Circularly Polarized Luminescence of Some [2]Paracyclo[2](5,8)quinoliphane Derivatives with Planar and Central Chirality

Abstract

With the aim of finding and characterizing new simple organic molecules (SOM) generating circularly polarized luminescence (CPL), we test here nine [2]paracyclo[2](5,8)‐quinoliphane derivatives, whose circular dichroism (CD) spectra were previously measured at short wavelengths in a study encompassing also OR and VCD (CD in the IR). Completion of the CD spectra is carried out with attention paid to weaker and longer wavelength features. The observed signs of the CPL spectra are compared to the signs of the CD band at the longest wavelength and are found coincident except in two cases. The magnitudes of dissymmetry ratios g in luminescence are of the order 10−3, like the corresponding |g| values for the absorption case. TD‐DFT calculations for the two simplest cases provide details on the molecular orbitals involved in the transitions responsible for the observed signals of these molecules. The calculations allow us to provide also a first explanation of the two observed behaviors of the |glum|/|gabs| ratios.

Circularly polarized luminescence of natural products lycorine and narciclasine: role of excited-state intramolecular proton-transfer and test of pH sensitivity

“…CPL spectra were recorded on a home-built system in our lab, 9 and a second CPL system based on a Jasco ''reversed J-715'' CD instrument. 44 2 mm  10 mm fluorescence quartz cuvettes were employed with a 901 scattering geometry, 30 scans at 100 nm/min have been run. With the same system also fluorescence spectra were recorded.…”

“…These values are quite standard 4 for merely organic compounds, since, as demonstrated in ref. 44, g is limited above to twice the fine structure constant, namely (2/137), at least considering electric dipole moment allowed transitions. Finally, we notice that the UV-Vis absorption band at 294 nm and the fluorescence band have the same shape, analyzing the former from high to low wavelengths and the latter from low to high wavelengths; this is referred to as the two complementary spectra being ''mirror-symmetric''.…”

Strong Chiroptical Effects in the Absorption and Emission of Macrocycles Based on the 2,5‐Diaminoterephthalate Minimal Fluorophore

“…In chiral molecules composed of a number of repeatable chromophores, the macrocyclic architecture helps to achieve C n or D n molecular symmetry ( n >1) with an almost parallel orientation of the electric and magnetic transition dipole moments, which is optimal to enhance chiroptical responses [2–6] . This translates to large absorption and emission dissymmetry factors ( g abs , g lum ) observed in electronic circular dichroism (ECD) and circularly polarized luminescence (CPL) spectra [7–16] . Consequently, chiral fluorescent macrocycles are currently an emerging class of efficient CPL emitters [2] .…”

Chiral Optical Properties of Möbius Graphene Nanostrips

“…The relative strength of the optical activity of circular graphene nanostrips can be conveniently characterized by the dissymmetry factor ( g -factor) of optically active transitions g μk ; νk ′ = 4 R μk ; νk ′ / D μk ; νk ′ and the g -factor spectrum g ( ℏω ) = 2CD­( ℏω )/ A ( ℏω ). The typical g -factors of small chiral molecules and semiconductor nanocrystals range between ±(10 –3 –10 –2 ), ,,− while the maximum values of g -factor (±2) describe the situation when the system totally transmits one circular polarization. The data of Table show that the g -factors of optically active transitions in circular graphene nanostrips scale linearly with the nanostrip’s radius as g μk ; νk ′ ∝ ± qρ , where q = ω/ c is the wavenumber of light.…”