120th General Meeting of the KCS

Type Poster Presentation
Area Industrial Chemistry
Room No. Exhibition Hall 2+3
Time 10월 20일 (금요일) 13:00~14:30
Code IND.P-66
Subject New Solid State Photochemistry of Siloles Driven by ortho-Carborane: Insight on Structure-Property Relationships
Authors Hyun Wook Cha, Chul Hoon Kim, Sang Ook Kang, Ho-Jin Son*
Department of Advanced Materials Chemistry, Korea University, Korea
Abstract Regioisomeric silole-carboranes, Si-p-Cb and Si-m-Cb, were prepared. As incorporating ortho-carboranes onto the silole, their emissions in solution state were quenched due to the electron transfer from silole core to the ortho-Cb groups. Furthermore, Si-p-Cb and Si-m-Cb showed different photophysical properties. In THF solution, even though their emissions were weak, Si-p-Cb reveals competitive radiative process from local excited state and charge transfer state which produced dual emissions at 480 nm and 570 nm, while Si-m-Cb showed emission from LE state at 480 nm. Most interesting features of regioisomeric silole-carboranes were found in their solid state photochemistry. In amorphous phase, Si-p-Cb showed strong emission at 570 nm along with weak emission at 480 nm while Si-m-Cb showed single emission at 480 nm. In crystalline phase, on the other hand, major radiative process for Si-p-Cb was changed to LE state which showed hypsochromic shift to 480 nm. Completely reversed phenomenon was observed for Si-m-Cb which showed bathochromic shift to 570 nm in crystalline phase. Namely, CT states of regioisomeric Si-Cb can be turn-on or turn-off depending on substitution positions. This phenomenon was explained by variation of dihedral angles between silacyclopentadiene ring and phenyl rings at 2- and 5-positions. When they are in orthogonal positions, electronic communications between silole ring and ortho-carborane groups are retarded which results dominant emission from LE state, which refers CT state is turn-off. On the other hand, when they are in horizontal position, CT state is turn-on and reveals CT emission. Namely, small modification on their substitution position changed their excited state properties and results different radiative processes.
E-mail gugu154@korea.ac.kr