Ya. D. Lampeka

Cyclic voltammetry study of the electrocatalysis of carbon dioxide reduction by bis(polyazamacrocyclic) nickel complexes

Abstract Two series of binuclear macrocyclic nickel(II) complexes with varying lengths of the chain linking the two macrocyclic rings were characterised by cyclic voltammetry under argon and CO 2 . The first series consisted of binuclear complexes [Ni 2 L 2–6 ] 4+ containing pentaaza macrocycles with (CH 2 ) n bridges ( n =2, 3, 4, 6) or a p -xylyl linkage (L 6 ). In general, the two nickel sites in the binuclear complexes behave independently with the currents corresponding to the simultaneous transfer of two electrons. The redox potentials are remarkably constant along this series, but the peak separations increase, reflecting slower electron transfer due to more effective adsorption on the electrode. Electrochemical data for the electrocatalytic reduction of CO 2 in MeCN/10% H 2 O revealed catalytic waves for CO 2 reduction with E p c close to −1.7 V and catalytic currents ( i p c ) which are about half those of the mononuclear complex, proposed to be due to steric constraints allowing strong interaction of only one nickel centre of the binuclear one on the surface. The catalytic currents increased slightly as the linking chain length increased as the stereochemical constrains were relaxed somewhat. There was also a splitting in the catalytic peaks of the bismacrocyclic complexes which could reflect two types of adsorbed catalyst sites. In the more sterically crowded series of complex, [Ni 2 L 7 ] 4+ along with the series of linked heptaaza macrocyclic complexes [Ni 2 L 9–11 ] 4+ much more positive redox potentials were observed due to both alkylation of the coordinated nitrogen atoms, which decreases the ligand field, and the introduction of steric barriers to axial coordination. These steric barriers prevented strong electrode interaction and led to a lower catalytic activity. Indeed, the complex [Ni 2 L 7 ] 4+ did not even show any interaction with CO 2 in dry acetonitrile. The complexes showed well separated peaks due to solution and surface catalytic activity, and the surface catalytic currents were now comparable to mononuclear complexes at the same effective concentration. We proposed that the less effective absorption on the electrode arising from ligand steric interactions places far fewer stereochemical constraints on the adsorption of both nickel centres to the same extent as the binuclear complex, and hence the catalytic currents for binuclear complex and mononuclear complex are comparable.

Framework materials based on azamacrocyclic complexes of transition metals and carboxylates

Published data on the molecular and crystal structure and characteristics of coordination polymers and metal-organic frameworks based on the macrocyclic complexes of transition metals and aromatic carboxylates are analyzed. The prospects for the use of such materials as selective sorbents for gases and organic molecules are demonstrated.

Nanocomposites of Two-Dimensional Molybdenum and Tungsten Dichalcogenides with Metal Particles: Preparation and Prospects for Application

Literature data related to methods for the preparation, structure, electronic characteristics, and functional properties of composites consisting of nanosheets of layered dichalcogenides with metal nanoparticles have been analyzed. Prospects are discussed for the use of such materials in catalysis and for sensing as well as for construction of various other electronic devices.

Two-dimensional coordination polymers based on pyridine-containing cations of cu(II) and Ni(II) and 1,3,5-benzenetricarboxylate anion and their supramolecular structure

New coordination compounds based on 1,3,5-benzenetricarboxylate (btc3−) and complex cations of copper(II) and nickel(II) with monodentate ligands {{[Cu(py)3]3(btc)2}·4,5H2O}n (1) and {[Ni(py)3(H2O)]3(btc)2}n (2) were obtained. The molecular and crystal structures of these compounds and their isomorphism were determined by X-ray diffraction analysis. Crystals of 1 and 2 are characterized by a layered structure due to the stacking of two-dimensional coordination-polymer layers interacting with each other through C-H…π non-covalent interactions and C-H…O weak hydrogen bonds. It is shown that these compounds are potentially highly porous materials with coordinatively unsaturated metal ions (Lewis acid sites).

Nickel(II) Complexes as Electron Transfer Mediators in the Electrochemical Activation of Freons

Feasibility was demonstrated for the electrochemical activation of freons CF2ClCFCl2 (CFC113), CF3Br (FC13B1), and CF2Cl2 (CFC12) as well as CF3I using nickel complexes with azamacrocyclic and bipyridyl ligands as electron transfer mediators, permitting the reduction of freons under mild conditions at relatively low potentials. The catalytic efficiency of these complexes was determined for freon CFC113.

Catalysts of chain transfer to monomer in radical polymerization: Catalyst structure and donor-acceptor and redox properties

Information is presented on the catalytic properties of macrocyclic and polychelate complexes of cobalt in the reaction of methyl methacrylate polymerization. The catalytic activities of these compounds are compared with their donor-acceptor and redox properties.

Structural features of macrocyclic cobalt complexes —catalysts of chain transfer to a monomer in radical polymerization

Data are given on the catalytic activity of a series of cobalt coordination compounds with macrocyclic and acyclic Ligands of different structures in radical polymerization reactions of methacrylic monomers. The influence of various factors (especially the structure of the ligand) on the manifestation of catalytic properties of the compounds studied is discussed.

Effect of the Structure of Aromatic Nitro Compounds on the Efficiency of Luminescence Quenching of the Metal–Organic Framework of Zinc(II) 4,4ʹ-Diphenyldicarboxylate

The efficiency of luminescence quenching of the metal–organic framework {[Zn(L)(DPDC)]}n (L = 1,4,8,11-tetraazacyclotetradecane, DPDC2– = 4,4ʹ-diphenyldicarboxylate) by aromatic nitro compounds depends on their structure. Nitrobenzene and nitrotoluene derivatives are found to have a much smaller effect than phenol and aniline derivatives. It is suggested that there is no electron transfer due to π-stacking interactions in these systems and a mechanism involving resonance energy transfer due to overlap of the luminophore emission band and the absorption bands of the quenchers is more probable.

Heterophase synthesis of the high-porosity metal–organic framework compound copper(II) benzenetricarboxylate and its composite with phosphotungstic acid

We show that the metal–organic framework (MOF) material Cu3(BTC)2 can be synthesized in quantitative yield by reaction of 1,3,5-benzenetricarboxylic acid with copper(II) hydroxide in an aqueous/alcoholic medium at room temperature. The material obtained is characterized by high values of the specific surface area (1660 m2/g, BET) and the pore volume (0.69 cm3/g). We demonstrate the applicability of this method to obtaining nanocomposite materials containing polyoxometalate clusters encapsulated within the cavities of Cu3(BTC)2.

Adsorption Properties of Porous Materials Based on Macrocyclic Nickel(II) Complexes and Benzenetricarboxylate Relative to Water, Methanol, and Hexane Vapor

We have shown that varying the substituents in the cationic component of porous crystal compounds formed by azamacrocyclic nickel(II) complexes and the 1,3,5-benzenetricarboxylate anion has a substantial effect on their adsorption behavior relative to water, methane, and n-hexane vapor. The studied compounds are characterized by reversibility of the changes in the crystal lattices during adsorption/desorption, stoichiometry of the reaction with water vapor with relatively low and hydrolytic stability at high humidity.