Efficient 1,4-Addition of Enones and Boronic Acids Catalyzed by a Ni–Zn Hydroxyl Double Salt-Intercalated Anionic Rhodium(III) Complex

Specific lift-up behaviour of acetate-intercalated layered yttrium hydroxide interlayer in water: application for heterogeneous Brønsted base catalysts toward Knoevenagel reactions

The basal (00l) plane of acetate-intercalated layered yttrium hydroxide (CH3COO−/Y-LRH), synthesised by an anion exchange using Cl−/Y-LRH as a parent material, increased in water, and the lifted-up layered structure was generated immediately.

The study of Rh(iii) hydroxocomplexes using capillary zone electrophoresis with a UV-Vis detector: the development of the method

The expediency of capillary zone electrophoresis application in the study of a mixture of rhodium(iii) hydroxocomplexes is shown for the species formed during the thermal treatment of [Rh(OH)₆]^3- at 60 °C in alkaline media. As these compounds are unstable in solution because of polycondensation at pH > 10 and the formation of insoluble rhodium(iii) hydroxides at pH 5-10, their acidic derivatives with terminal aqua ligands acted as the objects of the study. Optimal separation conditions were achieved using sodium perchlorate as a background electrolyte, a voltage of +20 kV and pH 2.6. Rhodium(iii) species with different nuclearities were identified in accordance with their UV spectra and the regularities of electrophoretic migration in the capillary. The presence of a dimer was also verified by the spiking of the mixture under investigation with a previously synthesised complex [Rh₂(μ-OH)₂(H₂O)₈](NO₃)₄, which confirms the correct identification.

Formation of porous Cu hydroxy double salt nanoflowers derived from metal-organic frameworks with efficient peroxidase-like activity for label-free detection of glucose

Currently, nanomaterials with peroxidase activity have become an important colorimetric tool for biomolecular detection. However, compared with natural enzymes, the efficiency of most nanozymes is still lower. Here, with a leaf-like metal-organic-framework-5 as both a precursor and a template and copper acetate as a second precursor, hierarchical Cu hydroxy double salt (HDS) nanoflowers have been prepared and used as a label-free glucose colorimetric detection platform. We have demonstrated a scalable and facile synthesis of hierarchical Cu HDS nanoflowers, and density functional theory (DFT) calculations confirmed that there exists a hydrogen bond between the terephthalate anions and the layer OH group. The composition of Cu hydroxyl double salt is [Cu4(OH)6][BDC]·2H2O. Importantly, for the first time, the as-prepared Cu HDSs were demonstrated as peroxidase mimics to catalyze the oxidation of the enzyme substrate, 3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2, which accompanies a color change from colorless to blue and followed classic Michaelis-Menten models. Based on these findings, a colorimetric method based on Cu HDSs that is highly sensitive and selective for the detection of glucose was developed, with a low detection limit of 0.5 μM. The clinical applicability of the sensor is also proven to be suitable for sensing glucose in blood, suggesting that Cu HDSs could be used in the construction of portable sensors for point-of-care diagnosis and on-site tests.

Spectroscopic and DFT Study of RhIII Chloro Complex Transformation in Alkaline Solutions

The hydrolysis of [RhCl₆]^3- in NaOH-water solutions was studied by spectrophotometric methods. The reaction proceeds via successive substitution of chloride with hydroxide to quantitatively form [Rh(OH)₆]^3-. Ligand substitution kinetics was studied in an aqueous 0.434-1.085 M NaOH matrix in the temperature range 5.5-15.3 °C. Transformation of [RhCl₆]^3- into [RhCl₅(OH)]^3- was found to be the rate-determining step with activation parameters of ΔH^† = 105 ± 4 kJ mol^-1 and ΔS^†= 59 ± 10 J K^-1 mol^-1. The coordinated hydroxo ligand(s) induces rapid ligand substitution to form [Rh(OH)₆]^3-. By simulating ligand substitution as a dissociative mechanism, using density functional theory (DFT), we can now explain the relatively fast and slow kinetics of chloride substitution in basic and acidic matrices, respectively. Moreover, the DFT calculated activation energies corroborated experimental data that the kinetic stereochemical sequence of [RhCl₆]^3- hydrolysis in an acidic solution proceeds as [RhCl₆]^3- → [RhCl₅(H₂O)]^2- → cis-[RhCl₄(H₂O)₂]^-. However, DFT calculations predict in a basic solution the trans route of substitution [RhCl₆]^3- → [RhCl₅(OH)]^3- → trans-[RhCl₄(OH)₂]^3- is kinetically favored.

Hydrophenylation of internal alkynes with boronic acids catalysed by a Ni–Zn hydroxy double salt-intercalated anionic rhodium(iii) complex

[Rh(OH)₆]³⁻ intercalated Ni–Zn mixed basic salt (Rh/NiZn) acts as an efficient catalyst for the hydrophenylation of internal alkynes with arylboronic acids under mild conditions.

Heterogeneous double-activation catalysis: Rh complex and tertiary amine on the same solid surface for the 1,4-addition reaction of aryl- and alkylboronic acids

Double-activation catalysis by a rhodium complex/tertiary amine catalyst for the 1,4-addition of organoboronic acids was investigated.