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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.

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.

We have prepared eight TEMPO-containing anions TEMPO – A – CO – ( n - ) C 6 H 4 S O 3 - (n = o, m, p for A = NH (N1, N2, N3), n = o, p for A = NCH3 (M1, M3), and n = o, m, p for A = O (O1, O2, O3)) as PPh4 salts. Metathesis of their salts with (TTF)3(BF4)2 gave their TTF salts. Electrocrystallization of BEDT-TTF with PPh4 · M1 yielded the α-(BEDT-TTF)3(M1)2 · 8H2O salt. We report their crystal structures, electrical resistivities, and magnetic properties. The relation between crystal structures and physical properties are discussed.

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.

In order to investigate molecular conductors containing magnetic anions, πd-interactions Jπd and dd-interactions Jd, have been estimated from the overlap of molecular orbitals by using the relation J = −2t2/U. In the present paper this method is applied to a new antiferromagnetic superconductor (BDA-TTP)2FeCl4, a semiconducting ferrimagnet (EDT-TTF-VO)2FeBr4, and a β′-type semiconductor (BEDT-TTF)3(MnCl4)2. The dd interaction of (BDA-TTP)2FeCl4 is as large as λ-(BETS)2FeCl4, guaranteeing the relatively high TN. The small Jπd of this compound is related to the steric effect of the outer trimethylene groups of the donor. The observed ferrimagnetism in (EDT-TTF-VO)2FeBr4 is related to the localization of the π-electrons associated with the charge order, as well as the fairy large πd-interactions bridging different anions. (BEDT-TTF)3(MnCl4)2 is a characteristic compound due to the extraordinarily large πd-interactions to the donors incorporated in the anion layer.

Five TEMPO-containing anions TEMPO - CONA ( CH 2 ) n SO 3 - (H0−, A = H, n = 0; H1−, A = H, n = 1; H2−, A = H, n = 2; H3−, A = H, n = 3; M2−, A = CH3, n = 2) have been prepared as PPh4 salts. So far three TTF salts ((TTF)(H1) · 2H2O, (TTF)(H2) · H2O, and (TTF)(M2) · 0.50H2O), one TMTSF salt ((TMTSF)(H1) · 2H2O · PhCl), and one BEDT-TTF salt (α-(BEDT-TTF)5(H1)2 · 6H2O) have been obtained. Their crystal structures, electrical resistivities, and magnetic properties are reported.

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.