Katsuya Sako

Photoinduced Color Change and Photomechanical Effect of Naphthalene Diimides Bearing Alkylamine Moieties in the Solid State

Photoinduced color change of naphthalene diimides (NDIs) bearing alkylamine moieties has been observed in the solid state. The color change is attributed to the generation of a NDI radical-anion species, which may be formed through a photoinduced electron-transfer process from the alkylamine moiety to the NDI. The photosensitivity of NDIs is highly dependent on the structures of the alkylamine moieties. Crystallographic analysis, kinetic analysis, UV/Vis/NIR spectroscopic measurements, and analysis of the photoproduct suggested that a radical anion was formed through an irreversible process initiated by proton abstraction between an amine radical cation and the neutral amine moiety. The radical anions formed stacks including mixed-valence stacks and radical-anion stacks, as shown by the broad absorption bands in near-IR spectra. These photosensitive NDIs also showed crystal bending upon photoirradiation, which may be associated with a change in the intermolecular distance of the NDI stacks by the formation of monomeric radical anions, mixed-valence stacks, and radical-anion stacks.

The intramolecular C–F⋯HO hydrogen bond of 2-fluorophenyldiphenylmethanol

The intramolecular C–F⋯HO hydrogen bond of 2-fluorophenyldiphenylmethanol was observed by X-ray crystallographic analysis and NMR spectroscopy. The features of the spectra were compared to triphenylmethanol (a fluorine-free analog) and 2-fluorophenyldiphenylmethane.

Synthesis and Properties of New Donors with an Ability of Metal-Coordination

Abstract Synthesis and properties of new donors with the function to control the electrical conductivity by coordination with various metal ions were described. Red shifts in the absorption spectra of donors were observed by coordination with ferrous ion and cyclic voltammetry suggested the ability of electron donation were slightly decreased by metal coordination. Metal complexes with both of ferrous and nickel ions were isolated.

Alternative General Synthetic Routes to [2.2]Cyclophanes and [3.2]Cyclophanes from [3.3]Cyclophane-2,11-diones by Photodecarbonylation, and a Structural Study of [3.2]Metacyclophanes

Photodecarbonylation of [3.3]cyclophane-2,11-diones, which are readily prepared by TosMIC coupling, affords [2.2]cyclophanes in high yield. This method also provides a general synthetic method for [3.2]cyclophan-2-ones by taking advantage of the fact that this photochemical reaction proceeds in a stepwise manner through [3.2]cyclophan-2-ones. A series of [2.2]cyclophanes, [3.2]cyclophanes, and [3.3]cyclophanes can thus be made available from the common precursor [3.3]cyclophane-2,11-diones. In sharp contrast to the preferred syn geometry of [3.3]metacyclophanes, [3.2]metacyclophanes adopt anti geometries and the aryl ring inversion process is observed by variable-temperature 1H NMR spectroscopy. In the crystalline state, the two aryl rings of anti-[3.2]metacyclophanes are almost parallel in spite of the unsymmetrical bridge length; they overlap only at the C-9 and C-17 positions, and the transannular distances are shorter than the corresponding distances in [3.3]metacyclophane-2,11-dione.

Crystal structural properties of a pinwheel compound: [36](1,2,3,4,5,6)cyclophane

In the crystal structures of [3 6 ](1,2,3,4,5,6)cyclophane 1 and the 1 :TCNQ (1:1) complex, the cyclophane moiety is observed as the D 6 h structure because of the disorder of the molecules with C 6 h symmetry. In contrast, the C 6 h structure is observed in the crystals of the 1 :TCNQ-F 4 (1:1) complex, and the complex shows an alternating donor–acceptor stacking with partial donor–acceptor overlap.

Macrocyclic Oligothiophene with Stereogenic [2.2]Paracyclophane Scaffolds: Chiroptical Properties from π‐Transannular Interactions

The enantiomers of a new cyclic oligothiophene, bridged by two pseudo-ortho[2.2]paracyclophanes, were synthesized as a new class of the chiral π-conjugated system. Single-crystal X-ray diffraction analysis revealed a twisted structure for these oligothiophenes induced by a torsion of the cyclophane moieties. The embedding oligothiophenes into the inherent planar chirality provided a significant enhancement in circular dichroism (CD) spectra thanks to the large magnetic/electric transition dipole moments. In the dicationic state, an intramolecular π dimer was formed due to the strong interactions of the oligothiophenes. We further recorded unprecedented wide ranges of CD spectra in 250-1800 nm region. The transitions are reasonably described by the exciton coupling of the oligothiophenes.

Dimeric Tetrathiafulvalene Linked to pseudo-ortho-[2.2]Paracyclophane: Chiral Electrochromic Properties and Use as a Chiral Dopant

A dimeric tetrathiafulvalene installed into a chiral pseudo-ortho-[2.2]paracyclophane framework was synthesized as a novel chiral electrochromic material. This compound exhibited pronounced chiroptical properties in the UV-Vis-NIR range depending on its redox states without racemization. Each enantiomer was examined as a chiral dopant for nematic liquid crystals (LCs), and the induced helicity of the LC solvent was in accord with that of the tetrathiafulvalene compound.

Synthesis and properties of bi- and ter-tetrathiafulvalenyls

Abstract New donors containing two or three TTF rings connecting directly to each other were synthesized and their electronic spectra showed the presence of hydrophobic interaction among the long chains of thioalkyl groups attached to TTF frameworks. Furthermore, their redox potential waves indicates the marked tendency to reducing on-site Coulombic repulsive forces in their dicationic states as increasing the number of incorporated TTF frameworks.

Synthesis and properties of new donors linked directly with two or three tetrathiafulvalene units

Abstract Synthesis and properties of new donors in which two or three TTF frameworks are linked with some dihedral angles to form extended π-conjugated systems are described. Complexation of these TTF derivatives with DDQ and iodine affords moderately conductive charge transfer complexes. Cyclic voltammetry indicates that the electron-ability of TTF-trimers is reduced by comparison of that of TTF-monomer but is slightly enhanced comparing with that of TTF-dimers.

SYNTHESIS OF HIGHER-NUCLEARITY CLUSTERS BY ASSEMBLING THE -CCo3(CO)9 UNITS INTO AROMATIC SPACER MOLECULES

Abstract p-[(CO)9Co3C]2C6H4 (1) has been synthesized by reacting Co2(CO)8 with p-(Cl3C)2C6H4. 4,4′-[(OC)9Co3CC(O)]C6H4-C6H4[C(O)CCo3(CO)9] (2) has been synthesized from p-LiC6H4-C6H4Li and BrCCo3(CO)9. Similarly m-[(OC)9Co3CC(O)CH2]2C6H4 (3) has been synthesized from m-(LiCH2)2C6H4 and BrCCo3(CO)9. X-ray analysis was done for 1 and 2; both compounds exhibit a stacked structure. Cyclic voltammetry and UV spectra revealed usual behavior for 1, that is, two cluster units interact strongly through the benzene spacer, which is not the case for clusters 2 and 3.