Circularly polarized luminescence of agglomerate emitters

Abstract

Circularly polarized luminescence (CPL) originates from the chiral emissive excited states. CPL materials have promising applications in 3D optical displays, encryptions, biological probes, chiral photoelectric devices, and CPL switches, most of which require excellent CPL performances including bright luminescence and high luminescence dissymmetry factor (g lum ) in the agglomerate state. This review systematically summarizes the progress about CPL of aggregate and solid materials, such as organic materials, metal-organic materials (such as coordination polymers, organic-inorganic metal halides, metal clusters, and cluster-assembled materials), the assembled materials by supramolecular interactions, and liquid crystals. We also present the current challenges and a future perspective of chiral emitting agglomerate materials.

Frontiers in circularly polarized luminescence: molecular design, self-assembly, nanomaterials, and applications

“…From the viewpoint of practical application, it is imperative to develop solid-state CPL materials while maintaining a high luminescence efficiency [42][43][44]. Unfortunately, π-conjugated luminophores always face a general situation of aggregationcaused quenching (ACQ) of luminescence effect in their aggregate or assembly state (Figure 5a), which dramatically deteriorates the CPL performance [45,46]. Recently, the AIE concept (Figure 5b), in which organic fluorophores emit brighter in aggregates caused by the restriction of intramolecular motion, including intramolecular rotation and vibration, has emerged as a potently valuable methodology to fabricate solid-state luminescent materials [47][48][49].…”

“…Chiral metal clusters that have discrete energy level for promising emission properties are potential candidates for CPL materials [10,46,[219][220][221][222][223][224][225][226]. In this section, we will highlight the recent advances in this emerging research area.…”

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

“…First, notice that some compounds are presented in couples for the discussion, apart from compounds (R P )-3 and (S P )-3 which are enantiomers, obviously presenting CD and CPL spectra as mirror-images. We may recognize that many of the presented compounds (1,3,(6)(7)(8)(9) show similar CD spectra: the long wavelength region contains a monosignated feature, which is positive for R p -cases and negative for S p -cases, extending from 370 to 300 nm, with two maxima at ca. 350 nm and 310 nm.…”

“…Exceptions to this evaluation can be found in particular cases of electric forbidden magnetic allowed transitions typically observed in Lanthanide complexes [15] or in case of enhancement due to aggregation state. [6][7][8] Among SOM carrying chiral moieties acting as CPL active fluorophores, a class of planar chiral molecules, namely, [2.2]paracyclophane derivatives, has been studied. Researches on those compounds have been recently reviewed in a nice work by Ken-ichi Sugiura, [16] pointing out the interest for a scaffold that bears some rigidity in maintaining the chiral shape and the possibility to control the reciprocal direction of electric and magnetic dipole transition moments.…”

Circular Polarization of Luminescence as a Tool To Study Molecular Dynamical Processes

“…After considering the above two extreme cases, one may recognize that in the supramolecular assemblies and molecular aggregates that have become amenable to detailed spectroscopic study thanks to progress in the field of supramolecular chemistry, [8,9] the distinction between the photon-emitting molecular center and off-resonant surrounding is often impossible to make. Thus, the mesoscopic structures may constitute an intermediate case where the circular polarization could originate partially at the site of photon emission and partly from passage of the emission light out of the structure with long range helical order.…”