Frontispiece: Circularly Polarized Luminescence Switching in Small Organic Molecules

Abstract

The circularly polarized luminescence (CPL) switching is of great interest for applications in security technologies and sensing devices. Small organic molecules (SOMs) show several advantages over metal complexes, supramolecular assemblies, and polymers. Therefore, the recent progress on the CPL switching in SOMs is here reviewed. The results are summarized based on the strategies used to tune the factors that influence the emission properties, and thus, to realize CPL switching. For more details see the Minireview by J.‐L. Ma, Q. Peng, and C.‐H. Zhao on page 15441 ff.

Circularly Polarized Luminescence Switching, Chirality Self‐Sorting, and Cell Imaging of Chiral Rhodamine Dyes

“…Although above considerable progress has been made, there are only a limited number of chiral rhodamine dyes reported in literatures ( Figure a). [ 28–32 ] Moreover, their circularly polarized luminescence (CPL), [ 33–38 ] and CPL switching, [ 39–41 ] properties have not been reported before because their chiral fragments is not π ‐conjugated incorporation into the chromophore core of rhodamine. This might hinder chiral transfer from chiral fragments into the chromophore core, leading to the absence of circular dichroism (CD) and CPL signals in longer wavelength regions.…”

Circularly polarized luminescence of coordination aggregates

“…[ 1–4 ] Especially in the past decade, a large amount of CPL‐active molecules and materials have been developed and investigated, including chiral organic small molecules and conjugated polymers, chiral lanthanide (Ln) and transition‐metal complexes, supramolecular assemblies and liquid crystalline (LC) materials, as well as chiral metal clusters and inorganic nanomaterials. [ 6–27 ] CPL performance is generally evaluated by the luminescence dissymmetry factor ( g lum ) and quantum yield ( Φ ). The former refers to the degree of “enantiorichness” of the emitted CP light, and its value is in the range of −2 to +2.…”

“…[ 3,28–31 ] Due to the trade‐off between these two parameters, materials with both large | g lum | and Φ values are still limited so far. [ 1–36 ]…”

“…As the homemade or commercial CPL measurement systems are gradually available in the past 10 years, the development of CPL‐active materials has been largely boosted. This is evidenced by appearance of numerous reviews on related topics, including CPL‐active organic small molecules, [ 4,12,13 ] metal complexes, [ 14–17 ] conjugated polymers, [ 18,19 ] supramolecular assemblies, [ 2,22,23 ] chiral metal clusters and inorganic nanomaterials, [ 25 –27, 48 ] and AIEgens and mesogens, [ 20,21,32–34 ] as well as optoelectronic and bioimaging applications of these materials. [ 6–10 ] Considering the importance of metal complexes in the development of CPL‐active materials and the aggregation strategy in enhancing the performance of isolated molecules, we summarize herein the recent advance in the development of CPL‐active aggregates based on metal‐ligand coordination materials (termed as “coordination aggregates”).…”

Multi‐Light‐Responsive Upconversion‐and‐Downshifting‐Based Circularly Polarized Luminescent Switches in Chiral Metal–Organic Frameworks

“…[ 20–26 ] One method for developing photoresponsive CPL switches involves covalently combining photochromic molecules with a chiral moiety. [ 27–30 ] Unfortunately, CPL activity cannot be reliably obtained in this manner because the chromophores are far from the chiral moiety. To address this challenge, supramolecular self‐assembly has been extensively demonstrated to be an efficient approach for amplifying the circular polarization of CPL emission.…”