Inversion of circularly polarized luminescence by electric current flow during transition.

The development of chiral compounds exhibiting circularly polarized luminescence (CPL) has advanced remarkably in recent years. Designing CPL-active compounds requires an understanding of the electric transition dipole moment () and the magnetic transition dipole moment () in the excited state. However, while the direction and magnitude of can, to some extent, be visually inferred from chemical structures, remains elusive, posing challenges for direct predictions based on structural information.

Visualization of the Plasmid DNA Delivery System by Complementary Fluorescence Labeling of Arginine-Rich Peptides.

Cell-penetrating peptides, such as arginine-rich peptides, encapsulate nucleic acid drugs and deliver them to intracellular compartments. Comprehensive tracking of drug delivery systems (DDSs) provides information about the behavior of the drug as well as the fate of the drug carrier after drug release, which is crucial for minimizing side effects. In this study, we labeled peptides designed to carry plasmid DNA with two types of dyes, traditional dye fluorescein and aggregation-induced emission (AIE) dye tetraphenylethylene, and subsequently tracked the DDS through the complementary ON and OFF fluorescence behaviors of the dyes.

Chromic properties of dibenzo[,]fluoranthenes exhibiting different resonance contributions.

Chromic molecules change colour in response to external stimuli and are utilized in applications such as food additive detection, light dimmers, and biological probes. One of the common design strategies for organic chromic molecules is based on changes in the π-conjugation. We have hypothesized that non-alternant polyaromatic hydrocarbon (PAH) skeletons can be used as backbones for chromic molecules.

Synthesis and Optical Properties of Binaphthyl Derivatives with Comprehensive Introduction of Phenylethynyl Groups.

In this study, compounds with phenylethynyl (PE) groups introduced at all of the possible positions of the methylene-bridged structure of the 1,1'-bi-2-naphthol backbone (3-PE to 8-PE) were synthesized. Compounds with four or six phenylethynyl groups (3,6-PE, 4,6-PE, 5,6-PE, 6,7-PE, and 3,4,6-PE) were also synthesized. The key reaction for the synthesis of these compounds was the Sonogashira reaction using halogen scaffolds.

Aggregation-induced enhanced fluorescence emission of chiral Zn(II) complexes coordinated by Schiff-base type binaphthyl ligands.

A pair of novel chiral Zn(II) complexes coordinated by Schiff-base type ligands derived from BINOL (1,1'-bi-2-naphthol), R-/S-Zn, were synthesized. X-ray crystallography revealed the presence of two crystallographically independent complexes; one has a distorted trigonal-bipyramidal structure coordinated by two binaphthyl ligands and one disordered methanol molecule (molecule A), while the other has a distorted tetrahedral structure coordinated by two binaphthyl ligands (molecule B). Numerous CH⋯π and CH⋯O interactions were identified, contributing to the formation of a 3-dimensional rigid network structure.

Aggregation-induced circularly polarized phosphorescence of Pt(II) complexes with an axially chiral BINOL ligand.

A pair of chiral Pt(II) complexes coordinated by simple BINOL and bipyridine ligands displaying aggregation-induced phosphorescence and circularly polarized luminescence were characterized by X-ray crystallography and absorption and emission spectroscopies. The emission of the powder sample was reddish whereas the thin film dispersed in PMMA ( = 1 wt%) exhibited a white emission.

Multiply Twisted Chiral Macrocycles Clamped by Tethered Binaphthyls Exhibiting High Circularly Polarized Luminescence Brightness.

Invited for the cover of this issue are Masashi Hasegawa and co-workers at Kitasto University and Kyoto Prefectural University. The image depicts the reported multiply twisted chiral macrocycles as objects in a kaleidoscope. Read the full text of the article at 10.

Multiply Twisted Chiral Macrocycles Clamped by Tethered Binaphthyls Exhibiting High Circularly Polarized Luminescence Brightness.

Chiral macrocyclic dimers, trimers, and tetramers composed of paraphenylene and tethered binaphthyl were synthesized, and their molecular structures and chiroptical properties were investigated. X-ray analysis and theoretical calculations revealed that multiple twisted molecular structures - dimers, trimers, and tetramers - adopt figure-of-eight, Möbius triangle, and concave rectangle structures, respectively. These homologues have large ϵ values in their UV-vis absorption spectra because of the π-conjugation of the naphthalene-phenylene-naphthalene frameworks.

Synthesis and Properties of V-Shaped Xanthene Dyes with Tunable and Predictable Absorption and Emission Wavelengths.

V-shaped xanthene dyes capable of predicting absorption and emission wavelengths are described. These dyes were synthesized by bridging a xanthene ring and an aryl moiety of fluorescein through ether covalent bonds. These dyes showed longer absorption and emission wavelengths than those of the parent fluorescein.

Synthesis of Bridged Indigos and Their Thermoisomerization and Photoisomerization Behaviors.

Bridged indigos were synthesized by bridging the two nitrogen atoms in the indigo structure with a carbon chain, and their properties were carefully examined. These bridged indigos have intrinsic planar chirality, and the enantiomers were separated using chiral high-performance liquid chromatography. When the chiral bridged indigos were subjected to thermo- and photoisomerization, the corresponding ()-indigo was not observed at all, and racemization was observed.

Total Syntheses of FR-901235, Auxarthrones A-D, and Lamellicolic Anhydride.

In our previous study, an unusual rearrangement reaction was discovered whereby dinaphthyl ketones with three hydroxy groups at restricted positions were transformed into a phenalenone ring and a benzene ring. Using the rearrangement as a key reaction, the first total syntheses of FR-901235 and auxarthrones A-D from an unstable triketone common intermediate are described. Furthermore, lamellicolic anhydride was synthesized from the triketone.

Nucleophilic Addition Reaction with Dearomatization of Naphthalene Ring.

Various aromatic lactones have been synthesized and their regioselectivity (1,2-addition vs. 1,4- or 1,6-addition) investigated in reactions with organolithium species, particularly n-BuLi and sec-BuLi. The regioselectivity varied greatly depending on various factors, such as the bulkiness of both substrates and organolithium species, and types of solvent and cosolvent.

Synthetic and Biological Studies of Juglorubin and Related Naphthoquinones.

Juglorubin, juglorescein, and juglocombins A/B are naturally occurring naphthoquinone dimers isolated from sp. These dimers are proposed to be biogenetically derived from juglomycin C, a monomeric naphthoquinone isolated from the same sp. In this study, the dimerization of a juglomycin C derivative, a key step in the total syntheses of these natural products, was investigated.

Unified Approach toward Syntheses of Juglomycins and Their Derivatives.

A unified and common intermediate strategy for syntheses of juglomycins and their derivatives is reported. The use of a 1,4-dimethoxynaphthalene derivative as a key intermediate enabled easy access to various juglomycin derivatives. In this study, juglomycins A-D, juglomycin C amide, khatmiamycin and its 4-epimer, and the structure proposed for juglomycin Z were synthesized from this intermediate.

Synthesis, antibacterial and cytotoxic evaluation of flavipucine and its derivatives.

The antibacterial and cytotoxic activity of seven racemic lactams and both enantiomers of flavipucine were evaluated. Of the compounds tested in this study, flavipucine and phenylflavipucine displayed bactericidal activity against Bacillus subtilis. These results indicate that the pyridione epoxide moiety is a pharmacophore for antibacterial activity against B.

Synthesis and Photochemical Properties of Axially Chiral Bis(dinaphthofuran).

Both enantiomers of axially chiral bis(dinaphthofuran) were prepared in only two steps from 1'-hydroxy-4'-methoxy-2,2'-binaphthalenyl-1,4-dione, followed by optical resolution via high-performance liquid chromatography (HPLC) using a chiral stationary phase (CSP). The absolute configurations were determined by comparison of experimental and calculated vibrational circular dichroism (VCD) spectra. Synthetic bis(dinaphthofuran) exhibited a broad and unstructured emission derived from an intramolecular excimer in both solution and solid state.

Synthesis and Properties of Tribenzocarbazoles via an Acid-Promoted Retro (2+2)-Cycloaddition of Azapropellanes.

We describe herein the development of a new method to synthesize tribenzocarbazoles via an acid-promoted retro (2+2)-cycloaddition of azapropellanes, which were prepared by potassium hexamethyldisilazide (KHMDS)-promoted (2+2)-cycloaddition. The tribenzocarbazoles showed strong fluorescence both in solution and the solid state. The structural, electronic, and optical properties of the synthetic tribenzocarbazoles are also described.

Bioinspired Synthesis of Juglorubin from Juglomycin C.

In this paper, the synthesis of juglorubin, a natural red dye, from juglomycin C, a plausible biogenetic precursor, is reported. Sequential intermolecular and intramolecular Michael additions of juglomycin C, oxidation, and skeletal transformation proceeded in phosphate buffer to afford an undehydrated derivative of juglorubin. Subsequent dehydration of the secondary alcohol afforded juglorubin.

Total Synthesis of Dendrochrysanene through a Frame Rearrangement.

The first total synthesis of dendrochrysanene (1) was achieved. The key reaction for the construction of dendrochrysanene was an oxidative frame rearrangement reaction from a phenanthrene dimer to a spiro-lactone skeleton, which we serendipitously identified. Owing to the steric hindrance of the substituent on the peri position of the phenanthrene dimer, high-temperature conditions were required for the rearrangement reaction; however, at such temperatures, the substrate decomposed.

Formation of Phenalenone Skeleton by an Unusual Rearrangement Reaction.

The frame rearrangement reaction of dinaphthyl ketones, possessing hydroxy groups at appropriate positions, into phenalenone derivatives under acidic conditions was discovered serendipitously. Although this rearrangement had limited scope, its mechanism was unusual, involving the division of naphthalene rings into one phenalenone ring and one benzene ring. The reaction mechanism was elucidated by direct determination of intermediate structures using H NMR measurements.

Synthesis and Structures of Zigzag Shaped [12]Cyclo-p-phenylene Composed of Dinaphthofuran Units and Biphenyl Units.

A [12]Cyclo-p-phenylene 9 composed of dinaphthofuran units and biphenyl units was synthesized through reductive elimination of the corresponding trinuclear complex by applying Yamago's method. The X-ray crystallographic analyses of 9 revealed that it adopts a zigzag conformation in the solid state. The UV-vis and fluorescence measurements of compound 9 indicated that it also preferentially took a zigzag conformation in the solution state.

Skeletal Rearrangements of Polycyclic α-Ketols.

It has been proposed that prekinamycin and kinobscurinone may biogenetically isomerize to isoprekinamycin and prefluostatin, respectively, through the corresponding bridgehead α-ketol intermediates. In this transformation, the 6-5 ring system is converted into a 5-6 ring system via an α-ketol rearrangement. In this report, the skeletal rearrangement of polycyclic α-ketols inspired by this hypothetical biosynthetic transformation is reported.

Syntheses and properties of the V-shaped dimeric xanthene dyes.

Two new types of V-shaped dimeric xanthene fluorescent dyes were synthesized and evaluated in terms of their optical properties. Based on differences in their resonance forms, these V-shaped dyes were able to adopt four different protonation states (i.e.

False HDAC Inhibition by Aurone Compound.

Fluorescence assays are useful tools for estimating enzymatic activity. Their simplicity and manageability make them suitable for screening enzyme inhibitors in drug discovery studies. However, researchers need to pay attention to compounds that show auto-fluorescence and quench fluorescence, because such compounds lower the accuracy of the fluorescence assay systems by producing false-positive or negative results.