Carbo[6]helicenes decorated with 3,4,5-tris(dodecyloxy)-N-(4-ethynylphenyl)benzamide moieties at their periphery give access to weak self-assemblies with circularly polarized luminescence and spin selectivity.

Abstract

Self-assembling features, chiroptical activity, and spin filtering properties are reported for 2,15- and 4,13-disubstituted [6]helicenes decorated in their periphery with 3,4,5-tris(dodecyloxy)-N-(4-ethynylphenyl)benzamide moieties. The weak non-covalent interaction between these units conditions the corresponding circularly polarized luminescence and spin polarization. The self-assembly is overall weak for these [6]helicene derivatives that, despite the formation of H-bonding interactions between the amide groups present in the peripheral moieties, shows very similar chiroptical properties both in the monomeric or aggregated states. This effect could be explained by considering the steric effect that these groups could generate in the growing of the corresponding aggregate formed. Importantly, the self-assembling features also condition chiral induced spin selectivity (CISS effect), with experimental spin polarization (SP) values found between 35–40 % for both systems, as measured by magnetic-conducting atomic force microscopy (AFM) technique.

A novel zwitterionic excited-state intramolecular proton transfer molecular system exhibits high affinity towards amyloid β (Aβ) aggregates and allows for in vivo near-infrared (NIR) imaging of amyloid plaques in transgenic Alzheimer's vs. wild-type mice.

Abstract

Chromophores with zwitterionic excited-state intramolecular proton transfer (ESIPT) have been shown to have larger Stock shifts and red-shifted emission wavelengths compared to the conventional π-delocalized ESIPT molecules. However, there is still a dearth of design strategies to expand the current library of zwitterionic ESIPT compounds. Herein, a novel zwitterionic excited-state intramolecular proton transfer system is reported, enabled by addition of 1,4,7-triazacyclononane (TACN) fragments on a dicyanomethylene-4H-pyran (DCM) scaffold. The solvent-dependent steady-state photophysical studies, pKa measurements, and computational analysis strongly support that the ESIPT process is more efficient with two TACN groups attached to the DCM scaffold and not affected by polar protic solvents. Impressively, compound DCM-OH-2-DT exhibits a near-infrared (NIR) emission at 740 nm along with an uncommonly large Stokes shift. Moreover, DCM-OH-2-DT shows high affinity towards soluble amyloid β (Aβ) oligomers in vitro and in 5xFAD mouse brain sections, and we have successfully applied DCM-OH-2-DT for the in vivo imaging of Aβ aggregates and demonstrated its potential use as an early diagnostic agent for AD. Overall, this study can provide a general molecular design strategy for developing new zwitterionic ESIPT compounds with NIR emission in vivo imaging applications.

Covalent organic frameworks (COFs) are an attractive class of electrode materials due to their outstanding advantages, such as structural designability, good stability, and ordered pore structure. The applications of COFs in the cathode, anode, and electrolyte of aqueous zinc-ion batteries (ZIBs) are summarized, and the relationship between the structure and electrochemical performance of COFs is elaborated.

Abstract

The development and utilization of green renewable energy are imperative with the aggravation of environmental pollution and energy crisis. In recent years, the exploration of electrochemical energy storage systems has gradually become a research hotspot in energy. Among them, aqueous zinc-ion batteries (ZIBs) have progressively developed into highly competitive and efficient energy storage devices owing to their inherent safety, natural abundance, and higher theoretical capacity. However, the practical application of ZIBs suffers from the limitation of challenges such as the absence of proper cathode materials and the unavoidable zinc dendrites and side reactions of Zn anode. Covalent organic frameworks (COFs) are an attractive class of electrode materials due to their inherent advantages, like structural designability, high stability, and ordered-open channels, bestowing them with great potential to overcome the problems of ZIBs. In this review, we concentrate on the discussion of designed strategies of COFs applied to ZIBs. Furthermore, the methods of using COFs to solve the challenging problems of cathode development, anode modification, and electrolyte optimization for ZIBs are summarized. Finally, the existing difficulties, solution measures, and prospects of COFs for ZIBs applications are discussed. Our commentary hopes to serve as a valuable reference for developing COFs-based ZIBs.

A novel strategy for fluorescence enhancement in aqueous solution with high inclusion equilibrium constant based on host-guest chemistry was proposed. Fluorescent dyes based on adamantane modification could be complexed with methylated β-cyclodextrin (M-β-CD). Consequently, fluorescent intensity of these dyes was significantly improved in water. And the work was further extended to fluorescent organelle targeting. Fluorescence enhancement was successfully realized in bioimaging with the addition of M-β-CD.

Abstract

The fluorescence of functional dyes was generally quenched in aqueous solution, which hindered their application in water-bearing detections. In this work, a novel strategy based on host-guest interaction was provided for the purpose of fluorescence enhancement in aqueous solution and cell imaging. Three adamantane-modified fluorescent dyes (Coum-Ad, NP-Ad, NR-Ad) with coumarin, 1,8-naphthalimide and Nile Red as fluorophores were initially designed and prepared. The ((adamantan-1-yl)methyl)amino group, as the auxochrome of those dyes, complexed with methylated β-cyclodextrin (M-β-CD) via supramolecular interaction, and then fluorescent supramolecular nanoparticles (FSNPs) were formed by self-assembly in water. The inclusion equilibrium constant (K) could be as high as 3.94×10⁴ M⁻¹. With the addition of M-β-CD, fluorescence quantum yields of these dyes were separately improved to 69.8 %, 32.9 % and 41.3 %. Inspired by the above satisfactory results, six adamantane-modified probes organelle-NPAds with organelle-targeting capability were further obtained. As the formation of hydrogen bonds between organelle-NPAd2 and M-β-CD verified by theoretical calculation, K of organelle-NPAd2 (5.13×10⁴ M⁻¹~4.53×10⁵ M⁻¹) with M-β-CD was higher than that of organelle-NPAd1 (1.15×10⁴ M⁻¹~3.66×10⁴ M⁻¹) and their fluorescence quantum yields increased to 32.8 %~83.6 % in aqueous solution. In addition, fluorescence enhancement was realized in cell imaging with the addition of M-β-CD.

Photoisomerization of “partially embedded fused-dihydropyridazine N-aryl aza[5]helicene derivatives” (PDH) with a helical structure inspires the demonstration of intrinsic photo-triggered multi-functional properties based on a Kekulé biradical and structural flexibility. Multiple functions, such as T-type photochromism, photo-excitation-mediated triplet biradical formation, and photoracemization, which are attributed to PDH, are revealed.

Abstract

Herein, we report the synthesis of two “partially embedded fused-dihydropyridazine N-aryl aza[5]helicene derivatives” (PDHs) and the demonstration of their intrinsic photo-triggered multi-functional properties based on a Kekulé biradical structure. Introducing bulky electron-withdrawing trifluoromethyl or pentafluoroethyl groups into the aza[5]helicene framework (PDH-CF₃ and −C₂F₅) gives PDH axial chirality based on the helicity of the P and M forms, even at room temperature. Upon photo-irradiation of PDH-CF₃ in a frozen solution, an ESR signal from the triplet biradical with zero-field splitting values, generated by N−N bond dissociation, was observed. However, when the irradiation was turned off, the ESR signal became silent, thus indicating the existence of two equilibria: between the biradical and quinoidal forms based on the Kekulé structure, and between N−N bond cleavage and recombination. The observed photo- and thermally induced behaviors indicate that T-type photochromic molecules are involved in the photoisomerization mechanism involving the two equilibria. Inspired by the photoisomerization, chirality control of PDH by photoracemization was achieved. Multiple functionalities, such as T-type photochromism, photo-excitation-mediated triplet biradical formation, and photoracemization, which are attributed to the “partially embedded dihydropyridazine” structure, are demonstrated.

• 1st Ge atom side-on coordination to C=N, • Novel mode of aromatic C−C bond activation by NHC, • Germanium atom transfer

Abstract

The germylone dimNHCGe (dimNHC=diimino N-heterocyclic carbene) reacts with azides N₃R (R=SiMe₃ or p-tolyl) to furnish the first examples of germanium π-complexes, i. e. guanidine-ligated compounds (dimNHI−SiMe₃)Ge (NHI=N-heterocyclic imine, R=SiMe₃) and (dimNHI−Tol)Ge (R=p-tolyl). DFT calculations suggest that these species are formed by a Staudinger type replacement of dinitrogen in the azide by a nucleophilic germylone, leading to a transient carbene adduct of iminogermylidene. Heating a solution of compound (dimNHI−SiMe₃)Ge to 70 °C results in extrusion of the iminogermylidene that further aggregates to produce the known [Me₃SiNGe]₄ tetramer, whereas the imidazolylidene fragment transforms into an unusual heptatriene species that can be considered as a product of carbene insertion into the C−C bond of a pendant Ar substituent at the imidazolylidene nitrogen of the dimNHC. Reaction of (dimNHI−SiMe₃)Ge with tetrachloro-o-benzoquinone results in the net transfer of a germanium atom and formation of the free diimino-guanidine ligand. This ligand also forms when (dimNHI−SiMe₃)Ge is treated with azide N₃(p−Tol), with the germanium product being [(p−Tol)NGe]_n

The so-called “trichlates” are the heavier but scarcely investigated homologues of the well-known triflates. Access to the acid (H₅O₂)[Cl₃CSO₃] is the key step for the synthesis of trichlates. The acid can be prepared by chlorination of CS₂, yielding Cl₃CSCl, and subsequent oxidation by H₂O₂ giving Cl₃CSO₂Cl, the chloride of the acid.

Abstract

Chlorination of CS₂ leads to trichloromethanesulfenyl chloride, Cl₃CSCl, in moderate yields. The oxidation of Cl₃CSCl with H₂O₂ gives Cl₃CSO₂Cl, the chloride of trichloromethanesulfonic acid. Cl₃CSO₂Cl is the crucial product for the preparation of trichloromethanesulfonates (“trichlates”) and has been characterized by IR spectroscopy, differential scanning calorimetry (DSC) and X-ray diffraction measurements (P-1, a=609.99(5) pm, b=727.45(6) pm, c=782.49(7) pm, α=80.644(3)°, β=85.175(3)°, γ=88.311(3)°. The acid Cl₃CSO₃H can be gained in form of the hydrate (H₅O₂)[Cl₃CSO₃] in two different modifications (I: monoclinic, P2₁/n, Z=8, a=1292.47(7) pm, b=605.89(2) pm, c=2661.1(1) pm, β=98.708(4)°, V=1672.8(1) ų; II: monoclinic, Cc, Z=4, a=699.80(5) pm, b=1054.72(8) pm, c=1139.88(8) pm, β=95.303(3)°, V=837.7(1) ų. Both modifications have been investigated by IR spectroscopy, thermal analyses and theoretical calculations.

In phage display selection using M13 bacteriophage, the M13 main body, which is a huge filament>10³ time larger than the displayed peptide, has been considered to interfere with the result of affinity selection. This interference can be attenuated by magnetically orienting the M13 main body vertical to the target surface, which results in the suppression of nonspecific adhesion and the change in the population of selected M13 clones.

Abstract

Although phage display selection using a library of M13 bacteriophage has become a powerful tool for finding peptides that bind to target materials on demand, a remaining concern of this method is the interference by the M13 main body, which is a huge filament >10³ times larger than the displayed peptide, and therefore would nonspecifically adhere to the target or sterically inhibit the binding of the displayed peptide. Meanwhile, filamentous phages are known to be orientable by an external magnetic field. If M13 filaments are magnetically oriented during the library selection, their angular arrangement relative to the target surface would be changed, being expected to control the interference by the M13 main body. This study reports that the magnetic orientation of M13 filaments vertical to the target surface significantly affects the selection. When the target surface was affinitive to the M13 main body, this orientation notably suppressed the nonspecific adhesion. Furthermore, when the target surface was less affinitive to the M13 main body and intrinsically free from the nonspecific adhesion, this orientation drastically changed the population of M13 clones obtained through library selection. The method of using no chemicals but only a physical stimulus is simple, clean, and expected to expand the scope of phage display selection.

CuAg(SO₄)₂, a novel mixed-metal sulfate, shows a layered structure, with [Ag(SO₄)₂]²⁻ sublattice (shown) hosting strong antiferromagnetic interactions. Calculations suggest that copper site could easily be changed for other small divalent cations, giving rise to a new family of two-dimensional magnetic materials.

Abstract

Copper(II) silver(II) sulfate crystallizes in a monoclinic CuSO₄-related structure with P2₁/n symmetry. This quasi-ternary compound features Ag(SO₄)₂ ²⁻ layers, while the remaining cationic sites may be occupied either completely or partially by Cu²⁺ cations, corresponding to the formula of (Cu _x Ag_1−x )[Ag(SO₄)₂], x=0.6−1.0. CuAg(SO₄)₂ is antiferromagnetic with large negative Curie-Weiss temperature of −140 K and shows characteristic ordering phenomenon at 40.4 K. Density functional theory calculations reveal that the strongest superexchange interaction is a two-dimensional antiferromagnetic coupling within Ag(SO₄)₂ ²⁻ layers, with the superexchange constant J _2D of −11.1 meV. This renders CuAg(SO₄)₂ the rare representative of layered Ag²⁺-based antiferromagnets. Magnetic coupling is facilitated by the strong mixing of Ag d(x ²−y ²) and O 2p states. Calculations show that M²⁺ sites in MAg(SO₄)₂ can be occupied with other similar cations such as Zn²⁺, Cd²⁺, Ni²⁺, Co²⁺, and Mg²⁺.

The annulation of a methylenecyclopropane with acyl cyanoalkenes using DABCO or quinuclidine as a catalyst was developed to give 2,3-dihydofurans. The stoichiometric amount of the Lewis bases promoted the isomerization of 2,3-dihydrofurans to furans. 1H NMR spectroscopy of the reaction in situ revealed that the methylenecyclopropane is opened by the Lewis base to form a reaction intermediate that is added to the cyanoalkenes.