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SummaryIn global genome repair (GGR), XPC detects damaged nucleotides and recruits TFIIH complex. The small acidic region of XPC binds to the pleckstrin homology (PH) domain of TFIIH subunit p62; however, the recognition mechanism remains elusive. Here, we use nuclear magnetic resonance to present the tertiary structure of XPC bound to the PH domain. The XPC acidic region forms a long string stabilized by insertion of Trp133 and Val136 into two separate hollows of the PH domain, coupled with extensive electrostatic contacts. Analysis of several XPC mutants revealed that particularly Trp133 is essential for binding to the PH domain. In cell lines stably expressing mutant XPC, alanine substitution at Trp133 or Trp133/Val136 compromised UV resistance, recruitment of TFIIH to DNA damage, and removal of UV-induced photoproducts from genomic DNA. These findings show how TFIIH complex is recruited by XPC to damaged DNA, advancing our understanding of the early stage of GGR.

Two polyferrocenylsilanes (PFSs) 1 and 2 with aniline and carbazolyl as side chains have been prepared by treating silyl-chloride functionalized PFS (PFS-Cl) with hydroxyl-ended aniline and carbazole compounds, respectively, and characterized by NMR, FT-IR, elemental analysis (EA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and cyclic voltammetry (CV). Both of them could be oxidized by iodine and 2,3-dichloro-5,6-dicyanoquinone (DDQ) to form complexes. PFS 1 could be oxidized by tetracyanoethylene (TCNE) too. The complexes are characterized by FT-IR, EA, Iron-57 Mossbauer spectroscopy. All of them are partially oxidized by the oxidants and both FeII and FeIII coexist in the complexes. Magnetic property measurement by superconducting quantum interference device (SQUID) shows their paramagnetic properties with somewhat antiferromagnetic interaction. Results show that the joint type between PFS backbone and the electron-rich side groups has less direct effect on the exhibition of ferromagnetic interaction in their complexes.

We performed the low-temperature and radio-frequency (rf) ESR of spherically molded single crystals of β-p-NPNN in order to re-investigate the ferromagnetic resonance (FMR). The symmetric FMR signals were clearly observed below 0.8 K for the first time. The resonance field for H//c is markedly shifted about 80 G higher than the EPR resonance field while the anisotropy of the resonance field is very weak when the magnetic field is applied within the ab-plane. These results clearly indicate the spin-hard axis is parallel to the c-axis. We estimate the magnetic anisotropy HK = 61 G using the FMR relation with uniaxial anisotropy.

A new intercalation compound of TTM-TTF (tetrathiomethyl tetrathiafulvalene) into MnPS 3 was obtained by treating the pre-intercalate Mn 0.83 PS 3 (bipy) 0.51 with (TTM-TTF)I x in acetonitrile. The new intercalate was characterized by X-ray powder diffraction, IR and element analysis. Its magnetic property was studied with SQUID. Three magnetic transitions occur in the range between 40 K and 5 K. The first magnetic transition at 40 K indicates a weak ferrimagnetic transition, but in the range of 30 K to 5 K, the antiferromagnetism plays the main role in it. The third magnetic transition at 5 K indicates that the intercalate exhibits bulk spontaneous magnetization below 5 K.

A novel series of poly(ferrocenylsilane)s (PFSs), i.e., poly(ferrocenylmethyl(N-ethyl-N-phenyl)propylsilane) (4a), poly(ferrocenylmethyl(3-(4-methoxylphenyl)propylsilane)) (4b), and poly(ferrocenylmethyl(3-(9-carbazolyl)propylsilane)) (4c), were synthesized by transition-metal-catalyzed ring-opening polymerization (ROP) of the corresponding substituted [1]silaferrocenophanes (3a−c). They were characterized by 1H and 13C NMR, FT-IR, elemental analysis, GPC, DSC, TGA, and cyclic voltammetry. Attempts have been made to dope PFSs 4 with 7,7,8,8-tetracyano-p-quinodimethane (TCNQ), chloranil (CA), tetracyanoethylene (TCNE), and iodine. Only iodine and TCNE were able to form charge transfer salts 5a−c and 6a−c, respectively. FT-IR, elemental analysis, and Mossbauer spectra results showed partially oxidized states for 5a−c and 6a−c, and magnetic measurements by a SQUID magnetometer demonstrated paramagnetic behavior with significant antiferromagnetic interactions for these complexes over a wide temperature range.

Two new intercalation compounds were prepared by the reactions of Ni(II) cyclopolyamine complex cations with a preintercalate Mn 1− x PS 3 K 2 x (H 2 O) y , respectively, through “ion exchange” process. Their structures were characterized by elemental analysis, X-ray powder diffraction and infrared spectroscopy. The lattice spacing increased 0.567 and 1.093 nm with respect to the pristine MnPS 3 . Ferrimagnetism of the intercalates was confirmed by SQUID experiment with T c at 40 and 33 K, respectively.

A microcosm constructed, in the present study, consisted of bacteria (five or more species), green algae and rotifers and maintained a steady state for more than 100 days. This microcosm formed numerous colonies at the bottom of the flask and demonstrated coupled oscillation in the population densities of bacteria. The population dynamics and the spatial patterns of organisms were simulated using a cellular automata method. From the calculation results, the following facts were inferred: (1) heterogeneous metabolite concentrations due to the diffusion phenomenon as well as the frequencies of interactions among rotifers, bacteria and green algae and the strengths of their interactions are the contributing factors to the colony formation; (2) the system becomes stable when colonies are formed; and (3) coupled oscillation occurres in the population densities of bacteria when certain combinations are selected for the specific growth rate coefficients of the coexisting bacteria, and the distribution of the ratios of specific growth rate coefficients of the bacteria which can coexist in a stable manner is discrete rather than continuous.

We have investigated the crystal structures and magnetic properties of the α- and δ-phases of an organic radical p -NPNN ( p -nitrophenyl α-nitronyl nitroxide), which yielded the first organic bulk ferromagnet, β- p -NPNN (the β-phase). The results are compared with those of the β- and γ-phases, which show distinct magnetic ordering due to intermolecular ferromagnetic couplings. Common structural features are found in the four phases. Unlike the other phases, the α-phase exhibits a weak antiferromagnetic interaction. This is attributable to phenyl–phenyl overlapping found only in the α-phase. The crystal structure of δ- p -NPNN contains a packing motif similar to that of the γ-phase. Though the δ-phase exhibits ferromagnetic interactions, it shows no magnetic ordering down to 0.46 K. It is suggested that ferromagnetic two-leg spin ladders are formed in the δ-phase, instead of a two-dimensional network as in γ- p -NPNN. This low dimensionality explains the absence of a magnetic transition.

A new intercalation compound,Fe0.81PS3(4-aminopyridineH)0.38, issynthesized by the direct reaction of4-aminopyridine with layered FePS3 inthe presence of acetic acid.From the XRD results it was found that there aretwo phases (Phase I and Phase II)in this intercalation compound and that4-aminopyridines as the guests adopt twodifferent orientations between theinterlayer region of the host (FePS3).In one of them with the latticeexpansion (Δd) of 6.0 A thering plane of the guest is perpendicular to thelayer and in the other with Δd of3.4 A the ring plane of the guest is parallel tothe layer of the host. The IR spectraimply that the inserted guests take theprotonated form to maintain the charge balanceof the intercalation compound.Magnetic measurements indicate thatFe0.81PS3(4-aminopyridineH)0.38 exhibitsparamagnetism in the range of measurementtemperature (1.8 ∼: 300 K),where the magnetic behavior is wellin agreement with the Curie-Weiss Lawabove 55 K.

Raman and infrared conductivity spectra are investigated to reveal two-dimensional patterns of stripe charge-ordering in θ-(BEDT-TTF) 2 RbZn(SCN) 4 and α'-(BEDT-TTF) 2 IBr 2 . Either compounds exhibit similar multiple peak pattern around the C=C stretching region in both Raman and infrared spectra owing to the electron-molecular vibration coupling and charge disproportionation. We discuss the spatial symmetry of the charge-ordering stripes from the group theoretical arguments on the selection rule of these peaks.

Five inorganic-organic intercalation compounds (I–V) with N-methylstilbazoliumderivatives (i–v) inserted into the interlayer space of FePS3, were synthesized,and characterized with X-ray diffraction (XRD), elemental analysis and infraredspectroscopy. The XRD results indicate that in all these intercalation compounds themolecular ring planes of the guests are almost perpendicular to the layers of thehost FePS3. From the lattice expansion of intercalates IV and V itcan be inferred that a dipolar interaction may exist between the guests in theinterlayer space of the host FePS3. Their magnetic properties were measuredwith the SQUID technique. All these intercalation compounds show similar magneticproperties. At the Neel temperature of about 80 K they exhibit the antiferromagnetictransition, although the lattice spacing and the electron-accepting ability of theguest are different. It may imply that the lattice spacing expansion and an electron-effectof the guests have not altered their antiferromagnetic property of these FePS3intercalation compounds.

Cs(TCNQ) 1.5 and [(CH 3 ) 4 N](TCNQ) 1.5 were prepared with using chemicals and solvents purified carefully and were recrystallized under an inert atmosphere to minimize the effect of air. We investigated their magnetic properties and the effect of oxygen on these magnetism. It was found that both paramagnetic susceptibilities (Z p ) of Cs(TCNQ) 1.5 and [(CH 3 ) 4 N](TCNQ) 1.5 were very small, especially Z p of Cs(TCNQ) 1.5 was remarkably small such as 10 ∼ 40 x 10 -6 emu.mol -1 all over the temperature region. After the specimen was exposed to air, X p was measured again; for Cs(TCNQ) 1.5 , X p increased clearly by about 20 × 10 -6 emu.mol -1 ; however for [(CH 3 ) 4 N](TCNQ) 1.5 , Z p was not changed. This result suggests that the magnetism of the Cs salt was sensitive to oxygen and that the Me 4 N salt is stable to air.

We have confirmed the pressure-induced crossover from the alternating to the uniform interaction in a one-dimensional (1D) organic antiferromagnet by the measurement of heat capacity. The pentafluorophenyl nitroxide radical (F5PNN), which is a S=1/2 1D Heisenberg antiferromagnet with the alternating interaction ratio α=|J 2 /J 1 |≃0.4(J 1 / k B =−3.1 K ) at ambient pressure, has transformed into the uniform one (α=1; J 1 / k B =−4.5 K ) under the pressure of 6.5 kbar. This pressure-induced crossover was made clear by observing the change of low-temperature gradient of heat capacity, which gradually transformed from exponential to linear dependence on temperature, by the pressurization.

The continuous variation of magnetic intermolecular interactions has been studied in the pressurized genuine organic ferromagnet, β -phase para -nitrophenyl nitronyl nitroxide ( T c = 0.61 K), in which a pressure-induced ferro- to antiferromagnetic transition was observed under pressure around 6.5 kbar at 0.45 K. The rotation of the radical group C 6 H 4 NO 2 around its symmetrical axis in crystallized molecules is pointed out to be essential to change magnitude and a sign of the dominant exchange interactions, rather than the shrinkage of the lattice parameters under pressure.

The ferromagnetic to antiferromagnetic transition in genuine organic ferromagnets has been observed for the first time in the pressurized β-phase p-nitrophenyl nitronyl nitroxide crystal at the pressure around pc = 6.5 ± 0.5 kbar below 0.5 K, through the measurements of magnetic susceptibility and magnetization. The pressure dependence of the lattice parameters of its F2dd crystal structure, examined up to 12.6 kbar at room temperature, shows an anomaly near pc. At ambient pressure, the effective intermolecular interaction is estimated to be zJ/kB= 2.3 K by the analysis of the magnetic heat capacity in the external field of 10 and 30 kOe. The Curie temperature in the ferromagnetic state at p pc, however, the transition temperature starts to increase. The variation of intermolecular interactions under pressure, including their signs, is discussed on the basis of the charge-transfer mechanism and the recent ab initio method for...

A pressure-induced ferro- to antiferromagnetic transition in genuine organic compounds has been observed in the \ensuremath{\beta}-phase para-nitrophenyl nitronyl nitroxide crystal. The transition temperature ${T}_{\mathrm{C}}(p)$ in the ferromagnetic state decreases as ${T}_{\mathrm{C}}{(p)=T}_{\mathrm{C}}{(p}_{0})(1+ap)$ for pressures $pl~{p}_{c}=6.5\ifmmode\pm\else\textpm\fi{}0.5\mathrm{kbar}$ [${T}_{\mathrm{C}}{(p}_{0})=0.61\mathrm{K},$ $a=\ensuremath{-}0.048({\mathrm{kbar}}^{\mathrm{\ensuremath{-}}1})$]. For $pg{p}_{c},$ however, experiment demonstrates intrinsically the existence of an antiferromagnetic state as well as a pressure-induced enhancement of ${T}_{\mathrm{C}}(p)$ with $a=0.004({\mathrm{kbar}}^{\mathrm{\ensuremath{-}}1}).$ The results are discussed within the context of theories derived from the unrestricted Hartree-Fock approximation.

Magnetic properties of two nitronyl nitroxide (4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide) radicals which show nearly isotropic S=½ alternating linear chains are investigated down to 0.5 K and up to 9 T. Pentafluorophenyl nitronyl nitroxide at low temperatures shows an antiferromagnetic chain with alternation, while the material at room temperature shows a uniform chain structure. 2-Methyl nitronyl nitroxide, which contains an alternating chain with ferromagnetic and antiferromagnetic interactions, exhibits a three-dimensional phase transition at 1.3 K.

Magnetic interactions in crystal of p-cyanophenyl nitronyl nitroxide (p-CNPNN) were theoretically investigated. Semiempirical and ab initio molecular orbital calculations were performed for pair models of p-CNPNN molecules in the crystal. Effective exchange integrals (Jab ) are positive for the pairs of neighboring molecules in a sheet parallel to the ac-plane of the crystal, suggesting pseudo-two-dimensional ferromagnetic interaction in the ac-plane. Close contact between p-CN-phenyl group and NO group of the adjacent molecules plays a dominant role for the ferromagnetic interaction. Inter-sheet interaction is weak and the sign of Jab depends on the pairs.

The packing of the two crystallographics forms the 2-hydro nitronyl nitroxide (HNN) molecule has been studied. Using the ab initio methodology described in the accompanying paper, the packing is rationalized. In both crystals the primary structure are the HNN dimers linked trough C(sp2)-H…O-N contacts. These dimers form planes of molecules, which constitute the secondary structure. The structure and stability of the planes are different in the two crystals. Finally, the planes form stacks, the tertiary and last structure in both crystals. The forces involved in each type of structure have been quantified. The relationship between the two polymorph crystal forms have been analyzed and rationalized.

The magnetic properties of galvinoxyl (4-[3,5-bis(1,1-dimethylethyl)-4-OXO-2,5-cyclohexadiene-1-ylidenemethyl]-2,6-bis (1,1-dimethyl-ethyl)-phenoxy) and F5PNN (2-pentafluorophenyl-4,4,5,5-tetramethyl-4,5-dihydro-lH-imidazol-1-oxyl 3-oxide) under pressure are presented. We have found that the structural changes of both compounds can be suppressed by pressurization. The phase transition to a diamagnetic state of galvinoxyl can be suppressed by applied pressure. It has been found that under 7 kbar, the transition is sufficiently suppressed and the ferromagnetic interactions are preserved down to low temperature. The temperature dependence of the paramagnetic susceptibility under 7 kbar obeys the ferromagnetic chain model with 2J/kB = 25 K. The room-temperature crystal structure of F5PNN involves a uniform chain, while the low-temperature magnetism can be interpreted by the alternating antiferromagnetic chain model with 2J/K B = -5.6 K and α = 0.4. We found that under 5 kbar, the low-temperature magn...

It has been long thought that microscopic mechanisms related to magnetic short-range order were responsible for the temperature dependence of the electron paramagnetic resonance g tensor in low-dimensional magnetic systems. We show here that the demagnetizing field can explain qualitatively and quantitatively the observed features, i.e., (i) the g shift, variation of the g value, (ii) the presence of magic angles where there is no g shift, and (iii) the reorientation of the g tensor with temperature. These features are discussed theoretically and supported experimentally in purely organic insulating compounds. Previous results obtained on two different nitroxide derivatives are revisited in this framework. The role of the demagnetizing field may probably be generalized to most low-dimensional molecular materials.

A planar nitronyl nitroxide radical, 2-phenylbenzimidazol-1-ylN,N′-dioxide, has been isolated in a stable single crystal form. X-Ray analysis has shown that the radical molecules form a dimeric two-dimensional structure. The dominant magnetic interactions have been found to be antiferromagnetic. Anomalous temperature dependence of susceptibility was observed below 10 K. The EPR study indicates that this is ascribable to spin-multiplet states generated in the crystal.

The crystal packing of the simplest member of the nitronyl nitroxide familyof compounds, the 2-hydro nitronyl nitroxide radical in its α phase, is analyzed by means of a combination of distance analysis and accurate ab initio computations using correlated methods and extended basis sets. The packing is found to be driven by two types of intermolecular interactions, the C(sp 2 )H ··· ON and C(sp 3 )H ··· ON interactions, both of them found to be stable by ab initio computations (by −3.71 and −0.40 kcal/mol, respectively). The packing can be rationalized as planes kept together by C(sp 2 H ··· ON interactions. The planes are then linked by C(sp 3 )H ··· ON interactions.

The crystal structure and phase transition of ZnInGaS 4 were described. The ZnInGaS 4 had both a defect chalcopyrite and a layered structure below 920 °C, and only the layered structure ZnInGaS 4 existed between 920 and 1020 °C. The layered structure ZnInGaS 4 was grown using the normal freezing method. The bandgap of the layered structure ZnInGaS 4 was estimated to be approximately 2.6 eV and it is possibly a direct bandgap. This is a first step toward realizing the novel functions of ZnInGaS 4 .

A novel molecular complex of tetramethyltetrathiafulvalene (TMTTF) was prepared by the treatment with TiF4. The X-ray analysis reveals the exsistence of a trimer of TMTTF’s and a Ti2F102− anion in a triclinic unit cell of the dimension; a = 10.934(3), b = 12.798(2), c = 8.000(1) A, α = 103.86(1), β = 107.08(2), γ = 75.02(2)°. All the molecular planes of TMTTF are nearly parallel. The trimers stack parallel to the a axis, and the intertrimer interaction is estimated to be weak. A semiconductive behavior with a relatively large Seebeck coefficient was observed (ρ = 3 × 102 Ω cm, Ea = 0.26 eV, and S = −0.41 mV K−1 along the a axis). Weak electron spin resonance (ESR) absorption was observed to be characteristic of low-dimensional diffusive spin systems.

The magnetic properties of the β -phase p-NPNN have been investigated by the simultaneous observation of heat capacity and ac-susceptibility under hydrostatic pressures in magnetic fields. A drastic reduction of the Curie temperature from 0.61 K at an ambient pressure to 0.35 K at 7.2 kbar has been observed. The magnetic heat capacity under 7.2 kbar shows a characteristic shoulder of a two-dimensional Heisenberg ferromagnet with spin S-½, just above the heat capacity peak. By the application of weak external fields up to 1 kOe, the peak disappears and the shoulder grows its height and shifts to higher temperatures, as in the case of one-dimensional Heisenberg ferromagnets in external fields.

New neutral radical, 2,5-dimethyl-6-oxophenalenoxyl radical was generated by oxidation of 2,5-dimethyl-6-hydroxyphenalenone. The ESR data and MO calculations show the direct evidence for spin distribution on the β-positions of the phenalenyl moiety.

Metal phosphides with skutterudite (CoAs 3 )-type structure have been prepared using a wedgetype cubic-anvil high pressure apparatus. NiP 3 , LaRu 4 − x Os x P 12 ( x : 0, 1, 2, 3, 4) and CeRu 4 P 12 were synthesized at around 1100 °C and 4 GPa. The electrical conductivity and superconductivity of these metal phosphides were studied at low temperatures. The resistivity of NiP 3 was 1.6 × 10 −3 Ω cm at room temperature and decreased with decreasing temperature. A magnetic susceptibility of the phosphide showed Pauli paramagnetism. NiP 3 behaves as a metal. The resistivity of CeRu 4 P 12 increased with decreasing temperature. The semiconductive behavior was observed for this phosphide. The superconductivity of LaRu 4 P 12 , LaRu 3 OsP 12 and LaRu 2 Os 2 P 12 was observed at around 7 K. The magnetic field dependence of the T c was studied for LaRu 4 P 12 . The upper critical field ( H c 2 ) of LaRu 4 P 12 was 3.65 tesla at 0 K. The superconductivity of LaOs 4 P 12 was not found above 2 K. The electronic states and the superconductivity of the metal phosphides with skutterudite-type structure are discussed.

New neutral radicals, 2-phenyl and 2- p -methoxyphenyl derivatives of 3-oxophenalenoxyl radical, were detected by ESR measurement. The radicals were generated by thermal decomposition of the dimers of the corresponding radicals and by oxidation of 2-phenyl-3-hydroxyphenalenone.

The ferromagnetism of β-phase p-nitrophenyl nitronyl nitroxide has been established by various measurements at an ambient pressure. To get further insight into the magnetic interactions, the pressure effect on the magnetic and thermal properties has been examined in the pressure range of 0–7.7 kbar. Important feature of the results is twofold. One is a reduction of the Curie temperature with applied pressure. This suggests that the exchange interactions are mainly responsible for determination of the Curie temperature. Dipolar couplings are estimated to be too small to explain the observed Curie temperature. The other is the lowering of the lattice dimensionality. The heat capacity curve under the pressure of 7.2 kbar coincides with the theory for a two-dimensional Heisenberg ferromagnet above the Curie temperature. This suggests that the interactions between the neighboring ac-plane are more affected by compression of the crystal.

Recent advances of our study of magnetic properties of a series of molecular conductors, Cu salts of DCNQIs, are presented. First, we have found weak ferromagnetism in the antiferromagnetically ordered state of Cu spins in the insulating phase. Second, the metal-insulator (M-I) transitions of these systems have been characterized by the abrupt change of Cu 3d spins from the itinerant state to the completely localized state, even in the metal-insulator-metal (M-I-M) reentrant system, (DMe-DCNQI-α,α'-d 2)2Cu. Finally, (DI-DCNQI)2Cu is found to exhibit enhanced and temperature dependent susceptibility, suggesting the effect of spin fluctuations of itinerant electrons in a Cu 3d narrow band.

Magnetic properties and crystal structures of α-and β-2-hydro nitronyl nitroxide radicals (2-hydro-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide) were investigated. Exchange couplings in both phases were estimated from the parainagnetic susceptibility (1.8-300 K) and magnetization (up to 400 kOc) measurements. Assignment of the couplings to molecular packings has been carried out. Close spacing between the ONCNO moietics yields various magnitude of exchange couplings from 0 to ca.-30 K. In α-phase crystal, short contacts between the central carbon atoms with negative spin density and the NO groups with positive spin density were observed. However, this packing is assigned to an antiferromagnetic exchange coupling, J/kB = −11 K (ℋ= −2JS 1.S 2). This case suggests that care must be taken when we refer to McConnell's proposal.

The Electron Spin Resonance in ferromagnetic β-p-NPNN (Tc = 0.6 K) has been studied for the spherically shaped samples down to 0.4 K. It is shown that the demagnetization effect is particularly important to understand the results both in paramagnetic and ferromagnetic states. The ESR measurements for the shaped samples down to 1 K reveal the completely different g-value temperature dependence from those for the unshaped samples due to the shape demagnetization effect. The resonance line shapes along a- and c-axes become rapidly asymmetric from 2K and below, indicating the existence of anisotropic relaxation process in the ferromagnetic state. It is shown that the sharp resonance g-shift exists at the ferromagnetic transition temperature in the magneic field along b. Such a shift had been unidentified in the early studies due to the aspheric sample shape. These results can be ascribed to the anisotropic susceptibility due to the low dimensionality of the system. The magnetic resonance below 1 K ca...

Recently, the transition to ferromagnetic order has been found in crystals of genuine organic compounds consisting only of light elements such as carbon, nitrogen and oxygen. The first example of an organic ferromagnet was the orthorhombic β-phase crystal of p-nitrophenyl nitronyl nitroxide (C13H16N4O3). Its ferromagnetism (Tc = 0.6 K) has been established by various experiments such as susceptibility, magnetization, heat capacity, zero-field muon spin rotation and ferromagnetic resonance. Details of these measurements are reviewed in this article. On the other hand, the triclinic γ-phase crystal of this compound becomes an antiferromagnet at TN = 0.65 K. Its magnetic properties are also described briefly.

The Cu salt of 2,5-diiodo-N,N′-dicyanoquinonediimine, (DI-DCNQI)2Cu, which is metallic down to 4 K, is found to exhibit enhanced and temperature dependent magnetic susceptibility, in contrast to other metallic DCNQI salts of Cu. The susceptibility shows a broad maximum around 110 K. The temperature dependence can be analyzed on the basis of a phenomenology using a characteristic temperature, T ∗ ≈ 200 K . This suggests an important role of spin fluctuations in a narrow 3d band near the Fermi level. To our knowledge, this is the first evidence for the effect of spin fluctuation in a molecular conductor based on π-d interactions.

Li + -doping in the Cu salt of deuterated DMe-DCNQI- d 7 has shown drastic effects on electrical and magnetic properties. Undoped (DMe-DCNQI- d 7 ) 2 Cu exhibits a first-order metal-insulator (M-I) transition at 80 K. A small amount of Li + -doping suppresses the M-I transition. The M-I-M (reentrant) transition, which is similar to that in selectively deuterated (DMe-DCNQI) 2 Cu, appears in a narrow region of Li content x . The x - T phase diagram under ambient pressure well reproduces the P - T phase diagram of the (DMe-DCNQI) 2 Cu system. This doping effect is explained by the change in charge transfer amount from metal ions to DCNQI molecules. The effect of pressure or deuteration on the M-I transition in the DCNQI 2 Cu system is generally understood from this viewpoint.

Shubnikov-de Haas (SdH) experiments on an organic conductor θ-(BEDT-TTF) 2 I 3 have been carried out. Besides the large quasi two-dimensional Fermi surface, small three-dimensional surfaces are found. Clear SdH oscillations are observed even for the magnetic fields parallel to the two-dimensional conducting plane. These three-dimensional surfaces have the cross-sectional areas of the order of only 0.1% of the first Brillouin zone. The cyclotron effective mass ratio of the carriers on the three-dimensional Fermi surface is estimated to be small, 0.05(±0.02) and 0.014(±0.002) for the magnetic fields perpendicular and parallel to the two-dimensional plane, respectively.

Growth, structure and physical properties of single crystals Y2Cu2O5, which is regarded as a family phase of the YBa2Cu3Oy high-temperature superconductor, have been investigated. Using the phase diagram of the Y2Cu2O5- (Cu2O+CuO) pseudo-binary system determined here, single crystals of Y2Cu2O5 have been obtained from a mixed solvent Cu2O+CuO. The obtained crystals are needle-shaped and the crystal system is orthorhombic with cell parameters a=10.814(1) A, b=12.480(2) A and c=3.5000(7) A, and space group Pn21a or Pnma. In the magnetic field parallel or perpendicular to the c-axis, the transition temperature TN of paramagnetic to antiferromagnetic state is around 13 K. In the field dependence of magnetization parallel to the c-axis, the antiferromagnetic state transits to a weakly ferromagnetic state above 30 kOe and then to the ferromagnetic state above 48 kOe. The hysteresis in the field transition is observed in the magnetization curve at 1.8 K.

Weak ferromagnetism has been found in (DBr-DCNQI) 2 Cu below the Neel temperature, T N =16 K. The remanent magnetization does not decrease with lowering temperature, which is in contrast to that observed for (DMe-DCNQI- d 8 ) 2 Cu. The results suggest that the weak ferromagnetism is a universal feature of the antiferromagnetically ordered state of the DCNQI 2 Cu system.

Temperature dependence of magnetic susceptibility of Cu salt of DMe-DCNQI-α, α'- d 2 has been investigated over the temperature range of the metal-insulator-metal (M-I-M) reentrant transition. The insulating phase of this salt has been revealed to exhibit the same temperature dependence of susceptibility as that of the insulator phase of (DMe-DCNQI- d 8 ) 2 Cu, which shows only a M-I transition. In the reentrant metallic phase, there is no sizable enhancement of susceptibility such as expected from the specific heat enhancement.

A peculiar magnetic structure has been found in the crystal of a stable organic biradical molecule with S = 1,4,4,4′,4′,5,5,5′,5′-octamethyl-2,2′-m-phenylenebis(4,5-dihydroimidazol-1-oxyl 3-oxide)(m-BNN). A high-field magnetization process up to 40 T at 1.8 K exhibits a two-fold saturation process. Powder X-ray diffraction reveals the breakdown of the translational equivalence between the biradical dimers at low temperature. From these results, it is concluded that there is a four-fold quasi-degeneracy associated with a singlet pair formation between two S= 1/2 spins in only half the biradical dimers in the crystal.

A series of radical cation salts (DMET-TSeF)2X (X = I3, AuI2, AuBr2, AuCl2, Au(CN)2) crystallize in the triclinic P 1 group. The DMET-TSeF molecules form zigzag columnar stacks. Short intermolecular chalcogen ⋯ chalcogen contacts are observed within and between stacks. The AuI2 salt exhibits a sample-dependent resistivity minimum around 25 K. The AuI2 salt without the resistivity minimum shows superconductivity with Tc = 0.58 K at ambient pressure. The AuBr2 salt exhibits a resistivity minimum around 35 K. Other salts remain metallic down to 4.2 K. These salts should be classified into a quasi one-dimensional system.

A novel phase transition is observed in the crystal of a triplet (S=l) biradical, m-BNN. The crystal is composed of equivalent dimers of the biradicals at room temperature. From susceptibility, high-field magnetization and X-ray diffraction at low temperatures, it is shown that below about 10 K imperfect cancellation of magnetic moment occurs between antiferromagnetically coupled S=1spins only in half the number of dimers in the crystal.

Our recent results of magnetization, susceptibility and electron paramagnetic resonance (EPR) measurements and crystal structure determinations for the organic radiclals based on a-nitronyl nitroxide are described. The 3-quinolyl derivative with ferromagnetic intermolecular interaction shows a considerable shift of resonance field in EPR at low temperature probably due to short-range magnetic-order formation. The p-diethylaminophenyl derivative is characterized as a typical one-dimensional Heisenberg antiferromagnet.

Magnetic properties and crystal structures of several derivatives of phenyl nitronyl nitroxide (abbreviated as PNN; 2-phenyl-4,4,5,5-tetramethyl-4,5-dihydro-lH-imidazol-l-oxyl-3-N-oxide) are investigated. Some of them have the intermolecular interactions between the nitroxide group and the phenyl group, which are suggested to be favorable to ferromagnetic coupling. As a result of the coexistence of different types of magnetic interactions, anomalies in the temperature dependence of paramagnetic susceptibility are found for some compounds.

The search for bulk ferromagnetism in a genuine organic substance has long been one of the major subjects in the field of molecular magnetism. Recently, we have reported the successful results for orthorhombic β-phase crystal of p-nitrophenyl nitronyl nitroxide (abbreviated as p-NPNN). This provides an example of the first genuine organic bulk ferromag-net composed only of light elements. In this article, our recent studies on the ferromagnetic properties of β-Phase of P-NPNN are reviewed.

Magnetic and structural studies of giant metal (M)-insulator (I)-metal reentrant transitions in the partially deuterated molecular conductors (DMe-DCNQI- d n ) 2 Cu ( n =2, 3) are presented. In the insulating phase, Curie-Weiss-like susceptibilities with reduced Curie constants and diffusive satellite reflections showing a threefold superstructure were observed. The results are discussed in terms of novel electronic states associated with the 3D narrow ` d -band' in the 1D 2 p π conduction band.