Hybrid Organic−Inorganic Conductor with a Magnetic Chain Anion: κ-BETS2[FeIII(C2O4)Cl2] [BETS = Bis(ethylenedithio)tetraselenafulvalene]

Humidity-Sensing Properties of an 1D Antiferromagnetic Oxalate-Bridged Coordination Polymer of Iron(III) and Its Temperature-Induced Structural Flexibility

A novel one-dimensional (1D) oxalate-bridged coordination polymer of iron(III), {[NH(CH₃)(C₂H₅)₂][FeCl₂(C₂O₄)]}_n (1), exhibits remarkable humidity-sensing properties and very high proton conductivity at room temperature (2.70 × 10⁻⁴ (Ω·cm)⁻¹ at 298 K under 93% relative humidity), in addition to the independent antiferromagnetic spin chains of iron(III) ions bridged by oxalate groups (J = −7.58(9) cm⁻¹). Moreover, the time-dependent measurements show that 1 could maintain a stable proton conductivity for at least 12 h. Charge transport and magnetic properties were investigated by impedance spectroscopy and magnetization measurements, respectively. Compound 1 consists of infinite anionic zig-zag chains [FeCl₂(C₂O₄)]_nⁿ⁻ and interposed diethylmethylammonium cations (C₂H₅)₂(CH₃)NH⁺, which act as hydrogen bond donors toward carbonyl oxygen atoms. Extraordinarily, the studied coordination polymer exhibits two reversible phase transitions: from the high-temperature phase HT to the mid-temperature phase MT at T ~213 K and from the mid-temperature phase MT to the low-temperature phase LT at T ~120 K, as revealed by in situ powder and single-crystal X-ray diffraction. All three polymorphs show large linear thermal expansion coefficients.

Modern History of Organic Conductors: An Overview

This short review article provides the reader with a summary of the history of organic conductors. To retain a neutral and objective point of view regarding the history, background, novelty, and details of each research subject within this field, a thousand references have been cited with full titles and arranged in chronological order. Among the research conducted over ~70 years, topics from the last two decades are discussed in more detail than the rest. Unlike other papers in this issue, this review will help readers to understand the origin of each topic within the field of organic conductors and how they have evolved. Due to the advancements achieved over these 70 years, the field is nearing new horizons. As history is often a reflection of the future, this review is expected to show the future directions of this research field.

Two new canted antiferromagnetic systems: magnetic, theoretical, and crystallographic studies on trans-bis(2-iodopyridine)dihalocopper(ii)

The two complexes Cu(2ip)X₂ were prepared (where 2ip = 2-iodopyridine and X = Cl or Br), and their crystal structures were determined. The two complexes are isomorphous and form a magnetic chain based on the two-halide exchange pathway. The powder and single crystal magnetic susceptibility data were measured down to 1.8 K. The exchange is antiferromagnetic along the chain; the exchange is stronger in the bromide complex than in the corresponding chloride complex. In the ordered state, weak moments appear along some of the axes, indicative of spin-canting. The calculated spin densities and the mapped surface of spin density on total electron density were used to rationalize qualitatively the observed magnetic behavior. Low temperature structures are compared with the room temperature data; the C-IX-Cu and Cu-XX-Cu distances are shorter at low temperatures; in contrast, the covalent bonds of the organic ligand (2-iodopyridine) are longer (negative thermal expansion of the covalent bonds). The anomalous behavior is rationalized using charge transfer from Cu-X group to the anti-bonding orbital of the organic ligand. Quantum theory of atoms in molecules was used to analyze C-IX halogen bonding interactions.

[BEDT-TTF][Fe(C2O4)Cl2]: an organic-inorganic hybrid semiconductive antiferromagnet

A radical cation salt composed of an organic donor, BEDT-TTF^1.0+, and a one-dimensional inorganic anion, [Fe(C₂O₄)Cl₂^-]_n, was obtained by electrocrystallization, and was identified as a semiconductor with values of σ_300K = 3.0 × 10^-5 S cm^-1. Spin-canted antiferromagnetic long-range ordering was observed at 5.5 K from ZFCM/FCM/RM measurement and confirmed using AC measurement.

Unconventional Magnetic and Resistive Hysteresis in an Iodine-Bonded Molecular Conductor

Simultaneous manipulation of both spin and charge is a crucial issue in magnetic conductors. We report on a strong correlation between magnetism and conductivity in the iodine-bonded molecular conductor (DIETSe)2 FeBr2 Cl2 [DIETSe=diiodo(ethylenedithio)tetraselenafulvalene], which is the first molecular conductor showing a large hysteresis in both magnetic moment and magnetoresistance associated with a spin-flop transition. Utilizing a mixed-anion approach and iodine bonding interactions, we tailored a molecular conductor with random exchange interactions exhibiting unforeseen physical properties.

Synthesis, Structure, and Magnetic Properties of (A)[FeIII(oxalate)Cl2] (A = Alkyl Ammonium Cations) with Anionic 1D [FeIII(oxalate)Cl2]- Chains

The use of alkyl ammonium cations resulted in four compounds of (A)[FeIII(ox)Cl2] (A = Et3NH+ (1a, 1b), Me4N+ (2), and n-Bu4N+ (3); ox = oxalate), whose structures and magnetic properties were characterized. In all cases, the metal Fe(III) ions are six-coordinated by four oxygen atoms from two bischelating oxalate ligands and the two terminal Cl- ions in the cis position. Thus they form similar anionic 1D [FeIII(ox)Cl2]- chains. The chains are separated by alkyl ammonium cations in the lattice, and the cation size seems to control the interchain separation and packing patterns in the solid. A parallel arrangement of the [FeIII(ox)Cl2]- chains is observed for 1a, 2, and 3, while a crossed one is observed for 1b, which is a polymorph of 1a. Magnetic studies reveal the antiferromagnetic intrachain interactions in all compounds. The last three compounds, 1b, 2, and 3, show spin canting below 14.5, 9.5, and 3.8 K, respectively. The dipolar interaction over the interchain distance is proposed to be the result of 3D magnetic ordering in the materials.