Transient Circular Dichroism Measurement of the Excited Triplet State of Pristine Hexahelicene in Solution at Room Temperature

Transient circular dichroism (TR-CD) spectra of (P)- and (M)-hexahelicenes (HHs) in the excited triplet state, (P)- and (M)-3HH*, and their growth and decay behaviors in the µs time domains were recorded for the first time in toluene at room temperature, using an improved Kliger’s method. The TR-CD spectra of (P)- and (M)-3HH* obtained were mirror-imaged, exhibiting strong positive and negative Cotton effect, respectively, of |Δε| = 55 M−1 cm−1 for the lowest-energy band at 660 nm and additional sign-alternating less intense peaks in the higher energy region, the major features of which were well reproduced by the TD-DFT calculations at the UCAM-B3LYP/6-31G(d,p) level.