Title
A Combined Experimental and Theoretical Study on Circular Dichroism and Circularly Polarized Luminescence of Configurationally Robust D3-Symmetric Triple Pentahelicene
Author
Hiroki Tanaka, Yuka Kato, Prof. Michiya Fujiki, Yoshihisa Inoue, Tadashi Mori
Year
2018
Journal
The Journal of Physical Chemistry A
Abstract
Pentahelicene (PH) exhibits the largest absorption (gabs) and luminescence (glum) dissymmetry factors amongst the helicene family, but is configurationally and (photo)chemically labile, encumbering its application to chiroptical materials. To bypass the pitfalls, three PH units are merged in a single molecule to build D3-symmetric triple pentahelicene, hexabenzotriphenylene (HBT), which attains indeed the configurational and (photo)chemical robustness through equilibrium with a C2-symmetric conformer that interrupts the racemization and photocyclization. UV-vis, circular dichroism (CD) and circularly polarized luminescence (CPL) spectral examinations reveal the significantly larger gabs and glum values for HBT than for any of configurationally robust single [n]helicenes (n 6) and C2-symmetric triple pentahelicene, trinaphthotriphenylene (TNT). Theoretical calculations precisely reproduce the main features of the experimental CD and CPL spectra of PH, HBT, and TNT, and the relevant electric and magnetic transition moments and their mutual angles well rationalize the relative CD and CPL intensities of all the single and triple pentahelicenes.
Instrument
FP-6500
Keywords
Fluorescence, Quantum yield, Optical properties, Organic chemistry, Materials