Kazuyuki TAKAHASHI

Cooperative spin-crossover transition from three-dimensional purely π-stacking interactions in a neutral heteroleptic azobisphenolate FeIII complex with a N3O3 coordination sphere

Co-reporter:Suguru Murata;Tomoyuki Mochida;Takahiro Sakurai;Hitoshi Ohta;Takashi Yamamoto;Yasuaki Einaga

Dalton Transactions 2017 vol. 46(Issue 18) pp:5786-5789

Publication Date(Web):2017/05/09

DOI:10.1039/C7DT01030C

A novel neutral heteroleptic FeIII complex from two kinds of π-extended tridentate ligands was designed and prepared. The π-ligands formed a three-dimensional purely π-stacking interaction network. The present complex proved to be the first neutral spin-crossover (SCO) FeIII complex with a N3O3 coordination sphere exhibiting an abrupt SCO transition with a thermal hysteresis of 10 K and the light-induced excited spin-state trapping effect.

Single-crystal-to-single-crystal transformation in hydrogen-bond-induced high-spin pseudopolymorphs from protonated cation salts with a π-extended spin crossover Fe(III) complex anion

Co-reporter:Suguru Murata, Kazuyuki Takahashi, Takahiro Sakurai, Hitoshi Ohta

Polyhedron 2017 Volume 136(Volume 136) pp:

Publication Date(Web):4 November 2017

DOI:10.1016/j.poly.2017.03.046

Novel pseudopolymorphic Hdabco compounds with an Fe(III) complex anion, (Hdabco)[Fe(aznp)2]·CH2Cl2 1 and (Hdabco)[Fe(aznp)2]·0.5H2O 2 [dabco = 1,4-diazabicyclo[2.2.2]octane, H2aznp = (2′-hydroxyphenylazo)-2-hydroxynaphthalene], were prepared and characterized. The magnetic susceptibility for 1 and 2 revealed that both complexes were in a high-spin (HS) state in the whole temperature range and exhibited weak ferromagnetic interactions below 40 K. The crystal structural analyses suggested that strong N–H⋯O hydrogen bonding interactions between the Hdabco cation and [Fe(aznp)2] anion may induce the distortion of a coordination structure resulting in the HS complexes, whereas π-stacking interactions between the π-ligands in the [Fe(aznp)2] anion and additional C–H⋯N hydrogen bonding interactions between the Hdabco cation and [Fe(aznp)2] anion constructed a intermolecular interaction framework structure with one-dimensional channels. The thermogravimetry analysis for compound 1 indicated the adsorption of a water molecule took place after the desorption of a dichloromethane molecule. This transformation of 1 into 2 proved to proceed in a single-crystal-to-single-crystal way by powder X-ray diffractions and single crystal X-ray structural analysis.The crystal structures and magnetic properties of novel protonated dabco CH2Cl2-solvate compound 1 and hydrate compound 2 with a π-extended spin crossover Fe(III) anion revealed that hydrogen-bonding interactions induced the coordination structure distortion affording the high-spin Fe(III) anion and participated in intermolecular interaction frameworks which can support a single-crystal-to-single-crystal transformation of 1 into 2.Download high-res image (141KB)Download full-size image

A New Family of Anionic FeIII Spin Crossover Complexes Featuring a Weak-Field N2O4 Coordination Octahedron

Co-reporter:Dr. Kazuyuki Takahashi;Kiko Kawamukai;Mitsunobu Okai;Dr. Tomoyuki Mochida;Dr. Takahiro Sakurai;Dr. Hitoshi Ohta;Dr. Takashi Yamamoto;Dr. Yasuaki Einaga;Dr. Yoshihito Shiota;Dr. Kazunari Yoshizawa

Chemistry - A European Journal 2016 Volume 22( Issue 4) pp:1253-1257

Publication Date(Web):

DOI:10.1002/chem.201504883

Abstract

Unprecedented anionic Fe^III spin crossover (SCO) complexes involving a weak-field O,N,O-tridentate ligand were discovered. The SCO transition was evidenced by the temperature variations in magnetic susceptibility, Mössbauer spectrum, and coordination structure. The DFT calculations suggested that larger coefficients on the azo group in the HOMO−1 of a ligand might contribute to the enhancement of a ligand-field splitting energy. The present anionic SCO complex also exhibited the light- induced excited-spin-state trapping effect.

Novel Fe(II) spin crossover complexes involving a chalcogen-bond and π-stacking interactions with a paramagnetic and nonmagnetic M(dmit)2 anion (M = Ni, Au; dmit = 4,5-dithiolato-1,3-dithiole-2-thione)

Co-reporter:Mitsunobu Okai, Kazuyuki Takahashi, Takahiro Sakurai, Hitoshi Ohta, Takashi Yamamoto and Yasuaki Einaga

Journal of Materials Chemistry A 2015 vol. 3(Issue 30) pp:7858-7864

Publication Date(Web):13 May 2015

DOI:10.1039/C5TC00859J

To introduce both an inter-sulphur atom and π-stacking interaction between a spin crossover (SCO) cation and paramagnetic anion, we designed and synthesised two novel Fe(II) SCO compounds involving a terpyridine-type thiazole containing ligand with the paramagnetic Ni(dmit)2 and nonmagnetic Au(dmit)2 anion (dmit = 4,5-dithiolato-1,3-dithiole-2-thione). The temperature variations of magnetic susceptibility and Mössbauer spectroscopy revealed that both complexes exhibited an almost complete SCO conversion, and moreover, the Ni(dmit)2 anion was in a paramagnetic state down to 2 K. The crystal structures for the Ni(dmit)2 complex at 213 and 400 K indicated that the chalcogen-bond and π-stacking interaction would be enhanced by the electrostatic interaction between the cation and anion, preventing the π-radicals from dimerising. The light-induced excited spin state trapping effect was observed at 5 K.

Synergistic Spin Transition between Spin Crossover and Spin-Peierls-like Singlet Formation in the Halogen-Bonded Molecular Hybrid System: [Fe(Iqsal)2][Ni(dmit)2]CH3CNH2O

Co-reporter:Kappei Fukuroi;Dr. Kazuyuki Takahashi;Dr. Tomoyuki Mochida;Dr. Takahiro Sakurai;Dr. Hitoshi Ohta;Dr. Takashi Yamamoto;Dr. Yasuaki Einaga;Dr. Hatsumi Mori

Angewandte Chemie International Edition 2014 Volume 53( Issue 7) pp:1983-1986

Publication Date(Web):

DOI:10.1002/anie.201309865

Abstract

To introduce halogen-bond interactions between a cation and an anion, a novel Fe^III complex from iodine-substituted ligands involving a paramagnetic nickel dithiolene anion was prepared and characterized. The compound exhibited the synergy between a spin-crossover transition and a spin-Peierls-like singlet formation. The halogen-bond interactions between the iodine and the sulfur atoms stabilized the paramagnetic state of π-spins and played a crucial role in the synergistic magnetic transition between d- and π-spins. In addition, the compound showed the light-induced excited spin state trapping effect.

Synergistic Spin Transition between Spin Crossover and Spin-Peierls-like Singlet Formation in the Halogen-Bonded Molecular Hybrid System: [Fe(Iqsal)2][Ni(dmit)2]CH3CNH2O

Co-reporter:Kappei Fukuroi;Dr. Kazuyuki Takahashi;Dr. Tomoyuki Mochida;Dr. Takahiro Sakurai;Dr. Hitoshi Ohta;Dr. Takashi Yamamoto;Dr. Yasuaki Einaga;Dr. Hatsumi Mori

Angewandte Chemie 2014 Volume 126( Issue 7) pp:2014-2017

Publication Date(Web):

DOI:10.1002/ange.201309865

Abstract

To introduce halogen-bond interactions between a cation and an anion, a novel Fe^III complex from iodine-substituted ligands involving a paramagnetic nickel dithiolene anion was prepared and characterized. The compound exhibited the synergy between a spin-crossover transition and a spin-Peierls-like singlet formation. The halogen-bond interactions between the iodine and the sulfur atoms stabilized the paramagnetic state of π-spins and played a crucial role in the synergistic magnetic transition between d- and π-spins. In addition, the compound showed the light-induced excited spin state trapping effect.

Novel Fe(II) spin crossover complexes involving a chalcogen-bond and π-stacking interactions with a paramagnetic and nonmagnetic M(dmit)2 anion (M = Ni, Au; dmit = 4,5-dithiolato-1,3-dithiole-2-thione)

Co-reporter:Mitsunobu Okai, Kazuyuki Takahashi, Takahiro Sakurai, Hitoshi Ohta, Takashi Yamamoto and Yasuaki Einaga

Journal of Materials Chemistry A 2015 - vol. 3(Issue 30) pp:NaN7864-7864

Publication Date(Web):2015/05/13

DOI:10.1039/C5TC00859J

To introduce both an inter-sulphur atom and π-stacking interaction between a spin crossover (SCO) cation and paramagnetic anion, we designed and synthesised two novel Fe(II) SCO compounds involving a terpyridine-type thiazole containing ligand with the paramagnetic Ni(dmit)2 and nonmagnetic Au(dmit)2 anion (dmit = 4,5-dithiolato-1,3-dithiole-2-thione). The temperature variations of magnetic susceptibility and Mössbauer spectroscopy revealed that both complexes exhibited an almost complete SCO conversion, and moreover, the Ni(dmit)2 anion was in a paramagnetic state down to 2 K. The crystal structures for the Ni(dmit)2 complex at 213 and 400 K indicated that the chalcogen-bond and π-stacking interaction would be enhanced by the electrostatic interaction between the cation and anion, preventing the π-radicals from dimerising. The light-induced excited spin state trapping effect was observed at 5 K.

Cooperative spin-crossover transition from three-dimensional purely π-stacking interactions in a neutral heteroleptic azobisphenolate FeIII complex with a N3O3 coordination sphere

Co-reporter:Suguru Murata, Kazuyuki Takahashi, Tomoyuki Mochida, Takahiro Sakurai, Hitoshi Ohta, Takashi Yamamoto and Yasuaki Einaga

Dalton Transactions 2017 - vol. 46(Issue 18) pp:NaN5789-5789

Publication Date(Web):2017/03/31

DOI:10.1039/C7DT01030C

A novel neutral heteroleptic FeIII complex from two kinds of π-extended tridentate ligands was designed and prepared. The π-ligands formed a three-dimensional purely π-stacking interaction network. The present complex proved to be the first neutral spin-crossover (SCO) FeIII complex with a N3O3 coordination sphere exhibiting an abrupt SCO transition with a thermal hysteresis of 10 K and the light-induced excited spin-state trapping effect.