Mio Kondo - Academia.edu (original) (raw)
Papers by Mio Kondo
Angewandte Chemie, 2006
For decades, much attention has focused on crystallization from a mixture of electron-donor (D) a... more For decades, much attention has focused on crystallization from a mixture of electron-donor (D) and -acceptor (A) molecules, forming D-and/or A-stacked column structures that exhibit unique physical properties such as ferromagnetism, [1] strong absorption of Vis/NIR light, [2] and high electronic conductivity. [3] The tendency toward DA stacking in the crystal indicates that D-A conjugated molecules can form network structures which may manifest interesting physical properties. We are interested in the chemistry of a new class of D-A conjugated systems, namely, ferrocenylethynylanthraquinones (FcAq), from two viewpoints: protonation-induced intramolecular electron transfer resulting in valence tautomers, [4] and the construction of D-A stacked nanoporous network structures, which have attracted much recent attention because of great potential for applications such as selective gas adsorption, heterogeneous catalysts, and molecular recognition. In the present study, we found that the new T-shaped FcAq compound 1,4-bis(ferrocenylethynyl)anthraquinone (1,4-Fc 2 Aq (1); a) in the presence of guest solvent molecules forms single crystals, which show instant and reversible crystal-to-crystal transformation on heating or treatment with guest vapors. Recently, several reversible crystal-to-crystal transformations have been reported, among which examples accompanying a significant conformational change are few. The present study demonstrates an instant and reversible trans-
Dalton Trans., 2015
Four novel phosphine-substituted ruthenium(ii) polypyridine complexes with nitrogen oxides-trans(... more Four novel phosphine-substituted ruthenium(ii) polypyridine complexes with nitrogen oxides-trans(P,NO2)-[Ru(trpy)(Pqn)(NO2)]PF6 (trans-NO2), cis(P,NO2)-[Ru(trpy)(Pqn)(NO2)]PF6 (cis-NO2), [Ru(trpy)(dppbz)(NO2)]PF6 (PP-NO2), and cis(P,NO)-[Ru(trpy)(Pqn)(NO)](PF6)3 (cis-NO)-were synthesised (trpy = 2,2':6',2''-terpyridine, Pqn = 8-(diphenylphosphanyl)quinoline, and dppbz = 1,2-bis(diphenylphosphanyl)benzene). The influence of the number and position of the phosphine group(s) on the electronic structure of these complexes was investigated using single-crystal X-ray structural analysis, UV-vis absorption spectroscopy, and electrochemical measurements. The substitution lability of the nitrogen oxide ligand of each complex is discussed in comparison with that of the corresponding acetonitrile complexes.
Dalton Trans., 2015
The incorporation of active sites into metal-organic frameworks (MOFs) or porous coordination pol... more The incorporation of active sites into metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) is an attractive way to functionalise these materials. However, the methodology to organise substitution-inert metal-based secondary building units (SBUs) with active sites into MOFs or PCPs via coordination driven self-assembly is severely limited. In this study, we successfully assembled substitution-inert paddle-wheel Rh(II) dimers to afford three novel porous frameworks, Rh2(ppeb)4(THF)2 (1-THF), Rh2(ppeb)4(3-pentanone)2 (1-PN) and Rh2(ppeb)4(1-adamantylamine)2 (1-AD) (ppeb = 4-[(perfluorophenyl)ethynyl]benzoate), by using non-covalent interactions. Multipoint arene-perfluoroarene (Ar-Ar(F)) interactions, which allow the unidirectional face-to-face interaction mode of aromatic rings, were used to assemble the substitution-inert paddle-wheel Rh(II) dimers. The obtained frameworks were structurally characterisation by single crystal X-ray diffraction, and it is found that all structures exhibited a one-dimensional channel with active axial sites exposed to the pores. The porous properties of the obtained frameworks were also investigated by thermogravimetric analysis, gas adsorption and powder X-ray diffraction measurements. Moreover, the ligand substitution reaction at the active axial sites was examined at the crystalline state and the flexible structural transformation with the change of channel shapes and sizes was observed.
Angewandte Chemie (International ed. in English), Jan 26, 2015
Rational molecular design of catalytic systems capable of smooth OO bond formation is critical t... more Rational molecular design of catalytic systems capable of smooth OO bond formation is critical to the development of efficient catalysts for water oxidation. A new ruthenium complex was developed, which bears pendant SO3 (-) groups in the secondary coordination sphere: [Ru(terpy)(bpyms)(OH2 )] (terpy=2,2':6',2''-terpyridine, bpyms=2,2'-bipyridine-5,5'-bis(methanesulfonate)). Water oxidation driven by a Ce(4+) oxidant is distinctly accelerated upon introduction of the pendant SO3 (-) groups in comparisons to the parent catalyst, [Ru(terpy)(bpy)(OH2 )](2+) (bpy=2,2'-bipyridine). Spectroscopic, electrochemical, and crystallographic investigations concluded that the pendant SO3 (-) groups promote the formation of an OO bond via the secondary coordination sphere on the catalyst, whereas the influence of the pendant SO3 (-) groups on the electronic structure of the [Ru(terpy)(bpy)(OH2 )](2+) core is negligible. The results of this work indicate that modificat...
Angewandte Chemie (International ed. in English), Jan 20, 2014
A series of [{(terpy)(bpy)Ru}(μ-O){Ru(bpy)(terpy)}](n+) ([RuORu](n+), terpy=2,2';6',2'... more A series of [{(terpy)(bpy)Ru}(μ-O){Ru(bpy)(terpy)}](n+) ([RuORu](n+), terpy=2,2';6',2''-terpyridine, bpy=2,2'-bipyridine) was systematically synthesized and characterized in three distinct redox states (n=3, 4, and 5 for Ru(II,III)2, Ru(III,III)2, and Ru(III,IV)2, respectively). The crystal structures of [RuORu](n+) (n=3, 4, 5) in all three redox states were successfully determined. X-ray crystallography showed that the Ru-O distances and the Ru-O-Ru angles are mainly regulated by the oxidation states of the ruthenium centers. X-ray crystallography and ESR spectra clearly revealed the detailed electronic structures of two mixed-valence complexes, [Ru(III)ORu(IV)](5+) and [Ru(II)ORu(III)](3+), in which each unpaired electron is completely delocalized across the oxo-bridged dinuclear core. These findings allow us to understand the systematic changes in structure and electronic state that accompany the changes in the redox state.
Inorganic chemistry, Jan 21, 2014
A series of phosphine-substituted ruthenium polypyridine complexes, cis(P,Cl)-[Ru(trpy)(Pqn)Cl]PF... more A series of phosphine-substituted ruthenium polypyridine complexes, cis(P,Cl)-[Ru(trpy)(Pqn)Cl]PF6 (cis-Cl), trans(P,MeCN)-[Ru(trpy)(Pqn)(MeCN)](PF6)2 (trans-PN), cis(P,MeCN)-[Ru(trpy)(Pqn)(MeCN)](PF6)2 (cis-PN), and [Ru(trpy)(dppbz)(MeCN)](PF6)2 (PP), were synthesized and crystallographically characterized (trpy = 2,2':6',2″-terpyridine, Pqn = 8-(diphenylphosphanyl)quinoline, and dppbz = 1,2-bis(diphenylphosphanyl)benzene). In electrochemical measurements for cis-PN and PP, the reduction of cis-PN resulted in the formation of trans-PN via cis-trans isomerization and that of PP proceeded via a two-electron-transfer reaction. The mechanism of the electrochemical behaviors is discussed through consideration of five-coordinated species, [Ru(trpy)(Pqn)](n+) or [Ru(trpy)(dppbz)](n+) (n = 0-2), formed by liberation of a monodentate labile ligand.
Journal of Inorganic and Organometallic Polymers and Materials, 2007
The ethynylene-bridged ferrocene-anthraquinone system exhibits unique protonation-induced electro... more The ethynylene-bridged ferrocene-anthraquinone system exhibits unique protonation-induced electron transfer reactions to form multi-dentate valence tautomerization states. In this study, we newly synthesized ethynylene-bridged ferrocene-anthraquinone alternating oligomers by a reaction of 1,1 0 -bis(trimethylstannylethynyl)ferrocene with 1,8-dibromoanthraquinone in the presence of a Pd catalyst. An insoluble 1:1-donor/acceptor polymer, (1,1 0 -Fc-1,8-Aq) n , was obtained and characterized by IR and UV-vis spectra and elemental analysis. The molecular weight of the soluble portion of the oligomers was M w = 2.6 Â 10 3 (M w /M n = 1.4). A cyclic dimer, cyclic-(FcAq) 2 , was also obtained and characterized by the 2D-NMR spectra. The behavior of the insoluble polymer (1,1 0 -Fc-1,8-Aq) n upon the addition of an organic acid such as CF 3 SO 3 H was examined and compared with that of the monomer exposed to the same conditions. The addition of CF 3 SO 3 H to the insoluble polymer rendered soluble in organic solvent, and the changes in the UV-vis-NIR and IR absorption spectra reflected the structural changes to the protonated form with valence tautomers; this reaction was similar to the reactions with 1-ferrocenylethynylanthraquinone (1-FcAq) and 1,8-bis(ferrocenylethynyl) anthraquinone (1,8-Fc 2 Aq).
Nature communications, 2013
Functional cellular substrates for localized cell stimulation by small molecules provide an oppor... more Functional cellular substrates for localized cell stimulation by small molecules provide an opportunity to control and monitor cell signalling networks chemically in time and space. However, despite improvements in the controlled delivery of bioactive compounds, the precise localization of gaseous biomolecules at the single-cell level remains challenging. Here we target nitric oxide, a crucial signalling molecule with site-specific and concentration-dependent activities, and we report a synthetic strategy for developing spatiotemporally controllable nitric oxide-releasing platforms based on photoactive porous coordination polymers. By organizing molecules with poor reactivity into polymer structures, we observe increased photoreactivity and adjustable release using light irradiation. We embed photoactive polymer crystals in a biocompatible matrix and achieve precisely controlled nitric oxide delivery at the cellular level via localized two-photon laser activation. The biological rel...
Scientific Reports, 2014
The electrochemical detection of metal complexes in the photoexcited state is important for under... more The electrochemical detection of metal complexes in the photoexcited state is important for understanding photoinduced electron transfer (PET) processes, which play a central role in photo-energy conversion systems. In general, however, the redox potentials of excited states have been indirectly estimated by a combination of spectroscopic properties and ground-state redox potentials. To establish a simple method for directly determining the redox potentials of the photoexcited states of metal complexes, electrochemical measurements under several conditions were performed. The electrochemical response was largely influenced not only by the generation of photoexcited molecules but also by the convection induced by photoirradiation, even when the global temperature of the sample solution was unchanged. The suppression of these unfavourable electrochemical responses was successfully achieved by adopting well-established electrochemical techniques. Furthermore, as an initial demonstration, the photoexcited state of a Ru-based metal complex was directly detected, and its redox potential was determined using a thin layer electrochemical method.
Acta crystallographica. Section C, Crystal structure communications, 2013
The title compound, [Fe2(C5H5)2(C40H22O2)] or 1,4-(FcPh)2Aq [where FcPh is 2-(4-ferrocenylphenyl)... more The title compound, [Fe2(C5H5)2(C40H22O2)] or 1,4-(FcPh)2Aq [where FcPh is 2-(4-ferrocenylphenyl)ethynyl and Aq is anthraquinone], was synthesized in an attempt to obtain a new solvent-incorporating porous material with a large void space. Thermodynamic data for 1,4-(FcPh)2Aq show a phase transition at approximately 430 K. The crystal structure of solvent-free 1,4-(FcPh)2Aq was determined at temperatures of 90, 300 and 500 K using synchrotron powder diffraction data. A direct-space method using a genetic algorithm was employed for structure solution. Charge densities calculated from observed structure factors by the maximum entropy method were employed for model improvement. The final models were obtained through multistage Rietveld refinements. In both phases, the structures of which differ only subtly, the planar Aq fragments are stacked alternately in opposite orientations, forming a one-dimensional column. The FcPh arms lie between the stacks and fill the remaining space, leavin...
Science, 2013
Flexible porous coordination polymers change their structure in response to molecular incorporati... more Flexible porous coordination polymers change their structure in response to molecular incorporation but recover their original configuration after the guest has been removed. We demonstrated that the crystal downsizing of twofold interpenetrated frameworks of [Cu(2)(dicarboxylate)(2)(amine)](n) regulates the structural flexibility and induces a shape-memory effect in the coordination frameworks. In addition to the two structures that contribute to the sorption process (that is, a nonporous closed phase and a guest-included open phase), we isolated an unusual, metastable open dried phase when downsizing the crystals to the mesoscale, and the closed phase was recovered by thermal treatment. Crystal downsizing suppressed the structural mobility and stabilized the open dried phase. The successful isolation of two interconvertible empty phases, the closed phase and the open dried phase, provided switchable sorption properties with or without gate-opening behavior.
Nature Materials, 2012
The spatial organization of porous coordination polymer (PCP) crystals into higher-order structur... more The spatial organization of porous coordination polymer (PCP) crystals into higher-order structures is critical for their integration into separation systems, heterogeneous catalysts, ion/electron transport and photonic devices. Here, we demonstrate a rapid method to spatially control the nucleation site, leading to the formation of mesoscopic architecture made of PCPs, in both two and three dimensions. Inspired by geological processes, this method relies on the morphological replacement of a shaped sacrificial metal oxide used both as a metal source and as an 'architecture-directing agent' by an analogous PCP architecture. Spatiotemporal harmonization of the metal oxide dissolution and the PCP crystallization allowed the preservation of very fine mineral morphological details of periodic alumina inverse opal structures. The replication of randomly structured alumina aerogels resulted in a PCP architecture with hierarchical porosity in which the hydrophobic micropores of the PCP and the mesopores/macropores inherited from the parent aerogels synergistically enhanced the material's selectivity and mass transfer for water/ethanol separation.
Nature Communications, 2011
Chemosensors detect a single target molecule from among several molecules, but cannot differentia... more Chemosensors detect a single target molecule from among several molecules, but cannot differentiate targets from one another. In this study, we report a molecular decoding strategy in which a single host domain accommodates a class of molecules and distinguishes between them with a corresponding readout. We synthesized the decoding host by embedding naphthalenediimide into the scaffold of an entangled porous framework that exhibited structural dynamics due to the dislocation of two chemically non-interconnected frameworks. An intense turn-on emission was observed on incorporation of a class of aromatic compounds, and the resulting luminescent colour was dependent on the chemical substituent of the aromatic guest. This unprecedented chemoresponsive, multicolour luminescence originates from an enhanced naphthalenediimide-aromatic guest interaction because of the induced-fit structural transformation of the entangled framework. We demonstrate that the cooperative structural transition in mesoscopic crystal domains results in a nonlinear sensor response to the guest concentration.
Molecules, 2010
Two thioacetyl-terminated ferrocene-anthraquinone donor-acceptor molecules with different π-elect... more Two thioacetyl-terminated ferrocene-anthraquinone donor-acceptor molecules with different π-electron conjugative units have been synthesized via a series of Stille and Sonagashira reactions. Their photochemical and electrochemical properties before and after addition of an organic acid are investigated, indicating that these complexes are sensitive to external perturbation of protonation, leading the structural change to an expansion of π-conjugated system by cyclocondensation reaction and promoting intramolecular electron transfer from donor to acceptor. They would be good candidates for studies of novel SAMs, and the properties triggered by protonation-induced intramolecular electron transfer will make the SAMs be useful in designing new functional molecular devices.
Journal of the American Chemical Society, 2011
A new strategy to synthesize monodispersed porous coordination polymer (PCP) nanocrystals at room... more A new strategy to synthesize monodispersed porous coordination polymer (PCP) nanocrystals at room temperature was developed and utilized for the formation of PCP thin films on gold substrates with fine control over the crystal sizes using the coordination modulation method. Hybridization of these PCP thin films with an environment-controlled quartz crystal microbalance system allowed determining the adsorption properties for organic vapors (methanol and hexane). In the case of high sensitivity (at the low-concentration dosing of analytes), the sensor response depended on the crystal size but not on the type of analyte. In contrast, at the high-concentration dosing, a clear dependence of the sorption kinetics on the analyte was observed due to significant sorbate-sorbate interaction.
Journal of the American Chemical Society, 2014
Structural transformability accompanied by molecular accommodation is a distinguished feature of ... more Structural transformability accompanied by molecular accommodation is a distinguished feature of porous coordination polymers (PCPs) among porous materials. Conventional X-ray crystallography allows for the determination of each structural phase emerged during transformation. However, the propagation mechanism of transformation through an entire crystal still remains in question. Here we elucidate the structural nature of the spatial transient state, in which two different but correlated framework structures, an original phase and a deformed phase, simultaneously exist in one crystal. The deformed phase is distinctively generated only at the crystal surface region by introducing large guest molecules, while the remaining part of crystal containing small molecules maintains the original phase. By means of grazing incidence diffraction techniques we determine that the framework is sheared with sharing one edge of the original primitive cubic structure, leading to the formation of crystal domains with four mirror image relationships.
Journal of the American Chemical Society, 2009
1-Ferrocenylethynylanthraquinone (1-FcAq), which is a donor (D)-acceptor (A) conjugated compound ... more 1-Ferrocenylethynylanthraquinone (1-FcAq), which is a donor (D)-acceptor (A) conjugated compound consisting of a ferrocene (Fc) acting as a donor, an anthraquinone (Aq) acting as an acceptor, and an ethynyl linker, undergoes a cyclocondensation reaction with strong organic acid, and forms 2-ferrocenyloxodihydrodibenzochromenylium salts ([1-FcPyl](+)X(-) where X = TFSI, TfO, PF(6), and BF(4)). [1-FcPyl](+) were also characterized as conjugated donor-acceptor compounds, and electrochemical properties, UV-vis absorption spectra, single-crystal X-ray analysis, and TD-DFT calculations have indicated that the LUMO level of [1-FcPyl](+) is lower than that of 1-FcAq because of the much larger pi-conjugated system in [1-FcPyl](+). Variable-temperature Mossbauer spectroscopy (12-300 K) showed that Fe(II) was dominant for the TFSI(-), PF(6)(-), and BF(4)(-) salts of [1-FcPyl](+); although the Fe(III) species was also observed at all temperature ranges, the molar ratio of Fe(III) species increased at higher temperatures in the TFSI(-) and PF(6)(-) salts. This finding indicates that valence tautomerization (VT) between 1-FcPyl(+) and 1-Fc(+)Pyl occurs in the solid state of the TFSI(-) and the PF(6)(-) salts, but not in the BF(4)(-) salt. Variable-temperature (3.5-310 K) IR spectroscopy showed that the frequencies of the skeletal vibration of the ferrocene moiety decreased with increasing temperature in the TFSI(-) and PF(6)(-) salts, indicating the development of a ferrocenium-like character. The precision of the bond lengths of the [1-FcPyl](+) moiety (0.003-0.004 A) determined by single-crystal X-ray analysis (113 and 273 K) is not sufficient to demonstrate the effect of the counterion on VT. The dihedral angle between the ferrocene and the pyrylium moieties in the BF(4)(-) salt (11.25(15) degrees) is larger than that in the TFSI(-) (6.63(12) degrees) and PF(6)(-) (9.55(15) degrees) salts. Furthermore, the planarity of the acceptor moiety (estimated from the dihedral angle between Ph1 and Ph2) is lower in the BF(4)(-) salt compared with that of other salts. These increased dihedral angles might cause a weaker D-A interaction and a destabilization of the acceptor moiety (i.e., raising a LUMO level), leading to lower stability of the Fe(III) (1-Fc(+)Pyl) species. Variable-temperature X-ray powder diffraction (VT XRPD, 100-300 K) revealed that the temperature dependence of the Fe-P distance in the PF(6)(-) salt was smaller than that of the Fe-B distance in the BF(4)(-) salt. Our interpretation of this phenomenon is that the molar ratio of the Fe(III) species is increased in the PF(6)(-) salt, and that the Coulombic force between the ferrocene moiety and PF(6)(-) anion increases, preventing an increase in the Fe-P distance. This indicates that the electrostatic interaction between the [1-FcPyl](+) moiety and the counteranion may affect the occurrence of VT.
Angewandte Chemie, 2006
For decades, much attention has focused on crystallization from a mixture of electron-donor (D) a... more For decades, much attention has focused on crystallization from a mixture of electron-donor (D) and -acceptor (A) molecules, forming D-and/or A-stacked column structures that exhibit unique physical properties such as ferromagnetism, [1] strong absorption of Vis/NIR light, [2] and high electronic conductivity. [3] The tendency toward DA stacking in the crystal indicates that D-A conjugated molecules can form network structures which may manifest interesting physical properties. We are interested in the chemistry of a new class of D-A conjugated systems, namely, ferrocenylethynylanthraquinones (FcAq), from two viewpoints: protonation-induced intramolecular electron transfer resulting in valence tautomers, [4] and the construction of D-A stacked nanoporous network structures, which have attracted much recent attention because of great potential for applications such as selective gas adsorption, heterogeneous catalysts, and molecular recognition. In the present study, we found that the new T-shaped FcAq compound 1,4-bis(ferrocenylethynyl)anthraquinone (1,4-Fc 2 Aq (1); a) in the presence of guest solvent molecules forms single crystals, which show instant and reversible crystal-to-crystal transformation on heating or treatment with guest vapors. Recently, several reversible crystal-to-crystal transformations have been reported, among which examples accompanying a significant conformational change are few. The present study demonstrates an instant and reversible trans-
Dalton Trans., 2015
Four novel phosphine-substituted ruthenium(ii) polypyridine complexes with nitrogen oxides-trans(... more Four novel phosphine-substituted ruthenium(ii) polypyridine complexes with nitrogen oxides-trans(P,NO2)-[Ru(trpy)(Pqn)(NO2)]PF6 (trans-NO2), cis(P,NO2)-[Ru(trpy)(Pqn)(NO2)]PF6 (cis-NO2), [Ru(trpy)(dppbz)(NO2)]PF6 (PP-NO2), and cis(P,NO)-[Ru(trpy)(Pqn)(NO)](PF6)3 (cis-NO)-were synthesised (trpy = 2,2':6',2''-terpyridine, Pqn = 8-(diphenylphosphanyl)quinoline, and dppbz = 1,2-bis(diphenylphosphanyl)benzene). The influence of the number and position of the phosphine group(s) on the electronic structure of these complexes was investigated using single-crystal X-ray structural analysis, UV-vis absorption spectroscopy, and electrochemical measurements. The substitution lability of the nitrogen oxide ligand of each complex is discussed in comparison with that of the corresponding acetonitrile complexes.
Dalton Trans., 2015
The incorporation of active sites into metal-organic frameworks (MOFs) or porous coordination pol... more The incorporation of active sites into metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) is an attractive way to functionalise these materials. However, the methodology to organise substitution-inert metal-based secondary building units (SBUs) with active sites into MOFs or PCPs via coordination driven self-assembly is severely limited. In this study, we successfully assembled substitution-inert paddle-wheel Rh(II) dimers to afford three novel porous frameworks, Rh2(ppeb)4(THF)2 (1-THF), Rh2(ppeb)4(3-pentanone)2 (1-PN) and Rh2(ppeb)4(1-adamantylamine)2 (1-AD) (ppeb = 4-[(perfluorophenyl)ethynyl]benzoate), by using non-covalent interactions. Multipoint arene-perfluoroarene (Ar-Ar(F)) interactions, which allow the unidirectional face-to-face interaction mode of aromatic rings, were used to assemble the substitution-inert paddle-wheel Rh(II) dimers. The obtained frameworks were structurally characterisation by single crystal X-ray diffraction, and it is found that all structures exhibited a one-dimensional channel with active axial sites exposed to the pores. The porous properties of the obtained frameworks were also investigated by thermogravimetric analysis, gas adsorption and powder X-ray diffraction measurements. Moreover, the ligand substitution reaction at the active axial sites was examined at the crystalline state and the flexible structural transformation with the change of channel shapes and sizes was observed.
Angewandte Chemie (International ed. in English), Jan 26, 2015
Rational molecular design of catalytic systems capable of smooth OO bond formation is critical t... more Rational molecular design of catalytic systems capable of smooth OO bond formation is critical to the development of efficient catalysts for water oxidation. A new ruthenium complex was developed, which bears pendant SO3 (-) groups in the secondary coordination sphere: [Ru(terpy)(bpyms)(OH2 )] (terpy=2,2':6',2''-terpyridine, bpyms=2,2'-bipyridine-5,5'-bis(methanesulfonate)). Water oxidation driven by a Ce(4+) oxidant is distinctly accelerated upon introduction of the pendant SO3 (-) groups in comparisons to the parent catalyst, [Ru(terpy)(bpy)(OH2 )](2+) (bpy=2,2'-bipyridine). Spectroscopic, electrochemical, and crystallographic investigations concluded that the pendant SO3 (-) groups promote the formation of an OO bond via the secondary coordination sphere on the catalyst, whereas the influence of the pendant SO3 (-) groups on the electronic structure of the [Ru(terpy)(bpy)(OH2 )](2+) core is negligible. The results of this work indicate that modificat...
Angewandte Chemie (International ed. in English), Jan 20, 2014
A series of [{(terpy)(bpy)Ru}(μ-O){Ru(bpy)(terpy)}](n+) ([RuORu](n+), terpy=2,2';6',2'... more A series of [{(terpy)(bpy)Ru}(μ-O){Ru(bpy)(terpy)}](n+) ([RuORu](n+), terpy=2,2';6',2''-terpyridine, bpy=2,2'-bipyridine) was systematically synthesized and characterized in three distinct redox states (n=3, 4, and 5 for Ru(II,III)2, Ru(III,III)2, and Ru(III,IV)2, respectively). The crystal structures of [RuORu](n+) (n=3, 4, 5) in all three redox states were successfully determined. X-ray crystallography showed that the Ru-O distances and the Ru-O-Ru angles are mainly regulated by the oxidation states of the ruthenium centers. X-ray crystallography and ESR spectra clearly revealed the detailed electronic structures of two mixed-valence complexes, [Ru(III)ORu(IV)](5+) and [Ru(II)ORu(III)](3+), in which each unpaired electron is completely delocalized across the oxo-bridged dinuclear core. These findings allow us to understand the systematic changes in structure and electronic state that accompany the changes in the redox state.
Inorganic chemistry, Jan 21, 2014
A series of phosphine-substituted ruthenium polypyridine complexes, cis(P,Cl)-[Ru(trpy)(Pqn)Cl]PF... more A series of phosphine-substituted ruthenium polypyridine complexes, cis(P,Cl)-[Ru(trpy)(Pqn)Cl]PF6 (cis-Cl), trans(P,MeCN)-[Ru(trpy)(Pqn)(MeCN)](PF6)2 (trans-PN), cis(P,MeCN)-[Ru(trpy)(Pqn)(MeCN)](PF6)2 (cis-PN), and [Ru(trpy)(dppbz)(MeCN)](PF6)2 (PP), were synthesized and crystallographically characterized (trpy = 2,2':6',2″-terpyridine, Pqn = 8-(diphenylphosphanyl)quinoline, and dppbz = 1,2-bis(diphenylphosphanyl)benzene). In electrochemical measurements for cis-PN and PP, the reduction of cis-PN resulted in the formation of trans-PN via cis-trans isomerization and that of PP proceeded via a two-electron-transfer reaction. The mechanism of the electrochemical behaviors is discussed through consideration of five-coordinated species, [Ru(trpy)(Pqn)](n+) or [Ru(trpy)(dppbz)](n+) (n = 0-2), formed by liberation of a monodentate labile ligand.
Journal of Inorganic and Organometallic Polymers and Materials, 2007
The ethynylene-bridged ferrocene-anthraquinone system exhibits unique protonation-induced electro... more The ethynylene-bridged ferrocene-anthraquinone system exhibits unique protonation-induced electron transfer reactions to form multi-dentate valence tautomerization states. In this study, we newly synthesized ethynylene-bridged ferrocene-anthraquinone alternating oligomers by a reaction of 1,1 0 -bis(trimethylstannylethynyl)ferrocene with 1,8-dibromoanthraquinone in the presence of a Pd catalyst. An insoluble 1:1-donor/acceptor polymer, (1,1 0 -Fc-1,8-Aq) n , was obtained and characterized by IR and UV-vis spectra and elemental analysis. The molecular weight of the soluble portion of the oligomers was M w = 2.6 Â 10 3 (M w /M n = 1.4). A cyclic dimer, cyclic-(FcAq) 2 , was also obtained and characterized by the 2D-NMR spectra. The behavior of the insoluble polymer (1,1 0 -Fc-1,8-Aq) n upon the addition of an organic acid such as CF 3 SO 3 H was examined and compared with that of the monomer exposed to the same conditions. The addition of CF 3 SO 3 H to the insoluble polymer rendered soluble in organic solvent, and the changes in the UV-vis-NIR and IR absorption spectra reflected the structural changes to the protonated form with valence tautomers; this reaction was similar to the reactions with 1-ferrocenylethynylanthraquinone (1-FcAq) and 1,8-bis(ferrocenylethynyl) anthraquinone (1,8-Fc 2 Aq).
Nature communications, 2013
Functional cellular substrates for localized cell stimulation by small molecules provide an oppor... more Functional cellular substrates for localized cell stimulation by small molecules provide an opportunity to control and monitor cell signalling networks chemically in time and space. However, despite improvements in the controlled delivery of bioactive compounds, the precise localization of gaseous biomolecules at the single-cell level remains challenging. Here we target nitric oxide, a crucial signalling molecule with site-specific and concentration-dependent activities, and we report a synthetic strategy for developing spatiotemporally controllable nitric oxide-releasing platforms based on photoactive porous coordination polymers. By organizing molecules with poor reactivity into polymer structures, we observe increased photoreactivity and adjustable release using light irradiation. We embed photoactive polymer crystals in a biocompatible matrix and achieve precisely controlled nitric oxide delivery at the cellular level via localized two-photon laser activation. The biological rel...
Scientific Reports, 2014
The electrochemical detection of metal complexes in the photoexcited state is important for under... more The electrochemical detection of metal complexes in the photoexcited state is important for understanding photoinduced electron transfer (PET) processes, which play a central role in photo-energy conversion systems. In general, however, the redox potentials of excited states have been indirectly estimated by a combination of spectroscopic properties and ground-state redox potentials. To establish a simple method for directly determining the redox potentials of the photoexcited states of metal complexes, electrochemical measurements under several conditions were performed. The electrochemical response was largely influenced not only by the generation of photoexcited molecules but also by the convection induced by photoirradiation, even when the global temperature of the sample solution was unchanged. The suppression of these unfavourable electrochemical responses was successfully achieved by adopting well-established electrochemical techniques. Furthermore, as an initial demonstration, the photoexcited state of a Ru-based metal complex was directly detected, and its redox potential was determined using a thin layer electrochemical method.
Acta crystallographica. Section C, Crystal structure communications, 2013
The title compound, [Fe2(C5H5)2(C40H22O2)] or 1,4-(FcPh)2Aq [where FcPh is 2-(4-ferrocenylphenyl)... more The title compound, [Fe2(C5H5)2(C40H22O2)] or 1,4-(FcPh)2Aq [where FcPh is 2-(4-ferrocenylphenyl)ethynyl and Aq is anthraquinone], was synthesized in an attempt to obtain a new solvent-incorporating porous material with a large void space. Thermodynamic data for 1,4-(FcPh)2Aq show a phase transition at approximately 430 K. The crystal structure of solvent-free 1,4-(FcPh)2Aq was determined at temperatures of 90, 300 and 500 K using synchrotron powder diffraction data. A direct-space method using a genetic algorithm was employed for structure solution. Charge densities calculated from observed structure factors by the maximum entropy method were employed for model improvement. The final models were obtained through multistage Rietveld refinements. In both phases, the structures of which differ only subtly, the planar Aq fragments are stacked alternately in opposite orientations, forming a one-dimensional column. The FcPh arms lie between the stacks and fill the remaining space, leavin...
Science, 2013
Flexible porous coordination polymers change their structure in response to molecular incorporati... more Flexible porous coordination polymers change their structure in response to molecular incorporation but recover their original configuration after the guest has been removed. We demonstrated that the crystal downsizing of twofold interpenetrated frameworks of [Cu(2)(dicarboxylate)(2)(amine)](n) regulates the structural flexibility and induces a shape-memory effect in the coordination frameworks. In addition to the two structures that contribute to the sorption process (that is, a nonporous closed phase and a guest-included open phase), we isolated an unusual, metastable open dried phase when downsizing the crystals to the mesoscale, and the closed phase was recovered by thermal treatment. Crystal downsizing suppressed the structural mobility and stabilized the open dried phase. The successful isolation of two interconvertible empty phases, the closed phase and the open dried phase, provided switchable sorption properties with or without gate-opening behavior.
Nature Materials, 2012
The spatial organization of porous coordination polymer (PCP) crystals into higher-order structur... more The spatial organization of porous coordination polymer (PCP) crystals into higher-order structures is critical for their integration into separation systems, heterogeneous catalysts, ion/electron transport and photonic devices. Here, we demonstrate a rapid method to spatially control the nucleation site, leading to the formation of mesoscopic architecture made of PCPs, in both two and three dimensions. Inspired by geological processes, this method relies on the morphological replacement of a shaped sacrificial metal oxide used both as a metal source and as an 'architecture-directing agent' by an analogous PCP architecture. Spatiotemporal harmonization of the metal oxide dissolution and the PCP crystallization allowed the preservation of very fine mineral morphological details of periodic alumina inverse opal structures. The replication of randomly structured alumina aerogels resulted in a PCP architecture with hierarchical porosity in which the hydrophobic micropores of the PCP and the mesopores/macropores inherited from the parent aerogels synergistically enhanced the material's selectivity and mass transfer for water/ethanol separation.
Nature Communications, 2011
Chemosensors detect a single target molecule from among several molecules, but cannot differentia... more Chemosensors detect a single target molecule from among several molecules, but cannot differentiate targets from one another. In this study, we report a molecular decoding strategy in which a single host domain accommodates a class of molecules and distinguishes between them with a corresponding readout. We synthesized the decoding host by embedding naphthalenediimide into the scaffold of an entangled porous framework that exhibited structural dynamics due to the dislocation of two chemically non-interconnected frameworks. An intense turn-on emission was observed on incorporation of a class of aromatic compounds, and the resulting luminescent colour was dependent on the chemical substituent of the aromatic guest. This unprecedented chemoresponsive, multicolour luminescence originates from an enhanced naphthalenediimide-aromatic guest interaction because of the induced-fit structural transformation of the entangled framework. We demonstrate that the cooperative structural transition in mesoscopic crystal domains results in a nonlinear sensor response to the guest concentration.
Molecules, 2010
Two thioacetyl-terminated ferrocene-anthraquinone donor-acceptor molecules with different π-elect... more Two thioacetyl-terminated ferrocene-anthraquinone donor-acceptor molecules with different π-electron conjugative units have been synthesized via a series of Stille and Sonagashira reactions. Their photochemical and electrochemical properties before and after addition of an organic acid are investigated, indicating that these complexes are sensitive to external perturbation of protonation, leading the structural change to an expansion of π-conjugated system by cyclocondensation reaction and promoting intramolecular electron transfer from donor to acceptor. They would be good candidates for studies of novel SAMs, and the properties triggered by protonation-induced intramolecular electron transfer will make the SAMs be useful in designing new functional molecular devices.
Journal of the American Chemical Society, 2011
A new strategy to synthesize monodispersed porous coordination polymer (PCP) nanocrystals at room... more A new strategy to synthesize monodispersed porous coordination polymer (PCP) nanocrystals at room temperature was developed and utilized for the formation of PCP thin films on gold substrates with fine control over the crystal sizes using the coordination modulation method. Hybridization of these PCP thin films with an environment-controlled quartz crystal microbalance system allowed determining the adsorption properties for organic vapors (methanol and hexane). In the case of high sensitivity (at the low-concentration dosing of analytes), the sensor response depended on the crystal size but not on the type of analyte. In contrast, at the high-concentration dosing, a clear dependence of the sorption kinetics on the analyte was observed due to significant sorbate-sorbate interaction.
Journal of the American Chemical Society, 2014
Structural transformability accompanied by molecular accommodation is a distinguished feature of ... more Structural transformability accompanied by molecular accommodation is a distinguished feature of porous coordination polymers (PCPs) among porous materials. Conventional X-ray crystallography allows for the determination of each structural phase emerged during transformation. However, the propagation mechanism of transformation through an entire crystal still remains in question. Here we elucidate the structural nature of the spatial transient state, in which two different but correlated framework structures, an original phase and a deformed phase, simultaneously exist in one crystal. The deformed phase is distinctively generated only at the crystal surface region by introducing large guest molecules, while the remaining part of crystal containing small molecules maintains the original phase. By means of grazing incidence diffraction techniques we determine that the framework is sheared with sharing one edge of the original primitive cubic structure, leading to the formation of crystal domains with four mirror image relationships.
Journal of the American Chemical Society, 2009
1-Ferrocenylethynylanthraquinone (1-FcAq), which is a donor (D)-acceptor (A) conjugated compound ... more 1-Ferrocenylethynylanthraquinone (1-FcAq), which is a donor (D)-acceptor (A) conjugated compound consisting of a ferrocene (Fc) acting as a donor, an anthraquinone (Aq) acting as an acceptor, and an ethynyl linker, undergoes a cyclocondensation reaction with strong organic acid, and forms 2-ferrocenyloxodihydrodibenzochromenylium salts ([1-FcPyl](+)X(-) where X = TFSI, TfO, PF(6), and BF(4)). [1-FcPyl](+) were also characterized as conjugated donor-acceptor compounds, and electrochemical properties, UV-vis absorption spectra, single-crystal X-ray analysis, and TD-DFT calculations have indicated that the LUMO level of [1-FcPyl](+) is lower than that of 1-FcAq because of the much larger pi-conjugated system in [1-FcPyl](+). Variable-temperature Mossbauer spectroscopy (12-300 K) showed that Fe(II) was dominant for the TFSI(-), PF(6)(-), and BF(4)(-) salts of [1-FcPyl](+); although the Fe(III) species was also observed at all temperature ranges, the molar ratio of Fe(III) species increased at higher temperatures in the TFSI(-) and PF(6)(-) salts. This finding indicates that valence tautomerization (VT) between 1-FcPyl(+) and 1-Fc(+)Pyl occurs in the solid state of the TFSI(-) and the PF(6)(-) salts, but not in the BF(4)(-) salt. Variable-temperature (3.5-310 K) IR spectroscopy showed that the frequencies of the skeletal vibration of the ferrocene moiety decreased with increasing temperature in the TFSI(-) and PF(6)(-) salts, indicating the development of a ferrocenium-like character. The precision of the bond lengths of the [1-FcPyl](+) moiety (0.003-0.004 A) determined by single-crystal X-ray analysis (113 and 273 K) is not sufficient to demonstrate the effect of the counterion on VT. The dihedral angle between the ferrocene and the pyrylium moieties in the BF(4)(-) salt (11.25(15) degrees) is larger than that in the TFSI(-) (6.63(12) degrees) and PF(6)(-) (9.55(15) degrees) salts. Furthermore, the planarity of the acceptor moiety (estimated from the dihedral angle between Ph1 and Ph2) is lower in the BF(4)(-) salt compared with that of other salts. These increased dihedral angles might cause a weaker D-A interaction and a destabilization of the acceptor moiety (i.e., raising a LUMO level), leading to lower stability of the Fe(III) (1-Fc(+)Pyl) species. Variable-temperature X-ray powder diffraction (VT XRPD, 100-300 K) revealed that the temperature dependence of the Fe-P distance in the PF(6)(-) salt was smaller than that of the Fe-B distance in the BF(4)(-) salt. Our interpretation of this phenomenon is that the molar ratio of the Fe(III) species is increased in the PF(6)(-) salt, and that the Coulombic force between the ferrocene moiety and PF(6)(-) anion increases, preventing an increase in the Fe-P distance. This indicates that the electrostatic interaction between the [1-FcPyl](+) moiety and the counteranion may affect the occurrence of VT.