Tetsuro Kusamoto

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Organization: The University of Tokyo , Japan

Department: Department of Chemistry

Title: Assistant Professor(PhD)

TOPICS

Inorganic Chemistry

Chemicals
References

Supramolecular Two-Dimensional Network Mediated via Sulfur’s σ-Holes in a Conducting Molecular Crystal: Effects of Its Rigidity on Physical Properties and Structural Transition

Co-reporter:Chie Ohde, Tetsuro Kusamoto, Koji Nakabayashi, Shin-ichi Ohkoshi, and Hiroshi Nishihara

Crystal Growth & Design April 5, 2017 Volume 17(Issue 4) pp:2203-2203

Publication Date(Web):March 3, 2017

DOI:10.1021/acs.cgd.7b00165

This study reveals that noncovalent intermolecular interactions mediated by σ-holes on sulfur atoms can function as an efficient tool to design and construct a novel supramolecular motif, and that these noncovalent bonds are rigid enough to regulate the displacement of molecules at the structural transition. A novel two-dimensional cation···anion supramolecular structure via sulfur’s σ-holes was constructed in a functional molecular crystal, (ethyl-4-bromothiazolium)2[Pt(mnt)2]3 (mnt = maleonitriledithiolato). The unit cell contained two crystallographically independent anions A and B. Electrostatic σ-hole bonds were detected between σ-holes on sulfur in the cation and lone pairs of −CN moieties in B, while A did not form such S···N σ-hole bonds. This salt exhibited a structural transition at ca. 150 K, in which B did not show apparent displacement, while A shifted along the anion’s stacking direction. This shift enhanced trimerization of the anion in the low-temperature phase, leading to the enhanced antiferromagnetic exchange interaction and the increased activation energy in the electrical conduction. We showed that sulfur-based σ-hole bonds are rigid enough to contribute to modulating the physical properties through regulating the displacement of molecules in molecular materials.

Solvent-Controlled Doublet Emission of an Organometallic Gold(I) Complex with a Polychlorinated Diphenyl(4-pyridyl)methyl Radical Ligand: Dual Fluorescence and Enhanced Emission Efficiency

Co-reporter:Yasuyo Ogino, Tetsuro Kusamoto, Yohei Hattori, Masaki Shimada, Mizuho Tsuchiya, Yoshinori Yamanoi, Eiji Nishibori, Kunihisa Sugimoto, and Hiroshi Nishihara

Inorganic Chemistry April 3, 2017 Volume 56(Issue 7) pp:3909-3909

Publication Date(Web):March 15, 2017

DOI:10.1021/acs.inorgchem.6b02864

A paramagnetic, luminescent organometallic gold(I) complex AuI(C6F5)(PyBTM), where PyBTM is a photostable fluorescent polychlorinated diphenyl(4-pyridyl)methyl radical, was prepared, and its crystal and electronic structures and magnetic and optical properties were investigated. Magnetic studies using electron spin resonance spectroscopy and a superconducting quantum interference device magnetometer indicated the existence of S = 1/2 spin per molecule, with the spin density distributed mainly on the PyBTM ligand. The complex exhibited fluorescence in CHCl3 with emission peak wavelength (λem) of 619 nm and the absolute fluorescence quantum yield (ϕem) of 0.04, confirming that AuI(C6F5)(PyBTM) is the first luminescent organometallic complex with a coordinated luminescent radical. Solvent-dependent unique luminescent characteristics were observed in halogenated solvents (CCl4, CHCl3, CH2Cl2, and ClCH2CH2Cl). ϕem decreased, and λem shifted to longer wavelengths as the polarity (dielectric constant) of the solvent increased. Notably, the complex in CCl4 displayed fluorescence with ϕem = 0.23, which was quite high in radicals, while showed dual fluorescence in CH2Cl2 and ClCH2CH2Cl with lifetimes of around 1 and 7 ns for two emissive components. Density functional theory (DFT) and time-dependent (TD)-DFT calculations indicated that the fluorescence occurred from an interligand charge transfer (CT) excited state in CCl4, in which the C6F5 and PyBTM moieties acted as electron donor and acceptor, respectively, while the fluorescence was centered at the PyBTM ligand in the other three solvents. This method, i.e., the formation of an interligand CT state, to enhance ϕem is distinctly different from the methods reported previously. The present study revealed that a coordination bond is available for forming emissive CT excited states that lead to high ϕem, providing a novel method with greater capability for realizing highly emissive radicals.

Spin-Reconstructed Proton-Coupled Electron Transfer in a Ferrocene–Nickeladithiolene Hybrid

Co-reporter:Akira Tanushi; Tetsuro Kusamoto; Yohei Hattori; Kenji Takada;Hiroshi Nishihara

Journal of the American Chemical Society 2015 Volume 137(Issue 20) pp:6448-6451

Publication Date(Web):May 14, 2015

DOI:10.1021/jacs.5b02118

A proton–electron dual-responsive system based on a hybrid of ferrocene and metalladithiolene (1) was developed. The formation of the dithiafulvenium moiety was driven by protonation of the metalladithiolene unit of 1 and by oxidation. The change in the electronic structure caused by the protonation was combined with the redox properties of the two components of 1, generating two radical species with different spin density distributions (3d spin and π spin). Furthermore, a spin-reconstructed proton-coupled electron transfer, i.e., the transformation from 3d spin to π spin accompanied by deprotonation, was achieved by a temperature change, the third external stimulus.

Intramolecular Ferromagnetic Radical–CuII Coupling in a CuII Complex Ligated with Pyridyl-Substituted Triarylmethyl Radicals

Co-reporter:Tetsuro Kusamoto, Yohei Hattori, Akira Tanushi, and Hiroshi Nishihara

Inorganic Chemistry 2015 Volume 54(Issue 9) pp:4186-4188

Publication Date(Web):April 17, 2015

DOI:10.1021/acs.inorgchem.5b00499

Novel metal complexes M(hfac)2(PyBTM)2 [M = CuII, ZnII; hfac = hexafluoroacetylacetonato; PyBTM = (3,5-dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radical] were prepared. Both hexacoordinated complexes had elongated octahedral geometry, in which two PyBTM molecules coordinated at the equatorial positions in CuII(hfac)2(PyBTM)2 but at the axial positions in ZnII(hfac)2(PyBTM)2. Magnetic studies revealed an intramolecular ferromagnetic exchange interaction between the spins on PyBTM and CuII (JCu–R/kB = 47 K) based on the orthogonality of the two spin orbitals.

Highly photostable luminescent open-shell (3,5-dihalo-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radicals: significant effects of halogen atoms on their photophysical and photochemical properties

Co-reporter:Yohei Hattori, Tetsuro Kusamoto and Hiroshi Nishihara

RSC Advances 2015 vol. 5(Issue 79) pp:64802-64805

Publication Date(Web):29 Jul 2015

DOI:10.1039/C5RA14268G

Novel luminescent radicals, Br2PyBTM and F2PyBTM were synthesized and their structures, spectroscopic properties, photostability, and electronic structures were compared with those of Cl2PyBTM. Br2PyBTM showed the highest photostability and F2PyBTM displayed the highest photoluminescence quantum yield of the three radicals.

Enhanced Luminescent Properties of an Open-Shell (3,5-Dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl Radical by Coordination to Gold

Co-reporter:Yohei Hattori;Dr. Tetsuro Kusamoto;Dr. Hiroshi Nishihara

Angewandte Chemie International Edition 2015 Volume 54( Issue 12) pp:3731-3734

Publication Date(Web):

DOI:10.1002/anie.201411572

Abstract

A gold(I) complex containing an open-shell luminescent (3,5-dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl (PyBTM) radical was prepared. The complex showed fluorescence centered mainly on the coordinated PyBTM ligand. The photophysical and photochemical properties were positively modulated upon coordination to Au^I; the photoluminescence quantum yield, fluorescence wavelength, and the stability in the photoexcited state all increased.

Enhanced Luminescent Properties of an Open-Shell (3,5-Dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl Radical by Coordination to Gold

Co-reporter:Yohei Hattori;Dr. Tetsuro Kusamoto;Dr. Hiroshi Nishihara

Angewandte Chemie 2015 Volume 127( Issue 12) pp:3802-3805

Publication Date(Web):

DOI:10.1002/ange.201411572

Abstract

Luminescence, Stability, and Proton Response of an Open-Shell (3,5-Dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl Radical

Co-reporter:Yohei Hattori;Dr. Tetsuro Kusamoto;Dr. Hiroshi Nishihara

Angewandte Chemie 2014 Volume 126( Issue 44) pp:12039-12042

Publication Date(Web):

DOI:10.1002/ange.201407362

Abstract

A luminescent open-shell organic radical with high chemical stability was synthesized. (3,5-Dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radical (PyBTM) was photoluminescent under various conditions. Fluorescence quantum yields of 0.03, 0.26, and 0.81 (the highest value reported for a stable organic radical) were obtained in chloroform, in poly(methyl methacrylate) film at room temperature, and in an EPA matrix (diethyl ether:isopentane:ethanol) at 77 K, respectively. The photostability of PyBTM is up to 115 times higher than that of the tris(2,4,6-trichlorophenyl)methyl radical, a previously reported luminescent radical. The pyridine moiety of PyBTM acts as a proton coordination site, thereby allowing for control of the electronic and optical properties of the radical by protonation and deprotonation.

Luminescence, Stability, and Proton Response of an Open-Shell (3,5-Dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl Radical

Co-reporter:Yohei Hattori;Dr. Tetsuro Kusamoto;Dr. Hiroshi Nishihara

Angewandte Chemie International Edition 2014 Volume 53( Issue 44) pp:11845-11848

Publication Date(Web):

DOI:10.1002/anie.201407362

Abstract

Bilayer Mott System with Cation···Anion Supramolecular Interactions Based on a Nickel Dithiolene Anion Radical: Coexistence of Ferro- and Antiferromagnetic Anion Layers and Large Negative Magnetoresistance

Co-reporter:Tetsuro Kusamoto, Hiroshi M. Yamamoto, Naoya Tajima, Yugo Oshima, Satoshi Yamashita, and Reizo Kato

Inorganic Chemistry 2013 Volume 52(Issue 9) pp:4759-4761

Publication Date(Web):April 5, 2013

DOI:10.1021/ic400285a

A novel bilayer Mott system, (Et-4BrT)[Ni(dmit)2]2 (Et-4BrT = ethyl-4-bromothiazolium; dmit = 1,3-dithiole-2-thione-4,5-dithiolate), contains two nonequivalent Ni(dmit)2 anion layers, where both layers form Mott insulating states. Supramolecular Brcation···Sanion and Scation···Sanion interactions play a crucial role in constructing the bilayer structure. The ferro- and antiferromagnetic short-range-ordering layers coexist in the crystal, which achieves large negative magnetoresistance (Δρ/ρ0 ≈ −75% at 70 kOe) at 5 K under 1 GPa.

Substituent-Dependent Spin-Density Distribution and Coexistence of Fe 3d and π Spins on Ferrocene–Tetrathiafulvalene Hybrids

Co-reporter:Tetsuro Kusamoto ; Hiroshi Nishihara ;Reizo Kato

Inorganic Chemistry 2013 Volume 52(Issue 24) pp:13809-13811

Publication Date(Web):November 26, 2013

DOI:10.1021/ic4022678

Ferrocene (Fc) and tetrathiafulvalene (TTF) moieties were incorporated into novel hybrid molecules of structure FcS4TTF(R)2 (R = CF3 and SMe). [FcS4TTF(R)2]•+ exhibited R-dependent spin-density distribution, and [FcS4TTF(CF3)2]••2+ showed the coexistence of Fc-centered Fe 3d and TTF-centered π spins. The solid-state molecular structures in different oxidation states reflect their characteristic spin states.

Utilization of σ-Holes on Sulfur and Halogen Atoms for Supramolecular Cation···Anion Interactions in Bilayer Ni(dmit)2 Anion Radical Salts

Co-reporter:Tetsuro Kusamoto, Hiroshi M. Yamamoto, and Reizo Kato

Crystal Growth & Design 2013 Volume 13(Issue 10) pp:4533-4541

Publication Date(Web):September 11, 2013

DOI:10.1021/cg401028u

We prepared novel Ni(dmit)2 anion radical salts with ethyl-4-halothiazolium cations (Et-4XT, with X denoting the halogen: I, Br, or Cl), (Et-4IT)[Ni(dmit)2]2 (1), (Et-4BrT)[Ni(dmit)2]2 (2), and (Et-4ClT)2[Ni(dmit)2]5 (3). Single-crystal X-ray diffraction analysis of 1–3 indicates that, unlike the halogen atoms that have only one σ-hole each, the cations’ sulfur atoms each have two σ-holes that lie approximately along the extensions of the C–S bonds. The presence of the σ-holes is supported by electrostatic potential of the cations calculated based on the density functional theory method. In the crystals of 1–3, these σ-holes interact with lone pairs on the terminal thioketone moieties in the Ni(dmit)2 anion radicals to form electrostatic σ-hole bonds (halogen bonds and chalcogen bonds). This results in supramolecular cation···anion networks. Crystal and electronic structure analyses, and electrical and magnetic measurements reveal that the salts 1 and 2 are isostructural bilayer Mott systems, in which two crystallographically different Mott-insulating anion layers coexist in one crystal. The unusual magnetic properties, including the ferromagnetic anomalies of 1 and 2, are consistent with one of the anion layers forming an antiferromagnetic short-range ordering (SRO) state and the other layer forming a ferromagnetic SRO state. The spin-polarization of the Ni(dmit)2 anion radical was shown to influence significantly the observed ferromagnetic interactions, while the antiferromagnetic interactions resulted from π–π overlapping in the anions. The competition between these two interactions dominates the low-temperature magnetic properties of the present bilayer Mott systems. This study reveals that noncovalent intermolecular interactions mediated by σ-holes are influential in preparing novel crystal and electronic structures and that they have the potential to allow the development of materials with unusual physical properties.