阿部 正明

This study reports an effective peripheral decoration of organic donor-acceptor diads with B(C6F5)3 for stabilizing electrogenerated radical ions. By employing a common p-type organic semiconductor benzothienobenzothiophene (BTBT) as the donor, tetracoordinate boron complexes showed improved solution electrochemiluminescence (ECL) intensity, reaching a 156-fold increase compared to that of the parent diad. The unprecedented Lewis-pairing-induced ECL enhancement is attributed to the multiple roles of B(C6F5)3: 1) redistributing frontier orbitals, 2) facilitating electrochemical excitation, and 3) restricting molecular motions. Furthermore, B(C6F5)3 converted the molecular arrangement of BTBT from conventional 2D herringbones into 1D π-stacks. This robust, highly ordered columnar nanostructure allowed red-shifting of the crystalline film ECL with electrochemical doping through the electronic coupling pathways of BTBT. Our approach will facilitate the development of elaborate metal-free ECL systems.

分子内部に４面体金属コアを有し、フォトルミネッセンスを示す銅 (I) ４核金属錯体 [Cu₄I₄(PPh₃)₄] の対称性の低い単斜晶多形結晶について高圧単結晶Ｘ線回折実験を行った。ダイヤモンドアンビルセル (DAC) 内の試料からのＸ線回折データのコンプリートネス向上のために、複数の結晶をアンビル中に設置した回折実験を試みた。4.4 GPa の圧力下での結晶構造解析を行った結果、分子中心のキュバン型 Cu₄I₄ クラスター骨格の変形と Cu···Cu 距離の短縮を見出した。

Mixed-valence ruthenium trinuclear clusters containing dichloroacetates were synthesized, and the self-assembly of a single molecular adlayer composed of these clusters on a graphite surface was investigated by atomic force microscopy (AFM). AFM clearly revealed the dynamics of two-dimensional (2D) structure formation as well as the molecular characteristics of the adlayers at different electrochemical interfaces. The results verified that the design of metal complexes is important not only for redox chemistry but also for molecular assembly and nanoarchitecture construction.

The use of earth-abundant and inexpensive Co catalysts for carbon-hydrogen (CH) bond activation has received increasing attention because of the advantages including air stability. Although directing groups have been effectively introduced in substrates to promote C(sp3)H activation through chelation assistance, there is a lack of basic information about the isolated alkyl-Co complexes containing directing groups as polydentate ligands. In this study, we report the synthesis and characterization of an alkyl-Co(III) complex 2Co, prepared from a N,N -bis(8-quinolyl)malonamide derivative, the malonyl fragment of which was disubstituted by two ethyl groups. 2Co was straightforwardly obtained from a Co(II) salt without any use of chemical oxidants but in the presence of air, through selective -C(sp3)H activation. The combined NMR spectroscopic and X-ray crystal structural analyses revealed that the malonamide substrate was converted into a pentadentate ligand with an N4C set, acquiring a helical configuration around the Co(III) center. The non-innocent ligand properties of 2Co were unambiguously confirmed by UVvis spectroscopic, electrochemical, and DFT studies. Thermolysis of 2Co enabled C(sp3)N reductive elimination in the absence of chemical oxidants. The present study provides important insights into the reactivity of alkyl- Co(III) complexes with a defined coordination geometry around the Co center toward designing elaborate C(sp3)H functionalization systems.

Two hexanuclear paddlewheel-like clusters appending six carboxylic-acid pendants have been isolated with the inclusion of polar solvent guests: [Cu6(Hmna)6]·7DMF (1·7DMF) and [Ag6(Hmna)6]·8DMSO (2·8DMSO), where H2mna = 2-mercaptonicotininc acid, DMF = N,N’-dimethylformamide, and DMSO = dimethyl sulfoxide. The solvated clusters, together with their fully desolvated forms 1 and 2, have been characterized by FTIR, UV–Vis diffuse reflectance spectroscopy, TG-DTA analysis, and DFT calculations. Crystal structures of two solvated clusters 1·7DMF and 2·8DMSO have been unambiguously determined by single-crystal X-ray diffraction analysis. Six carboxylic groups appended on the clusters trap solvent guests, DMF or DMSO, through H-bonds. As a result, alternately stacked lamellar architectures comprising of a paddlewheel cluster layer and H-bonded solvent layer are formed. Upon UV illumination (λex = 365 nm), the solvated hexasilver(I) cluster 2·8DMSO gives intense greenish-yellow photoluminescence in the solid state (λPL = 545 nm, ΦPL = 0.17 at 298 K), whereas the solvated hexacopper(I) cluster 1·7DMF displays PL in the near-IR region (λPL = 765 nm, ΦPL = 0.38 at 298 K). Upon complete desolvation, a substantial bleach in the PL intensity (ΦPL < 0.01) is observed. The desorption–sorption response was studied by the solid-state PL spectroscopy. Non-covalent interactions in the crystal including intermolecular H-bonds, CH⋯π interactions, and π⋯π stack were found to play decisive roles in the creation of the lamellar architectures, small-molecule trap-and-release behavior, and guest-induced luminescence enhancement.

In this study, we report the generation of new mixed-valence (MV) subspecies with charge-separated (CS) characters from an unsymmetrical acceptor-donor-donor (A D D) triad. The triad was synthesized by attaching a dimesitylboryl group (A) to a D D conjugate that consisted of triarylamine (NAr3) units. The MV radical cation, obtained by chemical oxidation of the triad, exhibited a strong intervalence charge transfer (IVCT) absorption derived from the bis(NAr3)(center dot+) moiety in the near-IR region. The charge-separated MV (CSMV) state, obtained by photoexcitation of the triad, caused a blue shift in IVCT energy in the femtosecond transient absorption spectra, reflecting a bias of positive charge distributions to the D end site. This resulted from increased electron density at the A site and restructuring of the central D site from NAr3 to NAr2 sites. Interestingly, any shift in the IVCT energy that was caused by the polarity of the solvent was minimal, reflecting the unique characteristics of the CSMV state. These findings represent the first detailed analysis of the CSMV state, including a comparison with conventional MV states. Therefore, this work provides new insights into counterion-free MV systems and their applications in molecular devices.

© 2019 The Royal Society of Chemistry. Benzothienobenzothiophene (BTBT) and derivatives have received increasing attention as organic field-effect transistor materials and molecular conductors. This report presents the first synthesis of metal complexes involving a BTBT moiety, which was achieved by complexation of 2,2′-bipyridyl complexes of Pt(ii) and Pd(ii) with dihydroxy-substituted BTBT (1) as a new π-extended catecholato ligand (tBu2Bpy = 4,4′-di-tert-butyl-2,2′-dipyridyl). The resulting complexes M(tBu2Bpy)(O2BTBT) (M = Pt (3Pt) and Pd (3Pd)) were characterized by UV-vis spectroscopy, density functional theory (DFT) calculations, and cyclic voltammetry. The electron donating ability of BTBT was substantially enhanced upon including two oxygen substituents followed by metal coordination. This enabled chemical oxidation of 3Pt and 3Pd with a mild chemical oxidant (ferrocenium hexafluorophosphate) and formation of the one-electron-oxidized state. While 3Pt and 3Pd exhibited an absorption band originating from a catecholate → Bpy ligand-to-ligand charge transfer transition typical of this class of catecholato complexes, the radical cations exhibited a unique π-π∗ intramolecular charge transfer (ICT) transition absorption in which the π and π∗ orbitals were the newly incorporated benzothienothiophene-based donor and semiquinonato-based acceptor, respectively. The BTBT+ skeleton was electronically divided into two sites by the present chemical modification. The ICT properties of the complexes were found to be modulated by varying the metal ions. These findings offer a new approach to molecular design for (semi)conducting materials using optical properties.

In this study, we report synthesis of a new series of mixed-valence (MV) complexes having intervalence charge transfer (IVCT) energies variable from the first to the third telecommunication window. This wide-range modulation was achieved by variation of covalently-dimerized catecholato ligands, in combination with Pd(II) ions, which lowered the oxidation potentials and enabled access to MV states. Importantly, we found that regulation of the conjugation lengths enabled energy gap control and annulation of an additional benzene ring switched the nature of the IVCT transitions. These changes were accompanied by a cross-over from moderately delocalized Class II to delocalized Class III character according to the Robin-Day classification. Through accurate comparisons with well-known ferrocene counterparts and their heteroconjugate, our non-innocent ligand-based approach is found to be effective for controlling IVCT parameters. These findings offer a new approach to materials design for electro-optic switching.

We demonstrate herein a novel molecular strategy for crystalline-state luminescence color tuning in the entire visible region by adopting thermochromic dual phosphorescence of coordination complexes. As crystals, a new cubane-type tetranuclear copper(I)-idodido complex with 2-benzylpyridine N-donor ligands 1 shows a sequential phosphorescence color change from yellow (298 K) to red and finally to blue (78 K) in the crystalline state across the color space area, in which relative intensity ratio of the triplet cluster-centered ((CC)-C-3) and triplet charge transfer ((CT)-C-3) bands in the dual-emission is reversibly controlled with temperature.

The distinct piezochromic luminescent responses of charge-transfer inclusion crystals, which consist of small aromatic guest molecules with naphthalenediimide derivatives, are reported. Reversible multichromism is observed over the entire visible region in response to high pressure, whereas a weak response to mechanical grinding is evident. High-pressure single-crystal X-ray diffraction analysis and TD-DFT calculations clearly suggest that high compression induces a closer arrangement with a short interfacial distance between small aromatic guest molecules and naphthalenediimide derivatives, which is proposed as the origin of the drastic luminescent color change.

A phosphorus(v) complex of porphycene [P(OEPc)(OMe)2]PF6 (OEPc = 2,3,6,7,12,13,16,17-octaethylporphycenato dianion) has been synthesized and structurally characterized as the first porphycene derivative incorporating nonmetal elements in the macrocyclic cavity. An extremely low energy level of the LUMO is observed, which is rationalized by the low-lying π* orbital of the porphycene ring coupled with the insertion of the highly-inductive pentavalent phosphorus centre. The compound is luminescent in bright red with a quantum yield of 22.7% in CH2Cl2 at 298 K.

Among the coenzyme B-12-dependent enzymes, methylmalonyl-CoA mutase (MMCM) catalyzes the carbon-skeleton rearrangement reaction between R-methylmalonyl-CoA and succinyl-CoA. Diethyl 2-bromomethyl-2-phenylmalonate, an alkyl bromide substrate having two different migrating groups (phenyl and carboxylic ester groups) on the beta-carbon, was applied to the electrolysis mediated by a hydrophobic vitamin B-12 model complex, heptamethyl cobyrinate perchlorate in this study. The electrolysis of the substrate at -1.0 V vs. Ag-AgCl by light irradiation afforded the simple reduced product (diethyl 2-methyl-2-phenylmalonate) and the phenyl migrated product (diethyl 2-benzyl-2-phenylmalonate), as well as the electrolysis of the substrate at -1.5 V vs. Ag-AgCl in the dark. The electrolysis of the substrate at -2.0 V vs. Ag-AgCl afforded the carboxylic ester migrated product (diethyl phenylsuccinate) as the major product. The selectivity for the migrating group was successfully tuned by controlling the electrolysis potential. We clarified that the cathodic chemistry of the Co(III) alkylated heptamethyl cobyrinate is critical for the selectivity of the migrating group through mechanistic investigations and comparisons to the simple vitamin B-12 model complex, an imine/oxime-type cobalt complex.

Metal-coordinated por-phyrin and related compounds are important for developing, molecular architectures that mimic enzymes. Porphycene, a structural isomer of porphyrin, has shown unique properties in semiartificial myoglobin. To explore its potential as a molecular building block, we studied the molecular assembly of nickel(II) tetra(n-propyl)porphycene (NiTPrPc), a metalloporphycene with introduced tetra n-propyl moieties, on the Au(111) electrode surface using in situ scanning tunneling microscopy. Because of the low molecular symmetry of NiTPrPc, the molecular assembly undergoes unique phase transitions due to conformational change of the n-propyl moieties. The phase transitions can be precisely controlled by the electrode potential, demonstrating that the latter can play an important role in the porphycene molecular assembly on Au surface. This new discovery indicates possible uses of this porphycene framework in molecular engineering.

Two new porphycenes functionalized with ferrocenyl pendants have been synthesized and characterized spectroscopically and structurally. The porphycene-based emission in porphycene-ferrocene dyads was switched on and off by the reversible control of the ferrocenyl pendant redox states. Transient absorption spectroscopy with a femtosecond laser-pulsed technique has successfully detected the picosecond charge-separated excited state of the dyad upon Q-band excitation of the porphycene ring.

Oxidative electropolymeization of an axially bound, bithiophene-pyridine complex of ruthenium(III)-porphycene [Ru(TPrPc) (btp)2]PF6 (1) gives a submicrometer-thick, polymeric film on an ITO electrode with a crystalline morphology. The polymeric film, the first example of axially linked multimetalloporphycene coordination arrays, exhibits highly stable and reproducible electrochromic response with high electrochromic efficiency upon electrochemical control over the metal-centered electron transfer process (Ru(II)/Ru(III)).

© 2015 Elsevier B.V. All rights reserved. Preparation, characterization, and properties of a cyano bridged complex containing the Ru<inf>3</inf>(μ<inf>3</inf>-O) cores, [{Ru<inf>3</inf>(μ<inf>3</inf>-O) (μ-CH<inf>3</inf>COO)<inf>6</inf>(py)<inf>2</inf>}<inf>2</inf>(μ-CN)](PF<inf>6</inf>) ([1]PF<inf>6</inf>) (py = pyridine), are reported and compared with the properties of [{Ru<inf>3</inf>(μ<inf>3</inf>-O)(μ-CH<inf>3</inf>COO)<inf>6</inf>(py)<inf>2</inf>}(μ-CN){Ru<inf>3</inf>(μ<inf>3</inf>-O)(μ-CH<inf>3</inf>COO)<inf>6</inf>(py)(CO)}] (2). The cyclic voltammogram of [1]<sup>+</sup> in 0.1 M (n-Bu)<inf>4</inf>NPF<inf>6</inf>-CH<inf>2</inf>Cl<inf>2</inf> solution with an Ag/AgCl reference electrode showed a series of redox waves assigned to the processes Ru<inf>3</inf><sup>II,II,III</sup>/Ru<inf>3</inf><sup>II,III,III</sup> (-1.70 V, -1.52 V), Ru<inf>3</inf><sup>II,III,III</sup>/Ru<inf>3</inf><sup>III,III,III</sup> (-0.37 V, -0.19 V), Ru<inf>3</inf><sup>III,III,III</sup>/Ru<inf>3</inf><sup>III,III,IV</sup> (+1.08 V), and Ru<inf>3</inf><sup>III,III,IV</sup>/Ru<inf>3</inf><sup>III,IV,IV</sup> (+2.03 V). Upon bridge formation the redox waves of the C-bonded Ru<inf>3</inf> moiety of [1]<sup>+</sup> stay at the similar potential region to those of Ru<inf>3</inf>(μ<inf>3</inf>-O)(μ-CH<inf>3</inf>COO)<inf>6</inf>(py)<inf>2</inf>(CN) (3) with a unidentate CN<sup>-</sup>, so that the enhancement of the π-back donation does not operate, indicating that the Ru<inf>3</inf>O core is not a good π-donor. Complex 2 showed five redox waves for the processes Ru<inf>3</inf><sup>II,II,III</sup>/Ru<inf>3</inf><sup>II,III,III</sup> (-1.15 V), Ru<inf>3</inf><sup>II,III,III</sup>/Ru<inf>3</inf><sup>III,III,III</sup> (-0.21 V, +0.55 V), and Ru<inf>3</inf><sup>III,III,III</sup>/Ru<inf>3</inf><sup>III,III,IV</sup> (+1.05 V, +1.35 V). The redox potential (-1.15 V) of the Ru<inf>3</inf><sup>II,II,III</sup>/Ru<inf>3</inf><sup>II,III,III</sup> process of the Ru<inf>3</inf>(py) (CO) unit in 2 showed a negative shift in comparison to that (-0.84 V) of [Ru<inf>3</inf><sup>II,III,III</sup>(μ<inf>3</inf>-O) (μ-CH<inf>3</inf>COO)<inf>6</inf>(py)<inf>2</inf>(CO)]. The infrared spectroelectrochemistry of [1]<sup>+</sup> and 2 in 0.1 M n-Bu<inf>4</inf>NPF<inf>6</inf>-CH<inf>2</inf>Cl<inf>2</inf> solutions revealed that the frequencies of the stretching vibration ν(CN) of the cyanide increased with the increase in the isovalent oxidation states of [1]<sup>+</sup> but those in the Ru<inf>3</inf>O-based mixed-valence states, Ru<inf>3</inf><sup>II,III,III</sup>-Ru<inf>3</inf><sup>III,III,III</sup>, and Ru<inf>3</inf><sup>III,III,III</sup>-Ru<inf>3</inf><sup>III,III,IV</sup>, were significantly smaller, which was possibly due to the effective electronic coupling through the CN<sup>-</sup> bridge between the two Ru<inf>3</inf> units with different oxidation states. In contrast, such coupling was not observed for 2 that has two Ru<inf>3</inf> units with significantly different ligand environment.

© 2015 Elsevier Ltd. All rights reserved. Crystal structures and solid-state emission properties of tetraalkyl 4,4′-dimethyl-2,2′-bipyrrole-3,3′,5,5′-tetracarboxylates (alkyl = methyl, ethyl, and isopropyl) have been investigated. Single crystal X-ray diffraction studies revealed that all bipyrroles are co-planar due to an intramolecular hydrogen bonding. The isopropyl derivative exhibited a C=O·π interaction in the solid-state and showed the longest emission wavelength because of increase in structural flexibility.

Two ruthenium(II) carbonyl complexes of porphycene, (carbonyl)(pyridine)(2,7,12,17-tetra-n-propylporphycenato) ruthenium(II) (1) and (carbonyl)(pyridine)(2,3,6,7,12,13,16,17-octaethylpor-phycenato) ruthenium(II) (2), have been structurally characterized by single-crystal X-ray diffraction analysis. Cyclic voltammetry has revealed that the porphycene complexes undergo multiple oxidations and reductions in dichloromethane and the reduction potentials are highly positive compared to porphyrin analogs. UV-light irradiation (400 nm or shorter wavelength region) of a benzene solution of 1 and 2 containing external pyridine leads to dissociation of the carbonyl ligand from the ruthenium(II) centers to give the corresponding bis-pyridine complexes. The identical reaction has been also studied for a porphyrin derivative (carbonyl)(pyridine)(2,3,7,8,12,13,17,18-octaethylporphyriato) ruthenum(II) (3). The first-order kinetic analysis has revealed that the photosubstitution of all of the compounds occurs in the order of 10(-3) s(-1) at 298 K but proceeds faster for complexes of porphycene (1 and 2) than that of porphyrin (3).

A series of multiply meso-substituted porphycenes has been prepared by acetoxylation of 2,7,12,17-tetra-n-propylporphycene (H2TPrPc), and the molecular structure of 9,10-diacetoxy-2,7,12,17-tetra-n-propylporphycene (2a) determined by single-crystal X-ray diffraction analysis. The H-1 NMR and optical properties have also been investigated. (C) 2014 Elsevier Ltd. All rights reserved.

A new heterometallic diruthenium(III) magnesium(II) complex functionalized with four pyrenecarboxylate fluorophores 1 has been synthesized and structurally characterized. Fluorescence from the pyrene moieties in 1 was nearly completely quenched in CH2Cl2 (>98%), but turn-on fluorescence was successfully observed after regioselective substitution of the carboxylates bridging the heterometallic Ru(III)center dot center dot center dot Mg(II) sites.

A new cyano-bridged dimeric oxo-centered triruthenium complex [{Ru-3(mu(3)-O)(mu-CH3COO)(6)(py)(2)}(mu-CN){Ru-3(mu(3)-O)(mu-CH3COO)(6)(py)(Lpy-ss)}](+) (py = pyridine, Lpy-ss = (C5H4N-CH2NHC(O)(CH2)(4)CH(CH2)(2)SS) ([1](+)) has been prepared, characterized, and confined on an Au(111) surface to form self-assembled monolayers (SAMs) (1/Au). The redox and IR spectroscopic properties observed for the discrete ions are essentially preserved in its SAMs. The molecules of SAMs 1/Au stand up with the cyano groups tilted to the gold surface. The electronic structures of 1/Au in different oxidation states have been studied by in situ infrared spectroscopy monitoring the stretching modes of the cyano group. The extent of cyano-mediated electronic communications between two triruthenium units in the SAMs has been successfully tuned by simply changing the electrolyte solutions from 0.1 M n-Bu4NPF6-CH2Cl2 to aqueous 0.1 M HClO4. (C) 2013 Elsevier B.V. All rights reserved.

A post-synthetic method has been developed to synthesize novel asymmetric porphycenes bearing two different substituents on the meso-positions. Nitration of 9-acetoxy-2,7,12,17-tetra-n-propylporphycene with AgNO3 in CH3COOH/CH2Cl2 occurs regioselectively at the 19-position of the macrocycle to give 9-acetoxy-19-nitro-2,7,12,17-tetra-n-propylporphycene (3a) which was readily converted to 9-acetoxy-19-amino-2,7,12,17-tetra-n-propylporphycene (4a) by the reduction with SnCl2 in pyridine. (C) 2013 Elsevier Ltd. All rights reserved.

A new mu-oxo-bis(mu-acetato)diruthenium(III) complex bearing two pyridyl disulfide ligands {[Ru-2(mu-O)(mu-OAc)(2)(bpy)(2)(L-py center dot SS)(2)](PF6)(2) (OAc = CH3CO2-, bpy = 2,2'-bipyridine, L-py center dot SS = (C5H4N)CH2NHC(O)(CH2)(4)CH(CH2)(2)SS) (1)} has been synthesized to prepare self-assembled monolayers (SAMs) on the Au(111) electrode surface. The SAMs have been characterized by contact-angle measurements, reflection absorption surface infrared spectroscopy, cyclic voltammetry, and reductive desorption experiments. The SAMs exhibited proton-coupled electron transfer (PCET) reactions when the electrochemistry was studied in aqueous electrolyte solution (0.1 M NaClO4 with Britton Robinson buffer to adjust the solution pH). The potential-pH plot (Pourbaix diagram) in the pH range from 1 to 12 has established that the dinuc.lear ruthenium moiety was involved in the interfacial PCET processes with four distinct redox states: (RuRuIII)-Ru-III(mu-O), (RuRuIII)-Ru-II(mu-OH), (RuRuII)-Ru-II(mu-OH), and (RuRuII)-Ru-II(mu-OH2). We also demonstrated that the interfacial redox processes were modulated by the addition of Lewis acids such as BF3 or Al3+ to the electrolyte media, in which the externally added Lewis acids interacted with mu-O of the dinuclear moiety within the SAMs.

Novel oxo-centered, acetate-bridged trinuclear ruthenium clusters functionalized with two pyridine ligands with thienyl substituents, [Ru3O(CH3COO)(6)(CO)(L1)(2)] (1) and [Ru3O(CH3COO)(6)(CO)(L2)(2)] (2), where L1 = 4-(2-thienyl)pyridine and L2 = 4-(2,2'-bithienyl)pyridine, have been synthesized and characterized. The molecular structure of 2 has been determined by single-crystal X-ray diffraction. One-electron oxidation of 2 with silver(I) cation has led to the isolation of a CO-dissociated product, [Ru3O(CH3COO)(6)(H2O)(L2)(2)]PF6 (3 center dot PF (6) ), and subsequent reaction with 4-dimethylaminopyridine (dmap) gave [Ru3O(CH3COO)(6)(dmap)(L2)(2)]PF6 (4 center dot PF (6) ). Linear metallopolymers containing the {Ru3O(CH3COO)(6)} groups have been deposited onto indium-tin oxide surface via oxidative electropolymerization of 2, 3 center dot PF (6) , and 4 center dot PF (6) . These metallopolymer thin films exhibit three-color electrochromism in the UV/Vis and near-IR region associated with the Ru-3 (II,III,III), Ru-3 (III,III,III), and Ru-3 (III,III,IV) oxidation states.