We have previously found that the introduction of alkoxy-groups at the C(2) position of cyclopentane-1,3-diyls makes the singlet the ground-state spin-multiplicity. The lifetime of the singlet biradicals was found to be dependent on the chain-length of the alkoxy-group. In this study, we investigated the substituents effects at the C(2) position and solvent effect on the reactivity of the singlet 1,2-diaza-4,4-dialkoxy-3,5-diyl derivatives.

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Tetraradicals TR, in which the two biradical units are connected with a p-phenylene or m-phenylene linker, were generated in a low temperature MTHF matrix using the photochemical denitrogenation of the corresponding azo compounds. Spectroscopic analyses, including EPR measurements and UV-vis absorption spectra, were performed to reveal the spinmultiplicity.

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A 1,3-diphosphacyclobutane-2,4-diyl is one of the air-stable P-heterocyclic singlet biradicals. This biradical has C₂P₂ four membered ring skeleton, and is highly kinetically and thermodynamically stabilized by bulky Mes*(2,4,6-tri-tBuC₆H₂) groups and phosphorous atoms, respectively. Previously, we succeeded in synthesizing the biradical oligomers bearing two and three biradical units in one molecule, and we found the peculiar electric interaction between biradical units. To understand this intriguing interaction in detail, in this paper we design bis(biradicals) bearing diphenylether spacers and tris(biradicals) in which biradical units were combined in linear arrangements, and evaluate this interaction by electrochemical analysis. It is plausible that bis(biradicals) whose distances between the biradical units are within 7 angstrom display the interaction. This result indicates that distances between two biradical units are decisive for this interaction. Additionally, radical cations generated from the biradical were analyzed by spectroscopy technique.

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Reactive radicals trapping experiments where short-lived radicals generated by the YAG laser photolysis of the radical precursors in the gas-phase are reacted with scavenger stable radicals such as 2,2- diphenyl-1-picrylhydrazyl: DPPH) have been carried out. Identification of the radical adducts formed between reactive radicals and scavenger stable radical, trapping efficiency and the evaluation of the amount of trapped reactive radicals were done by the spectroscopic analyses using ESR (Electron Spin Resonance), soft-ionizing Mass, UV-Vis, and IR spectrometers. Reaction mechanism for the radical trapping was considered on the basis of the theoretical evaluation of the spin densities and the reported literature data of the mean bond enthalpies for the relevant chemical bonds.

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We have synthesized amphiphilic nitroxide (+-)-1 which formed micelles in H2O by ultrasonication. The concentration dependence of the EPR spectrum was measured for (+-)-1 in H2O. When the concentration of (+-)-1 was higher than 2*10-4 mol/L, the EPR spectra were apparently composed of two different components; one is a broad line which originates from spin-spin exchange interactions in the micells and the other is a triplet line derived from free molecules which did not form micells. With decreasing concentration of (+-)-1, the broad line gradually diminished and finally disappeared. Thus, the critical micelles concentration of (+-)-1 in H2O was determined to be approximately 2*10-4 mol/L.

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Pincer-type Pt-complexes have attracted much attention as new materials possibly applied to molecular electronics. In order to add a new functionality to pincer type Pt-complexes, we designed and synthesized (nitronyl nitroxide)-directly introduced Pt-complexes. The oxidation of these radical-Pt-complexes selectively produced the tetravalent Pt(IV) complex or the cationic (nitrosonium nitroxide)-Pt(II) complex, depending on the oxidation conditions. We report the detailed synthetic procedures and crystal structures of these complexes.

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Trioxotriangulene (TOT) is a neutral pi-radical possessing a 25 pi-electronic system, and exhibits a high stability and four-step redox processes. In the present study, in order to explore intriguing functions of the TOT-based neutral pi-radicals, we have designed and synthesized a carbazole-substituted derivative of TOT. Its crystal structure and physical properties in the solid and solution states were investigated.

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1,4-Diarylbutane-1,4-diyl radical cation (3^•+) is an important intermediate generated by electron-transfer reaction of cis- and trans-1,2-diarylcyclobutane (cis- and trans-1) or styrene derivatives (2). Nanosecond absorption spectra on independent laser flash photolyses (LFP) indicated that the anisyl derivative cis-1a, trans-1a, and 2a gave trans-3a^•+. Time-dependent density function theory (TD-DFT) calculation also supports this conduction.

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10-(9-anthryl)anthroxyl radical was prepared and was isolated in a crystalline form. This species were found to be stable in air and could be purified by silica-gel column chromatography. X-ray crystallographic analysis revealed that the radical has a short C-O bond of 1.242(3) Å, suggesting appreciable contribution of the structures containing the C=O double bond to the ground state. In addition to the isolation of the anthroxyl radical, a solution containing both the radical and the alcohol precursor afforded brown single crystals of a hydrogen-bonded complex consisting of radical/alcohol (1:1). X-ray crystallographic analysis at 100 K revealed that a hydrogen atom locates on one side of the O-H-O hydrogen bond. The complex can be regarded as an analogue of the intermediate in phenoxyl/phenol hydrogen self-exchange reaction.

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In order to develop new organomagnetic materials with photo-responsive and FET property, a naphthalenediimide derivative with a TEMPO and 4-dimethylaminoazobenzene substituent was prepared. Antiferromagnetic interactions of CW behavior were observed in the spins of the trans-isomer and occurrence of photo-isomerization was clarified by irradiation to the compound. Although the mobility is small, n-type FET property was discerned for the compound and the change of its mobility and Vt-value was found by the photo-isomerization. The results will be reported in comparison with the structure and properties of the corresponding unsubstituted-azobenzene derivative.

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Ferrocenyl compounds are expected to exhibit redox properties and to form CT complexes based on the donor property. This time, some ferrocene derivatives carrying nitroxide radical have been prepared and their crystal structures have been clarified together with their magnetic, redox and secondary battery properties. The results on the investigations of their structure and property relationships will be reported.

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Azafullerene C₅₉N, i.e., one carbon atom of the C₆₀ cage replaced by a nitrogen atom, has attracted attention because of its superior electron affinity and unique reactivity. In order to establish the efficient way to functionalize C₅₉N core, we first studied the reaction of the dimer (C₅₉N)₂ with some pyrrole derivatives under the presence of oxidizing reagents such as 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), iodine, and p-chloranil. As a result, the electrophilic substitution reaction of 2-acetylpyrrole was found to proceed smoothly at 70 ˚C in 1,2-dichlorobenzene when DDQ was employed. Then, we extended the scope of this reaction to a typical pyrrole-containing fluorescent dye, BODIPY, and actually obtained the desired dyad in which a BODIPY unit was directly connected to the C₅₉N core via a C-C single bond. The transient absorption spectra and fluorescent lifetime measurements revealed that ultrafast intramolecular photoinduced energy transfer from the BODIPY unit to the C₅₉N core occurred on the femtosecond time scale.

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Cycloaddition reactions of fullerenes at the [6,6] conjunct double bond are of valuable methods for chemical modification and have attracted continuous attention in view of the synthesis of fullerene derivatives and new materials. Especially, a vast amount of study has been made of the thermally allowed [2 + 4] and [2 + 3] concerted reactions such as Diels-Alder and 1,3-dipolar cycloadditions. In contrast, however, the thermal [2 + 2] cycloaddition of fullerenes is very scarcely known in fullerene chemistry. Here, we report that morpholinocycloalkenes (enamines) react with C₆₀ to give exclusively [2 + 2] monoadducts in high yields in refluxing toluene. We also proposed a possible mechanism of this cyclobutanation of C₆₀ in view of the single electron transfer (SET). The subsequent acid-catalyzed hydrolysis of the [2+2] adduct gave cyclopentanofullerene.

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Linked fullerene dimers have much interest in their structure and interaction between fullerene moieties. In this context, we synthesized and characterized p-phenylene-linked C₆₀-C₆₀ dimer. Its structure, photophysical and redox properties will be discussed in comparison with the corresponding monomer. In addition, we synthesized endohedral metallofullerene dimer.

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We have already reported that the reaction of La@C₈₂ with AdN₂ resulted in the formation of La@C₈₂Ad in a regioselective manner. Herein, we successfully synthesized the bis-adducts of paramagnetic endohedral metallofullerene; La@C₈₂Ad₂. Their characterization was carried out by HPLC, Vis-NIR, ESR and MALDI-TOF Mass spectroscopic analyses and theoretical calculations.

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Single crystal X-ray diffraction studies of Ce2@D5h-C80•NiII(OEP) (OEP = octaethylporphinate) reveal that the motion of Ce2 in D5h-C80 cage was nearly frozen at 90 K. Detailed analysis demonstrates that each Ce atom with major occupancy is approaching to a pyracylene unit of D5h-C80 cage with the Ce-C distance ranging from 2.287 Ǻ to 2.944 Ǻ. Therefore, it appears that the presence of the pracylene unit of D5h-C80 cage is crucial in freezing the motion of endohedral Ce2.

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Here we report on the reaction of La₂@C₇₂with 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine and its characterization by means of spectroscopic analysis and theoretic calculation.

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Supramolecule systems, which show photoinduced electron or energy transfer, are promising for application in construction of photosynthetic reaction center and molecular electronic devises. Toward developing such systems, fullerenes attract the attention as electron acceptors because of their specific structures and properties. The construction of various non-covalently linked donor-acceptor systems based on pyridine functionalized C₆₀ fullerene derivatives and metal porphyrins have been reported. On the other hand, endohedral metallofullerenes have higher electron-accepting ability and form more stable anions compared to the empty fullerenes.
Recently, we have investigated the complexation behavior of the endohedral metallofullerene ligands with the organic molecules by electron transfer between them. The facile electron transfer is characteristic of endohedral metallofullerenes.
In this work, we focused on the paramagnetic metallofullerene La@C₈₂ and investigated the interaction between the paramagnetic endohedral metallofullerene ligand and fused zinc porphyrin dimer in toluene.

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We report here the synthesis of a new type of electron donor-acceptor conjugates containing endohedral metallofullerene as an electron donor,and tetracyanoanthraquinodimethane (TCAQ) as an electron acceptor. The target molecule was prepared by 1,3-dipolar cycloaddition of an azomethine ylide generated in situ by Prato reaction and isolated by HPLC. Characterization using spectroscopic methods and electrochemical analysis has been accomplished.

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A significant number of application studies of phthalocyanines (Pcs) have been devoted due to their unique optical properties and high chemical stability. Although expanded Pc analogues have attracted much attention as near-IR absorbing dyes and novel functional metal ligands, the reports on the synthesis of this kind of analogues have been very limited. Recently we successfully synthesized novel expanded Pc analogues under Pc synthetic reaction using excess amount of urea and appropriate amount of molybdenum or tungsten salt instead. Their structure was characterized by the NMR spectroscopy and X-ray crystallographic analysis. Their electronic structure was explicitly revealed by the absorption and magnetic circular dichroism spectra and the theoretical calculations. In this presentation, the synthesis and properties of this novel expanded Pc analogues will ne reported.

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Near-IR dyes are required for various advanced technologies. Phthalocyanines (Pcs) show intense absorptions in the visible region (the so-called Q band), which can be shifted to the near-IR region by making some changes to the structure. The Q band is composed mainly of the HOMO - LUMO transition. Since the size of the carbon atomic orbital coefficients of α-positions are large in the HOMO, we anticipated that the introduction of an electron donating group to the α-positions will destabilize the energy of the HOMO level significantly. In a similar anticipation, the insertion of a high-valence element (as an electron withdrawing group) into the central cavity appears to stabilize the energy of the LUMO level. As a result, a decrease of the HOMO - LUMO gap is inferred, resulting in a shift of the Q band to longer wavelength. On the basis of this concept, we designed and synthesized some Pcs absorbing in the near-IR region.

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Various porphyrinoids have been invented due to their characteristic properties. Nevertheless, thiacorrole, one of porphyrinoids, is unexplored despite the simple structure. In this work, we have succeeded in synthesis of thiacorrole and dithiaporphyrin through thiolation of dipyrrin derivatives. We will report synthesis and property of thiacorrole and dithiaporphyrin.

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We reported a stable meso-unsubstituted hexaphyrin, meso-free hexaphyrin, and its metal complexes. meso-Diketo hexaphyrin which is remarkably stable and can be manipulated like usual organic molecules was synthesized by the demetalation of the Ni complex. Its structure was determined by X-ray diffraction analysis to be meso,meso-diketo, non-Kekulé biradicaloid hexaphyrin. Singlet ground-state with non-Kekulé structure was revealed by ESR and SQUID measurements. The optical and electrochemical properties will be also reported.

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Linear hexapyrroles were easily synthesized by taking advantage of highly reactive bisazafulvenes that were derivatized from 2,2,-bipyrrole and 1,3-bis(2-pyrryl)arenes. X-ray crystallography revealed helical structure of these hexapyrroles. Binding homochiral carboxylic acids to hexapyrroles developped a strong induced CD in the visible region. The hexapyrrole with the 1,3-phenylene spacer bound 2 equiv of (-)-dibenzoyl-(L)-tartaric acid, where allosteric binding behavior was observed. The formyl groups at the both ends of the hexapyrroles were converted into the imine groups and amine groups that causes variation in the structure and function.

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In recent years there has been a growing focus on the chemistry of ring-expanded porphyrins such as hexaphyrins and octaphyrins, because their properties differ markedly from those of conventional porphyrins in a manner that makes them potentially suitable for a number of novel practical applications. First cyclo[8]pyrrole ([30]octaphyrin(0.0.0.0.0.0.0.0)) has been reported by Sessler and his co-workers based on an oxidative-coupling of 2,2'-bipyrrole in 2002. Recently, we reported the first successful synthesis of cyclo[8]isoindole based on an oxidative-coupling of bicyclo[2.2.2]octadiene(BCOD)-fused 2,2'-bipyrrole, followed by the retro-Diels-Alder reaction. Herein we report synthesis 9,10-anthracene- and 1,2-acenaphthylene-fused cyclo[8]pyrroles by oxidative-coupling of 2,2'-bipyrrole and their vis-NIR absorptions, fluorescence spectra and molecular structures by X-ray crystal structural analysis.

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We have shown that cyclooctapyrroles consisting of eight pyrroles are used for chirality sensing of carboxylic acids. In this research, the cooperative coordination behavior and coordination structure in the binding of carboxylic acids to hybrid-type cyclooctapyrrole containing two 1,4-phenylene linkers and highly symmetric cyclooctapyrrole containing four 1,4-phenylene linkers were studied on the basis of titration experiments by UV-vis, CD and H-NMR.

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Previously, only one typed N-confused porphyrin (NCP) rhenium(I) complex was reported. Because NCP have stabilization ability of high oxidation state of metal, we examined the synthesis of rhenium complex other valency. In addition, when outer-N-methylated NCP was reacted with rhenium reagent in the presence of 2,6-lutidine, NCP rhenium(V) complex bearing external fused rings was obtained.

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N-confused porphyrin (NCP) contains two NH tautomers (2H & 3H type) whose electronic states and pi conjugation systems differ largely. The 2H type tautomer has a proton on its nitrogen of the confused pyrrole ring. On the other hand, the 3H type bears the imino nitrogen atom. To control this NH tautomerism, pyridyl ethenyl NCPs in which hydrogen bonding acceptor group, pyridyl moiety, is introduced through the olefenic bond of the alpha position of the confused pyrrole ring, was synthesized.
In the cis form, 2H type is predominantly formed due to stabilization by a hydrogen bonding between the pyridyl group and NCP. Additionally, thermal isomerization is observed which lead to the 3H type along with isomerization to the trans form.
This time, We report the thermal isomerization and substituent effect of pyridyl ethenyl NCPs and their complexes, as well as a steric effect of quinlyl ethenyl NCP.

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Most porphyrinoids have been synthesized by acid-catalyzed condensation of aldehydes and pyrroles, while there are few reports of other synthetic strategy. Recently, we have reported the synthesis of quadruply-benzo-fused porphyrin by annulation reaction of butadiyne-bridged cyclic carbazole dimer. Here, we report the synthesis of sextuply-benzo-fused rubyrins by annulation reaction of butadiyne-bridged cyclic indolocarbazole dimer.

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In recent years, we found the first examples of isolated and characterized 16pi porphyrins, showing unique spectroscopic properties and structural deformation. However, NICS calculations revealed that the highly distorted 16pi porphyrins were essencially non-aromatic with only weak antiaromatic character. In order to obtain 16pi porphyrin with more antiaromatic nature, the following methods were considered to be effective: 1) introduction of meso-alkyl substituents and 2) usage of the benzo-fused structure. As a result of the former, the relevance between the structure and antiaromaticity using novel 16pi porphyrin metal complexes with meso-alkyl substituents was revealed by ¹H NMR spectroscopic measurements and NICS calculations. In addition, the meso-alkyl substituents were found to be very effective for the stabilization of the 16pi species. In the latter, the unique spectroscopic properties of the antiaromatic 16pi prophryin metal complexes with the benzo-fused structure were revealed by various spectroscopic measurements.

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Aromatic secondary amides such as benzanilide exist in trans-amide form, whereas N-methylated benzanilides exist in cis form in the crystal and predominantly in cis form in solution. The cis conformational preference is also observed in N,N'-dimethylated ureas, and can be applied to construct the aromatic molecules with unique conformational properties. In this study, we designed functional porphyrin derivatives bearing trans (-NH-CO-R) or cis (-NMe-CO-R) amide/urea bond, including porphyrin dimers or porphyrin-benzene-hybrid type compounds by using 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP) as the porphyrin unit. N-Porphyrylbenzamide existed in trans form in the crystal, while the N-methyl derivative existed in cis form. The comparison of chemical shifts of ¹H-NMR spectra showed that each amide existed in the conformation corresponding to the crystal structure. Thus, porphyrylamide also changed the conformation by N-methylation. Interestingly, N,N'-bis(porphyryl)urea showed solvent-dependent conformational change, and afforded two types of crystal bearing different conformations.

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Porphyrin-silicon complexes seem interesting in terms of the interaction between the 18π aromatic ring and the hexacoordinate silicon atom. We synthesized a tetraphenylporphyrin-fluoromethylsilicon complex, and its structure and properties were studied. This compound was reduced with potassium graphite to form a radical anion and a dianion. The electronic properties of these anionic species are discussed with ESR and UV-Vis-NIR spectra.

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We prepared an artificial allosteric system that has a Zn-porphyrin unit at the middle of a oligo(phenylene-ethynylene) chain. A bipyridyl terminal was incorporated at the one end of the conjugated chain and two alkly chains with bipyridyl terminals were connected to the phenyl group at the other terminal of the conjugated chain. By addition of Fe(II), a tris(bipyridyl)Fe(II) complex was formed across the Zn-porphyrin. As a result, binding of imidazole derivatives to the porphyrin-Zn center was allosterically inhibited. The detailed synthesis, Fe(II) complexation, and allosteric properties will be reported.

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Previously we prepared zinc porphyrin derivatives possessing 2,2'-bipyridyl units at the peripheral end of both conjugated and alkyl side chains. The formation of the [Fe(II)(bpy)3]-type complexes induced a large conformational change, which further induced a slight increase in the binding between zinc porphyrin and imidazole axial ligand. Sterically bulky substituents were incorporated at meso-positions to enhance steric demand around the axial coordination sites. We investigated the steric effect of meso-substituents on the axial binding constant after and before the Fe(II) complexation.

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Whereas an increasing number of the procedures for the meso-functionalization of porphyrin have been reported, many of them require an activation of the porphyrin core or an addition of suitable transition metal catalysts. Previously, we have reported the facile meso-azidation and phenoxylation of porphyrins through the catalyst-free nucleophilic substitution reaction. Herein, we report that this procedure is useful in introducing a wide variety of functional groups to the porphyrin. For example, various the S- or N-substituted porphyrins are easily obtained in high yield without any catalysts. The reactivity of each nucleophile and the structural elucidation of the obtained porphyrins will be also discussed.

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For cancer treatment, prompt and precise detection of the affected part is important in addition to urgent development of less-invasive approach to normal tissues. Herein, we investigated to utilize tumor-selective aggregation nature of a porphyrin derivative as an anchor structure of SPECT imaging protocol. Chelating sites for radioactive isotope elements were introduced into porphyrin periphery, which were not coordinated in a porphyrin core due to the large ion size.

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We have studied the synthesis and crystal structure of a porphyrin nanotube formed through the self-assembly of the cyclic porphyrin dimer Ni2-CPDpy. In our continuing efforts along this line, we wish to report the synthesis of new cyclic porphyrin dimers. The new dimers have longer linkers than the previous dimer.

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3-Vertex-colourability problem is one of the NP-complete problems which contain socially important problems. We planned to solve it using molecules. In order to realize it, we need many types of porphyrin arrays whose shapes are suitable for STM observation. For this purpose, a synthetic route was developed for automated organic synthesis of the arrays.

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Directly .alpha.-.alpha.-linked pyrrole oligomers, which are potential .pi.-conjugated units that construct functional materials, have not been investigated in detail due to their reactivities derived from excess .pi.-electrons. Modification at the terminal .alpha.-positions by introduction of aryl rings by cross-coupling reaction provided aryl-substituted pyrrole trimers (terpyrroles), which were found to be spontaneously transformed to radical species. After the addition of an oxidant (BAHA), radical species exhibited the formation of oxidized species, suggested by NMR and MALDI-TOF-MS. In order to prepare more stable oligopyrroles, synthesis of .beta.-fluorine-substituted derivatives was also attempted; in fact, formation of .beta.-fluorine-substituted oligopyrroles was suggested by MALDI-TOF-MS. Furthermore, synthesis of anion-responsive dipyrrolyldiketone BF2 complexes containing terpyrrole moieties was also attempted.

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Bacteriochlorophyll-c molecule self-aggregates without any assistance of proteins in chlorosomes of green photosynthetic bacteria. Here, we prepared PEG appended zinc 3¹-hydroxy-chlorins and their dyads as models for bacteriochlorophyll-c. The amphiphilic zinc chlorins formed J-aggregates and gave supramolecular gels in aqueous organic solvents. The supramolecular structure of the zinc chlorin chromophores was similar to that of chlorosomal aggregate of natural bacteriochlorophyll-c.

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We have been synthesized the acyl semicarbazide derivatives (1-3) bearing aliphatic moieties, which formed a gel in hexane and cyclohexane. These cyclohexane gels showed the enhancement of the fluorescent intensity. 1H-NMR and FT-IR spectroscopy studies revealed that intermolecular hydrogen bonding formation plays an important role for the formation of the gels. Sacnning electron microscopy (SEM) measurements demonstrated that the aggregation behaviors of the compounds are greatly affected by the structure of the linkers. SEM images of the xerogel showed that 1/cyclohexane possesses a layered structure. For 2/cyclohexane system, the xerogel is characterized by fibrous structures.

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It has been known that Eu3+ ion shows very strong red fluorescence by forming the complex using a suitable ligand. In general these complexes do not dissolve in water. In this study, we have built a hybrid system of the Eu(III)-diketone complex and the bilayer membrane in order to dissolve in water. It was found out that the hybrid system can be dissolved in water with a suitable combination of the complex and the bilayer membrane. Details are now under investigation.

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We designed amphiphiles worked as low molecular weight gelator by hydrophilic modification of periphery of hydrophobic tris-urea. Some of amphiphiles geled water, however compounds with insufficient hydrophilicity did not form gels. These molecules were able to form hydrogels in the presence of surfactant such as sodium dodecyl sulfate (SDS).

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Non-equilibrium state of soft interfaces generally exhibits interesting phenomena such as a non-linear response of liquid interface, unique self-assembly of molecules or nanometer-/micrometer-sized particles and autonomous dynamics of these assemblies. So far we have shown the oil droplets exhibiting the self-propelled motion in a surfactant solution. Generally, the mechanism of this motion is argued that the heterogeneous adsorption of the surfactant around the oil droplet affords the driving force due to the interfacial tension, hence the oil droplet stops when it is uniformly covered, namely equilibrated, by the surfactant. However we found that oil droplets of 4-n-octyloxybenzaldehyde in an aqueous solution of trimethylalkylammonium bromide exhibits on-and-off self-propelled motion , i.e. the self-propelled oil droplet slowed down and stopped, but restarted the autonomous motion after separation of assemblies formed on the droplet. This phenomenon is of great interest as a novel motion coupling between the self-propelled motion and phase separation.

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Transalkylation between two amphiphiles to form a membrane molecule would be attractive because of the similarity to transacylation in the biosynthesis of phospholipids. It was suggested that the chain transfer reaction between an double chained reactive amphiphile bearing an imine bond in its hydrophobic chain and one with a formyl group in its hydrophobic end proceeded in the direction to form the amphiphile of which the imine moiety was located in more hydrophilic environment. Morphological changes of giant vesicles accompanied with the chain transfer also will be reported.

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The redox reactions of the dynamic redox systems are accompanied by reversible C-C bond cleavage/formation, which endows the systems with high electrochemical bistability based on their geometrical/electronic structural changes. In this study, we have designed the novel redox systems with the bis(styrene)-type skeleton 1 the hexaphenylethane-type skeleton 2, which can form self-assembled monolayer (SAM) on an Au(111) electrode by using the lipoic/isolipoic ester moieties attached on the 6,6'-positions of biphenyl unit. Those molecules were successfully prepared from the corresponding 6,6'-bis(methanol)s by esterification using lipoic/isolipoic acid. Their redox properties are investigated in solution and on SAM made on the Au surface. The SAMs are also used for the study using scanning tunneling microscopy (STM) and electrochemical STM.

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A novel chiral metal organic framework (MOF) was synthesized by mixing optically active 2,2'-dihydroxy-1,1'-binaphthalene-3,3'-dicarboxylic acid and MnCl₂ in pyridine. The crystal structure of the chiral MOF was determined by X-ray analysis.

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Based on the chemistry of dipyrrin as monoanionic bidentate ligands for metal cations, we prepared meso-linked dipyrrin dimers, which afforded Zn^II-bridged coordination polymers. Interestingly, meso-linked dimer was found to be spontaneously transformed to singly fused tetrapyrrolylketone derivative in solution state, concomitantly with the shift of absorption maximum from 444 to 329 nm. Nonfused and singly fused tetrapyrrolylethenes can behave as dianionic bidentate ligands for each dipyrrolyl unit, resulting in the formation of Sn^IV-bridged polymers.

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We have recently revealed an intriguing feature of oligo(imidazole)s forming stable multi-nuclear triple-helicates with various metal ions having the octahedral coordination geometry. Furthermore, it has been also clarified that oligo(imidazole)s-based helicates have an advantage to form outward-directed hydrogen-bonds constructing multi-dimensional network structures. In this presentation, we will show the synthesis and structure of trinuclear triple-helicates composed of sexiimidazole and metal ion.

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Polynuclear complexes with regular arrays of metal ions show unique properties based on the interactions between metal ions. In this study, two nonanuclear copper [3X3] grid-shaped complexes were synthesized using a multidentate ligand; H₂L(= 2,6-bis-[5-(2-pyridinyl)-1H-pyrazol-3-yl]-pyridine) which has three different coordination sites, and a flat, rigid structure. Here we discuss the magnetic and electrochemical properties of the grid compounds. Magnetic susceptibility measurements suggested that antiferromagnetic interactions were dominant between the copper(II) ions, while cyclic voltammetry data showed four quasi-reversible waves, each corresponding to one electron reduction events.

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