Molecular metal complexes with interactions between localized spins and conduction electrons are expected to show interesting electronic and magnetic properties. We prepared magnetic molecular conductors of iron complexes with extended TTF ligands and investigated their crystal structures and electronic and magnetic properties, from which we concluded that the single-component molecular iron complex has the dimeric form of [Fe(dmdt) ) and a coupled electric and antiferromagnetic phase transition near 95 K. 5,6 The three-dimensionally arranged spin 1/2 moments embedded in the "sea of ³-conduction electrons" of [Cu(dmdt) 2 ] cannot be realized in D 2 X-type conventional molecular conductors. Molecular alloys with diluted magnetic moments [Ni 1¹x Cu x (tmdt) 2 ] (x µ 0.0980.18) were synthesized, where magnetic moments (S = 1/2) are considered to exist at the central {CuS 4 } part of the [Cu(tmdt) 2 ] molecule and to have large coupling between the magnetic moments and the ³-conduction electrons. 7 We observed evidence that these mixed alloy systems are a molecular Kondo system, which cannot be realized in conventional D 2 X-type molecular metals. Recently, systems comprising iron arsenide superconductors and those comprising biomaterials with iron active centers have been attracting considerable interest. The next target of magnetic molecular metals with localized magnetic moments on the central transition-metal atom is a single-component molecular iron complex. Here, we present iron complexes with dmdt ligands, [Fe(dmdt) 2 ] n¹ (n = 0, 1, and 2). We succeeded in obtaining the unstable [Fe(dmdt) 2 ] 2¹ dianionic complex as (TPP) 2 [Fe(dmdt) 2 ] (TPP: tetraphenylphosphonium) and determined the crystal structure before electrochemical oxidation. However, after electrochemical oxidation, we noted that the central metal Fe 2+ was oxidized to Fe 3+ . All synthetic procedures were carried out under a strictly inert atmosphere using Schlenk techniques.8 Synthesis of the ligand moieties with a cyanoethyl-protecting group was performed according to the reported method. The synthesis of neutral [Fe(dmdt) 2 ] is described in the following procedures and shown in Scheme 1.The synthesis of (Me 4 N) 2 [Fe(dmdt) 2 ] was performed as follows: The dmdt ligand (121.0 mg, 0.30 mmol) was dissolved in dry THF (10.0 mL), and the solution was hydrolyzed with a 25 wt % MeOH solution of tetramethylammonium hydroxide (Me 4 NOH) (510 mg, 1.40 mmol) at room temperature in an argon atmosphere. The solution was stirred for 30 min, and the color of the solution changed from orange to reddish. After cooling to ¹78°C in a dry ice/MeOH bath, a solution of (Me 4 N) 2 [FeCl 4 ] (52.0 mg, 0.150 mmol) in dry MeOH (5.0 mL) was added dropwise to the reaction mixture. In the present synthesis, purified (Me 4 N) 2 [FeCl 4 ] was used instead of FeCl 3 as an iron source, with the expectation of synthesizing a neutral complex with Fe 2+

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Crystals of [Pd(tmdt)2] (tmdt = trimethylenetetrathiafulvalenedithiolate) were prepared in order to investigate their physical properties. The electrical resistivity of [Pd(tmdt)2] was measured on single crystals using two-probe methods and showed that the room-temperature conductivity was 100 S·cm(-1). The resistivity behaviors implied that [Pd(tmdt)2] was a semimetal at approximately room temperature and became narrow-gap semiconducting as the temperature was decreased to the lowest temperature. X-ray structural studies on small single crystals of [Pd(tmdt)2] at temperatures of 20-300 K performed using synchrotron radiation at SPring-8 showed no distinct structural change over this temperature region. However, small anomalies were observed at approximately 100 K. Electron spin resonance (ESR) spectra were measured over the temperature range of 2.7-301 K. The ESR intensity increased as the temperature decreased to 100 K and then decreased linearly as the temperature was further decreased to 50 K, where an abrupt decrease in the intensity was observed. To investigate the magnetic state, (1)H nuclear magnetic resonance (NMR) measurements were performed in the temperature range of 2.5-271 K, revealing broadening below 100 K. The NMR relaxation rate gradually increased below 100 K and formed a broad peak at approximately 50 K, followed by a gradual decrease down to the lowest temperature. These results suggest that most of the sample undergoes the antiferromagnetic transition at approximately 50 K with the magnetic ordering temperatures distributed over a wide range up to 100 K. These electric and magnetic properties of [Pd(tmdt)2] are quite different from those of the single-component molecular (semi)metals [Ni(tmdt)2] and [Pt(tmdt)2], which retain their stable metallic states down to extremely low temperatures. The experimental results and the band structure calculations at the density functional theory level showed that [Pd(tmdt)2] may be an antiferromagnetic Mott insulator with a strong electron correlation.

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