A copper molybdovanadate with mixed-valent vanadium (V⁴⁺/V⁵⁺=4/3) and molybdenum (Mo⁵⁺/Mo⁶⁺=8/2) cations exhibits improved catalytic activity (conv.: 96.8 %) compared with the complex (Cpyr)₅PV₂Mo₅W₅O₄₀ [conv.: 88.51 %, Cpyr=(C₁₆H₃₂C₅H₄N)⁺)] and could serve as a highly efficient heterogeneous catalyst in the selective oxidation of benzyl alcohols to benzaldehydes.

Abstract

A new organic-inorganic hybrid open-framework molybdovanadate with mixed-valences of vanadium (V⁴⁺/V⁵⁺=4/3) and molybdenum (Mo⁵⁺/Mo⁶⁺=8/2) cations has been synthesized. The complex possesses the unique V/Mo ratio (7/10), fascinating 8-C topological network and 1D 4-MR channels (7.793 Å×6.699 Å). Importantly, its catalytic activities for the selective oxidation of benzyl alcohol to benzaldehyde (oxidant: H₂O₂, 30 wt %) have been well evaluated. The results indicated that it exhibited improved catalytic activities (conv.: 96.8 %) compared with the catalyst (Cpyr)₅PV₂Mo₅W₅O₄₀ [conv.: 88.51 %, Cpyr=(C₁₆H₃₂C₅H₄N)⁺)], high recyclability and structural stability. Moreover, the conversions and selectivities (conv.: 82.4–92.5 %; sele.: 91.5–95.7 %) of the substrates containing electron donating groups (−OH, −CH₃, −OCH₃ and −Cl) were significantly higher than those of the substrate containing electron withdrawing group (−NO₂) (conv. 67.4 %; sele.: 80.8 %). This is due to the fact that the −NO₂ with a large Hammett substituent constant is not conducive to the generation of transition state products. The studies revealed the complex could act as a highly efficient heterogeneous catalyst in selective oxidation of benzyl alcohols.

Sulfone or carbonyl-based acceptor units were used to construct donor-acceptor conjugate organic fluorophores. Both TPA-SO and TPA-CO have solvent polarity-dependent photophysical properties for strong intramolecular charge transfer. As sulfone has weak intersystem crossing ability, TPA-SO has high fluorescence efficiency in solution and nanoparticles, and is a promising fluorescence dye.

Abstract

Electron-accepting units play vital roles in constructing donor-acceptor (D-A) conjugated organic optoelectronic materials; the electronic structures and functions of the acceptors need to be carefully unveiled to controllably tailor the optoelectronic properties. We have synthesized two D-A conjugated organic fluorophores, TPA-SO and TPA-CO, with similar molecular skeletons based on sulfone- or carbonyl-containing polycyclic aromatic acceptors. Both TPA-SO and TPA-CO display obvious solvent polarity-dependent photophysical properties and large Stokes shift of over 100 nm for strong intramolecular charge transfer processes. Experimental evidence indicates that the sulfone group in TPA-SO merely serves as a strong electron-withdrawing unit. TPA-SO shows yellowish-green emission with a peak at 542 nm and an absolute photoluminescence quantum yield (PLQY) of 98 % in solution, whereas the carbonyl group in TPA-CO can act as both an electron-withdrawing unit and spin transition convertor, so TPA-CO displays red emission with a low absolute PLQY of 0.32 % in solution. Impressively, upon going from solution to aggregate state, TPA-SO nanoparticles keep a high PLQY of 9.5 % and moderate biocompatibility, thus they are good nano-agents for cellular fluorescence imaging. The results reveal that the inherent acceptor characteristic acts as a crucial effect in the photophysical properties and applications of the organic fluorophores.

Controlled/living supramolecular polymerization has enabled the synthesis of well-defined nanostructures which are otherwise inaccessible under thermodynamically controlled, spontaneous self-assembly process. Yet, there is still room for improvement; here we show two-dimensional living supramolecular polymerization improved using an additive, which permits the synthesis of supramolecular nanosheets of better quality.

Abstract

Supramolecular polymers are formed through nucleation (i. e., initiation) and polymerization processes, and kinetic control over the nucleation process has recently led to the realization of living supramolecular polymerization. Changing the viewpoint, herein we focus on controlling the polymerization process, which we expect to pave the way to further developments in controlled supramolecular polymerization. In our previous study, two-dimensional living supramolecular polymerization was used to produce supramolecular nanosheets with a controlled area; however, these had rough edges. In this study, the growth of the nanosheets was controlled by using a ‘dummy’ monomer to produce supramolecular nanosheets with smoothed edges.

The chemistry at the germylene and dithiolene interface has rarely been explored. Here, we report a series of Lewis base-coordinated germanium(II) dithiolene complexes. Controlled hydrolysis of the carbene-coordinated germanium(II) dithiolene complex affords a dianionic bis-dithiolene-based germanium(II) species.

Abstract

The 1 : 2 reaction of the imidazole-based dithiolate (2) with GeCl₂ • dioxane in THF/TMEDA gives 3, a TMEDA-complexed dithiolene-based germylene. Compound 3 is converted to monothiolate-complexed (5) and N-heterocyclic carbene-complexed (7) germanium(II) dithiolene complexes via Lewis base ligand exchange. A bis-dithiolene-based germylene (8), involving a 3c–4e S-Ge-S bond, has also been synthesized through controlled hydrolysis of 7. The bonding nature of 3, 5, and 8 was investigated by both experimental and theoretical methods.

Changes in the assembly of Pt^II complexes on layered double hydroxide (LDH) nanoparticles. Under dry conditions, Pt^II complexes are attached to the LDH nanoparticles like starfish on the rocks, and exhibit a monomer-derived green emission. Under humid conditions, the mobility of Pt^II complexes increases due to the adsorption of water, like fish swimming among the rocks, resulting in an assembly-derived orange emission. More information can be found in the Research Article by M. Yoshida, M. Kato and co-workers (DOI: 10.1002/chem.202301993). Cover art by Hibiki Asahori.

The large-scale synthesis of cycloparaphenylene building blocks is illustrated. It represents the different syntheses in continuous flow and how the building blocks can be assembled. The final robotic arm allows aromatization to the macrocyclic CPP ring; the color change showing that all the phenyl units are now the same. More information can be found in the Research Article by H. A. Wegner and co-workers (DOI: 10.1002/chem.202302173).

We report herein a mild stereo- and regioselective dearomatization of quinolines using the simple low valent HCo(N2)(PPh3)3 complex that exhibits labile ligands. Conditions to form selectively, at room temperature, high-valued 1,4-bis-borylated tetrahydroquinolines from simple starting heteroaromatic compounds have been developed. The efficient and selective functionalization of a large scope of quinolines bearing various electron-donating or electron-withdrawing substituents is presented, as well as the post-modification of the resulting C–B bond. NMR and labelling studies are consistent with a cascade mechanism pathway, starting from an in situ generated paramagnetic bis-quinoline cobalt(I) hydride complex. A first quinoline dearomatization followed by a cobalt(I)-catalyzed Markovnikov hydroboration of the remaining double bond allows the introduction of the boronic ester group only at C4 position. DFT calculations particularly highlight the importance of the cobalt triplet state throughout the reaction pathway, and bring some rationalization for the observed C4 selective borylation.

Efficient hydrogenations of terminal alkenes with molecular hydrogen catalyzed by well-defined bench stable Mn(I) complexes containing an N-heterocyclic carbene-based PCP pincer ligand are described. These reactions are environmentally benign and atom economic, implementing an inexpensive, earth abundant non-precious metal catalyst. A range of aromatic and aliphatic alkenes were efficiently converted into alkanes in good to excellent yields. The hydrogenation proceeds at 100 oC with catalyst loadings of 0.25-0.5 mol %, 2.5 - 5 mol % base (KOtBu) and a hydrogen pressure of 20 bar. Mechanistic insight into the catalytic reaction is provided by means of DFT calculations.

Temperature-modulated colloidal phase of plasmonic nanoparticles is a convenient playground for resettable soft-actuators or colorimetric sensors. To render reversible clustering under temperature change, bulky ligands are required, especially if anisotropic morphologies are of interest. Here, we showcase thermoresponsive gold nanorods by employing small surface ligands, bis (p-sulfonatophenyl) phenyl-phosphine dihydrate dipotassium salt (BSPP) and native cationic surfactant. Temperature-dependent analysis in real-time allowed us to describe the structural features (interparticle distance and cluster size) as well as thermal parameters, melting and freezing temperatures. Our findings suggest that neither covalent Au-S bonds nor bulky ligands are required to obtain a robust thermoresponsive system based on anisotropic gold nanoparticles, paving the way to stimuli-responsive nanoparticles with a wide range of sizes and geometries.

We use confocal laser scanning microscopy on the small, fluorescent resorufin dye molecule to visualize molecular accessibility and diffusion in the hierarchical, anisotropic pore structure of large (~10 µm-sized) zeolite-β crystals. The resorufin dye is widely used in life and materials science, but only in its deprotonated form because the protonated molecule is barely fluorescent in aqueous solution. In this work, we show that protonated resorufin is in fact strongly fluorescent when confined within the zeolite micropores enabling fluorescence microimaging experiments. We find that J-aggregation guest–guest interactions lead to a decrease in the measured fluorescence intensity, but is prevented by using non-fluorescent spacer molecules. By introducing resorufin from the outside solution and following its diffusion into zeolite-β crystals, we characterize the pore space. The eventual homogeneous distribution of resorufin molecules throughout the zeolite indicates a fully accessible pore network. This enables the quantification of its diffusion coefficient in the straight pores of zeolite-β without the need for complex analysis, and we find a value of 3 × 10−15 m2 s−1. Furthermore, we visualize that diffusion through the straight pores of zeolite-β is impeded when crossing the boundaries between zeolite sub-units.