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
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.