Akira Izuoka

An organic ferromagnet: α-phase crystal of 2-(2′,5′-dihydroxyphenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxy-3-oxide (α-HQNN)

The α-phase crystal of 2-(2′,5′-dihydroxyphenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxy-3-oxide (α-HQNN), which consists of one-dimensional arrays formed by intra- and inter-molecular hydrogen bonds, showed a ferromagnetic phase transition at 0.5 K.

NOVEL SPIN-POLARIZED TTF DONORS AFFORDING GROUND STATE TRIPLET CATION DIRADICALS

Abstract The concept of “spin-polarized” donor was successfully extended to TTF-based donor radicals. A series of TTF derivatives carrying a phenyl nitronyl nitroxide group were prepared, and they turned out to afford ground state triplet cation diradicals through one-electron oxidation. Such “spin-polarized” TTF donors are expected to become building blocks for organic conducting ferromagnets.

Organic hydrogen‐bonded dielectrics: Quantum paraelectricity based on tautomerization of 9‐hydroxyphenalenone derivatives

Dielectric properties based on tautomerization in 9‐hydroxyphenalenone derivatives were examined. While the 5‐methyl derivative 2 exhibits an antiferroelectric transition at 41 K, such a phase transition was not observed in 5‐bromo derivative 3 down to 4.2 K. Suppression of the phase transition in the latter may be interpreted in terms of quantum paraelectricity based on proton‐tunneling along the hydrogen bond. The reason for the appearance of antiferroelectric ordering coupled with the phase transition in 2 may be ascribed to reduction of the tunneling frequency due to symmetry breaking caused by the methyl group. The present system can be regarded as zero‐dimensional hydrogen‐bonded system and is interesting in reference to inorganic hydrogen‐bonded dielectrics.

Calorimetric study of proton tunneling in solid 5-bromo-9- hydroxyphenalenone and deuteration-induced phase transitions in its deuteroxy analog

The heat capacities of 5-bromo-9-hydroxyphenalenone (BHP) and its deuteroxy derivative (BDP) were measured at temperatures between 2 and 310 K. The heat capacity of BHP is a smooth function of temperature and that of BDP has two peaks at 21.3 and 33.9 K. By analyzing the data on BHP, a tunnel splitting of (64±2) cm−1 associated with the quantum mechanical motion of the hydrogen atom in the intramolecular O–H–O hydrogen bond was derived along with the Debye temperature 60.8 K and two Einstein temperatures 131.4 (nondegenerate) and 210.4 K (doubly degenerate). The enthalpy change of 225 J mol−1 and entropy change of 6.8 J K−1 mol−1 were determined for the total thermal effects associated with the two phase transitions in BDP. The value of the transition entropy is consistent with the twofold disorder in the high temperature phase. The tunneling energy and transition enthalpy satisfy an inequality demanded, on the assumption that the potential energies experienced by the proton and deuteron are the same, by ...

Design and preparation of pyrrole-based spin-polarized donorsElectronic supplementary information (ESI) available: cyclic voltammograms for N-PN, β-PN, N-TPN, PhNN and TPP. See http://www.rsc.org/suppdata/jm/b2/b211986b/

As a fundamental building block of a conductive magnetic macromolecule, a series of pyrrole derivatives carrying a nitronyl nitroxide (NN) group was prepared. Some of these derivatives afforded ground-state triplet diradical cations upon one-electron oxidation, and the difference in the spin multiplicities of the singly oxidized pyrrolylNNs was rationalized on the basis of a perturbational molecular orbital method. The electronic interaction between the pyrrole and the nitronyl nitroxide parts was also confirmed by cyclic voltammetry and UV-Vis absorption spectroscopy. In spite of the vacancy of the 2 and 5 positions of the pyrrole ring, electrochemical polymerization of these derivatives was not observed, except for an extended α-thienyl derivative.

Preparation of isolable ion-radical salt derived from TTF-based spin-polarized donor

Abstract Galvanostatic electrocrystallization of a TTF-based donor-radical (ETBN) has afforded an ion-radical salt. The radical site of ETBN is intact in the prepared salt and showed paramagnetic behavior. The salt is a semiconductor with conductivity of 10 −2 S/cm at room temperature. Conductivity and magnetic properties are explained as a new type of an ion-radical salt derived from a π-conjugated donor-radical.

Preparation and properties of double-bridged BEDT-TTF dimer and its perchlorate salt

Abstract A novel twin donor with double ethylene bridges (1) was synthesized and perchlorate salt of its cation radical was prepared. The salt showed a metallic temperature dependence of conductivity from room temperature down to about 100 K. In the salt the donor molecule takes a V-shape conformation and a donor packing shows a unique three dimensional arrangement. A bridging thia-crown moiety may play an important role in determining the conformation and the arrangement of the donor.

Isotope Effect on the Dielectric Phase Transitions of 5-Bromo-9-Hydroxyphenalenone

Dielectric properties have been investigated for proton-deuteron mixed crystals of 5-bromo-9-hydroxyphenalenone with strong intramolecular hydrogen bonds. The fully deuterated compound shows two successive structural transitions, i.e. , incommensurate (IC) transition ( T IC ∼ 37 K) and lock-in transition ( T C ∼20 K). With increasing proton concentration ( x ), both of the critical temperatures decrease and the transitions disappear at x IC ∼ 0.65 and x C ∼ 0.25, respectively. This observation suggests that intramolecular tunneling motion of the protons significantly influences the structural phase transitions via the molecular tautomerization process.

New synthesis of 2-[1,3-dithiol-2-ylidene]-5,6-dihydro-1,3-dithiolo[4,5-b][1,4]dithiins with formyl group on fused benzene, [1,4]dithiin, or thiophene ring

Abstract As novel TTF-based annelated donors, 2-[1,3-dithiol-2-ylidene]-5,6-dihydro-1,3-dithiolo[4,5- b ][1,4]dithiins with a formyl group on fused benzene, [1,4]-dithiin, or thiophene ring, respectively, were prepared using Diels-Alder or an intramolecular aldol reaction.

Preparation of Tetrathiafulvaleno-Nitronylnitroxide and Magnetic Properties of Its DDQ Complex

Abstract Tetrathiafulvalenonitronylnitroxide (1) which consists of a donor site and a stable radical site was prepared in order to construct organic ferromagnets. The electronic feature of the donor is that two sites becomes cross-conjugated through trimethylenemethane-type conjugation upon one-electron oxidation of the donor unit. The complex of donor molecule 1 with DDQ shows unusual magnetic behavior.