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An N-heterocyclic carbene containing a pendant triphenylphosphonium group is an excellent new charge-tagged ligand for mass spectrometry. 

Abstract Au nanoclusters often demonstrate useful optical properties such as visible/near‐infrared photoluminescence, in addition to remarkable thermodynamic stability owing to their superatomic behavior. The smallest of the 8e⁻superatomic Au nanoclusters, Au₁₁, has limited applications due to its lack of luminescence and relatively low stability. In this work, we investigate the introduction of a single Pt dopant to the center of a halide‐ and triphenylphosphine‐ligated Au₁₁nanocluster, affording a cluster with a proposed molecular formula PtAu₁₀(PPh₃)₇Br₃. Electrochemical and spectroscopic analysis reveal an expansion of the HOMO–LUMO gap due to the Pt dopant, as well as relatively strong near‐infrared (NIR) photoluminescence which is atypical for an M₁₁cluster (λ_max= 700 nm, Φ = 1.88 %). The Pt dopant additionally boosted photostability; more than tenfold. Lastly, we demonstrate the application of the PtAu₁₀cluster's NIR photoluminescence in the detection of the nitroaromatic compound 2,4‐dinitrotoluene, with a limit‐of‐detection of 9.52 μM (1.74 ppm). The notable ability of a single central Pt dopant to unlock photoluminescence in a non‐luminescent nanocluster highlights the advantages of heterometal doping in the tuning of both the optical and thermodynamic properties of Au nanoclusters. 

Methyl 2-acetamido-2-deoxy-β-D-glucopyranosyl-(1→4)-2-acetamido-2-deoxy-β-D-glucopyranoside (methyl β-chitobioside), (IV), crystallizes from aqueous methanol at room temperature to give a structure (C₁₇H₃₀N₂O₂₂·CH₃OH) containing conformational disorder in the exocyclic hydroxymethyl group of one of its βGlcNAc residues. As observed in other X-ray structures of disaccharides containing β-(1→4)O-glycosidic linkages, inter-residue hydrogen bonding between O3H of the βGlcNAc bearing the OCH₃aglycone and O5 of the adjacent βGlcNAc is observed based on the 2.79 Å internuclear distance between the O atoms. The structure of (IV) was compared to that determined previously for 2-acetamido-2-deoxy-β-D-glucopyranosyl-(1→4)-2-acetamido-2-deoxy-β-D-glucopyranose (β-chitobiose), (III). TheO-glycosidic linkage torsion angles,phi(ϕ) andpsi(ψ), in (III) and (IV) differ by 6–8°. TheN-acetyl side chain conformation in (III) and (IV) shows some context dependence, with the C1—C2—N—C_cartorsion angle 10–15° smaller for the βGlcNAc residue involved in the internalO-glycosidic linkage. In (IV), conformational disorder is observed in the exocyclic hydroxymethyl (–CH₂OH) group in the βGlcNAc residue bearing the OCH₃aglycone, and a fitting of the electron density indicates an approximate 50:50 distribution of thegauche–gauche(gg) andgauche–trans(gt) conformers in the lattice. Similar behavior is not observed in (III), presumably due to the different packing structure in the vicinity of the –CH₂OH substituent that affects its ability to hydrogen bond to proximal donors/acceptors. Unlike (IV), a re-examination of the previously reported electron density of (III) revealed conformational disorder in theN-acetyl side chain attached to the reducing-end βGlcNAc residue caused by rotation about the C2—N bond. 

Ultra-high vacuum scanning tunneling microscopy (UHV-STM) was used to investigate two related molecules pulse-deposited onto Au(111) surfaces: indoline-2-carboxylic acid and proline (pyrrolidine-2-carboxylic acid). 

Redox-inert metal cations change the reaction between thiolate anions and elemental sulfur. Spectroscopic and electrochemical data show that metal–sulfur covalency determines the favorability of sulfur catenation vs. sulfur reduction.