Faculty Profiles - FURUKAWA Ko

Papers - FURUKAWA Ko

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Photoelectric Covalent Organic Frameworks: Converting Open Lattices into Ordered Donor-Acceptor Heterojunctions Reviewed

Long Chen, Ko Furukawa, Jia Gao, Atsushi Nagai, Toshikazu Nakamura, Yuping Dong, Donglin Jiang

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 136 ( 28 ) 9806 - 9809 2014.7

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Ordered one-dimensional open channels represent the typical porous structure of two-dimensional covalent organic frameworks (COFs). Here we report a general synthetic strategy for converting these open lattice structures into ordered donor acceptor heterojunctions. A three-component topological design scheme was explored to prepare electron-donating intermediate COFs, which upon click reaction were transformed to photoelectric COFs with segregated donor acceptor alignments, whereas electron-accepting buckyballs were spatially confined within the nanochannels via covalent anchoring on the channel walls. The donor acceptor heterojunctions trigger photoinduced electron transfer and allow charge separation with radical species delocalized in the pi-arrays, whereas the charge separation efficiency was dependent on the buckyball content. This new donor acceptor strategy explores both skeletons and pores of COFs for charge separation and photoenergy conversion.

DOI： 10.1021/ja502692w

Covalently Linked 5,15-Diazaporphyrin Dimers: Promising Scaffolds for a Highly Conjugated Azaporphyrin pi System Reviewed

Yoshihiro Matano, Daisuke Fujii, Tarou Shibano, Ko Furukawa, Tomohiro Higashino, Haruyuki Nakano, Hiroshi Imahori

CHEMISTRY-A EUROPEAN JOURNAL 20 ( 12 ) 3342 - 3349 2014.3

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

The first examples of - directly linked, acetylene-bridged, and butadiyne-bridged 5,15-diazaporphyrin dimers have been prepared by palladium-catalyzed coupling reactions of nickel(II) and copper(II) complexes of 3-bromo-10,20-dimesityl-5,15-diazaporphyrin (mesityl=2,4,6-trimethylphenyl). The effects of the linking modes and meso-nitrogen atoms on the structural, optical, electrochemical, and magnetic properties of the distributed systems were investigated by using X-ray crystallography, UV/Vis absorption spectroscopy, DFT calculations, cyclic voltammetry, and ESR spectroscopy. Both the electronic and steric effects of the meso-nitrogen atoms play an important role in the highly coplanar geometry of the directly linked dimers. The direct - linkage produces enhanced conjugation and electron-spin coupling between the two diazaporphyrin units.

DOI： 10.1002/chem.201304626

Indolo[2,3-b]carbazoles with tunable ground states: how Clar's aromatic sextet determines the singlet biradical character Reviewed

Ding Luo, Sangsu Lee, Bin Zheng, Zhe Sun, Wangdong Zeng, Kuo-Wei Huang, Ko Furukawa, Dongho Kim, Richard D. Webster, Jishan Wu

CHEMICAL SCIENCE 5 ( 12 ) 4944 - 4952 2014

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Polycyclic hydrocarbons (PHs) with a singlet biradical ground state have recently attracted extensive interest in physical organic chemistry and materials science. Replacing the carbon radical center in the open-shell PHs with a more electronegative nitrogen atom is expected to result in the more stable aminyl radical. In this work, two kinetically blocked stable/persistent derivatives (1 and 2) of indolo[2,3-b]carbazole, an isoelectronic structure of the known indeno[2,1-b]fluorene, were synthesized and showed different ground states. Based on variable-temperature NMR/ESR measurements and density functional theory calculations, it was found that the indolo[2,3-b]carbazole derivative 1 is a persistent singlet biradical in the ground state with a moderate biradical character (y(0) = 0.269) and a small singlet-triplet energy gap (Delta E-S-T congruent to -1.78 kcal mol(-1)), while the more extended dibenzo-indolo[2,3-b]carbazole 2 exhibits a quinoidal closed-shell ground state. The difference can be explained by considering the number of aromatic sextet rings gained from the closed-shell to the open-shell biradical resonance form, that is to say, two for compound 1 and one for compound 2, which determines their different biradical characters. The optical and electronic properties of 2 and the corresponding aromatic precursors were investigated by one-photon absorption, transient absorption and two-photon absorption (TPA) spectroscopies and electrochemistry. Amphoteric redox behaviour, a short excited lifetime and a moderate TPA cross section were observed for 2, which can be correlated to its antiaromaticity and small biradical character. Compound 2 showed high reactivity to protic solvents due to its extremely low-lying LUMO energy level. Unusual oxidative dimerization was also observed for the unblocked dihydro-indolo[2,3-b]carbazole precursors 6 and 11. Our studies shed light on the rational design of persistent aminyl biradicals with tunable properties in the future.

DOI： 10.1039/c4sc01843e

Near-IR absorbing nickel(II) porphyrinoids prepared by regioselective insertion of silylenes into antiaromatic nickel(II) norcorrole Reviewed

Fukuoka, T., Uchida, K., Sung, Y.M., Shin, J.-Y., Ishida, S., Lim, J.M., Hiroto, S., Furukawa, K., Kim, D., Iwamoto, T., Shinokubo, H.

Angewandte Chemie - International Edition 53 ( 6 ) 1506 - 1509 2014

A kinetically blocked 1,14:11,12-dibenzopentacene: a persistent triplet diradical of a non-Kekule polycyclic benzenoid hydrocarbon Reviewed

Yuan Li, Kuo-Wei Huang, Zhe Sun, Richard D. Webster, Zebing Zeng, Wangdong Zeng, Chunyan Chi, Ko Furukawa, Jishan Wu

CHEMICAL SCIENCE 5 ( 5 ) 1908 - 1914 2014

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

The synthesis of high-spin polycyclic hydrocarbons is very challenging due to their extremely high reactivity. Herein, we report the synthesis and characterization of a kinetically blocked 1,14:11,12-dibenzopentacene, DP-Mes, which represents a rare persistent triplet diradical of a non-Kekule polycyclic benzenoid hydrocarbon. In contrast to its structural isomer 1,14:7,8-dibenzopentacene (heptazethrene) with a singlet biradical ground state, DP-Mes is a triplet diradical as confirmed by ESR and ESTN measurements and density functional theory calculations. DP-Mes also displays intermolecular antiferromagnetic spin interactions in solution at low temperature.

DOI： 10.1039/c3sc53015a

A stable metallic state of (TTPCOO)(2)NH4 with a mobile dopant Reviewed

Takeshi Terauchi, Satoshi Sumi, Yuka Kobayashi, Toshikazu Nakamura, Ko Furukawa, Yohji Misaki

CHEMICAL COMMUNICATIONS 50 ( 54 ) 7111 - 7113 2014

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Ammonium tetrathiapentalene carboxylate [(TTPCOO)(2)NH4] was prepared via protonic defect-induction doping without electrochemical oxidation. The high electric conductivity of 13 S cm(-1) and Pauli paramagnetic-like behavior of magnetic susceptibility in a wide temperature range exhibit a melting of the charge degrees of freedom induced by a mobile dopant in a salt bridge. Solid-state H-1 NMR strongly indicates a stable metallic state of this compound down to 4 K.

DOI： 10.1039/c4cc00678j

Redox Modulation of para-Phenylenediamine by Substituted Nitronyl Nitroxide Groups and Their Spin States Reviewed

Akihiro Ito, Ryohei Kurata, Daisuke Sakamaki, Soichiro Yano, Yosuke Kono, Yoshiaki Nakano, Ko Furukawa, Tatsuhisa Kato, Kazuyoshi Tanaka

JOURNAL OF PHYSICAL CHEMISTRY A 117 ( 48 ) 12858 - 12867 2013.12

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Three kinds of para-phenylenediamine (PDA) derivatives bearing nitronyl nitroxide (NN) groups were prepared and characterized on the basis of the electrochemical, electron spin resonance (ESR) spectroscopic, absorption spectroscopic, and magnetic susceptibility measurements. It was clarified that the oxidation potential of the central PDA unit is strongly influenced by the numbers of substituted electron-withdrawing NN groups. In addition, the intervalence charge transfer in the central PDA unit was detected in the monocationic states of the PDAs with two NN groups, indicating the coexistence of the localized spins and the delocalized spin on theses molecules. Moreover, pulsed ESR measurements confirmed that the delocalized spin on the central PDA unit and the localized two spins on the NN groups were ferromagnetically coupled in the monocationic states.

DOI： 10.1021/jp4095613

Meta - Para -linked octaaza[18]cyclophanes and their polycationic states Reviewed

Daisuke Sakamaki, Akihiro Ito, Ko Furukawa, Tatsuhisa Kato, Kazuyoshi Tanaka

Journal of Organic Chemistry 78 ( 7 ) 2947 - 2956 2013.4

Language：English Publishing type：Research paper (scientific journal)

Octaazacyclophanes, octaaza[18]m,p,m,p,m,p,m,p-cyclophane (2) and octaaza[18]m,p,p,p,m,p,p,p-cyclophane (3), as ring-size extended congeners of tetraaza[14]m,p,m,p-cyclophane were synthesized, and the electronic states of their polycationic species were investigated by quantum chemical calculations, electrochemical measurements (cyclic voltammetry (CV) and differential pulse voltammetry (DPV)), UV-vis-NIR spectroelectrochemical measurements, and pulsed electron spin resonance (ESR) spectroscopy. These octaazacyclophanes exhibited multiredox activities depending on different linkage patterns along the macrocyclic molecular skeletons, and both molecules were oxidizable up to their respective octacations. Spectroelectrochemical measurements demonstrated that p-phenylenediamine (PD) moieties in 2 could be converted from the semiquinoidal structure to the quinoidal sturcture with increasing oxidation number, whereas higher oxidation states of 3 did not show definite quinoidal deformation of PD moieties. A pulsed ESR spectrum gave evidence about formation of the almost pure spin-triplet state for 3 2+, whereas the high-spin states of 22+ and 24+ are virtually degenerate with the competing low-spin states even at low temperatures, probably due to the fragility of spin-coupling pathway caused by facile conformational changes. © 2013 American Chemical Society.

DOI： 10.1021/jo3026884

X-ray observation of a helium atom and placing a nitrogen atom inside He@C-60 and He@C-70 Reviewed

Yuta Morinaka, Satoru Sato, Atsushi Wakamiya, Hidefumi Nikawa, Naomi Mizorogi, Fumiyuki Tanabe, Michihisa Murata, Koichi Komatsu, Ko Furukawa, Tatsuhisa Kato, Shigeru Nagase, Takeshi Akasaka, Yasujiro Murata

NATURE COMMUNICATIONS 4 1554 2013.3

Language：English Publishing type：Research paper (scientific journal) Publisher：NATURE PUBLISHING GROUP

Single crystal X-ray analysis has been used as a powerful method to determine the structure of molecules. However, crystallographic data containing helium has not been reported, owing to the difficulty in embedding helium into crystalline materials. Here we report the X-ray diffraction study of He@C-60 and the clear observation of a single helium atom inside C-60. In addition, the close packing of a helium atom and a nitrogen atom inside fullerenes is realized using two stepwise insertion techniques, that is, molecular surgery to synthesize the fullerenes encapsulating a helium atom, followed by nitrogen radio-frequency plasma methods to generate the fullerenes encapsulating both helium and nitrogen atoms. Electron spin resonance analysis reveals that the encapsulated helium atom has a small but detectable influence on the electronic properties of the highly reactive nitrogen atom coexisting inside the fullerene, suggesting the potential usage of helium for controlling electronic properties of reactive species.

DOI： 10.1038/ncomms2574

Charge Dynamics in A Donor-Acceptor Covalent Organic Framework with Periodically Ordered Bicontinuous Heterojunctions Reviewed

Shangbin Jin, Xuesong Ding, Xiao Feng, Mustafa Supur, Ko Furukawa, Seiya Takahashi, Matthew Addicoat, Mohamed E. El-Khouly, Toshikazu Nakamura, Stephan Irle, Shunichi Fukuzumi, Atsushi Nagai, Donglin Jiang

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 52 ( 7 ) 2017 - 2021 2013

Organometallic ionic liquids from alkyloctamethylferrocenium cations: thermal properties, crystal structures, and magnetic properties Reviewed

Yusuke Funasako, Takashi Inagaki, Tomoyuki Mochida, Toshihiro Sakurai, Hitoshi Ohta, Ko Furukawa, Toshikazu Nakamura

DALTON TRANSACTIONS 42 ( 23 ) 8317 - 8327 2013

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Alkyloctamethylferrocenium salts with the Tf2N anion ([Fe(C5Me4CnH2n+1)(C5Me4H)][Tf2N]; Tf2N = bis(trifluoromethanesulfonyl)amide) were prepared, and their ionic liquid properties, thermal properties, crystal structures, and magnetic properties were investigated. The melting points of the Tf2N salts were near room temperature, and decreased with increasing alkyl chain length up to n = 8 and then increased. The salts with PF6 and NO3 anions were also prepared. The melting points of the PF6 salts were higher than 100 degrees C. Most of these salts exhibited phase transitions in the solid state. The sum of the entropies of the melting and solid phase transitions was nearly independent of the alkyl chain length for salts with short alkyl chains, whereas those for salts with longer alkyl chains (n >= 10 for Tf2N salts, n >= 6 for PF6 salts) increased with increasing alkyl chain length. Crystal structure determinations revealed that the short chain salts form simple alternately packed structures of cations and anions in the solid state, and that the long chain salts form lamellar structures, in which the alkyl chains are aligned parallel between the layers. The effects of magnetic fields on the crystallization of the paramagnetic ionic liquids were investigated, and revealed that the Tf2N salts with n = 4 exhibited magnetic orientation when solidified under magnetic fields. The magnetic orientation was shown to be a bulk phenomenon, and the importance of the magnetic anisotropy of the crystal structure was suggested in comparison with the response of other Tf2N salts.

DOI： 10.1039/c3dt00084b

Large pore donor-acceptor covalent organic frameworks Reviewed

Shangbin Jin, Ko Furukawa, Matthew Addicoat, Long Chen, Seiya Takahashi, Stephan Irle, Toshikazu Nakamura, Donglin Jiang

CHEMICAL SCIENCE 4 ( 12 ) 4505 - 4511 2013

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

We report the synthesis and structural characterization of large pore covalent organic frameworks (COFs) integrated with donor and acceptor building blocks. The donor and acceptor, based on triphenylene and diimide, respectively, are topologically linked to form COFs with stacked donor and acceptor columns and 5.3 nm width channels, which show high crystallinity and large surface area. By varying donor-acceptor structure in conjunction with time-resolved spectroscopy, these large-pore COFs constitute benchmark frameworks to elucidate not only the importance of donor-acceptor pairing but also the role of lattice structure in charge transfer and separation, thereby casting a general principle for the structural design of optoelectronic and photovoltaic COFs.

DOI： 10.1039/c3sc52034j

Simultaneous Control of Carriers and Localized Spins with Light in Organic Materials Reviewed

Toshio Naito, Tomoaki Karasudani, Keishi Ohara, Takahiro Takano, Yukihiro Takahashi, Tamotsu Inabe, Ko Furukawa, Toshikazu Nakamura

ADVANCED MATERIALS 24 ( 46 ) 6153 - 6157 2012.12

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

An organic insulating crystal reversibly becomes a magnetic conductor under UV irradiation. The rapid and qualitative change in the physical properties is wavelength selective and explained by charge transfer between donor and photochemically active acceptor molecules. The photochemical redox reaction in the crystal produces a partially filled band and localized spins simultaneously.

DOI： 10.1002/adma.201203153

Switchable Intermolecular Communication in a Four-Fold Rotaxane Reviewed

Y. Yamada, M. Okamoto, K. Furukawa, T. Kato, K. Tanaka

Angew. Chem. Int. Ed. 51 709 - 713 2012.1

A Polymacrocyclic Oligoarylamine with a Pseudobeltane Motif: Towards a Cylindrical Multispin System Reviewed

Daisuke Sakamaki, Akihiro Ito, Ko Furukawa, Tatsuhisa Kato, Motoo Shiro, Kazuyoshi Tanaka

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 51 ( 51 ) 12776 - 12781 2012

Physical properties of a molecular conductor (BEDT-TTF)(2)I-3 nanohybridized with silica nanoparticles by dry grinding Reviewed

Akira Funabiki, Hiroki Sugiyama, Tomoyuki Mochida, Kunihiro Ichimura, Takashi Okubo, Ko Furukawa, Toshikazu Nakamura

RSC ADVANCES 2 ( 3 ) 1055 - 1060 2012

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

The dry grinding of a mixture of bis(ethylenedithio) tetrathiafulvalene (BEDT-TTF) and silica nanoparticles has produced powdery (BEDT-TTF)-silica nanocomposites. The (BEDT-TTF)-silica nanocomposites are readily doped with iodine in hexane dispersion to give powdery nanocomposites of (BEDT-TTF)(2)I-3-silica. XRD and TEM measurements suggest that (BEDT-TTF)(2)I-3 in the nanocomposite exists as shell layers of core-shell-type nanoparticles and as nanometre-sized crystals incorporated into hollow sites of aggregated silica nanoparticles. Magnetic susceptibility measurements reveal that the nanocomposites accompanied a large number of Curie spins attributable to surface molecules of the core-shell-type nanoparticles. The nanocomposites show a magnetic susceptibility change corresponding to the metal-insulator transition of alpha-(BEDT-TTF)(2)I-3 in a broad temperature range of 110-140 K, which is attributed to the properties of the nanocrystalline components. Doping in diethyl ether dispersion leads to higher amounts of the nanocrystalline component being obtained. The doping of (BEDT-TTF)-silica nanocomposites by dry grinding produces a paramagnetic powder containing amorphous (BEDT-TTF)(2)I-3, which possesses a Curie spin concentration of 50%. The effects of annealing on these nanocomposites are investigated. The electrical conductivity of the compaction pellets of (BEDT-TTF)-silica nanocomposites is enhanced by iodine doping to reach approximately 10(-6) S cm(-1), but the value is much lower than that of the bulk crystals (10(1) S cm(-1))

DOI： 10.1039/c1ra00590a

1,3,5-Benzenetriamine Double- and Triple-Decker Molecules Reviewed

Daisuke Sakamaki, Akihiro Ito, Kazuyoshi Tanaka, Ko Furukawa, Tatsuhisa Kato, Motoo Shiro

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 51 ( 33 ) 8281 - 8285 2012

13C NMR study of the magnetic properties of the quasi-one-dimensional conductor (TMTTF)2SbF6 Reviewed

F. Iwase, K. Sugiura, K. Furukawa, T. Nakamura

Physical Review B - Condensed Matter and Materials Physics 84 ( 11 ) 2011.9

Language：English Publishing type：Research paper (scientific journal)

Magnetic properties in the quasi-one-dimensional organic salt, (TMTTF) 2SbF6, where TMTTF is tetramethyltetrathiafulvalene, are investigated by 13C NMR under pressures. Antiferromagnetic phase transition at ambient pressure (AFI) is confirmed. Charge ordering is suppressed by pressure and is not observed under 8 kbar. For 5&lt
P&lt
20 kbar, a sharp spectrum and the rapid decrease of the spin-lattice relaxation rate 1/T1 were observed below about 4K, which is attributed to a spin-gap transition. Above 20 kbar, an extremely broadened spectrum and a critical increase of 1/T1 were observed. This indicates that the system enters into another antiferromagnetic phase (AFII) under pressure. The slope of the antiferromagnetic phase transition temperature TAFII, dT AFII/dP, is positive, while TAFI decreases with pressure. The magnetic moment is weakly incommensurate with the lattice at 30 kbar. © 2011 American Physical Society.

DOI： 10.1103/PhysRevB.84.115140

C-13 NMR study of the magnetic properties of the quasi-one-dimensional conductor (TMTTF)(2)SbF6 Reviewed

F. Iwase, K. Sugiura, K. Furukawa, T. Nakamura

PHYSICAL REVIEW B 84 ( 11 ) 115140 2011.9

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER PHYSICAL SOC

Magnetic properties in the quasi-one-dimensional organic salt, (TMTTF)(2)SbF6, where TMTTF is tetramethyltetrathiafulvalene, are investigated by C-13 NMR under pressures. Antiferromagnetic phase transition at ambient pressure (AFI) is confirmed. Charge ordering is suppressed by pressure and is not observed under 8 kbar. For 5 < P < 20 kbar, a sharp spectrum and the rapid decrease of the spin-lattice relaxation rate 1/T-1 were observed below about 4 K, which is attributed to a spin-gap transition. Above 20 kbar, an extremely broadened spectrum and a critical increase of 1/T-1 were observed. This indicates that the system enters into another antiferromagnetic phase (AFII) under pressure. The slope of the antiferromagnetic phase transition temperature T-AFII, dT(AFII)/dP, is positive, while TAFI decreases with pressure. The magnetic moment is weakly incommensurate with the lattice at 30 kbar.

DOI： 10.1103/PhysRevB.84.115140

Gd-2@C79N: Isolation, Characterization, and Monoadduct Formation of a Very Stable Heterofullerene with a Magnetic Spin State of S=15/2 Reviewed

Wujun Fu, Jianyuan Zhang, Tim Fuhrer, Hunter Champion, Ko Furukawa, Tatsuhisa Kato, James E. Mahaney, Brian G. Burke, Keith A. Williams, Kenneth Walker, Caitlyn Dixon, Jiechao Ge, Chunying Shu, Kim Harich, Harry C. Dorn

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 133 ( 25 ) 9741 - 9750 2011.6

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

The dimetallic endohedral heterofullerene (EHF), Gd-2@C79N, was prepared and isolated in a relatively high yield when compared with the earlier reported heterofullerene, Y-2@C79N. Computational (DFT), chemical reactivity, Raman, and electrochemical studies all suggest that the purified Gd-2@C79N, with the heterofullerene cage, (C79N)(5-) has comparable stability with other better known iso electronic metallofullerene (C-80)(6-) cage species (e.g., Gd3N@C-80). These results describe an exceptionally stable paramagnetic molecule with low chemical reactivity with the unpaired electron spin density localized on the internal diatomic gadolinium cluster and not on the heterofullerene cage. EPR studies confirm that the spin state of Gd-2@C79N is characterized by a half-integer spin quantum number of S = 15/2. The spin (S =1/2) on the N atom of the fullerene cage and two octet spins (S = 7/2) of two encapsulated gadoliniums are coupled with each other in a ferromagnetic manner with a small zero-field splitting parameter D. Because the central line of Gd-2@C79N is due to the Kramer's doublet with a half-integer spin quantum number of S = 15/2, this relatively sharp line is prominent and the anisotropic nature of the line is weak. Interestingly, in contrast with most Gd3+ ion environments, the central EPR line (g = 1.978) is observable even at room temperature in a toluene solution. Finally, we report the first EHF derivative, a diethyl bromomalonate monoadduct of Gd-2@C79N, which was prepared and isolated via a modified Bingel-Hirsch reaction.

DOI： 10.1021/ja202011u

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