Presentations

Organic radical derivatives such as TEMPO with a localized spin density distribution over NO bond have enhanced chemical stability compared to -conjugated radical, however, they have not been used for spin center of molecular-based magnet. In the present study, a spinlocalized nitroxide radical carrying a naphthalene backbone (1) was synthesized and their crystal structures and magnetic property were analyzed. Two polymorphs with needle and plate shapes were obtained. Their magneto-structural correlation will be discussed.

Taking advantage of rigid structure and electron-donating nitrogen atom of 9,10-dihydroacridine, asymmetrically substituted derivatives were synthesized by introducing two different electron-accepting substituents at 2,7-positions. Their fluorescence properties were strongly affected by substituent. In the present paper, dihydroacridine derivatives carrying a precursor of verdazyl 1 have been newly synthesized and the effect of the substitution on fluorescent spectra will be discussed in connection with electronic structural analysis. 1 exhibited a noticeable fluorescence solvatochromism and emission in the solid-state. DFT calculation suggested that a precursor of verdazyl has electron donating property.

Molecules with ground spin multiplet can be designed by connecting plural paramagnetic spin center to appropriate spin coupler unit. Taking advantage of the steric effect of 1,5-diisopropyl-6-oxoverdazyl (VZ) unit, biradical derivatives have been designed and their magneto-structural correlation has been investigated. In the present research, diphenylamine derivative carrying two VZ units (1-VZ) was synthesized, its physicochemical properties were investigated. Solid-state SQUID measurement revealed that there is weak antiferromagnetic interaction following the Curie-Weiss law. The interaction was attributed to intramolecular interaction based on DFT calculation.

The intramolecular magnetic interaction through non-conjugated framework has not been studied in detail. We have studied the intramolecular magnetic interaction through non-conjugated framework in the biradicals including pyrroline N-oxyl as a basic skeleton.1 The intramolecular ferromagnetic interaction was observed in hetero biradical 1 because of the spin-spin interaction between both spin sites.2 In the present study, the magneto-structural correlation of pyrroline N-oxyl based hetero biradicals 2 and 3 carrying diphenyloxoverdazyl radical will be discussed. The single crystals suitable for crystallographic study were obtained by slow evaporation. The dihedral angle between pyrroline ring and verdazyl ring is 18.5(1)degree, which was larger than that of 1 (5.0(2)degree), and one of phenyl is twisted due to the packing effect. Regarding the molecular packing, 3 forms a columnar structure with 3.97 Å separation. DFT calculations (UB3LYP/6-31G(d) level) using crystal coordinate implied intramolecular ferromagnetic interaction. There were small intermolecular antiferromagnetic interactions within and between the columns. The physicochemical properties will be discussed.

For the construction of molecule-based magnet and conductor, various type of neutral radicals or ion radicals have been utilized. Electron donating dihydrophenazine unit is oxidized to form a stable cation radical species. In the present research, ion radical salt of 5,10-dimethyldihydrophenazine (1•+BF4-) was prepared and its crystal structure was measured at several temperatures. According to the X-ray structural analysis, the cation radical formed a columnar assembly. Detailed magneto-structural correlation will be discussed.

During the study of magneto-structural correlation for Schiff base oxovanadium(IV) and nitridechromium(V), we found that ligand structure strongly affects the self-association of metal complexes. As for copper(II) complexes, dimer formation was reported for salen-basedcomplex. In the present study, relation between steric effect of Schiff base ligand and dimeric structure is discussed in connection with magnetic interaction. Two Cu(II) complexes, 2-Cu and 3-Cu, carrying bulky substituents at bridging phenylenediamine unit have been synthesized. Single crystal X-ray analysis revealed that both 2-Cu and 3-Cu form a dimer and intermolecular close contact between imine N and Cu was observed. Detailed magneto-structural correlation will be discussed.

Only a limited number of organic crystal exhibit thermosalient effect, and there are few reports that discuss the relationship between substituent groups and the phenomenon. We reported that 1-OC4 exhibited thermosalient effect at ca. 180 ℃, and the crystal of 1-OC6 shows thermomechanically response of peeling off to some thin layers at ca. 100 ℃. In the present research, 1-OC7, 1-OC8, 1-OC9, and 1-OC10 with longer alkoxy chains were prepared and studied their thermo-mechanically responses. While the thin layers peeled off from the crystal surface of 1-OC8 at ca. 80 ℃, the crystal of 1-OC10 collapsed before melting temperature at ca. 60 ℃. The crystals of 1-OC7 and 1-OC9 did not show the thermo-mechanically responses. Endothermic peaks were observed for the crystals of 1-OC4, OC6, OC8 and 1-OC10 at the temperature corresponding to the thermomechanically response. This indicate that phase transition by external heating induces thermomechanically response.