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

Abstract

Rhodamine dyes, as star molecules of fluorescent dyes, are critical tools in modern analytical and biochemical research. However, switching their chiroptical properties still remains a big challenge because of the absence of a suitable synthesis method to incorporate through conjugation a chiral fragment into the chromophore core of rhodamine. Herein, a simple and straightforward way is utilized to link two rhodamine chromophores by different chiral bridges. The conjugated RRR/SSS birhodamine dyes with one axial chirality, which is constructed directly by two rhodamine chromophores, and two spirocyclic chiralities show the interesting circular dichroism and circularly polarized luminescence switching and lysosome‐targetable properties. On the other hand, the unconjugated RR/SS birhodamine dyes with two chiral carbons do not have such chiroptical switching properties but do have different amazing cellular staining properties. The RR birhodamine dye can stain both lysosomes and mitochondria, but SS birhodamine dye can stain lysosomes only. Moreover, the mechanisms of chiroptical switching and diastereoselectivity are investigated as well, based on single‐crystal structures and density functional theory calculations. Therefore, a new platform is afforded here in designing chiral dyes for chiroptical switching and cell imaging applications.

“Point-Line-Plane-Helix” Binuclear Platinum(II) Complexes: Metal-Induced Chirality, Chirality Self-Sorting, and Chiroptical Properties

“…As depicted in Figures 3 and 4, the point and axial chiralities of the bridging ligands remain constant in the single crystals of (R,R,R,R p ,M)/ (S,S,S,S p ,P)-Me and (S,S,S,S p ,P)-iPr, revealing the fact that the point chirality and even axial chirality are stable enough to avoid racemization during the synthesis process. 29,30 As expected, not only molecular structures but also molecular arrangements of (R,R,R,R p ,M)/(S,S,S,S p ,P)-Me are mirrored, 24,25,31,32 because they are a pair of enantiomers (Figure 3a). As an example, (R,R,R,R p ,M)-Me is a two-layer-helix structure.…”

“…In general, there are four types of chiralities including point, axial, planar, and helical chirality (Figure ). − So far, the majority of reported chiral molecules have possessed one or two distinct types of chiralities. − Our research group recently demonstrated some double-chirality molecules for chiroptical applications as well. − Herein, under intense curiosity, we have designed and synthesized a new series of “point-line-plane-helix” binuclear Pt­(II) complexes ( ( R,R,R,R p ,M ) / ( S,S,S,S p ,P )-Ak , Ak: Me = methyl or iPr = isopropyl, Figure ) bearing point, axial, planar, and helical chiralities for the first time. To effectively incorporate four types of chiralities into a single molecule, the bridging ligands with point and axial chiralities were prepared first, and then, planar and helical chiralities could be achieved by metal coordination and stabilized by intramolecular π–π and Pt–Pt interactions.…”

Induced Absolute Configuration of Achiral Tetradentate Ligands in Metal–Organic Frameworks for Circularly Polarized Luminescence

“…In recent years, circularly polarized luminescence (CPL)‐active materials have attracted more and more attention because of their significant prospects in three‐dimensional displays, [ 10 ] biological probes [ 11 ] and chiral photochemical reaction. [ 12 ] It provides the direct information to understand the structures of excited states of chiroptical materials.…”