期刊论文详细信息
Molecules
Questions of Mirror Symmetry at the Photoexcited and Ground States of Non-Rigid Luminophores Raised by Circularly Polarized Luminescence and Circular Dichroism Spectroscopy: Part 1. Oligofluorenes, Oligophenylenes, Binaphthyls and Fused Aromatics
JulianR. Koe1  Takashi Mori2  Yoshihiro Kimura2  Michiya Fujiki2 
[1] Department of Natural Sciences, International Christian University (ICU), 3-10-2 Mitaka, Tokyo, 181-8585, Japan;Division of Materials Science, Graduate School of Science and Technology, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama, Ikoma, Nara 630-0036, Japan;
关键词: circularly polarized luminescence;    circular dichroism;    symmetry breaking;    parity violation;    weak neutral current;    tunneling;    Z0 boson;    fluorene;    camphor;    binaphthyl;    laser dyes;   
DOI  :  10.3390/molecules23102606
来源: DOAJ
【 摘 要 】

We report experimental tests of whether non-rigid, π-conjugated luminophores in the photoexcited (S1) and ground (S0) states dissolved in achiral liquids are mirror symmetrical by means of circularly polarized luminescence (CPL) and circular dichroism (CD) spectroscopy. Herein, we chose ten oligofluorenes, eleven linear/cyclic oligo-p-arylenes, three binaphthyls and five fused aromatics, substituted with alkyl, alkoxy, phenyl and phenylethynyl groups and also with no substituents. Without exception, all these non-rigid luminophores showed negative-sign CPL signals in the UV-visible region, suggesting temporal generation of energetically non-equivalent non-mirror image structures as far-from equilibrium open-flow systems at the S1 state. For comparison, unsubstituted naphthalene, anthracene, tetracene and pyrene, which are achiral, rigid, planar luminophores, did not obviously show CPL/CD signals. However, camphor, which is a rigid chiral luminophore, showed mirror-image CPL/CD signals. The dissymmetry ratio of CPL (glum) for the oligofluorenes increased discontinuously, ranging from ≈ −(0.2 to 2.0) × 10−3, when the viscosity of the liquids increased. When the fluorene ring number increased, the glum value extrapolated at [η] = 0 reached −0.8 × 10−3 at 420 nm, leading to (–)-CPL signals predicted in the vacuum state. Our comprehensive CPL and CD study should provide a possible answer to the molecular parity violation hypothesis arising due to the weak neutral current mediated by the Z0-boson.

【 授权许可】

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