研究成果

ジピロエテンの酸化カップリングを利用した非対称ポルフィセンの合成とその光・電気化学特性

Symmetry reduction of porphycenes with finely tuned optical and electronic properties through oxidative cyclization of E/Z-mixed dipyrroethenes

Ning Xu, Toshikazu Ono, Yoshio Hisaeda

Chem. Eur. J. 2019, 25, 11680-11687.

ジピロエテンを前駆体とした非対称ポルフィセンの合成法に関する報告です。光物性、電気化学特性も併せて評価を行いました。以前に報告した、グラムスケールポルフィセン合成法の開発に関する研究(RSC Adv. 2018, 8, 39269-39273)の続報となります。

The main obstacle to a widespread application of porphycenes lies in the lack of efficient and economical method of their production. Discovery of new synthetic methodology of porphycene derivatives are important for fine‐tuning of optical and electrochemical properties. Herein, the preparation of a set of AABB‐, ABAB‐, and ABBA‐type meso‐tetrasubstituted unsymmetric porphycenes is reported. Their synthesis involved the acid‐catalyzed oxidative coupling of AA‐ and BB‐dipyrroethenes, or AB‐type dipyrroethenes, as precursors in yields of up to 19%. The structures were unambiguously confirmed by X‐ray crystallography. The type and position of substituents in the unsymmetric porphycenes enabled fine‐tuning of the optical and electronic properties, which are discussed using UV/vis absorption, fluorescence spectroscopies, cyclic voltammetry, and density functional theory calculations.

塩ー共結晶連続体を活用した光機能性材料:ピリジン修飾ICT色素と酸複合体による外部刺激応答材料

Salt–cocrystal continuum for photofunction modulation: Stimuli-responsive fluorescence color-tuning of pyridine modified intramolecular charge-transfer dyes and acid complexes

Yoshio Yano, Toshikazu Ono, Sou Hatanaka, Daniel T. Gryko, Yoshio Hisaeda

J. Mater. Chem. C. 2019, 7, 8847-8854. (Inside Back Cover)

本研究では、ピリジンを含む有機色素と有機酸との酸ー塩基複合体を調製し、その固体発光色が有機色素へのプロトン化度の違いにより制御可能なことを見出しました。プロトン化度の違いは、酸と塩基のpKaの差(ΔpKa)および結晶構造に決定付けられます。中でも0 < ΔpKa < 3の領域が共結晶になるか塩になるかの不安定領域であることに着目し、これを溶媒分子の吸脱着を刺激とすることでプロトン化度の切り替えを生じ、結果としてその固体発光色制御が可能なことを見出しました。塩ー共結晶連続体を利用した新たな材料設計の報告です。
本研究は、ポーランド科学アカデミーのDaniel T. Gryko教授との共同研究の成果です。本研究は高い評価を受け、Inside Back Coverに選ばれました。

The regulation of proton transfer dynamics between acid–base complexes is of significant interest in the pharmaceutical industry and materials chemistry. However, the extent of proton transfer in the solid state is difficult to predict, and identifying the salts (protonation), cocrystals (hydrogen bond), and salt–cocrystal continuum (partially protonated states) remain challenging topics. Here we report the three states (salts/cocrystals/salt–cocrystal continuum) can be distinguished by photoluminescent color changes based on acid–base complexes consisting of a pyridine-modified pyrrolopyrrole dye and organic acids. Structure-property relationships of 10 complexes indicated that ΔpKa value (pKa (protonated base) – pKa (acid)) and the crystalline environment determine the extent of proton transfer, which governs the intramolecular charge–transfer (ICT) strength of the complexes and tunes the photoluminescence properties. Enhancement of the ICT strength leads to a bathochromic shift of emission from blue to green to yellow under UV-light. The salt–cocrystal continuum (0 < ΔpKa < 3) showed vapochromism/vapofluorochromism against CH2Cl2, owing to the extent of proton transfer from the acid to the pyridine moiety of the dye being modulated by inclusion and desorption of CH2Cl2. This study suggests that the rational design of photoluminescence acid–base complexes is useful for obtaining novel photofunctional materials.

ビタミンB12酵素反応に学ぶ電解ジフルオロアルキル化反応

Learning from Vitamin B12-mediated reactions: Cobalt(III)–carbon bond‐assisted catalytic C–H difluoroacylation of (hetero)arenes by controlled‐potential electrolysis

Md. J. Hossain, Toshikazu Ono, Yoshio Yano, Yoshio Hisaeda

ChemElectroChem, 2019, in press. (Front Cover, Cover Profile)

This paper is dedicated to special collections for  “Organic Electrosynthesis”, Guest Editors: Profs.Robert Francke, Dan Little, and Shinsuke Inagi.

有機化合物へのジフルオロアルキル基の導入は、医薬品、農薬、機能性材料等の開発の観点から重要です。本研究では、ビタミンB12酵素反応に学び、電解ジフルオロアルキル化反応を達成しました。以前に報告したビタミンB12を用いた電解トリフルオロメチル化反応、パーフルオロアルキル化反応 (Chem. Commun., 2017, 53, 10878-10881)の続報となります。

The synthesis of difluoromethylated (CF2R) (R = H, alkyl/aryl, CO2R, etc) compounds has received considerable attention in recent years. In this study, the cobalt(III)–carbon bond‐mediated catalytic C–H difluoroacylation of unactivated arenes and heteroarenes using BrCF2CO2Et is reported. This catalytic cycle is based on a valence change of the cobalt catalyst, a naturally derived vitamin B12 derivative, driven by controlled‐potential electrolysis at ‐0.8 V vs. Ag/AgCl under visible‐light irradiation in DMSO. A broad substrate scope is demonstrated and two compounds were characterized by X‐ray crystal structures. Mechanistic studies showed that the reaction proceeds through a radical pathway mediated by homolytic cleavage of the cobalt(III)–carbon bond. Over 100 turnover number was observed due to the inherent stability of vitamin B12 framework. This naturally derived catalytic system has potential applications in medicinal chemistry and materials science.

超分子集積化技術を利用した多色・白色発光材料の開発

Flexible-Color Tuning and White-Light Emission in Three-, Four-, and Five-component Host/Guest Co-crystals by Charge–Transfer Emissions as well as Effective Energy Transfers

Toshikazu Ono, Yoshio Hisaeda

J. Mater. Chem. C, 2019, 7, 2829-2842. (Front Cover, Hot Paper)

本研究では、3成分、4成分、5成分結晶の創製を通じて、励起光照射下にて多色・白色発光を示す超分子発光体の開発を行いました。ナフタレンジイミド誘導体(NDI)とトリスペンタフルオロフェニルボラン(TPFB)から形成される超分子ホスト(NDI-TPFB)が、複数種の芳香族ゲストを取り込み、結晶を生成します。得られた多成分結晶は、NDIとゲストの間で発光性電荷移動錯体を形成し、取り込むゲスト分子の種類に依存して青色〜近赤外発光を示します。水色と橙色発光を示すゲスト分子を混合することで、白色発光が得られることを見出しました。本論文は高い評価を受け、J. Mater. Chem. C誌の表紙絵に採択され、Hot Paperに選出されました。

Three-, four-, and five-component host/guest crystals with multi-color and white light emission is described. Our strategy is based on confinement of aromatic donor guests in supramolecular acceptor hosts. The supramolecular acceptor hosts (NDI–TPFB) were composed of N,N’-dipyrid-3-yl-1,4,5,8-naphthalenediimide (NDI) with two tris(pentafluorophenyl)borane (TPFB) linked by boron–nitrogen dative bonds as Lewis acid–base pairs, which spontaneously formed upon mixing the components. In the first part, a set of three-component crystals with 14 different aromatic guests were characterized to elucidate the structure–property relationships. In the latter part, a series of 17 types of four- and five-component crystals were formed with the use of binary or ternary guest inclusion systems, and their structural and photophysical properties were investigated. Among them, 14 types of crystals were formed effectively without destroying the crystal structure, as determined by X-ray diffraction and fluorescence microscope. Notably, flexible color tuning, including white light emission, was realized by tuning the guest ratio and the combinations. Various intermolecular interactions such as C–H•••F interactions, π-π stacking, charge-transfer interactions, and inclusion phenomena were important to forming the crystals. This approach yields a rational solution of multicomponent crystals could be potentially useful for obtaining novel photofunctional solid-state systems.

 

空気と可視光を資源とする有用化合物合成

Visible Light-driven One-pot Amide Synthesis Catalyzed by the B12 Model Complex under Aerobic Conditions

Hui Tian, Hisashi Shimakoshi, Toshikazu Ono, Yoshio Hisaeda

ChemPlusChem, 2019, 84, 237-240.

DOI: 10.1002/cplu.201800522

本研究では、可視光を駆動力とし、空気中の酸素を酸素源として、有害なトリクロロメチル化合物からワンポットで、有用なアミド化合物を合成する手法を見出しました。触媒には天然由来のビタミンB12の誘導体を用い、クーリンで高効率な反応システムの開発に成功しました。本論文は、Front coverに採択され、またeditor’s choiceに選出され、とても高い評価を受けました。本研究は、分子システム化学国際コース一期生の田輝さん(博士)の研究成果です。

A visible light responsive catalytic system with the B12 complex as the catalyst and [Ir(dtbbpy)(ppy)2]PF6 as the photosensitizer was developed, which provides a convenient and efficient way for the amide synthesis.  Based on this method, trichlorinated organic compounds were converted to amides in the presence of an amine under aerobic conditions at room temperature in an one-pot procedure.  As this protocol is free from hazardous reagents, extra additives, noble metals, and dangerous gas, the present method provides a novel and efficient approach for the amide synthesis under mild and easily controlled conditions.

グラムスケールのポルフィセン合成法の開発

Gram-scale synthesis of porophycene derivatives by oxidative macrocyclizations of E/Z-mixed 5,6-diaryldipyrroethenes 

Toshikazu Ono, Ning Xu, Daiki Koga, Toshihiro Ideo, Manabu Sugimoto, Yoshio Hisaeda

RSC Adv. 2018, 8, 39269-39273. (Open Access)

グラムスケールのポルフィセン合成法に関する報告です。5,6-ジアリルジピロロエテンを前駆体とし、酸触媒と酸化剤を最適化することにより、3段階合成で総収率20%を超えるポルフィセン誘導体の合成を達成しました。熊本大学の杉本先生との共同研究の成果です。Open Accessの論文です。

The gram-scale production of porphycene derivatives is reported. This has been achieved by acid-catalyzed ring closure of an E/Z-mixture of 5,6-diaryldipyrroethenes, resulting in the formation of meso-tetraarylporphycenes in yields of up to 80%. E/Z-isomerization of the 5,6-diaryldipyrroethenes under acidic conditions was key to proceed the effective macrocyclization.

超分子集積化技術を用いた固体発光特性のチューニング

Switching of Monomer Fluorescence, Charge‐Transfer Fluorescence, and Room‐Temperature Phosphorescence Induced by Aromatic Guest Inclusion in a Supramolecular Host

Toshikazu Ono, Ai Taema, Aiko Goto, Yoshio Hisaeda

Chem. Eur. J. 2018, 24, 17487-17496. (Cover Picture)

超分子ホストとゲストから構成される有機固体発光材料の創製を行い、ゲスト分子の種類に依存した(i)モノマー蛍光発光、(ii)電荷移動錯体からの蛍光発光、(iii)常温燐光発光材料、となる材料を見出しました。結晶のすりつぶし、ゲスト除去に伴う興味深い発光特性チューニングを達成しました。本研究は高い評価を受け、Chem Eur J誌のHot Paperに選ばれました。Cover Pictureに選ばれました。

Crystal engineering of three‐component crystals with guest‐dependent photoluminescence switching, including (i) crystallization‐induced emission enhancement, (ii) intermolecular charge‐transfer emission, and (iii) room‐temperature phosphorescence under ultraviolet irradiation, was demonstrated. This strategy was based on the confinement of aromatic guests in a supramolecular host (denoted as EBPDI‐TPFB) composed of 5,5′‐(ethyne‐1,2‐diyl)bis(2‐pyridin‐3‐yl‐isoindoline‐1,3‐dione (EBPDI) with two tris(pentafluorophenyl)borane (TPFB) molecules linked by B−N dative bonds that acted as Lewis pairs. The single‐crystal X‐ray structures of complexes with eight different guests were collected, revealing that the size and/or shape of the supramolecular host EBPDI‐TPFB was modulated by the included guest molecules. The excellent guest inclusion ability of EBPDI‐TPFB allowed systematic photoluminescence regulation of the complexes, which exhibited multicolor emissions in the crystalline state. Photoluminescence switching characteristics of the complexes were observed upon removing the guests or mechanical grinding of the crystals. These results indicated that using the host–guest chemistry of multicomponent crystals not only facilitates crystallization, but also can reveal hidden optical functions by combining molecules of interest, which should contribute to the fields of physical chemistry and materials science.

ビタミンB12触媒に関する総説

Learning from B12 enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

Keishiro Tahara, Ling Pan, Toshikazu Ono, Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553-2567. 

ビタミンB12触媒に関するレビューがBeilstein Journal of Organic Chemistryに掲載されました。兵庫県立大学の田原先生、東北師範大学の藩先生との共同執筆です。

Cobalamins (B 12) play various important roles in vivo. Most B 12-dependent enzymes are divided into three main subfamilies: adenosylcobalamin-dependent isomerases, methylcobalamin-dependent methyltransferases, and dehalogenases. Mimicking these B 12 enzyme functions under non-enzymatic conditions offers good understanding of their elaborate reaction mechanisms. Furthermore, bio-inspiration offers a new approach to catalytic design for green and eco-friendly molecular transformations. As part of a study based on vitamin B 12 derivatives including heptamethyl cobyrinate perchlorate, we describe biomimetic and bioinspired catalytic reactions with B 12 enzyme functions. The reactions are classified according to the corresponding three B 12 enzyme subfamilies, with a focus on our recent development on electrochemical and photochemical catalytic systems. Other important reactions are also described, with a focus on radical-involved reactions in terms of organic synthesis.

トリフルオロメチル基を軸配位子に持つビタミンB12誘導体とその光分解挙動

Synthesis of Trifluoromethylated B12 Derivative and Photolysis of Cobalt(III)–Trifluoromethyl Bond

Toshikazu Ono, Kosuke Wakiya, Md. Jakir Hossain, Hisashi Shimakoshi, Yoshio Hisaeda

Chem. Lett. 2018, 47, 979-981. 

トリフルオロメチル基を軸配位子に持つビタミンB12誘導体とその光分解挙動に関する報告です。以前に報告したビタミンB12を用いた電解トリフルオロメチル化反応、パーフルオロアルキル化反応 (Chem. Commun., 2017, 53, 10878-10881)にて、Co-CF3結合のホモリシス開裂によるトリフルオロメチルラジカルの発生が触媒反応の中間体であることを同定しました。

A vitamin B12 derivative with a trifluoromethyl group as an axial ligand, heptamethyl trifluoromethylaquacobyrinate perchlorate, [[(CF3)(H2O)Cob(III)7C1ester]ClO4], is prepared and characterized by elemental analysis, 1H NMR, 19F NMR, ESI-MS, UV-vis absorption, and cyclic voltammetry. The Co–CF3 complex shows homolysis of the Co(III)–CF3 bond under visible light irradiation, which releases a CF3 radical that can be detected by a radical trapping experiment.

発光性電荷移動錯体の超高圧下に対するピエゾクロミズム発光特性

Piezofluorochromism in Charge‐Transfer Inclusion Crystals: The Influence of High Pressure versus Mechanical Grinding

Toshikazu Ono, Yoshifumi Tsukiyama, Ai Taema, Hiroyasu Sato, Hidetoshi Kiyooka, Yuma Yamaguchi, Ayumi Nagahashi, Manami Nishiyama, Yuichi Akahama, Yosiki Ozawa, Masaaki Abe, Yoshio Hisaeda

ChemPhotoChem 2018, 2, 416-420. (Front Cover)

ナフタレンジイミド誘導体と芳香族ゲスト分子からなる発光性電荷移動錯体のメカノクロミズム特性に関する報告を行いました。メノウ乳鉢をもちいた粉砕では発光色の変化が殆ど観測されないが、ダイアモンドアンビルセルを用いた超高圧下では、劇的な発光色の長波長シフトが観測される興味深い挙動を見出しました。高圧下での単結晶X線構造解析、計算化学を駆使することにより、外部圧力による圧縮によりナフタレンジイミド誘導体と芳香族ゲスト分子との分子間距離が近接することで電子的な摂動が生じた結果、発光色変化が観測されることを明らかとしました。本研究成果は、ChemPhotoChemの表紙を飾りました。兵庫県立大学の阿部教授、赤浜教授、小澤准教授およびリガクの佐藤博士との共同研究の成果です。

The   distinct   piezochromic   luminescent   responses   of charge-transfer  inclusion  crystals,  which  consist  of  smallaromatic guest molecules with naphthalenediimide derivatives,are reported. Reversible multichromism is observed over theentire visible region in response to high pressure, whereas aweak response to mechanical grinding is evident. High-pressuresingle-crystal X-ray diffraction analysis and TD-DFT calculationsclearly suggest that high compression induces a closer arrange-ment with a short interfacial distance between small aromaticguest molecules and naphthalenediimide derivatives, which isproposed as the origin of the drastic luminescent color change.