Akio Ichimura

Synthesis of 1,3-bis(diarylamino)benzenes as model precursors for one-dimensional organic ferromagnetic metals; characterization of the dications by cyclic voltammetry and electron spin transient nutation spectroscopy

Abstract A series of 1,3-bis(diarylamino)benzenes as model precursors for 1D organic ferromagnetic metals were synthesized. Cyclic voltammetric measurements showed that the corresponding monoand dication radicals with protecting groups were stable enough even at ambient temperature. A triplet state for the dication was unequivocally identified by a novel electron spin transient nutation spectroscopy.

Photoinduced electron transfer of N-[(3- and 4-diarylamino)phenyl]-1,8-naphthalimide dyads: orbital-orthogonal approach in a short-linked D-A system.

The photoinduced electron transfer of a series of meta- and para-linked triphenylamine-naphthalimide dyads, N-{3- and 4-[bis(4-R-substituted phenyl)amino]phenyl}-1,8-naphthalimide, 1m,p (R = H), 2m,p (R = Me), 3m,p (R = OMe), and 4m,p (R = NMe2) was investigated in toluene and DMF. The singlet charge-transfer (CT) states were observed in all cases. The decay rates were found to be faster in DMF (tau = 6.5 ps to 100 ps) than those in toluene (tau = 190 ps to 7 ns). The long-lived triplet CT states were observed in toluene for 3 (ca. 10% contribution, tau = 670 ns for 3m, 240 ns for 3p). No long-lived species were detected in DMF. The decay rates were somewhat faster in the para-isomers than in the meta-isomers in most cases. The photolysis of 5 (p-phenylene extended analogue of 3, R = OMe) gave a singlet CT state and a locally excited triplet state on the naphthalimide chromophore.

Novel building blocks for crystal engineering: the first synthesis of oligo(imidazole)sElectronic supplementary information (ESI) available: synthetic procedures and characterisation details for 2, 3, 4 and 5, and X-ray crystallographic data and packing views. See http://www.rsc.org/suppdata/p1/b2/b208777d/

A 4,4′-biimidazole, two kinds of quaterimidazoles, and a sexiimidazole were designed and synthesized for the first time as novel building blocks for supramolecules. The one-dimensional zigzag ribbonlike hydrogen-bonded structure of 4,4′-biimidazole containing protonated 4,4′-biimidazole was confirmed by single crystal structure analysis.

Redox behaviour of the oxo-bridged diruthenium(III) complex, [Ru2(µ-O)(µ-MeCO2)2(bpy)2(mim)2]2+ in acetonitrile in the presence of various proton donors (bpy = 2, 2′-bipyridine, mim = 1-methylimidazole)

Redox potentials of the Ru2III,III–Ru2III,II and Ru2III,II–Ru2II,II processes of [Ru2(µ-O)(µ-MeCO2)2(bpy)(mim)2]2+ in acetonitrile, move to the positive direction remarkably on addition of a strong acid such as toluene-p-sulfonic acid, while two processes are coalesced to show apparent one-step two-electron reduction on addition of weaker proton donors.

The mono- and dinuclear copper(II) complexes containing tripodal ligand and pyridine, imidazole or pyrazole

Abstract Monomeric and dimeric copper(II) complexes containing tris(2-benzimidazylmethyl)amine (L 1 ) or its derivatives (L 2 , L 3 , L 4 and L 5 ) and pyridine (Py), imidazole (ImH) or pyrazole (Pz) have been prepared and characterized by their magnetic susceptibilities, electric conductivities, cyclic voltammetric half-wave potentials, and visible absorption and ESR spectra. The compounds made of L 2 , L 3 or L 4 and imidazole are dinuclear copper(II) complexes bridged by imidazolate, while other complexes are mononuclear ones. The susceptibility of [Cu 2 (L 2 ) 2 (Im)](ClO 4 ) 3 ·3H 2 O shows an antiferromagnetic interaction ( J = −30 cm −1 ) and the X-band ESR spectrum for the powdered sample of this complex exhibits the triplet state of such a dimer in the Δ M s = 2 region. Likewise, the signals due to the Δ M s = 2 transition were also observed for the complexes [Cu 2 (L 3 ) 2 (Im)](ClO 4 ) 3 ·2H 2 O and [Cu 2 (L 4 ) 2 (Im)](ClO 4 ) 3 ·2H 2 O. From the comparison of half-wave potentials ( E 1 2 ) in a series of monomeric copper(II) complexes, the E 1 2 values for the reduction of Cu(II) to Cu(I) decrease in the order Py > Pz > ImH in DMF and CH 3 CN solutions.

Thiacalix[3]pyridine produces a stable mononuclear rhodium(II) complex with mutual Jahn–Teller effect

Thiacalix[3]pyridine (Py3S3) consists of pyridines and bridging sulfur atoms producing a stable octahedral mononuclear Rh(II) complex [Rh(II)(Py3S3)2]2+ showing mutual Jahn-Teller effect, a metal based reversible redox couple of Rh(III/II) at 0.02 V vs. SCE and a g(perpendicular) > g(||) relationship in EPR measurements.

Ground-state high-spin iron (III) octaethylporphyrin as studied by single-crystal cw/pulsed ESR spectroscopy

The g-tensor and relaxation mechanism of ground-state high-spin [Fe(III)OEP]Cl (OEP:octaethylporphyrin) magnetically diluted in diamagnetic Ni(II)OEP single crystals were determined by cw- and pulsed-ESR spectroscopy. From cw-ESR measurements the degree of the rhombicity in fine-structure interaction was determined. It was suggested that the rhombicity is attributable to the pseudo Jahn-teller effect and that the line broadening with increasing temperature is due to the dynamic Jahn-Teller phenomenon among the distorted structures. The large fine-structure constant D was determined to be +7 cm -1 by measuring the dependences of the spin-lattice relaxation rate on the temperature with the magnetic field perpendicular to the porphyrin plane. The spin-lattice relaxation times highly depend on the direction of the static magnetic field. The orientation dependence was interpreted in terms of the spin sublevel mixing by the spin-orbit interaction.

A complete series of copper(II) halide complexes (X = F, Cl, Br, I) with a novel Cu(II)–C(sp3) bond

A complete series of copper(ii) halide complexes [CuX(tptm)](X = F (), Cl (), Br (), I (); tptm = tris(2-pyridylthio)methyl) with a novel Cu(II)-C(sp(3)) bond has been prepared by the reactions of [Cu(tptm)(CH(3)CN)]PF(6)(.PF(6)) with corresponding halide sources of KF or n-Bu(4)NX (X = Cl, Br, I), and the trigonal bipyramidal structures have been confirmed by X-ray crystallography and/or EPR spectroscopy. The iodide complex easily liberates the iodide anion in acetonitrile forming the acetonitrile complex as a result. The EPR spectra of the complexes showed several superhyperfine structures that strongly indicated the presence of spin density on the halide ligands through the Cu-X bond. The results of DFT calculations essentially matched with the X-ray crystallographic and the EPR spectroscopic results. Cyclic voltammetry revealed a quasi-reversible reduction wave for Cu(II)/Cu(I) indicating a trigonal pyramidal coordination for Cu(I) states. A coincidence of the redox potential for all [CuX(tptm)](0/+) processes indicates that the main oxidation site in each complex is the tptm ligand.

(μ-Oxo or hydroxo)bis(μ-carboxylato)diruthenium(III) complexes with tris(1-pyrazolyl)borate face-capping ligand, affording versatile oxidation states via a protonation/deprotonation couple

(µ-Oxo or µ-hydroxo)bis(µ-acetate)diruthenium(III) complexes with tris(1-pyrazolyl)borate, [Ru2III(µ-O)(µ-CH3COO)2(HBpz3)2] (1) and [Ru2III(µ-OH)(µ-CH3COO)2(HBpz3)2](PF6) (2), have been prepared and characterized by X-ray crystallography, and showed a wide range of redox processes, Ru2II↔RuIIRuIII↔Ru2III↔RuIIIRuIV↔Ru2IV, coupled with protonation/deprotonation at the bridged monoatom.

Models for positive charge fluctuation vs. spin polarization in organic systems; synthesis and cyclic voltammetry of 2D and 1D hyperbranched π -aryl-based amines

Abstract A series of substituted N,N,N′,N′,N″,N″hexaphenyl-1,3,5-triaminobenzene(TAB) and N,N,N′,N′tetraphenyl-1,3,5 triaminobenzene(DAB) were synthesized as models for positive charged fluctuation vs. spin polarization in organic systems. CV measurements at low temperature showed that the chemical stability-in-solution of mono and poly-cationic oxidation states of the various HPTABs and TPDABs derivatives depend on their molecular structures and substituents.