Oxidation of an Internal-Edge-Substituted [5]Helicene-Derived Phosphine Synchronously Enhances Circularly Polarized Luminescence.

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.

Oxidation of an Internal-Edge-Substituted [5]Helicene-Derived Phosphine Synchronously Enhances Circularly Polarized Luminescence.

Invited for the cover of this issue are the groups of Kazuteru Usui and Satoru Karasawa at Showa Pharmaceutical University, and Yoshitane Imai at Kindai University. The image depicts how a phosphine-oxide-bearing helicene exhibits markedly enhanced CPL response in the excited state compared with that of one with a corresponding phosphine. Read the full text of the article at 10.1002/chem.202202922.

Sign inversion of magnetic circularly polarized luminescence in Iridium(iii) complexes bearing achiral ligands.

Optically inactive, paramagnetic Ir(iii)(ppy)3 and Ir(iii)(ppy)2(acac) (ppy: 2-phenylpyridinate and acac: acetylacetonate) showed nearly mirror-symmetric magnetic circularly polarised luminescence (MCPL) spectra in dilute dichloromethane and dimethyl sulfoxide under N-up and S-up geometries in a 1.6-T magnetic field. However, the MCPL signs of Ir(iii)(ppy)3 and Ir(iii)(ppy)2(acac) under the same N-up (or S-up) Faraday geometry were opposite to each other when one ppy was replaced with an acac. This ligand exchange approach provides facile control of the MCPL sign, irrespective of the Faraday geometry.

Control of Axial Chirality by Planar Chirality Based on Optically Active [2.2]Paracyclophane.

Optically active X-shaped molecules based on the planar chiral [2.2]paracyclophane building block were prepared, in which di(methoxy)terphenyl units were stacked on the central benzene rings. At 25 °C, anisolyl rings freely rotate in solution, while in the crystal form, they are fixed by intramolecular CH-π interactions, thereby leading to the expression of the axial chirality, i.e., propeller chirality was exhibited by the planar chiral [2.2]paracyclophane moiety. The X-shaped molecule exhibited good circularly polarized luminescence (CPL) profiles with moderate ΦPL and a large glum value in the order of 10-3 at 25 °C, in solution. In contrast, at -120 °C, dual CPL emission with opposite signs was observed. According to the theoretical studies, the rotary motion of the anisolyl units is suppressed in the excited states, and so emission from two isomers could be observed. These results demonstrate that the axial chirality was controlled by the planar chirality, leading ultimately to propeller chirality.

Circular dichroism and circularly polarised luminescence of bipyrenyl oligopeptides, with piperidines added in the peptide chains.

Upon combining chiral peptides (the most basic chiral source) with pyrene moieties, we found that chiral oligopeptides bearing two-pendant pyrenyl units exhibited circularly polarised luminescence (CPL) originating from intramolecular excimers at 450-490 nm in various solvents, and the sign of their CPL signals depended on the type of solvent employed. The CPL and circular dichroism signs and intensities could be tuned by the introduction of a piperidine unit into the chiral peptide chain; thus, the obtained structure could be considered a practical Lock ON-OFF system for oligopeptide luminophores.

Circularly polarised luminescence of pyrenyl di- and tri-peptides with mixed d- and l-amino acid residues.

Multiple pyrenes as pendants of enantioimpure di-/tripeptides (abbreviated as N-LD-C, N-DL-C, N-LLD-C and N-DDL-C) showed pyrene-origin CPL and CD signals, which were associated with conflicting CPL-/CD-signs, compared to the corresponding enantiopure di-/tri-peptides.

Magnetic Circularly Polarized Luminescence from PtII OEP and F2 -ppyPtII (acac) under North-up and South-up Faraday Geometries.

The magnetic circularly polarized luminescence (MCPL) and photoluminescence (PL) spectra of achiral (2,3,7,8,12,13,17,18-octaethylporphyrinato)platinum(II), PtOEP, and [2-(4',6'-difluorophenyl)pyridinato-N,C2' ]platinum(II) acetylacetonate-O,O, F2 -ppyPt(acac), in toluene and dichloromethane solutions were recorded under an external magnetic field of 1.6 T with N-up and S-up Faraday geometries. The MCPL signs of PtOEP and F2 -ppyPt(acac) were controlled solely by changing the N-up and S-up geometries. The MCPL/PL wavelengths of F2 -ppyPt(acac) in solutions were varied by the ratio of the monomeric and excimeric species.

Isolation and characterization of cancer stem cells derived from human glioblastoma.

Cancer stem cell (CSC) is considered as a cause of cancer recurrence and metastasis. Simultaneously CSCs are responsible for the heterogeneous population in tumor tissues due to their differentiation potential. However, the characterizations of CSCs are still not enough and cancer stem cell lines widely available is desired to be established for the advancement of cancer research. In this study, we tried to isolate and characterize stem like cells from human glioblastoma cell line U-251MG cells. U-251MG P1 cells, which was previously condensed in the presence of hyaluronic acid as CD44 positive population were subjected to single cell isolation procedure. Although 5 clones were isolated, only one clone exhibited high expression of CD44, Nanog, OCT3/4 and SOX2, and named U-251MGSC1. The sphere forming ability of U-251MGSC1 cell was significantly higher than the parental U-251MG cells. Tumorigenicity of U-251MG-SC1 cells were higher than that of U-251MG cells. U-251MGSC1 cells exhibited higher expression of CD44, SOX2, Nestin and A2B5 than U-251MG cells in vitro and in vivo. The expression of GFAP and NF-M was enhanced when the cells were treated with the conditioned medium of U-251MG cells indicating the potential of differentiation. Sphere forming ability was more efficient than that of U-251MG cells and was enhanced in the presence of hyaluronic acid, which enhanced the cell growth as well. U-251MGSC1 cells exhibited rapid growth tumor in nude mice and efficient metastatic ability in transmembrane assay when compared with U-251MG cells. As the result, we concluded U-251MGSC1 cell was a glioblastoma CSC line derived from the parental U-251MG cells. U-251MGSC1 cells will be a good tool to develop effective therapeutic agents against CSCs and to elucidate the properties of glioma derived CSCs and the mechanism of tumor development in brain.

Circularly polarised luminescence (CPL) control of oligopeptide-Eu(iii) hybridized luminophores by interaction with peptide side chains.

Chiral oligopeptide-naphthalene/Eu(iii) hybridized luminophores emit strong circularly polarised solution-state luminescence (CPL) from Eu(iii) at 592 and 614 nm (|g CPL| ≤ 2.1 × 10-2). Although the peptide ligands have matching absolute configurations, the CPL sign is controllable by varying the number of naphthalene units and peptide/Eu(iii) coordination ratio.

Mirror-image magnetic circularly polarized luminescence (MCPL) from optically inactive EuIII and TbIIItris(ß-diketonate).

Five optically inactive EuIII(hfa)3, TbIII(hfa)3, EuIII(acac)3·Phen, TbIII(acac)3·Phen and EuIII(hfa)3·BDPB (hfa: hexafluoroacetylacetonate, acac: acetylacetonate, BDPB: 2,2'-bis(diphenylphosphino)biphenyl and Phen: phenanthroline) complexes showed clear mirror-image magnetic circularly polarised luminescence (MCPL) spectra in CHCl3, acetone, and DMF solutions, in a poly(methyl methacrylate) film, a KBr pellet and bulk powder at room temperature under 1.6 T as an external magnetic field with Faraday geometry. The signs of the MCPL signals were determined via N-up and S-up geometries. The gMCPL values of EuIII(hfa)3 and TbIII(hfa)3 were ±(0.046-2.0) × 10-2 T-1 at the 5D0 → 5FJ transitions (J = 1-4) in the range of 590 nm and 703 nm and ±(0.0081-1.0) × 10-2 T-1 at the 5D4 → 7FJ transitions (J = 3-6) in the range of 480 nm and 630 nm, respectively. Interestingly, the photoluminescence spectra of EuIII(hfa)3 and TbIII(hfa)3 in CHCl3 and acetone under 1.6 T considerably redshifted by 10-114 cm-1, while those of EuIII(acac)3·Phen and TbIII(acac)3·Phen did not reveal detectable redshifts.