Search

A new BEDT-TTF-based salt with an organic free radical, α′-α′-(BEDT-TTF)2(PO-CONH-m-C6H4SO3)·H2O, has been prepared. The crystal structure consists of alternating donor and anion/water layers propagated along the c axis. The anisotropic radical anions form a head-to-head arrangement, which provides a permanent dipole moment. The effect on the nearest donor layer has been estimated to be 4.0 V. The salt has two crystallographically independent donor layers (A and B), one of which (A) is surrounded by the negative ends of the anion layer dipole whereas the B layers are bordered by the positive ends of the dipole. This structural feature suggests that layers A and B have different Fermi levels. To eliminate the imbalance, self-doping occurs whereby electron density is transferred from layer A to B. The temperature dependence of the magnetic susceptibility has 11.1% of extra Curie spins, from which a doping ratio of 12.7% has been estimated.

The chiral TTF-based donor molecule bis(2′-hydroxylpropylthio)(ethylenedithio)tetrathiafulvalene (BHPT-EDT-TTF) has produced enantiopure R,R and S,S radical-cation salts with polyiodide anions I3− and I82−. Enantiomorphic 6 : 6 donor : I3 phases grown from either the R,R or S,S donor are semiconducting with similar activation energies of 0.24–0.30 eV and 0.22–0.23 eV, respectively, and contain three unique face-to-face donor pairs whose relative orientation is determined by side chain conformations and hydrogen bonding. Racemic material under the same conditions gave an insulating centrosymmetric phase with R,R and S,S donor cations in a face-to-face pair partnered with an octaiodide dianion, and with a ca. 3 : 1 disorder between the enantiomers. Enantiopure BHPT-EDT-TTF yielded two further insulating crystalline phases of composition 2 : 2 with triiodide and 2 : 1 with octaiodide.

The structure and properties of a new semiconducting BEDT-TTF-based charge-transfer salt containing the magnetic monoanion octamethylferrocenedisulfonate (–O3SC5( CH3)4Fe+C5(CH3)4-SO3 – (ofds)), -(BEDT-TTF)5(ofds)2 is described (BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene). The salt is a semiconductor with RT = 5.6  103 ·cm and Ea = 0.11 eV. There are two types of spins not only on the ferrocenyl parts but also the 2D donor layers. The former and latter spins obey Curie-Weiss (C = 0.721 emu K mol-1and  = -5.5 K) and 2D Heisenberg (J2DH = - 80.3 K) models, respectively.

Electrocrystallisations of the chiral donor molecule S,S-bis(2-hydroxylpropylthio)ethylenedithiotetrathiafulvalene have produced a series of 1 : 1 semiconducting radical-cation salts with anions bromide, chloride, perchlorate and hexafluorophosphate. The flexibility and hydrogen bonding ability of the donor's chiral side chains lead to three quite different packing arrangements of donor cation pairs. Conductivity is maintained despite significant separations of donor cation pairs in some cases.

The new chiral TTF-based donor molecule bis(2-hydroxypropylthio)ethylenedithiotetrathiafulvalene has produced enantiopure R,R and S,S radical cation salts with the tetrafluoroborate anion as well as the nearly isostructural meso/racemate mixture. The enantiopure R,R or S,S salts are both 1:1 semiconducting salts with activation energies of 0.19–0.24 eV, both crystallising in the orthorhombic space group C2221. The semiconducting salt containing both meso and racemic donor cations has a very similar crystal structure but crystallising in the monoclinic space group C2/c (β = 91.39°) with similar S⋯S interactions but a smaller activation energy of 0.15–0.17 eV. This is in contrast to previous families of this type where the disordered racemate has a larger activation energy than its enantiopure salts.

While an addition product was formed by the reaction of AZADO (2-azaadamantane N-oxyl) with TCNQF4 (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane), the reaction of AZADO with thiourea provided an inclusion compound, in which AZADO molecules are incorporated in cylindrical channels formed by thiourea molecules.

A series of aryl-substituted naphthalenediimide derivatives that contain nitroxide radicals were prepared and their crystal structures were elucidated. Much stronger charge-transfer interactions were present in the derivatives with perfluorobenzene substituents than those with phenyl or 4-fluorophenyl substituents. These interactions result in the formation of single-component charge-transfer complexes by self-assembly of the naphthalenediimide derivatives to provide black crystals. As a consequence, the naphthalenediimide derivatives with perfluorobenzene substituents have better field-effect transistor (FET) properties than the other derivatives.

Three TCNQ derivatives carrying nitroxide radicals (3a–3c) were prepared and were found to form single-component charge-transfer (CT) complexes by self-assembly, in which outer nitroxide groups of a couple of different molecules work as donors and the inner TCNQ unit of another molecule as an acceptor. While the CT interactions found for the TEMPO (2,2,6,6-tetramethylpiperidin-1-oxy) derivative 3a and the PROXYL (2,2,5,5-tetramethylpirrolidin-1-oxy) derivative 3b are point-to-face fashion between the oxygen atom of each nitroxide group and the six-membered ring of inner TCNQ unit, the CT interactions found for the PO (2,2,5,5-tetramethyl-3-pyrrolin-1-oxy) derivative 3c are point-to-point contacts between the oxygen atoms of outer nitroxide groups and the carbon atoms of a couple of cyano groups.

Several ferrocene derivatives (1–6) carrying nitroxide radical were prepared as dual redox compounds. They have distorted molecular structures and exhibit oxidation potentials based on both ferrocene and nitroxide groups except 4. The multi-step charge–discharge processes are discriminated for mono-substituted derivatives with the first discharge capacity up to 400 Ah kg−1 for imino-derivative 3, while relatively characterless profiles are observed for bis-substituted derivatives 4 and 6 with capacity over 300 Ah kg−1.

An anionic weak acceptor, 2-sulfo-1,4-benzoquinone, has provided a new BEDT-TTF (bis(ethylenedithio)tetrathiafulvalene) salt (BEDT-TTF)2(2-sulfo-1,4-benzoquinone)·H2O. Single crystal X-ray analysis indicates that the unit cell has two crystallographically independent donor layers, one of which has a β″-type packing motif and the other being disordered. Population analysis and SQUID magnetometry suggests that non-β″-layer has an α‴-type packing motif. The dual-layered salt shows metallic behavior with a metal–insulator transition at 90 K.

We have prepared new organic anionic acceptors, Br2XQNHCH2SO3− (2: X=Br, 3: X=BryCl1−y (y≈0.5), 4: X=Cl; Q=1,4-benzoquinone), that possess both an electron acceptor part (1,4-benzoquinone) and an anionic part (sulfonate). The reduction potentials of the PPh4 salts of 2, 3 and 4 are −0.45, −0.45 and −0.46 V (vs. SCE in CH3CN), respectively. The results indicate that they are weaker acceptors than chloranil (−0.13 V) and bromanil (−0.12 V). Each anionic acceptor (AA) provided two BEDT-TTF salts, β-(ET)5(AA)2·DCE·zH2O and λ-(ET)2(AA)·CH3OH (AA=2, 3, or 4; z=2: 0.97, 3: 0.83 and 4: 0.40). The structures and transport properties of the salts are reported.

The synthesis, crystal structure, and conducting properties of two new BEDT-TTF charge-transfer salts containing tris(oxalato)germanate(IV) anions are described. (BEDT-TTF)5[Ge(C2O4)3]2 (1) crystal...

Series of radical salts derived from a 2,4,6-triphenylpyridinium (TPP) carrying TEMPO-substituent and transition metal complexes were prepared by the anion exchange of the TPP–TEMPO tetrafluoroborate with [n-Bu4N][Ni(dmit)2], [n-Bu4N]2[Pd(dmit)2], [n-Bu4N]2[Pt(dmit)2], [n-Bu4N][Ni(mnt)2], or [n-Bu4N]2[Ni(mnt)2] to give crystals with different structural features. While weak antiferromagnetic interactions of the Curie–Weiss behavior of S = 1/2 spin are predominantly observed in the salts of Pd(dmit)2, Pt(dmit)2 and Ni(mnt)2, the magnetic behavior of 1:1 Ni(dmit)2 salt can be explained by the additional contribution from the spins on Ni(dmit)2 anions (χ − χTEMPO), obeying the 2D Heisenberg model. A couple of the oxidized salts, [TPP][Ni(dmit)2] as well as [TPP]2[Pd(dmit)2], exhibit semi-conducting properties with relatively high room temperature conductivities.

Structures and properties of three Mn(hfac)2 (hfac = hexafluoroacetylacetonate) complexes derived from two kinds of bis-TEMPO (2,2,6,6-tetramethylpiperdinyl-1-oxy)-substituted diamines are reported. In a complex derived from bis-TEMPO-substituted ethylenediamine, the unit is coordinated to the manganese atom to afford a spin system with weak antiferromagnetic intermolecular interactions, while apparent ligations of both TEMPO groups to the metal atom are observed in a couple of Mn(hfac)2 complexes derived from bis-TEMPO-substituted piperadine to result in spin systems with fairly large antiferromagnetic interactions.

We have prepared a novel organic anionic weak acceptor, 2-aminomethylsulfo-3,5,6-trichloro-1,4-benzoquinone (1), as a PPh4 salt. Cyclic voltammetry indicates that its reduction potential is 0.53 V lower than that of chloranil. Electrocrystallisation with BEDT-TTF gave two salts, β - β -(BEDT-TTF)2(1)⋅0.5H2O (2) and β ″ - (BEDT-TTF)2(1)⋅CH3OH (3). Their crystal structures and physical properties are reported.

Series of organic radical compounds with trans -azobenzene chromophore have been prepared to see the photo-induced isomerizations to the corresponding cis -azobenzenes and the possible changes of intermolecular magnetic interactions based on the isomerizations. Although the cis -isomers with p -nitro- or p -dimethylamino-substituent on one side and TEMPO-attached long alkoxy group on the other side could not be isolated as stable solids, the cis -isomers of unsubstituted derivatives at 4-position and with a TEMPO group at 4′-position have successfully been isolated as relatively stable solid materials showing apparent changes of intermolecular magnetic interactions. A couple of Mn(hfac) 2 complexes derived from isomeric TEMPO-substituted esters were found to be reluctant to the photo-isomerization upon irradiation.

Several radical salts derived from a TEMPO-substituted 2,4,6-triphenyl pyridinium have been prepared by replacing the fluoroborate anion with an anionic metal-complex such as Ni(dmit) 2 , Pd(dmit) 2 or Ni(mnt) 2 and their structures and physical properties were investigated. The oxidized salts of the Ni(dmit) 2 as well as Pd(dmit) 2 complexes show semi-conducting properties with relatively high conductivities and low activation energies.

Three kinds of molecular complexes based on tetrathiafulvalene (TTF) and dialkylviologens were prepared and their crystal structures elucidated. While TTF-dimethylviologen complex forms a mixed stack arrangement of donors and acceptors in its crystal structure, TTF donors aggregate with long alkyl groups by CH/π and/or van der Waals interactions in a couple of TTF-heptylviologen complexes. Keywords: Molecular complex; CT complex; TTF; viologen; crystal structure Introduction Considerable attention has recently been paid in the field of supramolecular and materials chemistry to the incorporation of electroactive components into supramolecular assemblies. Among them, the supramolecular and macrocyclic assemblies derived from redox-controllable TTF 1 and dialkyl-4,4’-bipyridinium dications (dialkylviologens) such as 2 , have evoked attention, not only as catenanes and rotaxanes, but also as molecular switche s and potential molecular el ectronics devices [1]. The assembly of such kinds of molecular complexes relies strongly upon non-covalent charge-transfer (CT) interactions between donors and acceptors [2]. Since a dialkylviolgen

The first radical-cation salts in the extensive family (BEDT-TTF)x[(A)M(C2O4)3]·Guest containing lithium as the counter cation have been synthesized and characterised.

Series of organic biradical compounds 3a–3h consisting of a mesogenic core (biphenyl, naphthalene, azobenzene and azoxybenzene) and long alkoxy groups with PROXYL or TEMPO radicals were prepared. The TEMPO derivatives (3b, 3d, 3f, and 3h) were found to show fairly large antiferromagnetic interactions (J = −34 ∼ −45 K) being well expressed by singlet-triplet model irrespective of the mesogenic cores and the behavior is understandable by taking a hand-in-hand like assembled structure into consideration. On the other hand, only weak antiferromagnetic interactions with Curie–Weiss behavior were observed in all of the PROXYL derivatives (3a, 3c, 3e, and 3d) affording a sharp contrast with the TEMPO-based biradicals. Copyright © 2006 John Wiley & Sons, Ltd.

Series of monoradicals and biradicals having an aromatic core on one hand and long alkyl groups on the other hand have been prepared. It was found from their magnetic data that the biradical compounds having aromatic cores (azoxy, or azo) and long alkyl groups with TEMPO radicals at their ends showed fairly large antiferromagnetic interactions ( J = −34, −39 K) being well expressed by ST model, while only weak antiferromagnetic interactions were observed in the corresponding PROXYL derivatives together with the corresponding monoradicals. The change of intermolecular magnetic interactions based on the structural change from trans - to cis -isomer by irradiation was found to be possible in a couple of azobenzene derivatives with an aminoxyl radical.

New organic functional anions that includes the ferrocenyl group, CpFeCp-CONHCH 2 SO 3 − and Fe(Cp-CONHCH 2 SO 3 − ) 2 , are prepared as tetraphenylphosphonium (PPh4) salts. They reacted with (TTF) 3 (BF 4 ) 2 to give TTF monocation salts. The X-ray analyses indicate that for all salts TTF forms a dimer which is separated by the relatively larger anions. The oxidation reaction of (PPh 4 )(CpFeCp-CONHCH 2 SO 3 ) with I 2 gave the Zwitter-ion, CpFe + Cp-CONHCH 2 SO 3 − , which shows a Curie-Weiss behavior ( C = 0.800 emu·K/mol, θ = −1.13 K) with weak antiferromagnetic interaction. This magnetic moment is found to be attributed to the ferrocenyl radical.

We report here four novel purely organic magnetic conductors containing common electron donors together with an organic anion including an organic free radical, (TTF)(TEMPO-NHCOCH 2 SO 3 )·0.5H 2 O ( 1 ), (TMTSF)(TEMPO-NHCOCH 2 SO 3 )·2H 2 O ( 2 ), (BEDT-TTF) 3 (TEMPO-NHCOCH 2 SO 3 ) 2 ·2H 2 O ( 3 ), and α-(BEDT-TTF) 3 (TEMPO-NHCOCH 2 SO 3 ) 2 ·6H 2 O ( 4 ). The TTF complex was prepared by metathesis of (TTF) 3 (BF 4 ) 2 and the PPh 4 salt of the anion ( 5 ). The other complexes were obtained by electrocrystallization of the corresponding donors with the salt 5 as an electrolyte. Crystal structures of 2–4 have been solved. The salts 1 and 2 show relatively high resistivities (>10 7 and 5 × 10 3 Ω·cm), whilst the BEDT-TTF salts 3 and 4 have rather low room temperature resistivities (1.2 and 5.1 Ω·cm) with small activation energies (0.041 and 0.050 eV). The magnetic behavior of complex 1 obeys the Curie-Weiss law ( C = 0.379 emu·K/mol and θ = −3.29 K) and those of the other complexes obey the 1-D Heisenberg model ( C / J = 0.366/−0.32 for 2 , 0.373/−0.81 for 3 , and 0.380 emu·K·mol −1 /+0.42 K for 4 ). The relationships between the crystal structures and the physical properties are discussed.

We report the structures and physical properties of new β′-(BEDT-TTF)[Fe(oxalate)]·G salts where A = HO, G = PhCl; A = Rb G = Pyridine. The structure of the PhCl salt is isomorphous with β′-(BEDT-TTF)[(HO)M(oxalate)] with other guest molecules. PhCl is ordered in die hexagonal pockets formed by the [(HO)Fe(oxalate)] layer. The electrical conductivity is metallic down to 100 K, below which the resistivity increases with decreasing temperature. The specific conductivity at room temperature is about 10 S/cm. We also report the salt β′-(BEDT-TTF) [RbFe(oxalate)]·Pyridine where Rb replaces HO. The electrical resistivity shows metallic behavior down to 100 K. and turns up gradually to a maximum at 65 K below which the system re-enters the metallic state down to liquid helium temperature. Neither salt shows superconductivity down to 2 K. In addition, other new β′-(BEDT-TTF)[(HO)M(oxalate) ]·salts with M = Cr, Ga, Fe; G = CHCl , CHClBr, CHBr are also reported. © 2005 Elsevier B.V. All rights reserved.

The synthesis and structural characterization of new liquid-crystalline compounds containing ferrocene, azo-aromatic and cholesteryl groups are reported. Taking into account the advantage brought by chirality, ferrocene and azo units, these structures could be good precursors for obtaining materials capable of responding to magnetic and electric fields or to UV-light exposure. The influence of each structural unit (ferrocene, cholesterol, azo aromatic core and flexible chain length) has been studied by comparing analogous compounds possessing the same structure but without the element being analyzed. Ferrocene is a three-dimensional bulky unit, so that, regardless of the substituents' nature, this unit could cause steric repulsions with neighboring molecules. These interactions could lead to a decrease of the transition temperature domain. Surprisingly, a decrease in the clearing point was not observed for the compounds discussed. This behavior was possible because ferrocene is connected to the mesogen via a flexible unit. As a consequence, both phenyl analogues and ferrocene derivatives presented liquid-crystalline properties with similarly high clearing points, but above the thermal stability of derivatives with azo groups. Their melting points depend on the way the molecules are packed, with different crystalline states being detected in the case of ferrocene derivatives. In order to explain the liquid-crystalline behavior of the compounds synthesized, molecular simulations were performed using the Hyperchem program. Copyright © 2005 John Wiley & Sons, Ltd.

The preparation and magnetic properties of organic radical anion salts derived from styrylpyrylium derivatives 1a and 2a are described and compared to those of the corresponding photo-dimers. The magnetic properties of the radical anions for TCNQ salt 1b and TCNQF4 salt 1c are rather different, showing antiferromagnetic interactions based on the 1-D Heisenberg model in the former, and ferromagnetic interactions in the latter. This difference is considered to be a result of the fairly large difference in their crystal structures. A considerable change in the magnetic properties was found between the radical anion salts of monomers and the corresponding photo-dimers, in which magnetic susceptibilities are largely diminished.

Organic salts derived from the styrylpyrilium systems as well as anthracene derivatives with TEMPO substituents were prepared and their structures and properties, especially magnetic properties wer...

The study of three kinds of non-tetrathiafulvalene (TTF) donors, 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene (BDA), 2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene (BDH), and 2-(1,3-dithiolan-2-ylidene)-5-(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene (DHDA), which contain the bis-fused 1,3-dithiole-2-ylidene unit instead of the TTF unit as a π-electron system, has been undertaken to develop new molecular-based organic superconductors, magnetic conductors, and organic metals. The BDA donor produces the superconducting SbF 6 , AsF 6 , and PF 6 salts. The κ-(BDH) 2 FeCl 4 salt is a paramagnetic organic metal stable down to 1.5 K, whereas β-(BDA) 2 FeCl 4 exhibits metallic conducting behavior with a sharp metal-to-insulator (MI) transition (T MI = 113K), and antiferromagnetic ordering with a Neel temperature of near 8.5 K. Several salts of DHDA, a hybrid of BDA and BDH, are found to be metallic.

A novel ferrocene-containing dianion, Fe(C5H4–CH(CH3)NHCOCH2SO3–)2 (1), has been prepared. The oxidation potential of the PPh4 salt is + 0.35 V (vs. SCE in PhCN), indicating that it is a stronger donor than TTF (tetrathiafulvalene) by + 0.03 V. The dianion provided a TTF salt, the structure and physical properties of which are reported.

A naphthalenediimide derivative 3a carrying TEMPO radical and azobenzene substituent was found to show photoresponsive magnetic as well as FET properties upon illumination. The alteration of its mo...

Anthracene derivatives with several TEMPO radicals (2-4, 10) were prepared, and each photodimerization reaction was investigated. Although the photodimerization was unsuccessful in obtaining the dimers of anthracenes 2 and 3, which could be alternatively prepared in a stepwise manner, the photodimers of anthracenes 4 and 10 were available by the direct photoreaction. The dissociation reaction of the dimers proceeded well by heating them in solution to give the corresponding monomers in each case, and thus the reversible system could be constructed in the latter two systems. While no large difference was observed in their magnetic behaviors between the monomer/dimer pair of 4 and 8, an intriguing difference was found in the magnetic behaviors for the pair of 10 and 11 from ferromagnetic interactions in 10 to the variable magnetic interactions in 11 depending on the solvent molecules incorporated in the crystals.

A new π-electron donor, 2,5-bis(13-dithian-2-ylidene)-1,3,4,6-tetrathia-pentalene (BDA-TTP), which contains no tetrathiafulvalene (TTF) molecule, produces a series ambient-pressure superconductors β-(BDA-TTP) 2 X (X = SbF 6 - , AsF 6 - , and PF 6 - ), in which the values of intermolecular overlap integrals suggest loose donor packing motifs.

Series of biphenyl derivatives bearing TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy)-substituents on one hand and long alkyl- or alkoxy-substituent on the other hand have been prepared. Among them a mesogenic property has been found in a biphenyl derivative with N-methyl-amino-TEMPO-carboxamide-substituent having lamellar structure of the molecular arrangement to show local antiferromagnetic spin interactions.

Several anthracene derivatives with stable radical substituents have been prepared and their magnetic properties have been investigated together with those of some of the dimers available by photo-dimerization reaction. While weak magnetic interactions with Curie–Weiss behavior have been observed in most derivatives prepared, antiferromagnetic behavior being based on an S–T model has been found in the spins of TEMPO-substituted N-methylcarboxyamidoanthracene derivative 1c. The magnetic property of Mn(hfac)2 complex derived from 4-amino-TEMPO-substituted 9-methylanthracene (1d) is also described.

A synthetic study of the dioxolane derivatives of methylenedithio(ethylenedithio)-tetrathiafulvalene (MET), bis(methylenedithio)tetrathiafulvalene (MT), and methylene-dithiotetrathiafulvalene, their dithiolane analogues, and the oxathiolane derivative of MET has been undertaken to explore new organic metals. A practically useful preparation of the biheterocycle-fused 1,3-dithiol-2-ones as building blocks for these dichalcogenolane-linked tetrathiafulvalene (TTF) donors has been realized via the newly developed BF 3 -promoted reactions. The effect of the additional linked dichalcogenolane ring on the electron-donating ability is investigated by cyclic voltammetry. An X-ray crystallographic analysis of the oxathiolane-linked MET reveals that its molecular structure is isostructural with that of its dithiolane analogue but not bulkier than that of its dioxolane analogue. Several of the present TTF donors have produced metallic charge-transfer materials, two of which are characterized by X-ray crystallography. In the crystal structure of the 7,7,8,8-tetracyanoquinodimethane complex of the dioxolane-linked MT that exhibits metallic-like behavior around room temperature, the donor molecules are stacked head-to-tail to form the dimers, which are connected by C-H…O hydrogen bonds. On the other hand, in the metallic AsF 6 salt of the dioxolane-linked MET stable down to 2.0 K, the donor molecules are stacked head-to-head to form two-dimensional sheets despite the dioxolane ring being perpendicularly attached to the MET molecule.

Series of biphenyl as well as cholesterol derivatives with nitroxide radicals have been prepared to investigate their magnetic/liquid crystalline characters. Weak antiferromagnetic interactions in the low temperature region with no liquid crystalline character have been observed in all cholesterol and several biphenyl derivatives prepared while a cyanobiphenyl derivative with TEMPO substituent have been found to show ferromagnetic interactions in the low temperature region on the one hand and smectic liquid crystalline behavior at elevated temperatures on the other hand.

Series of TEMPO-substituted norbornadiene, spiropyran and anthracene derivatives have been prepared; their light-induced structural change to the corresponding qudricyclanes, merocyanines or anthracene-dimers and the reverse reactions to the starting materials have been studied. The antiferromagnetic or ferromagnetic behavior observed in norbornadienes/anthracenes was found to be preserved in the corresponding quadricyclanes/anthracene-dimers in spite of the difference of their Weiss temperatures, whereas switching of the intermolecular magnetic interactions was observed in spiropyran/merocyanine systems.

Investigations of the tetrathiafulvalene (TTF) derivatives extended by the [sgrave]-bond frameworks, such as saturated heterocycles (3–8) and alkyl groups (9), have been undertaken to explore new molecular-based organic metals. TTF donors with the periphery extended by the cis-fused dioxane ring (3) and by linkage of a dichalocogenolane or dioxane ring (4–6 or 7) produce metallic radical-cation salts. While radical-cation salts of the methylated TTF donor (9a) are semiconductive, the ClO4 and PF6 salts of the ethylated one (9b) exhibit metallic conducting behavior for compressed pellets. The crystal structure of the metallic (4)2AsF6 salt is also presented.

Novel CT complexes derived from 4-alkylamino-TEMPO radical and 2,4,6,8-tetracyanoazulene have been prepared. Curie-Weiss behavior has been observed in the magnetic susceptibility of each complex with antiferromagnetic spin-spin interactions in the low temperature region on one hand and rather high conductivity has been found in the electrical conductivity of each complex with semiconducting behavior on the other hand.

A couple of spin systems with photo-responsive property have been developed, i. e., norbor-nadiene and spiropyran derivatives carrying TEMPO-substituent and their light-induced structural changes to the corresponding quadricyclane or merocyanine derivatives have been investigated together with the changes of their properties in solution as well as in the solid state.

We have performed the electric conductivity measurements in the spin-density-wave (SDW) phase of (TMTSF) 2 ClO 4 to clarify the dynamics of SDW. The temperature dependence of threshold electric fie...

Several photo-responsive norbornadiene as well as spiropyran derivatives with TEMPO radical substituents were prepared and their light-induced structural changes to the corresponding quadricyclanes or merocyanine dyes and reverse reactions to the starting materials were investigated. While the intermolecular magnetic interactions tend to be preserved in norbornadiene–quadricyclane systems in spite of the differences of their Weiss temperatures, a switching of the intermolecular magnetic interactions was observed in the spiropyran–merocyanine systems.

Novel charge-transfer complexes have been prepared from organic stable radicals such as 4-dialkylamino-TEMPO or verdazyl radical and electron acceptors. Among them, the CT complexes from 4-dimethylamino- or 4-azetidino-TEMPO and DDQ formed salt-like complexes of protonated 4-dialkylamino-TEMPO and the substituted 1,4-benzoquinone-hydrox-ylate upon recrystallization from a moist acetone. A series of ternary complexes consisting of organic stable radicals with their corresponding cation salts have been prepared by ball-milling of the solids. The magnetic behavior of the ternary complexes is discussed.

Several biradicals consisting of 4-substituted-amino-TEMPO were prepared from 4-oxo-TEMPO with certain diamines as piperazine, ethylenediamine, 1,2-trans- or cis-cyclohexanediamine by reductive amination reaction. A series of CT complexes derived from the biradicals and acceptors was then prepared and their magnetic behavior was investigated comparing with the original biradicals. Although the ferromagnetic behavior was observed in the biradical derived piperazine, antiferromagnetic behavior was predominantly observed in other biradicals or CT complexes derived therefrom.

A series of CT (charge-transfer) complexes have been prepared, in which TEMPO (2,2,6,6-tetramethylpiperidinyloxyl) radical 1 and its derivatives (2 and 6-10) act as donors using TCNQF 4 (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) or DDQ (2,3-dichloro-5,6-dicyanobenzo-1,4-quinone) as acceptors. A sharp difference was observed in magnetic properties between the charge-transfer complexes derived from the TEMPO radicals 1 or 2 and amino-TEMPO radicals 6-10 and the distinct difference observed in the molecular/crystal structures in the complexes is thought to reflect the difference in their magnetic behaviour. The CT complexes from 4-dimethylamino- or 4-azetidino-TEMPO and DDQ formed salt-like complexes of protonated 4-dialkylamino-TEMPO and the substituted benzo-1,4-quinonehydroxylate upon recrystallization from moist acetone.TEMPO radicals are a well-known class of stable radicals mainly used as spin probes for biological studies and a number of derivatives have been prepared for the purpose until now. 1 On the other hand, it is of current interest to develop new molecular-based magnetic materials especially organomagnetic materials and numerous compounds carrying TEMPO radicals as the key building blocks have been prepared and their magnetic behaviour has been elucidated in recent years. 2 During the course of our studies to develop new organomagnetic materials, we have been interested in preparing some donor or acceptor molecules carrying stable radicals and the CT complexes derived therefrom to build up and to arrange the spins in the solid state/crystal structures 4 and we found recently that some TEMPO radicals (A) 5 or verdazyl radicals (B) 6

SQUID magnetometry and transport measurements combined with crystal structure refinement have been used to examine the variation in superconducting properties (Tc and Meissner fraction) in the molecular superconductor β″-(BEDT-TTF)4[(H3O)Fe(C2O4)3]·C6H5CN on replacing the C6H5CN guest molecule with pyridine (C5H5N). Up to approximately 65% pyridine substitution there is only a small decrease in Tc and Meissner fraction but above that the superconductivity is suppressed.

The charge-transfer (CT) complexes of a series of 4-substituted-amino-TEMPO radicals with some acceptors were prepared and their magnetic properties were investigated. The X-ray crystal structural analysis was carried out on the CT complex consisted of 4-azetidyl-TEMPO and TCNQF4; comparison with that of the complex derived from TEMPO and TCNQF4 showed a distinct difference in their molecular/crystal structures, which is considered to reflect the difference in their magnetic properties.

The title compound, C 10 H 12 S 4 + .Br - .0.5C 7 H 5 N.0.5H 2 O, is a cation-radical salt of tetramethyltetrathiafulvalene (TMTTF) and bromine with a ratio of TMTTF to Br of 1:1. The TMTTF cations have crystallographically imposed C s symmetry with mirror planes at y = 0 and y = 1/2 which lie along the central C=C bonds. The cations are stacked to form a column structure extending along the c axis and face each other to assume dimeric structures around the inversion centres, with short S...S contacts of 3.430 (2) and 3.508 (2) A. The central double-bond lengths of 1.394(9) and 1.413(8)A are longer than the reported value of the corresponding CC distance of 1.35 A in TMTTF 2 Br. This is consistent with the findings that the greater the charge on the tetrathiafulvalene cation the longer the C=C bond distance.

A series of nitronyl nitroxide derivatives of benzene, bearing halogen atoms at the ortho position, have been prepared and show a remarkable substituent effect of the ortho halogen atoms on their magnetic properties. Among them, the fluorine derivative 1 is found to behave as a ferromagnet with a Tc of around 0.3 K based on ac susceptibility and heat capacity measurements, and its X-ray analysis revealed that the crystals consist of three-dimensional networks of nitroxide radicals bonded through methyl or phenyl groups.