Helical Oligophenylene Linked with [2.2]Paracyclophane: Stereogenic π-Conjugated Dye for Highly Emissive Chiroptical Properties
Masashi Hasegawa, Yuki Ishida, Hiroaki Sasaki, Sumire Ishioka, Kazuteru Utsui, Nobuyuki hara, Maho Kitahara, Yoshitane Imai, Yasuhiro Mazaki
Chemistry A European Journal
A stereogenic π-system based on dimer (2) and trimer (3) of [2.2]paracyclophane (PC) and biphenyl was prepared and its structural, photophysical, and chiroptical properties were investigated. X-ray analysis revealed that the quaterphenyl moieties in 2 adopt a double helical structure anchoring [2.2]PC from both sides. Furthermore, 3 forms a isosceles triangle structure with a large chiral cavity. A homodesmotic reaction using DFT calculations revealed that 2 has a larger strain energy than 3 owing to its highly twisted phenylene linkers. Electronic and circular dichroic (CD) spectra were recorded in CH2Cl2 solution. The spectra of both 2 and 3 are similar, and their longest absorption band accompanying a remarkable Cotton effect is attributed to the transition from HOMO to LUMO, which is delocalized to the quaterphenyl moiety. These compounds exhibit fairly high fluorescence quantum yields (ϕ=0.70–0.83) and moderate dissymmetry factor (|gCPL|=1.6×10−3) in circularly polarized luminescence (CPL).
FT/IR-610, J-720, V-560, P-1030, CPL-300
dimer, reaction, CPL