxidized salts show almost the same plasma edge. On the other hand, the magnetic susceptibility of TPP[Fe(Pc)(CN)₂]₂ is quite different from that of TPP[Co(Pc)(CN)₂]₂; both of the magnetic moments originated from Fe^III and the π-radical seem to be localized in TPP[Fe(Pc)(CN)₂]₂, while the moments originated from the π-radical in TPP[Co(Pc)(CN)₂]₂ are interacting with each other to lead to temperature-independent Pauli-like susceptibility. At low temperatures, a decrease in the susceptibility has been observed, suggesting the existence of antiferromagnetic interactions.

Electrochemical oxidation of PTMA[M^III(Pc)(CN)₂] (PTMA = phenyltrimethylammonium, Pc = phthalocyaninato, and M = Co or Fe) gives partially oxidized salts (PTMA)_x[M^III(Pc)(CN)₂]·y(solvent) (solvent = acetonitrile or acetone). The obtained crystals in which the solvent molecules partially occupy the cationic sites are isomorphous regardless of M and solvent. They are highly conducting and metallic behavior is observed in the conductivity and thermoelectric power measurements. In contrast to the Pauli-like behavior of the Co^III salt, Curie-like behavior with an anomaly due to antiferromagnetic interactions was observed for the Fe^III salt in magnetic susceptibility measurements. The existence of local magnetic moments in the Fe^III salt leads to a significant influence on the transport properties, suggesting the existence of π–d interactions in this system.

A series of one-dimensional conductors, TPP[Fe^III(Pc)L₂]₂ with L = CN, Cl, and Br, have been prepared. These compounds show giant negative magnetoresistance due to the interaction between conduction π-electrons and localized Fe-centered d-spins, but the magnitude is found to vary based on the axial ligand, suggesting that the strength of the π–d interactions is sensitively influenced by the axial substituent. The magnetic susceptibility also shows the difference in the magnetic interactions by the axial substituent. The ab initio calculation of the isolated molecules has revealed that the Jahn–Teller effect in this system induces splitting of d_xz and d_yz orbitals, and that the energy shift of the d-orbital accommodating an unpaired electron is varied by the axial substituent. The axial-ligand dependence of the intramolecular π–d interaction is found to correlate with the magnitude of the magnetoresistance.