L. V. Tsymbal

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.

A ladder-type coordination polymer constructed from two macrocyclic units – calix[4]arene tetracarboxylate and azamacrocyclic nickel(II) complex

The crystal structures of a new type of coordination polymer formed by the high-spin form of a hexaazamacrocyclic nickel(II) complex and a lower rim calix[4]arene tetracarboxylate trianion (2) as well as the perchlorate salt of the low-spin form of this macrocyclic cation (1) are reported. The porosity of the network is characterized by the presence of polar and non-polar voids formed by carboxylate substituents/azamacrocyclic cations and aromatic/tert-butyl substituents of the calix[4]arene, respectively.

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).

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.

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.

Influence of reactant structure on composition and stability of adducts of bis-macrocyclic complexes of copper(II) with aliphatic α,ω-diamines

On the basis of spectrophotometric measurements, constants have been determined for adduct formation between bis-macrocyclic complexes of copper(II) and aliphatic diamines. For these systems, the influence of reactant structure on the specific features of complexation has been established.

SPR Study of the Blocking Activity of Soybean Trypsin Inhibitor by Macrocyclic Complexes of Nickel Immobilized on a Gold Surface

A method is proposed for the modification of metallic gold surfaces by self-organization of a nickel(II) macrocyclic complex containing a thiol substituent. Effective blocking of biologically active soybean trypsin inhibitor by the immobilized complex was observed. The prospects of using the given surface to create sensitive elements for sensors capable of detecting both small molecules (thiocyanate ions) and some protein substrates is demonstrated.

Functional Titanium Dioxide-Derived Materials of Different Morphology and Metal–Organic Framework Compounds

New approaches are examined for the creation of functional materials derived from composites of mesoporous nanocrystalline TiO2 with nanoparticles of nickel, copper, and silver, dyes, and also nanocomposites of new metal–organic frameworks formed by azamacrocyclic nickel and zinc complexes and aromatic carboxylates with acridine orange dye and iodine. Spectral, luminescent and electrophysical characteristics of these materials were determined. Examples are given for their possible use as photocatalysts, sensitive elements of luminescent sensors, and proton-conducting membranes.