Effect of Oxidation on the Chiroptical Properties of Sulfur-Bridged Binaphthyl Dimers

A series of axially chiral sulfur-bridged dimers were prepared from 1,1'-binaphthyl-2,2'-diol and subsequently oxidized to the respective sulfones. The chiroptical properties of the chiral chromophores were studied as a function of the oxidation state. Upon oxidation, an increase in quantum yields was observed for directly linked sulfur bridged binaphthyls (0.04 to 0.32), and a modest increase in dissymmetry factor was observed for diphenylsulfide-bridged binaphthyls (-8.9 × 10^-4 to -1.4 × 10^-3). Computational calculations were used to elucidate the changes in photophysical properties.

Axially chiral 1,1'-bicarbazolyls with near-ultraviolet circularly polarized luminescence

The facile synthesis and chiroptical properties of a new family of circularly polarized luminescence (CPL) materials, axially chiral 1,1'-bicarbazolyls (BiCz), are reported. The BiCz derivatives emitted intense near-ultraviolet photoluminescence, with a peak at ∼380 nm. The BiCz enantiomers showed mirror-image circular dichroism and CPL, with g_lum values on the order of 10^-4 in solution.

Circularly Polarized Luminescence Liquids Based on Siloxybinaphthyls: Best Binaphthyl Dihedral Angle in the Excited State

A series of axially chiral 1,1'-binaphthyls with trialkylsiloxy (OSiR₃ ) groups were synthesized. Among them, 1 a-c possessing OSiR₃ groups at the 7,7'-positions and methyl groups at the 2,2'-positions were liquids at room temperature, and the neat liquids showed circularly polarized luminescence (CPL) (R=Bu; Φ_fl,liquid =0.21, |g_lum,liquid |=1.6×10^-3 ). The |g_lum,liquid | value is the highest of pure liquids. These compounds remained liquid over a broad range of temperatures, down to -50 °C. Time-dependent DFT calculations indicated that in the excited state, the binaphthyls adopt a transoid conformation with a small angle between the electric and magnetic transition dipole moments (θ_μ,m =77°), which is a key factor in their CPL activity. The best binaphthyl dihedral angle in the excited state is approximately 110°.

Aggregation-Induced Circularly Polarized Luminescence from Boron Complexes with a Carbazolyl Schiff Base

A variety of carbazolyl-appended Schiff bases were readily synthesized from 1-formylcarbazoles and aniline derivatives. Boron complexation of the resulting ligands allowed for facile preparation of new carbazole-based BODIPY analogues showing solid-state fluorescence. Furthermore, some dyes were converted into chiral compounds through the Et₂ AlCl-mediated incorporation of a binaphthyl unit. The chiral dyes showed aggregation-induced fluorescence and circularly polarized luminescence (CPL) with the Φ_F and g_lum of up to 0.22 and -3.5×10^-3 , respectively, in the solid state. The solid-state fluorescence and CPL were well characterized by the crystal packing analyses and DFT calculations.

Chiroptical Properties in Thin Films of π-Conjugated Systems

Chiral π-conjugated molecules provide new materials with outstanding features for current and perspective applications, especially in the field of optoelectronic devices. In thin films, processes such as charge conduction, light absorption, and emission are governed not only by the structure of the individual molecules but also by their supramolecular structures and intermolecular interactions to a large extent. Electronic circular dichroism, ECD, and its emission counterpart, circularly polarized luminescence, CPL, provide tools for studying aggregated states and the key properties to be sought for designing innovative devices. In this review, we shall present a comprehensive coverage of chiroptical properties measured on thin films of organic π-conjugated molecules. In the first part, we shall discuss some general concepts of ECD, CPL, and other chiroptical spectroscopies, with a focus on their applications to thin film samples. In the following, we will overview the existing literature on chiral π-conjugated systems whose thin films have been characterized by ECD and/or CPL, as well other chiroptical spectroscopies. Special emphasis will be put on systems with large dissymmetry factors (g_abs and g_lum) and on the application of ECD and CPL to derive structural information on aggregated states.

Solvent-sensitive signs and magnitudes of circularly polarised luminescence and circular dichroism spectra: probing two phenanthrenes as emitters endowed with BINOL derivatives

A C₂-symmeric binaphthyl framework bearing phenanthrene as the emitter exhibited circularly polarised luminescence (CPL) in dilute solutions.

Circularly Polarized Luminescence from Simple Organic Molecules

This article aims to show the identity of "circularly polarized luminescent active simple organic molecules" as a new concept in organic chemistry due to the potential interest of these molecules, as availed by the exponentially growing number of research articles related to them. In particular, it describes and highlights the interest and difficulty in developing chiral simple (small and non-aggregated) organic molecules able to emit left- or right-circularly polarized light efficiently, the efforts realized up to now to reach this challenging objective, and the most significant milestones achieved to date. General guidelines for the preparation of these interesting molecules are also presented.

Solid-state circularly polarised luminescence of atropisomeric fluorophores embedded in achiral myo-inositol-containing polyurethanes

Two chiral binaphthyl fluorophores in two myo-inositol based polyurethane matrices with high grass transition temperatures emitted circularly polarised luminescence with a high circular anisotropy factor.

Circularly polarized luminescence of biaryl atropisomers: subtle but significant structural dependency

The signs of circularly polarised luminescence and circular dichroism of chiral biaryl organic fluorophores in CHCl₃⁻ and PMMA film were successfully controlled by the internal axial chirality and the axial bonding position of biaryl units.

Enhancing circularly polarised luminescence by extending the π-conjugation of axially chiral compounds

π-Conjugated (R)- and (S)-2,2′-diphenyl-4-biphenanthrol (VAPOL) exhibited an efficient circularly polarised luminescence (CPL) (∼1.3 × 10⁻³) at 376 nm. By comparison, (R)- and (S)-3,3-diphenyl-2,2-bi-1-naphthol (VANOL) exhibited no CPL.