The electron-donating [n]radialenes (n=3,4,5) were prepared with the aim of developing both new type of organic (super)conductors and unprecedented organic/molecular ferromagnets. The charge-transfer (CT) complexes of 1,3-dithiole[4]radialene with TCNQ and of 1,3-benzodithiole-[4]radialene with TCNQF4 and DDQ showed comparatively high electrical conductivities in compressed pellets. The single crystals of PF6 and CIO4 salts of 1,3-benzodithiole[4]radialene radical cation revealed temperature change of electrical conductivity characteristic of a semiconductor. The magnetic properties of the bis(trifluoroacetate)salt of thioxanthene[3]-radialene dication and of the CT complexes of 1,3-benzodithiole[5]-radialene with DDQ, TCNQF4, and hexacyanohexamethylenecyclopropane, were also investigated from the ESR and/or magnetic susceptibility measurements.

We describe a synthetic approach to the preparation of high spin density organic solid as a probe to organic ferromagnetism utilizing an external doping process to achieve a molecular sequence of alternate donors and acceptors in different spin states for, in principle, the ground state ferrimagnets. In contrast to the irreversibility of electron oxidations of many triaminobenzene derivatives, we found that, by substituting three hindered diisopropylamino groups on benzene, stable monocationic TDIAB radicals can be obtained. In the case of HDMAB its cationic radicals can be stabilized in a strong acid medium. The observed bulk spin densities of 0.18 — 0.23 spins 1/2 per donor molecule in TDIAB-PF6 and HDMAB-PF6 solids are significant comparing to the diamagnetic properties normally obtained in solids of simple cationic salts of planar organic donor molecules. The results imply that a small degree of molecular spin separation due to the steric effect can readily increase sharply the paramagnetic spin density of solids. We also found that the introduction of arsenic pentafluoride into molecular crystals disintegrates the long range order of crystal without rearranging the molecular stacking sequence in HMT complexes. Arsenic pentafluoride serves as not only the oxidant, but also the physical molecular separator. That results in a molecular spin separation of triplet dicationic HMT spins from each other at high doping level. This concept of molecular spin separation explains the observation of static magnetic data with an observed high spin density of many doped HMT charge transfer complexes. Without the molecular spin separation, the segregated-stack complexes, such as HMT-(AsF5.5)3.4 and HMT-DDQ-(AsF5.5)4.1, should instead give a low net bulk spin density with no triplet resonance after the intermolecular spin exchanges resemble to those observed in the case of HMT+2(CIO4)2 crystals.

In order to evaluate the potentiality of organic donor molecules for molecular organic ferromagnets, with in principle C3 molecular symmetry, as in the hexakis (alkylthio) benzene, we have prepared single crystals of the charge transfer complex of tris [ethylene dithio] benzene (tEDTB) with TCNQF4, which have been subsequently oxidized with bromine and arsenic pentafluoride gas. The stoichiometry of this complex is 2:1 and it crystallizes in the triclinic system, space group P1 with the following cell parameters: a=11.515, b=11.044, c=10.460 A, α=111.50°, β=122.50°, γ=93.82°. The crystal structure consists of columns of alternating donor dyads and acceptors monads (DDADDA). The degree of charge transfer is estimated to be 0.2-0.3 from the methods based on bond lengths. While (tEDTB)2- TCNQF4 does not give a significant ESR spectrum, after treatment with the bromine or AsF5 gas, a single intense line, centered around the free electron g value, appears without any evidence of either a ground or an excited triplet state.

The temperature dependence of the magnetic susceptibilities for several ±-nitronyl nitroxides have been measured. It is found that the intermolecular magnetic coupling in these radical crystals changes from antiferromagnetic to ferromagnetic depending on the substituents at ±-position. X-Ray crystal analysis and MO calculation have been carried out on the ferromagnetic ±-nitronyl nitroxide, 2-(4-nitrophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxy 3-oxide, revealing a two-dimensional ferromagnetic network linked by the Nδ+...0δ− Coulomb attraction.

1-Phenyl-l,3-butadiyne derivatives (3 and 4) carrying stable t-butylnitroxide and diazomethyl groups, respectively, have been prepared. Mixed crystals of 3 and the corresponding hydroxylamine 2 (x003c:1:1) polymerized in the solid state at 100°C to give black-violet microcrystals with a metallic luster. A microcrystalline sample of 4 underwent spontaneous polymerization at room temperature when crystallized to give an insoluble polymer which was then photolyzed at cryogenic temperature to generate triplet carbene centers attached to the phenyl rings of the poly(phenyldiacetylene). Some of these microcrystalline polymeric samples were responsive to a magnet at room temperature. Magnetic susceptibility measurements on the two samples revealed only weakly coupled independent spins Hydrogen bonding between the polydiacetylene chains as estimated by X-ray crystal structure of 2 is expected to be effective for increasing the dimension of the spin alignment.

It is shown that the spin alignment in organic molecules as determined by single crystal ESR is highly dependent on the topological nature of their molecular pi electron networks. The three topological isomers of a high-spin molecule, biphenyl-n,n′-bis(phenylmethylene), abbreviated as BP-3,3′-BPM, BP-3,4′-BPM and BP-4,4′-BPM are taken as model compounds. BP-3,3′-BPM has a unique spin alignment for which the simple molecular orbital and valence bond methods predict different ground-state spin multiplicities. The above remarkable feature of spin alignment in organic high-spin molecule is interpreted in terms of their spin density distributions which have been determined by a single crystal ENDOR technique and compared with theoretical values calculated on the basis of a generalized Hubbard model as well as the Heisenberg model. This approach is extended to magnetic polymers in order to characterize their structure of the spin sites.

A chemical modification exploiting functional groups such as ether and methylene as bridges between high-spin assemblies has been carried out as a usable method to increase dimensionality of spin structure. Exchange interaction via an ether or a methylene bridge between two high-spin assemblies has been studied by single-crystal ESR spectroscopy. Whether it is ferromagnetic or antiferromagnetic depends upon the substituted position of the bridge, demonstrating the important role of the topological nature in spin alignment. It turns out that superexchange interaction or hyperconjugation mechanism can dominate spin alignment between high-spin assemblies. Using the criteria obtained, model compounds for units of organic ferrimagnets have been synthesized. They possess antiferromagnetically-exchange coupled heterospins and the salient features of their spin structures are characterized in terms of the spin density distribution as determined by single-crystal 1H-ENDOR (Electron-Nuclear-DOuble Resonance) spectroscopy.

The stability of the magnetic properties of dehydrogenated triaryl-methane resins was investigated both at room temperature and at elevated temperatures. A magnetic property different from that reported in a previous paper was found in the course of studying the reproducibility of synthesis. This new property was examined through a mechanical response of the resins to a set of permanent magnets.

We evaluated the chemical stability of various polyphenoxy radicals prepared through the modified synthetic methods. The monomeric 3,5-di-t-butyl-4-hydroxyphenyl derivatized olefins and methacrylates were prepared in a multistep synthesis starting from 2,6-di-t-butylphenol. These monomers were polymerized in the presence of radical initiators at the refluxing temperature of aromatic solvents under an inert atmosphere. The most stable polyradicals were found to be highly hindered poly(DBPM) radicals.

A variety of model organic high spin molecules based upon coupled phenoxy and phenylnitrene systems has been examined by semiempirical MO-CI theory. Experimental methodology using photochemical and thermal methods in solution and solid phases to generate and study phenoxy groups for investigation of these models is presented.

Magnetization and frequency dependence a.c. magnetic susceptibility measurements of the metal-organic polymers of general formula {[M(C13H17N3)2]SO4 6H2O}n, where M = Fe(II) or Co(II), are indicative of superparamagnetic behavior as a consequence of the existence of strong ferromagnetic interactions in the materials. Scanning electron microscopy and X-ray dispersive spectrometry have been used to study the homogeneity in the composition of the iron polymer.

κ-(BEDT-TTF)2 [Cu(NCS)2] has a two-dimensional (2D) layered structure. The compound is metallic with the room temperature conductivity of 10–40 S/cm within the 2D plane but showed a semiconductive-like anomaly between 270 and 90K. The superconducting transition was observed at Tc=10.4K and Tc increased by 10% on the sample of deuterated BEDT-TTF (Tc=11.4K). The upper critical field, Hc2, was more than 20 Tesla below 2K within the 2D plane which is more than the expected value from the simple BCS theory. The transport critical current density was estimated as 100 A/cm2 (5.1K, 0 Tesla, l//b, H//c) which is an order of magnitude smaller than that obtained from the magnetization curve hysteresis. 1H-NMR showed a big enhancement of the relaxation rate well below Tc. The tunneling spectra showed anisotropic gap and the magnetic field penetration depth measurements strongly suggest that this system is a gapless superconductor. (BEDT-TTF)2[KHg(SCN)4] is an organic metal and showed both Shubnikov-de Haas effect and angle-dependent quantum oscillation indicating that this system has a warped 2D Fermi surface.

Recent progress on the superconducting and normal state properties characteristic to the organic metals β-(BEDT-TTF)2X are presented. Out of a systematic study on the β-(BEDT-TTF)2X salts, including β-(BEDT-TTF)2 trihalide mixed crystals, with the superconducting transition temperature (Tc) varying from 8 K to below 1 K, empirical rules for various factors governing the Tc in this class of organic metals have been extracted. In addition to the low- and high-Tc states, with Tc=l K and 8 K, respectively, a new superconducting state with Tc=2 K was found in α-(BEDT-TTF)2I3. A particular attention is paid for the correlation between Tc and resistivity. In addition, a correlation between Tc and the anisotropy of coherence length is also considered.

Transfer integrals (tij) between pairs of nearest neighbor ET molecules were calculated by an ab initio method. Tight-binding one-electron energy bands constructed from the tij are similar to those previously calculated by Mori and by Whangbo and their coworkers by semi-empirical, extended Hückel methods, but quite different from those found by Kübler et al. in β-(ET)2I3 using the augmented spherical wave (ASW) method. However, all these band models are suspect. The Hubbard on-site repulsion parameter U is estimated to be about twice the band widths, indicating that a full treatment of the Hubbard hamiltonian is needed. Also, polaron effects appear to control transport except at very low temperature.

We have measured the specific heat of κ-(BEDT-TTF)2Cu(NCS)2 from 4 to 14 K. The superconducting transition at 9.4 K is observed in zero applied magnetic field and in a field of 0.3 T. Both the magnitude of the change in Cp at Tc and the temperature dependence of Cp below Tc indicate a strong coupling superconductor. If the lattice specific heat is assumed to contain contributions due to the eighteen vibrational degrees of freedom, the phonon contribution to the specific heat in our temperature range can be represented by a Debye integral expression with a Debye temperature of 95 K. A model of collective modes suggesting the origin of the eighteen degrees of freedom is presented.

The pressure dependence (≤12 × 102 MPa) of the cell parameters of (TMTSF)2 - C104 and κ - (BEDT-TTF)2 - Cu(NCS)2 has been measured at room temperature. The magnitudes of the principal compressibilities calculated and the bulk modulus (B) do not vary all over the experimental pressure range for (TMTSF)2 - C104, while ki decrease slightly for κ - (ET)2 - Cu(NCS)2 and its Dulk modulus strongly increases. The directions of the principal compressibilities strongly varywith pressure for the former salt; in the latter case, the projections of the directions of the smallest and of the largest principal compressibilities remain parallel and perpendicular to the long molecular axis respectively whereas the intermediate is along the monoclinic b axis.

The crystal structures have been refined at 4 × 102 ,6 × 102 and 9.5 × 102 MPa (R = 0.05) for (TMTSF)2 - C104 and at 7 × 102 MPa (R = 0.095) for κ - (ET)2 - Cu(NCS)2. The transfer integrals have been calculated for the two compounds. In (TMTSF)2 - C104, both normal and transverse overlaps strongly increase with pressure; the dimerization is reduced under pressure and the two largest transverse interactions become identical. In κ - (ET)2 - Cu(NCS)2, the intra-dimer interaction strongly increases whereas the variations of the inter-dimer interactions may be very different.

Thin films of a charge transfer complex, hepta-(tetrathiafulvalene) pentaiodide ( TTF7I5, TTF:I0-71 ), were prepared by double source evaporation of TTF and iodine. Crystalline films of TTF:I0-7i were obtained when substrate temperatures were kept between 0°C and 25°C. Orientation alignment of the crystalline films were affected by supply rate of iodine. By controlling the substrate temprature and the supply rate of iodine, highly oriented crystalline films were grown on mica substrates. It showed strong dichroism and anisotropic electrical propert ies.

Two different tetrathiafulvalene radical cation salts of the [M06O19]2− polyoxoanion have been isolated and characterized. Compound 1 corresponds to the chemical formula (TTF)3[Mo6019]. The crystal structure shows a ID stack of the donor TTF molecule, and each stack fits into channels formed by the anions. Within the stack a chain of trimers is identified, the inter-trimeric distance being 3.51 Å. The I.R., electronic and XPS spectra suggest the compound to be a mixed-valence salt. The electrical conductivity at room temperature is σ = 10−4 Ω−1 cm−1 Compound 2 corresponds to the chemical+formula (TTF)2[M06019] . The compound consists of isolated (TTF+•)2 dimers, interspersed with the polyoxoanions. In agreement with this crystal structure the compound is a diamagnetic insulator.

The successful synthesis of dimethyltetrathiotetracene (DMTTT) has been achieved in our laboratory and an account of the details of the synthesis has been reported. Reported herein are studies of the physical properties of DMTTT and some of its chemistry. Both 1:1 and 2:1 DMTTTX charge transfer salts have been prepared and are in the process of being characterized in our laboratory. Comparisons of physical properties and the results of studies such as single crystal x-ray diffraction, solid state ESR spectra, cyclic voltammetry and electrical conductivity are reported. To date, these comparisons reveal considerable similarity between the properties of any given DMTTT charge transfer salt and its corresponding tetrathiotetracene (TTT) charge transfer salt.

Recently we have synthesized several new aryl compounds substituted with two or more trinitromethyl groups. Vacuum pyrolysis of one of these—±,±,±,±’,±’,±’-hexanitro-p-xylene (p-HNX)—gave the title compound via 1,6-elimination of N2O4. Structural assignment of TNQ is based on spectral evidence (UV, 1H NMR and mass spectrometry) and conversion to the known l,4-bis(bromodinitromethyl)benzene. Evidence for the formation of the TNQ radical anion has been obtained.