The field of photocatalysis has been evolving since 1972 since Honda and Fujishima’s initial push for using light as an energy source to accomplish redox reactions. Since then, many photocatalysts have been studied, semiconductors or otherwise. A new photocatalytic application to convert N2 gas to ammonia (N2 fixation or nitrogen reduction reaction; NRR) has emerged. Many researchers have steered their research in this direction due to developments in the ease of ammonia detection through UV-Vis spectroscopy. This concept will specifically discuss Bi2WO6-based materials, techniques to enhance their photocatalytic activity (CO2 reduction, H2 production, pollutant removal, etc.), and their current application in photocatalytic NRR. Initially, a brief introduction of Bi2WO6 along with its VB and CB potentials will be compared to various redox potentials. A final topic of interest would be a brief description of photocatalytic nitrogen fixation with additional consideration to Bi2WO6-based materials in N2 fixation. A major problem with photocatalytic NRR is the false ammonia quantification in Bi-based materials, which will be discussed in detail and also ways to minimize them.

Proton-coupled electron transfer (PCET) plays a crucial role in a diverse array of natural and artificial energy conversion processes. Herein, we will introduce the fundamentals of electrochemical PCET with a focus on its role in water splitting. Besides, perspectives of future development of PCET are presented with regard to the investigation of reaction mechanisms and the design of advanced electrocatalysts.

Iron(II) complexes containing ligands with a R2P–P–PR2 unit were synthesized by metathesis reactions. With R = tBu, a mixture of two isomers is formed; in one of them, the terminal phosphorus binds to the Fe center (ylidic structure), while in the other one, the central P atom is linked to Fe. Starting from differently functionalized parent triphosphanes and corresponding functionalized Fe complexes, the ratio of isomers does not change. The outcome of the reaction and therefore the binding modes of the triphosphane ligands in the resulting compounds can be influenced by the size of the substituents. In the case of R = iPr a chelate complex is formed (both terminal P atoms are linked to the Fe center). Applying the mixed-substituted triphosphane, the ylidic structure of the resulting complex is preferred. The new compounds were characterized by NMR spectroscopy in solution and single-crystal X-ray diffraction in solid-state. The synthetic work was supported by DFT calculations.

Bacterial β-glycosidases are hydrolytic enzymes that depolymerize polysaccharides such as β-cellulose, β-glucans and β-xylans from different sources, which are used in a myriad of biomedical and industrial applications. It has been shown that a conformational change of the substrate, from a relaxed 4C1 conformation to a distorted 1S3/1,4B conformation of the reactive sugar, is necessary for catalysis. However, the molecular determinants that stabilize the substrate’s distortion are poorly understood. Here we use quantum mechanics/molecular mechanics (QM/MM)-based molecular dynamics methods to assess the impact of the interaction between the reactive sugar, i.e. the one at subsite -1, and the catalytic nucleophile (a glutamate) on substrate conformation. We show that the hydrogen bond involving the C2 exocyclic group and the nucleophile controls substrate conformation: its presence preserves sugar distortion, whereas its absence (e.g. in an enzyme mutant) knocks it out. We also show that 2-deoxy-2-fluoro derivatives, widely used to trap the reaction intermediates by X-ray crystallography, reproduce the conformation of the hydrolysable substrate at the experimental conditions. These results highlight the importance of the 2-OH···nucleophile interaction in substrate recognition and catalysis in endo-glycosidases and can inform mutational campaigns aimed to search for more efficient enzymes.

The electron paramagnetic resonance (EPR) spectra of lanthanide(III) ions besides Gd(III), bound to small-molecule and protein chelators, are uncharacterized. Here, we systematically investigated the EPR properties of 7 lanthanide(III) ions bound to the natural lanthanide-binding protein, lanmodulin (LanM), and the synthetic small-molecule chelator, 3,4,3-LI(1,2-HOPO) (“HOPO”). Echo-detected pulsed EPR spectra reveal intense signals from ions for which the normal continuous-wave first-derivative spectra are negligibly different from zero. Spectra of Kramers lanthanide ions Ce3+, Nd3+, Sm3+, Er3+, and Yb3+, and non-Kramers Tb3+ and Tm3+, bound to LanM are more similar to the ions in dilute aqueous:ethanol solution than to those coordinated with HOPO. Lanmodulins from two bacteria, with distinct metal-binding sites, had similar spectra for Tb3+ but different spectra for Nd3+. Spin-echo dephasing rates (1/Tm) are faster for lanthanides than for most transition metals and limited detection of echoes to temperatures below ~6 to 12 K. Dephasing rates were environment dependent and decreased in the order water:ethanol > LanM > HOPO, which is attributed to decreasing librational motion. Our results demonstrate that the EPR spectra and relaxation times of lanthanide(III) ions are sensitive to coordination environment, motivating wider application of these methods for characterization of both small-molecule and biomolecule interactions with lanthanides.

A novel buckybowl catcher with an extended π-surface has been synthesized via cross-coupling of two bowl shaped bromoindacenopicene moieties with a tolyl linker. The obtained catcher has been unambiguously characterized by 2D-NMR and mass spectrometry. DFT calculations indicate that the curved shape of the receptor moieties is favourable for binding fullerenes. Effective binding was confirmed for interactions with C60 and C70 utilizing NMR spectroscopy and isothermal titration calorimetry (ITC). The resulting binding values show a higher affinity of the catcher towards C70 over C60. The designed catcher demonstrated the fundamental possibility of creating sensors for spherical aromaticity.

Excellent stability is an essential premise for organic diradicals to be used in organic electronic and spintronic devices. Herein, we attach two tris(2,4,6-trichlorophenyl)methyl (TTM) radical building blocks to the two sides of perylene bisimide (PBI) bridges and obtain two regioisomeric diradicals (1,6-TTM-PBI and 1,7-TTM-PBI). Both of the isomers show super stability rather than the monomeric TTM under ambient conditions, due to the enlarged conjugation as well as the electron withdrawing effects from the PBI bridges. The diradicals show distinct and reversible multi-step redox processes, and the spectroelectrochemistry investigation reveals the generation of organic mixed-valence (MV) species during reduction processes. The two diradicals have singlet ground states, very small singlet−triplet energy gaps (ΔES-T) and a pure open-shell character (with diradical character y0 = 0.966 for 1,6-TTM-PBI and 0.967 for 1,7-TTM-PBI). This work opens a window to develop very stable diradicals and offers them opportunity of further applications in optical, electronic and magnetic devices.

Efficient adsorption of palladium ions from acid nuclear waste solution is crucial for ensuring the safety of vitrification process for radioactive waste. However, the limited stability and selectivity of most current adsorbents hinder their practical applications under strong acid and intense radiation conditions. Herein, to address these limitations, we designed and synthesized an aryl-ether-linked covalent organic framework (COF-316-DM) grafted dimethylthiocarbamoyl groups on the pore walls. This unique structure endows COF-316-DM with high stability and exceptional palladium capture capacity. The robust polyarylether linkage enables COF-316-DM to withstand irradiation doses of 200 or 400 kGy of β/γ ray. Furthermore, COF-316-DM demonstrates fast adsorption kinetics, high adsorption capacity (147 mg g-1), and excellent reusability in 4 M nitric acid. Moreover, COF-316-DM exhibits remarkable selectivity for palladium ions in the presence of 17 interference ions, simulating high level liquid waste scenario. The superior adsorption performance can be attributed to the strong binding affinity between the thioamide groups and Pd2+ ions, as confirmed by the comprehensive analysis of FT-IR and XPS spectra. Our findings highlight the potential of COFs with robust linkers and tailored functional groups for efficient and selective capture of metal ions, even in harsh environmental conditions.

A practical and efficient propargylboration of ketones is presented using general allenylboronic acid pinacol esters (allenyl-Bpins) without a catalyst. This reaction is triggered by in-situ activation of stable allenyl-Bpins through the sequential addition of 1.25 equiv. of nBuLi and the prerequisite 2.0 equiv. of TFAA. Under the optimized reaction conditions, the versatile trisubstituted allenyl-Bpins react with various ketones smoothly to afford a wide range of tert-homopropargyl alcohols bearing vicinal stereocenters in high yields with good to excellent diastereoselectivities. Furthermore, propargylboration of ketones with chiral trisubstituted allenyl-Bpins allows for the asymmetric synthesis of chiral tert-homopropargyl alcohols with a full chirality transfer.

Extractants: The diphenylpyrrole-strapped calix[4]pyrrole and its dual host systems involving crown ethers enable the extraction of various fluoride and chloride salts from water.

Abstract

The anion binding features of diphenylpyrrole-strapped calix[4]pyrrole 1 have been investigated by means of ¹H NMR spectroscopy and ITC (isothermal titration calorimetry), as well as single crystal X-ray diffraction analyses. Receptor 1 bearing an auxiliary pyrrolic NH donor and solubilizing phenyl groups on the strap was found to bind F⁻, Cl⁻, and Br⁻ as their tetrabutylammonium salts with high affinity in DMSO-d₆ . In addition, receptor 1 was found to extract the fluoride anion (as both its tetraethylammonium (TEA⁺) and tetrabutylammonium (TBA⁺) salts), as well as the chloride anion into chloroform-d from an aqueous source phase. Cation metathesis using TBAI or the use of a dual host approach involving crown ethers enabled receptor 1 to extract simple alkali metal fluoride or chloride salts from water. Quantitative binding of NaF by receptor 1 was observed in 20 % D₂O-DMSO-d₆ allowing for the direct determination of the NaF concentration in an unknown sample.