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submitted on 16.07.2020 and posted on 16.07.2020by Haoke Zhang, Ryan Tsz Kin Kwok, Jacky W. Y. Lam, Ben Zhong Tang
Debates on the source
of chirality have lasted for several centuries due to its significance for the
exploration of the origin of life. It is
still a thorny scientific problem that how the first chiral molecule is
generated without any chiral factors. In this work, an interesting phenomenon,
aggregation-induced symmetry breaking (AISB), is observed in achiral diphenylethylene
and p-terphenyl derivatives. For
(2,4,5-TMe-DPE), there is no chiroptical signal both in its solution and
crystal state. However, unexpected chiroptical signals, circular dichroism (CD)
polarized luminescence (CPL), are observed in their aggregate state and the
emission dissymmetry factor is as high as 0.015 at 70% water fraction. Meantime,
time-dependent CD and CPL effect are also investigated which suggests that AISB
involves both dynamic and kinetic processes. Calculation is further carried out
to prove the existence of two enantiomers in diphenylethylene and p-terphenyl derivatives. Finally, we
propose that the symmetry breaking in aggregate state might be caused by the
difference of resolution rate to two enantiomers.