Carbazole-incorporated smaragdyrin BF2-complex 3 was synthesized by SNAr reaction of 3,5-dibromo-8-mesityl-BODIPY 1 with 3,6-di(tert-butyl)-1,8-di(pyrrol-2-yl)carbazole 2 as a nucleophile. Demetalation of 3 with ZrCl4 gave the corresponding smaragdyrin free base 4 in a good yield. Oxidations of 3 and 4 with MnO2 gave smaragdyrins 5 and 6, respectively, both followed by aromaticity switching, since the oxidized products showed a moderate paratropic ring current owing to their 20π-electronic circuits. Further, treatment of 4 with [RhCl(CO)2]2 in the presence of NaOAc gave RhI complex 7, and oxidation of 3 with RuCl3 in the presence of triethylamine led to the formation of a spiro dimer product, 8.

Novel styryl dye derivatives incorporating indolium and quinolinium cores are synthesized to examine their binding capability with tau aggregates. These dyes possess enhanced fluorescence in viscous environments. Among them, Dye 4, containing a quinolinium moiety, shows the most outstanding increase in fluorescence upon binding to tau aggregates in vitro and in cells. These probes exhibit potential for Alzheimer's disease detection.

Abstract

A series of novel styryl dye derivatives incorporating indolium and quinolinium core structures were successfully synthesized to explore their interacting and binding capabilities with tau aggregates in vitro and in cells. The synthesized dyes exhibited enhanced fluorescence emission in viscous environments due to the rotatable bond confinement in the core structure. Dye 4, containing a quinolinium moeity and featuring two cationic sites, demonstrated a 28-fold increase in fluorescence emission upon binding to tau aggregates. This dye could also stain tau aggregates in living cells, confirmed by cell imaging using confocal fluorescence microscopy. A molecular docking study was conducted to provide additional visualization and support for binding interactions. This work offers novel and non-cytotoxic fluorescent probes with desirable photophysical properties, which could potentially be used for studying tau aggregates in living cells, prompting further development of new fluorescent probes for early Alzheimer's disease detection.

Boryl-group-assisted reductive C−C bond cleavage of 1,2-diaryl-1,2-diborylethanes is described. The substrates, 1,2-diaryl-1,2-diborylethanes, are synthesized by reductive diboration of stilbenes. The combination of these reactions, reductive diboration and reductive cleavage provides a new strategy for reductive C=C double bond cleavage.

Abstract

In contrast to the well-established oxidative C=C double bond cleavage to give the corresponding carbonyl compounds, little is known about reductive C=C double bond cleavage. Here we report that C−C single bond cleavage in 1,2-diaryl-1,2-diborylethanes proceeds by reduction with sodium metal to yield α-boryl benzylsodium species. In combination with our previous reductive diboration of stilbenes, the overall transformation represents reductive cleavage of the C=C double bonds of stilbene to yield α-boryl-α-sodiated toluenes. This reductive two-step C=C double bond cleavage is applicable to ring-opening or ring-expansion reactions of polycyclic aromatic hydrocarbons.

Low-dimensional hybrid bismuth halide perovskites have recently emerged as a class of non-toxic alternative to lead perovskites with promising optoelectronic properties. Here, we report three hybrid bismuth(III)-iodides: 0-D (H2DAC)2Bi2I10·6H2O (H2DAC_Bi_I), 0-D (H2DAF)4Bi2I10·2I3·2I·6H2O (H2DAF_Bi_I), and 1-D (H2DAP)BiI5 (H2DAP_Bi_I) (where H2DAC = trans-1,4-diammoniumcyclohexane; H2DAF = 2,7-diammoniumfluorene and H2DAP = 1,5-diammoniumpentane). Their synthesis, single-crystal X-ray structures, and photophysical properties are reported. The first two compounds comprise edge-sharing [Bi2I10]4- dimers, while the last compound has cis-corner-sharing 1-D chains of [BiI6]3- octahedra. Intercalation of triiodide (I3-) and iodide (I-) ions enhance electronic coupling between the [Bi2I10]4- of H2DAF_Bi_I, leading to enhanced optical absorption when compared to H2DAC_Bi_I which lacks such intercalants. Furthermore, calorimetric and variable temperature X-ray diffraction measurements suggest a centrosymmetric to non-centrosymmetric phase transition (monoclinic P212121 ↔ orthorhombic Pnma) of H2DAP_Bi_I at 448 K (in heating step) and 443 K (in cooling step).

N-Heterocyclic carbenes (NHCs) catalysts have been employed as effective tools in the development of various reactions, which have made notable contributions in developing diverse reaction modes and generating significant functionalized molecules. This review provides an overview of the recent advancements in the chemo- and regioselective activation of different aldehydes using NHCs, categorized into five parts based on the different activation modes. A brief conclusion and outlook is provided to stimulate the development of novel activation modes for accessing functional molecules.

This work reports the cooperative reactivity of rare-earth aryloxide complexes with N-heterocyclic carbene (NHC) or N-heterocyclic olefin (NHO), showcasing their synergistic effect in the activation of H2 and diverse organic substrates.  Reactions of RE(OAr)3 (RE = La, Sm, and Y; Ar = 2,6-tBu2-C6H3) with unsaturated NHC ItBu (:C[N(R)CH]2, R = tBu) isolate abnormally bound RE metal NHC complexes RE/aNHC. In contrast, no metal-NHO adducts were formed when RE(OAr)3 were treated with NHO (R2C=C[N(R)C(R)]2, R = CH3). Both RE/aNHC and RE/NHO Lewis pairs enabled cooperative H2 activation. Furthermore, RE(OAr)3 were found to catalyze the hydrogenation of exocyclic C=C double bond of NHO under mild conditions. Moreover, treatment of the La/aNHC complex with benzaldehyde produced a La/C4 1,2-addition product. The La/NHO Lewis pair could react with (trimethylsilyl)diazomethane and  a, b-conjugated imine, affording an isocyanotrimethylsilyl lanthanum amide complex and a La/C 1,4-addition product, respectively.

Using a new CuI/DMAP catalytic system, oxidative N-alkynylation of 7-azaindole has been discussed. A detailed mechanistic study has been performed based on the reactive intermediate [Cu^II(DMAP)₂I₂], supported by both DFT calculations and UV-visible spectroscopy. Further several 7-azaindole decorated 1,4 and 1,5 disubstituted 1,2,3-triazole derivatives has been synthesized via click chemistry.

Abstract

An efficient and practical method for the N-alkynylation of 7-azaindoles has been established by using CuI/DMAP catalytic system at room temperature and in open air. This simple protocol has been successfully employed in the synthesis of a wide range of N-alkynylated 7-azaindoles with good yields. Also, this approach is well-suited for large-scale N-alkynylation reactions. The designed N-alkynylated 7-azaindoles were further subjected to Cu-/Ir-catalyzed alkyne–azide cycloaddition (CuAAC/IrAAC) or “click” reaction for the rapid synthesis of 1,4-/1,5 disubstituted 1,2,3-triazole decorated 7-azaindoles. A mechanistic study based on density functional theory (DFT) calculations and ultraviolet–visible (UV) spectroscopic studies revealed that the CuI and DMAP combination formed a [Cu^II(DMAP)₂I₂] species, which acts as an active catalyst. The DFT method was used to assess the energetic viability of an organometallic in the C−N bond formation pathway originating from the [Cu^II(DMAP)₂I₂] complex. We expect that the newly designed Cu/DMAP/alkyne system will offer valuable insights into the field of Cu-catalyzed transformations.

The substituents effects in arene-fullerene interactions were examined by NMR titration experiments using an open-[60]fullerene as a host, revealing self-assembling behavior with substituted benzenes by a 1 : 2 stoichiometry. The destabilization of the OMe-substitution clearly indicates the presence of direct through-space substituent-π interactions describable by the Wheeler-Houk model.

Abstract

The arene-arene interactions between electron-rich and deficient aromatics have been less understood. Herein, we focus on a [60]fullerene π-surface as an electron-deficient aromatics. Using a ¹H signal of H₂O@C₆₀ as a magnetic probe, the presence of benzene–fullerene interactions was confirmed. To investigate substituent effects on the noncovalent arene-fullerene interactions, NMR titration experiments were carried out using an open-[60]fullerene and a series of substituted benzenes, i. e., PhX (X=NO₂, CN, Cl, OMe, H, CH₃, and NH₂), demonstrating a 1 : 2 stoichiometry with a positive correlation between stabilization energies upon the first association (ΔG ₁) and Hammet constants (σ _m). The destabilization of the self-assembled structure for X=OMe with a σ-withdrawing nature clearly showed direct through-space substituent-π interactions describable by the Wheeler-Houk model while the second association was suggested to be considerably perturbed by the secondary effects.

Circularly polarized luminescence (CPL) refers to the emission of light with distinguishable left or right circular polarization in non-racemic systems. CPL has attracted significant attention due to its potential applications in future displays, photonics technologiesIn recent years, there has been significant development in the field of circularly polarized luminescent (CPL) materials based on small organic molecules, attributed to their precise and tunable molecular structures and high luminescent efficiency. With the continuous investigation of chiral molecular frameworks and molecular derivatization, the performance of CPL small molecules has been comprehensively promoted. We herein provide a detailed discussion on commonly studied CPL chiral frameworks of small molecules, including axially chiral binaphthyls, axially chiral biphenyls, chiral helicenes, planar chiral cyclophanes, spirocycles, metal-centered chirality, and point chirality, aiming at providing readers with the basic understanding and research status about CPL as well as inspiration for future development.

Hydroxyl radical (•OH), a highly reactive oxygen species (ROS), is assumed as one of the most aggressive free radicals. This radical has a detrimental impact on cells as it can react with different biological substrates leading to pathophysiological disorders, including inflammation, mitochondrion dysfunction, and cancer. Quantification of this free radical in-situ plays critical roles in early diagnosis and treatment monitoring of various disorders, like macrophage polarization and tumor cell development. Luminescence analysis using responsive probes has been an emerging and reliable technique for in-situ detection of various cellular ROS, and some recently developed •OH responsive nanoprobes have confirmed the association with cancer development. This paper aims to summarize the recent advances in the characterization of •OH in living organisms using responsive nanoprobes, covering the production, the sources of •OH, and biological function, especially in the development of related diseases followed by the discussion of luminescence nanoprobes for •OH detection.