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Designing chiral AIEgens without aggregation‐induced emission (AIE)‐active molecules externally tagged to the chiral scaffold remains a long‐standing challenge for the scientific community. The inherent aggregation‐caused quenching phenomenon associated with the axially chiral (R)‐[1,1′‐binaphthalene]‐2,2′‐diol ((R)‐BINOL) scaffold, together with its marginal Stokes shift, limits its application as a chiral AIE‐active material. Here, in our effort to design chiral luminogens, we have developed a design strategy in which 2‐substituted furans, when appropriately fused with the BINOL scaffold, will generate solid‐state emissive materials with high thermal and photostability as well as colour‐tunable properties. The excellent biocompatibility, together with the high fluorescence quantum yield and large Stokes shift, of one of the luminogens stimulated us to investigate its cell‐imaging potential. The luminogen was observed to be well internalised and uniformly dispersed within the cytoplasm of MDA‐MB‐231 cancer cells, showing high fluorescence intensity. [ABSTRACT FROM AUTHOR]

Optically active dendrimers, containing a planar chiral [2.2]paracyclophane as the X ‐ shaped core unit, were synthesized. Gram ‐ scale optical resolution and transformations of 4,7,12,15 ‐ tetrasubstituted [2.2]paracyclophanes were also carried out. The high ‐ generation dendrons effectively absorbed UV light and transferred the energy to the core, resulting in high photoluminescence from the core. In addition, the dendrons sufficiently isolated the emissive X ‐ shaped core, and intense circularly polarized luminescence was observed from thin dendrimer films. More information can be found in the Full Paper by Y. Morisaki, Y. Chujo et al. on page 2291 ff. [ABSTRACT FROM AUTHOR]

A series of chiral mechanochromic copper(I) cAAC (cAAC=cyclic (alkyl)(amino)carbene) complexes with a variety of amide ligands have been studied with regard to their photophysical and chiroptical properties to elucidate structure‐property relationships for the design of efficient triplet exciton emitters exhibiting circularly polarized luminescence. Depending on the environment, which determines the excited state energies, either thermally activated delayed fluorescence (TADF) from 1/3LLCT states or phosphorescence from 3LLCT/LC states occurs. However, neither chiral moieties at the carbene nor at the carbazolate ligands provide detectable luminescence dissymmetries glum. An exception is [Cu(phenoxazinyl)(cAAC)], showing orange to deep red TADF with λmax=601–715 nm in solution, powders and in PMMA. In this case, the amide ligand can undergo distortions in the excited state. This design motif leads to the first linear, non‐aggregated CPL‐active copper(I) complex with glum of −3.4 ⋅ 10−3 combined with a high radiative rate constant of 6.7 ⋅ 105 s−1. [ABSTRACT FROM AUTHOR]

Planar chiral 4,7,12,15 ‐ tetrasubstituted [2.2]paracyclophane scaffolds stacked two AIE ‐ active monomers in close proximity at a chiral position. The resulting dimer exhibited strong emission even in a diluted solution by the suppression of the molecular motion. In particular, this binding effect could be readily released by heating. As a result, drastic changes in luminescent behavior were observed around room temperature regions. The dimers also showed excellent circular dichroism (CD) and circularly polarized luminescence (CPL) profiles. More information can be found in the Full Paper by M. Gon, Y. Morisaki and Y. Chujo on page 6323 ff. [ABSTRACT FROM AUTHOR]

With our new home-built circularly polarized luminescence (CPL) instrument, we measured fluorescence and CPL spectra of the enantiomeric pairs of two quasi-isomeric BODIPY DYEmers 1 and 2, endowed with axial chirality. The electronic circular dichroism (ECD) and CPL spectra of these atropisomeric dimers are dominated by the exciton coupling between the main π-π* transitions (550-560 nm) of the two BODIPY rings. Compound 1 has strong ECD and CPL spectra ( glum=4×10−3) well reproduced by TD-DFT and SCS-CC2 (spin-component scaled second-order approximate coupled-cluster) calculations using DFT-optimized ground- and excited-state structures. Compound 2 has weaker ECD and CPL spectra ( glum=4×10−4), partly due to the mutual cancellation of electric-electric and electric-magnetic exciton couplings, and partly to its conformational freedom. This compound is computationally very challenging. Starting from the optimized excited-state geometries, we predicted the wrong sign for the CPL band of 2 using TD-DFT with the most recommended hybrid and range-separated functionals, whereas SCS-CC2 or a DFT functional with full exact exchange provided the correct sign. [ABSTRACT FROM AUTHOR]

A novel enantiopure π‐allylruthenium(IV) precatalyst allowed the enantioselective and stereospecific allylations of indoles and gave access to indolin‐3‐ones, containing vicinal stereogenic centers. Facile separation of diastereoisomers exhibiting opposite circularly polarized luminescence (CPL) activities in diverse solvents, including water, demonstrated the potential of these sustainable transformations and of the newly prepared molecules. [ABSTRACT FROM AUTHOR]

Small chiral organic molecules with CD properties are in high demanded due to their potential use in promising electronic and biological applications. Herein, we reveal a system in which the oxidation of a phosphino group to the corresponding phosphine oxide on the inner rim of a helicene derivative induces a CPL response. Laterally π‐extended 7,8‐dihydro[5]helicenes bearing phosphine and phosphine oxide groups on their inner helical rims (i. e. the C1 position) were synthesized, and their helical structures were unambiguously determined by X‐ray crystallography. The photophysical (UV/visible and emission) and chiroptical properties of these compounds were investigated in various solvents. Despite their structural similarities, phosphine oxide showed a significantly better CPL response than phosphine, with a high dissymmetry factor for emission (|glum|=(1.3–1.9)×10−3) that can be attributed to structural changes in the interior of the helicene helix. [ABSTRACT FROM AUTHOR]

The pores/channels of porous 3D metal-organic frameworks (MOFs) have been widely applied to incorporate gas, solvent, or organic molecules. On the contrary, the utilization of the interlamellar void of layered metal-organic complexes (MOCs) remains underappreciated, although it is more flexible and available to accommodate molecules with different sizes. In this work, diverse sulfonates have been intercalated purposely into an identical layered MOC, which constructed various novel intercalation compounds possessing fluorescent, white-light emitting, photochromic, homochiral, or nonlinear optical (NLO) properties. With the help of single-crystal X-ray diffraction, their structures and the mutual interactions between the MOC host and the sulfonate guests were characterized. The properties of the guest molecules were tuned and meanwhile some new performances were generated after confining them into the interlayer region. Such a hybrid approach provides an efficient strategy to design and prepare multifunctional materials. [ABSTRACT FROM AUTHOR]

Optically active, Fréchet-type dendrimers containing an emissive X-shaped π-electron system as the core unit were synthesized. Gram-scale optical resolution and transformations of 4,7,12,15-tetrasubstituted [2.2]paracyclophanes were also carried out. The high-generation dendrons effectively absorbed UV light and transferred energy to the core, resulting in high photoluminescence (PL) from the core. In addition, the dendrons sufficiently isolated the emissive X-shaped conjugated core and bright emission was observed from both thin films and solutions. Intense circularly polarized luminescence (CPL) was observed from the thin film. The dendrimer films exhibited excellent optical properties, such as large molar extinction coefficients, high fluorescence quantum efficiencies, intense PL and CPL, and large CPL dissymmetry factors. [ABSTRACT FROM AUTHOR]

Highlights from the article: Front Cover: Near-Infrared Circularly Polarized Luminescence through Intramolecular Excimer Formation of Oligo(p-phenyleneethynylene)-Based Double Helicates (Chem. Eur. J. 39/2019) The "flexible" double helicate forms a tightly interlocked intramolecular excimer under photoirradiation, emitting near-infrared circularly polarized luminescence with high dissymmetry factor value. The "flexible" double helicate forms a tightly interlocked intramolecular excimer under photoirradiation, emitting near-infrared circularly polarized luminescence with high dissymmetry factor value.

We synthesized two bichromophoric difluoroboron‐β‐diketonates (DFB) connected in para and meta positions by using cyclohexane diamine as a chiral bridge (para and meta (R/S)‐CyDFB). TD‐DFT calculations revealed that the variation in connectivity of the DFB units leads to different spatial arrangements and a chirality inversion of the bichromophoric DFB. Higher gabs values were obtained in (R/S)‐CyDFB connected in para as compared to meta position. Aggregation of para (R/S)‐CyDFB in mixture of solvents increase the glum values as compared to its monomeric form. Ultrasonication and heating induced the formation of highly ordered nano‐helical wires of para (R/S)‐CyDFB that increased the glum values to 0.015. On the other hand, meta (R/S)‐CyDFB failed to form highly ordered self‐assembled wires due to hindered H‐binding sites. These observations indicate that the chiroptical properties of DFB bi‐chromophore system can be modulated with self‐assembly and spatial arrangement of the chromophores. [ABSTRACT FROM AUTHOR]

The twisting motion of 3,3‐bis(diphenylphosphoryl)‐2,2‐bipyridine (BIPYPO) provides s‐cis and s‐trans geometries of a chiral EuIII complex containing tris[3‐(trifluoromethylhydroxymethylene)‐(+)‐camphorate], inducing the sign inversion of the negative circularly polarized luminescence (CPL) signals at the 5D0→7F1 transition of EuIII. For more details see the Full Paper by J. Yuasa, H. Ueno, and T. Kawai on page 8621 ff. [ABSTRACT FROM AUTHOR]

Herein is reported a circularly polarized luminescent (CPL) probe that can respond to the chirality of nucleic acids. An achiral nanostructure was prepared by the hybridization of symmetric serinol nucleic acid (SNA) containing pyrene‐modified residues. When chiral oligomers that were complementary to the SNA were added, they induced helicity into the SNA nanowire. Efficient circular dichroism (CD) signal amplification was observed when pyrene was attached to uracil bases through a rigid alkynyl linker. Both CPL and CD signals were observed; they depended on the chirality of the added acyclic threoninol nucleic acid (aTNA) oligomer. This system can be used to convert the chirality of chiral biomolecules into chiroptical signals. [ABSTRACT FROM AUTHOR]

Keywords: chirality; dyes/pigments; heterocycles; luminescence; photophysics EN chirality dyes/pigments heterocycles luminescence photophysics 1 1 1 04/03/20 20200401 NES 200401 B Chiral BODIPY derivatives b and congeners have been recognized as promising circularly polarized luminescence (CPL) dyes. These chiral BODIPY congeners showed CPL both in solution and in the solid state with | I g i SB lum sb | values up to 3.8×10 SP -3 sp in the visible to NIR region. Chirality, dyes/pigments, heterocycles, luminescence, photophysics. [Extracted from the article]

A series of carbazole‐based boron dipyrromethenes (BODIPYs) 2 a–g bearing binaphthyl units have been synthesized by the Et2AlCl‐mediated reaction of the corresponding BODIPY difluorides 1 a–g with 1,1′‐binaphthalene‐2,2′‐diol. Substituents such as halogen, nitrile, and amino groups were tolerated under the reaction conditions, and the reaction of the phenylethynyl‐substituted 1 h gave (R,R)‐3 h bearing two binaphthyl units. The chiroptical properties of these dyes with different substituents were investigated by UV/Vis, CD, fluorescence, and circularly polarized luminescence (CPL) spectroscopy. The CD spectra showed Cotton effects in the absorption region of the BODIPY moieties. In addition, they showed CPL both in solution and in the solid state. Interestingly, several dyes recorded higher glum values in the solid state, probably due to intermolecular interactions. Because (R,R)‐3 h recorded relatively low glum values, the diastereomer (R,S)‐3 h was prepared. The (R,S) diastereomer showed intense CPL, which suggests a synergetic effect of the two binaphthyl groups. Finally, chiral carbazole‐based BODIPY dimers have been synthesized for the first time and their chiroptical properties were investigated. They showed redshifted fluorescence and CPL, which reached the near‐IR (NIR) region in the solid state. [ABSTRACT FROM AUTHOR]

Axially chiral BODIPY DYEmers display intense fluorescence and circularly polarized luminescence (CPL) spectra. Due to exciton coupling between the BODIPY rings the π* states split into two energy levels, giving strong ECD couplets. The strongly emitting excited state is the low ‐ lying exciton ‐ coupled level. TD ‐ DFT and CC2 calculations elucidated the photophysics behind the CPL of these systems. More information can be found in the Full Paper by M. Bröring, L. Di Bari, G. Pescitelli et al. on page 16089 ff. [ABSTRACT FROM AUTHOR]

Helically chiral N,N,O,O-boron chelated dipyrromethenes showed solution-phase circularly polarized luminescence (CPL) in the red region of the visible spectrum (λem(max) from 621 to 663 nm). The parent dipyrromethene is desymmetrised through O chelation of boron by the 3,5-ortho-phenolic substituents, inducing a helical chirality in the fluorophore. The combination of high luminescence dissymmetry factors (∣glum∣ up to 4.7 × 10–3) and fluorescence quantum yields (ΦF up to 0.73) gave exceptionally efficient circularly polarized red emission from these simple small organic fluorophores, enabling future application in CPL-based bioimaging. [ABSTRACT FROM AUTHOR]

This work demonstrates sign reversal of large circularly polarized luminescence (CPL) signal based on the hinge-like twisting motion of a bidentate ligand, 3,3-bis(diphenylphosphoryl)-2,2-bipyridine (BIPYPO), in a cis- trans isomerization of chiral europium(III) complexes. X-ray diffraction analysis revealed that twisting motion of BIPYPO provides s- cis and s- trans geometries of a chiral EuIII complex containing either tris[3-(trifluoromethylhydroxymethylene)-(+)-camphorate] ( D- 1) or tris[3-(heptafluoropropylhydroxymethylene)-(+)-camphorate] ( D- 2). The s- cis EuIII complexes show eight-coordinate geometry around the EuIII ion, in which the chelate between the phosphoryl oxygen and the EuIII ion forces the s- cis geometry of BIPYPO. In contrast, the phosphorus-nitrogen interaction provides a conformational lock for the s- trans geometry of the BIPYPO ligand, inducing a quasi-seven-coordinate EuIII complex. The difference in coordination geometry causes the sign change of the CPL signals between the s- cis and s- trans isomers, whereby the s- cis and s- trans isomers of EuIII complexes exhibit the positive and negative CPL signals, respectively, for the 5D0→7F1 transition. The proportion of the s- trans- D- 1 against s- cis- D- 1 increases upon changing the solvent from [D3]acetonitrile to [D6]acetone, inducing a sign change of the CPL signals. The complexes D- 1 and D- 2 show a biexponential decay with two different lifetimes, suggesting two emitting species, that is, the s- cis and s- trans isomers of EuIII complexes. In both cases, the proportions of the longer lifetime components ( τ1) decrease and instead the shorter lifetime components ( τ2) increase upon changing the solvent from [D3]acetonitrile to [D6]acetone. [ABSTRACT FROM AUTHOR]

Two chiral luminescent derivatives of pyridine bis(oxazoline) (Pybox), ( SS/ RR)- iPr-Pybox (2,6-bis[4-isopropyl-2-oxazolin-2-yl]pyridine) and ( SRSR/ RSRS)-Ind-Pybox (2,6-bis[8 H-indeno[1,2- d]oxazolin-2-yl]pyridine), have been combined with lanthanide ions (Gd3+, Nd3+) and octacyanotungstate(V) metalloligand to afford a remarkable series of eight bimetallic CN−-bridged coordination chains: {[LnIII( SS/ RR- iPr-Pybox)(dmf)4]3[WV(CN)8]3} n ⋅dmf ⋅4 H2O (Ln=Gd, 1- SS and 1- RR; Ln=Nd, 2- SS and 2- RR) and {[LnIII( SRSR/ RSRS-Ind-Pybox)(dmf)4][WV(CN)8]} n ⋅5 MeCN ⋅4 MeOH (Ln=Gd, 3- SRSR and 3- RSRS; Ln=Nd, 4- SRSR and 4- RSRS). These materials display enantiopure structural helicity, which results in strong optical activity in the range 200-450 nm, as confirmed by natural circular dichroism (NCD) spectra and the corresponding UV/Vis absorption spectra. Under irradiation with UV light, the GdIII-WV chains show dominant ligand-based red phosphorescence, with λmax≈660 nm for 1-( SS/ RR) and 680 nm for 3-( SRSR/ RSRS). The NdIII-WV chains, 2-( SS/ RR) and 4-( SRSR/ RSRS), exhibit near-infrared luminescence with sharp lines at 986, 1066, and 1340 nm derived from intra -f 4F3/2→4I9/2,11/2,13/2 transitions of the NdIII centers. This emission is realized through efficient ligand-to-metal energy transfer from the Pybox derivative to the lanthanide ion. Due to the presence of paramagnetic lanthanide(III) and [WV(CN)8]3− moieties connected by cyanide bridges, 1-( SS/ RR) and 3-( SRSR/ RSRS) are ferrimagnetic spin chains originating from antiferromagnetic coupling between GdIII ( SGd=7/2) and WV ( SW=1/2) centers with J 1-( SS)=−0.96(1) cm−1, J 1-( RR)=−0.95(1) cm−1, J 3-( SRSR)=−0.91(1) cm−1, and J 3-( RSRS)=−0.94(1) cm−1. 2-( SS/ RR) and 4-( SRSR/ RSRS) display ferromagnetic coupling within their NdIII-NC-WV linkages. [ABSTRACT FROM AUTHOR]