橋本 剛

The selective molecular recognition event by physical or chemical signals is a key concept for the design of novel supramolecular sensors. In this study, we designed a novel saccharide recognition system based on the self-assembly of phenylboronic acid azoprobes (1-BAzo-NPs) on the surface of the polyamidoamine (PAMAM) dendrimer in water. The two sulfonic acid moieties in 1-BAzo-NP enhanced the binding affinity of the azoprobe for the PAMAM dendrimer surface. UV-Vis spectral measurements indicated that 1-BAzo-NP showed poor saccharide recognition at pH 7.0, whereas the 1-BAzo-NP–PAMAM complex well recognized the saccharides, particularly glucose. The complexation with glucose yielded aggregates having diameters of 100–200 nm as determined by dynamic light scattering (DLS) measurements and transmission electron microscopy (TEM). The sensitivity to and selectivity for the saccharides were controlled by the density of the assembled phenylboronic acid azoprobes and PAMAM generation. Together, the results revealed that the selective saccharide recognition at pH 7.0 was feasible by boronic acid assembly on the PAMAM dendrimer surface.

We succeeded in controlling the wavelength range in which the photocurrent of porphyrin is enhanced by tuning as well as expanding the wavelength ranges in which the localized surface plasmon resonance (LSPR) occurs. We fabricated photoelectric conversion systems consisting of 5,10,15,20-tetrakis(p-carboxyphenyl) porphyrin (TCPP) and silver nanoprisms with small (SAgPRs) and large (LAgPRs) aspect ratios as plasmonic nano-antennae. Their photocurrents were much larger than those from TCPP-modified Ag planar electrodes at the specific wavelengths corresponding to their LSPR bands (SAgPRs: 460-610 nm; LAgPRs: 610-690 nm). The maximum enhancement factors (EFs) for the SAgPRs and the LAgPRs were 37 and 35, respectively. In order to enhance the photocurrents, we expanded the LSPR bands by the combined use of SAgPRs and LAgPRs. The system consisting of the mixture (MAgPRs) showed enhancement of the photocurrent over the entire Q-band region (480-690 nm). Finally, the total EFs of the photocurrents were evaluated by irradiation with AM1.5G sunlight through a long-pass filter of 480 nm and the results revealed that the EFs were in the order of MAgPRs > SAgPRs > LAgPRs. Furthermore, the system showed stability without loss of the enhancement property for at least 10 min under the solar irradiation.

Substituting effect of CF3 to the Ru-based binuclear complex [{Ru-III( acac)(2)}(2)(mu-OEt)(2)], in which S = 1/2 spin dimer takes the singlet ground state have been investigated by means of the magnetic susceptibility chi and the longitudinal nuclear spin relaxation rate T-1(-1) of H-1/F-19-NMR. In CF3-substituted complex [{Ru-III(fhma)(2)}(2)(chi-OMe)(2)], we have observed the prominent magnetic response both in chi and T-1(-1). This behavior is attributed to the slight change in the Ru valence state due to the substitution.

Phenylboronic acid azoprobe (B-Azo-Cb) for saccharide recognition was synthesized. B-Azo-Cb/polyamidoamine (PAMAM) complex was synthesized by the condensation reaction of terminal carboxylic group of B-Azo-Cb and surface amine of PAMAM dendrimer. Thin porous cellulose acetate membrane embedded with B-Azo-Cb/PAMAM dendrimer complex was prepared from cellulose acetate, formamide, acetone, and B-Azo-Cb/PAMAM dendrimer complex by casting on the glass plate at various temperatures. The saccharide transportability was evaluated by measuring the amount of saccharide in receiving solution. The amount of saccharide transport of porous cellulose acetate membrane embedded with B-Azo-Cb/PAMAM dendrimer complex was higher at low temperature-treated membrane, and low pH of receiving solution. In contrast, the saccharide transportabilities through non-treated cellulose acetate membrane were the same at any pH of receiving solution.

The fluorescence behavior of a probe dpa-HC, which has a coumarin derivative that acts as a fluorophore and a dipicolylamine (DPA) unit that functions as a metal ion-recognition site, was investigated with various metal ions in aqueous and several non-aqueous solvents. In aqueous solution, the fluorescence of dpa-HC was enhanced by Zn2+ and Cd2+, but was quenched by other metal ions. On the other hand, in an acetonitrile solution, only Mg2+ enhanced the fluorescence, and the addition of a small amount of water quenched this fluorescence. This dramatic selectivity change is explained by stabilization of a metal-dpa-HC complex due to acetonitrile coordination and ON-OFF switching of the intramolecular photoinduced electron transfer (PET) from the nitrogen lone pair of DPA to the coumarin derivative.

We report a novel supramolecular chirality induced by the twisted structural change of two ditopic azoprobes (15C5-Azo-dpa) inside the chiral cavity of γ-cyclodextrin (γ-CyD) due to multi-point recognition of guest ions by 15C5-Azo-dpa molecules in water. This journal is © the Partner Organisations 2014.

The construction of a novel electrochemical sugar recognition system using a tris(acetylacetonato)ruthenium complex and phenylboronic acid assembled on gold nanoparticles is described. This system showed excellent sensitivity compared to those by the assembly on the dendrimer and optical recognition.

An inclusion complex consisting of a boronic acid fluorophore (C1-APB) and beta-cyclodextrin (beta-CyD) acts as a supramolecular sugar sensor whose response mechanism is based on photoinduced electron transfer (PET) from the excited pyrene to the boronic acid. We have investigated the PET process in C1-APB/CyD complexes by using time-resolved photoluminescence (TRPL) measurements at room temperature, and have succeeded in estimating the electron-transfer time to be about 1 ns. We have also studied the effects of CyDs on the PET process by comparing two kinds of CyDs (alpha-CyD, beta-CyD) under different water-dimethylsulfoxide (DMSO) concentration conditions. We found that the CyDs interacting with the boronic acid moiety completely inhibits PET quenching and increases the monomer fluorescence intensity.

A supramolecular cyclodextrin (CyD) gel having selective monosaccharide recognition function was prepared by polymerization of gamma-CyD containing a lipophilic phenylboronic acid azoprobe. The non-template gel exhibited galactose selectivity in adsorption, whereas the glucose-template gel exhibited glucose selectivity.

The construction of a novel electrochemical sugar recognition system using a tris(acetylacetonato) ruthenium complex and phenylboronic acid assembled on gold nanoparticles is described. This system showed excellent sensitivity compared to those by the assembly on the dendrimer and optical recognition.

We report a novel supramolecular chirality induced by the twisted structural change of two ditopic azoprobes (15C5-Azo-dpa) inside the chiral cavity of gamma-cyclodextrin (gamma-CyD) due to multi-point recognition of guest ions by 15C5-Azo-dpa molecules in water.

The synthesis, structure and biological studies of cobalt(III) complexes supported by NNS-tridentate ligands are reported. Reactions of 2-acetylpyridine N-substituted thiosemicarbazone (HL1-3) with [CoCl2(PPh3)(2)] resulted [Co(L1-3)(2)]Cl (1-3) which were characterized by elemental analysis and various spectral studies. The molecular structure of the complex 1 has been determined by single crystal X-ray diffraction studies. In vitro DNA binding studies of complexes 1-3 carried out by fluorescence studies and the results revealed the binding of complexes to DNA via intercalation. The binding constant (K-b) values of complexes 1-3 from fluorescence experiments showed that the complex 3 has greater binding propensity for DNA. The DNA cleavage activity of the complexes 1 and 3 were ascertained by gel electrophoresis assay which revealed that the complexes are good DNA cleavage agents. Further, the interactions of the complexes with bovine serum albumin (BSA) were also investigated using fluorescence spectroscopic method, which showed that the complexes 1-3 could bind strongly with BSA. The antioxidant property of the complexes was evaluated to test their free-radical scavenging ability. Furthermore, in vitro cytotoxicity of the complexes against MCF-7 and A431 cell lines was assayed which showed higher activity and efficiently vanished the cancer cells even at low concentrations. (C) 2013 Elsevier B.V. All rights reserved.

A supramolecular cyclodextrin (CyD) gel having selective monosaccharide recognition function was prepared by polymerization of γ-CyD containing a lipophilic phenylboronic acid azoprobe. The non-template gel exhibited galactose selectivity in adsorption, whereas the glucose-template gel exhibited glucose selectivity. © 2014 The Chemical Society of Japan.

1,2-Naphthaquinone reacts with amines such as semicarbazide, isonicotinylhydrazide and thiosemicarbazide in high yield procedure with the formation of tridentate ligands HLn (n = 1-3). By reaction of ruthenium(II) starting complexes and quinone based ligands HLn (n = 1-3), a series of ruthenium complexes were synthesized and characterized by elemental and spectroscopic methods (FT-IR, electronic, H-1, C-13, P-31 NMR and ESI-MS). The ligands were coordinated to ruthenium through quinone oxygen, imine nitrogen and enolate oxygen/thiolato sulfur. On the basis of spectral studies an octahedral geometry may be assigned for all the complexes. Further, the catalytic oxidation of primary, secondary alcohol and transfer hydrogenation of ketone was carried out. The DNA cleavage efficiency of new complexes has also been tested. (C) 2012 Elsevier B.V. All rights reserved.

A new sugar recognition system using a combination of two methodologies (electrochemistry and self-assembly) and two materials (ruthenium complex and dendrimer) was constructed and evaluated. This system was shown to provide an efficient sugar recognition function.

水中でドーパミンに対し選択的に応答するプローブを開発することを目的として，クラウンエーテル及びボロン酸基を持つアゾプローブ1 {2-[3,4-(18-crown-6)phenylazo]-5-hydroxy-phenylboronic acid}を設計した．1は水に溶け，pHの増加に伴い黄色→赤色→橙色へと色変化した．また，ドーパミン及び類似化合物添加時の紫外─可視吸収スペクトルより，プローブとゲスト分子が1 : 1型の複合体を形成すると仮定して結合定数の算出を行ったところ，結合定数はドーパミンで最も高い値（1.11±0.021）×10<SUP>2</SUP> M<SUP>-1</SUP>が得られ，pH 8でドーパミンを添加すると赤色から橙色へ色変化した．この変化はフェノール水酸基のプロトン解離によるものであると示唆された．種々のゲスト分子との応答挙動から，本プローブは1,2-シスジオール部位を持つゲスト分子に大きく影響を受けることを明らかにした．

A boronic acid fluorophore (C1-APB)/boronic acid-modified gamma-cyclodextrin (3-PB-gamma-CyD) complex as a supramolecular sensor has been designed for selective glucose recognition in water. The fluorescent response behavior of the C1-APB/3-PB-gamma-CyD complex under various pH conditions revealed that a C1-APB/3-PB-gamma-CyD complex solution containing glucose showed a large increase in the fluorescence intensity under alkaline pH conditions. In contrast, only small increases in the fluorescence intensity were noted for fructose and without sugar solutions. The observed response selectivity for the C1-APB/3-PB-gamma-CyD complex was on the order of glucose >> galactose, mannose > fructose. The evidence on a large value of the inclusion constant (K-L.CyD = 6.5 x 10(3) M-1), a marked broadening of the H-1 NMR spectra, and an enhancement of induced circular dichloism (ICD) intensity for the C1-APB/3-PB-gamma-CyD complex by glucose binding supported the multi-point interaction of the C1-APB/3-PB-gamma-CyD complex with glucose. These results demonstrated that the C1-APB/3-PB-gamma-CyD complex functioned as an efficient supramolecular sensor for selective glucose recognition in water.

A series of novel binuclear Pd(II) complexes of the type [(PPh3)(2)ClPd(L)PdCI] [where L = dianionic bridged ligands derived from 2-oxo-1,2-dihydroquinoline-3-carbaldehyde or its derivatives with o-aminophenol/o-aminothiophenol] have been reported. The new complexes have been characterized by elemental analysis, FT-IR, UV-Vis and NMR (H-1 and P-31) spectroscopic techniques. The coordination mode of the ligands and the geometry of the complexes were confirmed by single crystal X-ray crystallography of one of the complexes. The catalytic efficiency of one of the binuclear Pd(II) complexes was tested for N-arylation of imidazole. (C) 2011 Elsevier Ltd. All rights reserved.

Four new Ni(II) complexes of the general formula [Ni(PPh(3))(L)](L = dibasic tridentate ligand derived from 4-diethylamino-salicylaldehyde and thiosemicarbazide or 4-N-substituted thiosemicarbazide) have been reported. The new complexes have been synthesized and characterized by analytical and spectroscopic (IR, electronic, (1)H NMR and (31)P NMR) techniques. Molecular structure of one of the complexes has been determined by X-ray crystallography. The complex. [Ni(PPh(3))(L4)] (H(2)L4 = thiosemicarbazone prepared from 4-diethylamino-salicylaldehyde and 4-phenylthiosemicarbazide) crystallized in monoclinic space group with two molecules per unit cell and has the dimensions of a = 13.232(6) angstrom, b= 10.181(5) angstrom, c = 13.574(7) angstrom, alpha = 90 degrees, beta = 98.483(2)degrees and gamma =90 degrees. Catalytic activity of the complexes has been explored for aryl-aryl coupling reaction. (C) 2011 Elsevier B.V. All rights reserved.

A novel cyclic dinuclear acetylacetonato ruthenium complex doubly bridged with sulfur and/or disulfur at the gamma-position of acetylacetonato ligand has been obtained by two different synthetic methods. The molecular structure of the dinuclear complex has been determined by single crystal X-ray diffraction study. Other two cyclic dinuclear beta-diketonato ruthenium complexes were also prepared in good yields by the reaction of single bridged dinuclear complexes as starting materials with disulfur dichloride. The cyclic voltammograms of all the dinuclear complexes exhibit two one-electron reduction and oxidation waves in acetonitrile (AN) and dichloromethane (DM). The comproportionation constants (K(c)) for mixed-valence state of both Ru(II)/Ru(III) and Ru(III)/Ru(IV) were evaluated in both solvents at 25 or -30 degrees C. The values of both K(c) (Ru(II)/Ru(III)) and log(10)K(c) (Ru(III)/Ru(IV)) for double bridged complex are large compared to those of corresponding single bridged complexes. This fact was rationally explained by the double bridging effect caused by the spread of electronic communication and also demonstrated the usefulness of the double bridged dinuclear complexes. (C) 2011 Elsevier B. V. All rights reserved.

The molecular structures of [CpCo(tdt)] and [CpCo(Cl(3)bdt)] were determined by X-ray diffraction studies. [CpCo(tdt)] was monomeric in the crystal, coordinatively unsaturated with 16-electrons and had a two-legged piano-stool geometry. [CpCo(Cl(3)bdt)] was dimeric, coordinatively saturated with 18-electrons and became a three-legged piano-stool geometry. There were two crystallographically independent molecules in [CpCo(tdt)] and both molecules were associated with intermolecular Cp center dot center dot center dot Cp face-to-face interaction. Some intermolecular Co center dot center dot center dot S interactions were also observed between the crystallographically identical molecules of [CpCo(tdt)]. The cyclic voltammograms of [CpCo(tdt)] and [CpCo(Cl(2)bdt)] exhibited single oxidation waves, but those of [CpCo(Cl(3)bdt)] and [CpCo(Cl(4)bdt)] showed two oxidation waves due to both the monomer and dimer in the solutions. Electrochemical oxidations of these monomers occurred dimerizations by EC reactions in the solutions, and the oxidized dimers could be rereduced to form the original monomers by EC reactions. Spectroelectrochemical data using OTTLE supported the reversible ECEC reactions. Abbreviations of dithiolene ligands are as follows: tdt = toluene-3,4-dithiolate, Cl(2)bdt = 3,6-dichlorobenzene-1,2-dithiolate, Cl(3)bdt = 3,4,6-trichlorobenzene-1,2-dithiolate, and Cl(4)bdt = tetrachlorobenzene-1,2-dithiolate. (c) 2010 Elsevier B. V. All rights reserved.

Novel photosignal transduction systems of benzo-15-crown-5 (B15C5) azoprobe/gamma-cyclodextrin (gamma-CyD) complexes were designed. Four B15C5 azoprobes were synthesized by azo coupling of 4'-aminobenzo-15-crown-5 with phenol (for 15C5-Az-Ph) and N,N-dialkylanilines (for 15C5-Az-Cn). These azoprobes exhibited strong induced circular dichroism (ICD) by forming an inclusion complex with gamma-CyD. Examination of the spectral responses and (1)H NMR analysis of the B15C5 azoprobe/gamma-CyD complexes in the presence of alkali metal cations revealed that K(+) binding selectively induced dimer formation of the B15C5 azoprobes inside the gamma-CyD cavity, which resulted in distinct changes in their UV-vis and ICD spectra in water. The effect of alkyl chain length of 15C5-Az-Cn (n=. 1, 2, 4)/gamma-CyD complexes was examined in 90% H(2)O/10% CH(3)CN (v/v). The highest K(+) ion response was noted for the 15C5-Az-C2/gamma-CyD complex. The 15C5-Az-C4/gamma-CyD complex was found to show abnormally high ICD responses for TMA(+) and Cs(+).

An inclusion complex consisting of a fluorescent phenylboronic acid (C1-APB) and beta-cyclodextrin (beta-CD) acts as a supramolecular saccharide sensor whose response mechanism is based on photoinduced electron transfer (PET). This study evaluated four kinds of cyclodextrins (alpha-CD, beta-CD, gamma-CD, and NH2-beta-CD) by comparing their pH profiles, and confirmed that beta-CD as the best host for C1-APB because the C1-APB/beta-CD complex exhibited high affinity for saccharides as well as high fluorescent recovery upon saccharide binding. An investigation of the beta-CD concentration effect revealed the formation of a 1: 1 inclusion complex of C1-APB with beta-CD. The observed saccharide selectivity of the C1-APB/beta-CD complex is in the following order: D-fructose (4039 +/- 69 M-1) > D-ribose (1083 +/- 26 M-1) > L-arabinose (474 +/- 11 M-1) > D-galactose (318 +/- 3 M-1) > maltotoriose (135 +/- 5 M-1) > D-glucose (114 +/- 2 M-1) > maltose (81 +/- 2 M-1). In addition to monomer emission, dimer emission from pyrene dimers was observed in the spectra for the C1-APB/gamma-CD complex, which allowed a ratiometric analysis. This study shows that the combination of a simple fluorescent probe, C1-APB, with various CDs diversifies the response systems for saccharide recognition.

超分子形成によるイオン認識, 分子認識では, 有機分子をプローブ分子として用いていることが多い。一方, 金属イオンと有機化合物による錯形成反応は, ホスト・ゲスト化学においても重要な役割を担っている。そこで本稿では, いわゆるウェルナー型の金属錯体を用いた, 「錯体による分子認識」に着目した。すなわち, 「ホスト (=センサーあるいはプローブ分子) が錯体 (金属-配位子結合をもつ化合物) であり, それを用いて各種のゲスト分子に特異的な応答挙動をすること」となる。以上を基に, 「金属錯体を用いた分子認識」に関する研究を対象として, 筆者らの興味を引いた研究を中心に1) イオン (陽イオン, 陰イオン) 認識2) 生体関連物質の認識3) 高分子錯体による認識について, 最近の報告を紹介した。

New thiosemicarbazone nickel(II) complex, derived from salicylaldehyde-N-phenylthiosemicarbazone, was synthesized and characterized by means of IR, electronic, and mass spectral techniques. Its two different types of crystal structures were also characterized by single crystal X-ray diffraction technique and reported here. In type A, the complex crystallizes in the monoclinic space group P2(1)/c with four molecules per cell and has the dimensions of a = 9.2066(7), b = 19.1090(13), c = 18.589(2) angstrom, beta = 92.87 (1)degrees. In type B, the complex crystallizes in the triclinic space group P (1) over bar with two molecules per cell and has the dimensions of a = 10.406(4), b = 10.876(4), c = 14.614(5) angstrom, alpha = 64.81(1), beta = 74,07(2), gamma = 70.85(2)degrees. (c) 2005 Elsevier B.V. All rights reserved.

Binuclear beta-diketonatoruthenium(III) complexes [{Ru(acac)(2)}(2)(tae)], [{Ru(phpa)(2)}(2)(tae)], and [(acac)(2)Ru(tae)Ru(phpa)(2)] and binuclear and mononuclear bipyridine complexes [{Ru(bpy)(2)}(2)(tae)](PF6)(2) and [Ru(bpy)(2)(Htae)]PF6 (acac = 2,4-pentanedionate ion, phpa = 2,2,6,6-tetramethyl-3,5-heptanedionate ion, tae = 1,1,2,2-tetraacetylethanate dianion, and bpy = 2,2'-bipyridine) were synthesized. The new complexes have been characterized by H-1 NMR, MS, and electronic spectral data. Crystal and molecular structures of [{Ru(acac)(2)}(2)(tae)] have been solved by single-crystal X-ray diffraction studies. Crystal data for the meso isomer of [{Ru(acac)(2)}(2)(tae)] have been confirmed by the dihedral angle result that two acetylacetone units of the bridging tae ligand are almost perpendicular to one another. A detailed investigation on the electrochemistry of the binuclear complexes has been carried out. The electrochemical behavior details of the binuclear complexes have been compared with those of the mononuclear complexes obtained from the half-structures of the corresponding binuclear complexes. Studies on the effects of solvents on the mixed-valence states of Ru-II-Ru-III and Ru-III-Ru-IV complexes have been carried out by various voltammetric and electrospectroscopic techniques. A correlation between the comproportionation constant (K-c) and the donor number of the solvent has been obtained. The K-c values for the binuclear complexes have been found to be low because of the fact that two acetylacetone units of the bridging tae ligand are not in the same plane, as revealed by the crystal structure of [{Ru(acaC)(2)}(2)(tae)].

The synthesis and characterization of a new cluster polymer with a sodium centered hexacopper(II) barrel portion, catena-[Nasubset ofCU(2){Cu(hpro)(2)}(4)(ClO4)(4)](ClO4).4H(2)O (hpro = 4-hydroxyL-prolinato) are described. The central sodium ion in the barrel portion is surrounded by eight carboxylate oxygen atoms from hpro ligands, which link the central metal to the copper atoms of four [Cu(hpro)(2)] units. These units are in turn connected to two further apical Cu-II centers. The central alkali ion is therefore octahedrally surrounded by six copper atoms. The hydroxyl oxygen atoms of two hpro groups are coordinated to the axial copper atoms of two neighboring barrel portions, so that a chain complex forms. Magnetic studies indicate weak ferromagnetic coupling between copper(II) ions within the complex leading to a high spin multiplicity in the ground state.