Tatiana V. Magdesieva

Electrochemical reduction of CO2 with transition metal phthalocyanine and porphyrin complexes supported on activated carbon fibers

Porphyrin and phthalocyanine transition metal complexes adsorbed on activated carbon fiber nanoporous supports are shown to be effective catalysts for CO 2 electroreduction in the form of gas diffusion electrodes, yielding carbon monoxide with current efficiencies up to ca. 70%. A comparison of the efficiency of activated carbon supports with a wide pore size distribution, and activated carbon fibers, with slit-shaped pores of ca. 2 nm width, demonstrates that an increase in the catalyst dimensions results in a decrease in the benefit of the so-called nanospace effect. For bulky molecules, e.g., tetra-tert-butyl-substituted phthalocyanines, activated carbon supports are more effective, with a current efficiency as high as 85% for CO production being achieved.

Electrocatalytic CO2 reduction in methanol catalyzed by mono-, di-, and electropolymerized phthalocyanine complexes

The electroreduction of CO2 was studied in methanol in the presence of mono- and diphthalocyanine complexes and phthalocyanine films prepared by electrochemical anodic polymerization. Methyl formate is the main reaction product of the reaction catalyzed by the mono- and diphthalocyanine complexes of rare-earth metals. Copper 2,9,16,23-tetra-tert-butylphthalocyanine allows the transformation of CO2 into methane in ∼30% yield. In the presence of both electropolymerized and graphite electrode-supported copper 2,9,16,23-tetraaminophthalocyanine, CO and methyl formate are the main reaction products.

A new heterobimetallic palladium–[60]fullerene complex with bidentate bis-1,1′-[P]2-ferrocene ligand

Abstract A new heterobimetallic palladium–[60]fullerene complex with ferrocene bis-phosphine ligand was prepared using alternative paths: either via addition reaction of Pd 2 (dba) 3 ·C 6 H 6 (dba=dibenzylidenacetone) in the presence of 1,1′-bis(diphenylphosphino)ferrocene ( dppf ) to C 60 , or via electrochemical activation of C 60 to generate C 60 2− anions, which then react with PdCl 2 and dppf to yield the target complex. The obtained (η 2 -C 60 )Pd( dppf ) complex was characterized by 1 H- and 31 P-{ 1 H}-NMR and electronic spectroscopy as well as electrochemically.

Lutetium monophthalocyanine and diphthalocyanine complexes and lithium naphthalocyanine as catalysts for electrochemical CO2 reduction

Phthalocyanine and naphthalocyanine complexes with redox-inactive metals adsorbed on activated carbon supports were shown to be effective catalysts for CO 2 electroreduction in the form of gas diffusion electrodes, yielding carbon monoxide with current efficiencies up to ca. 75%. A mechanism for CO 2 electroreduction catalyzed by these complexes has been proposed in which the key step is the coordination of a CO 2 molecule to the external N-atom of the phthalocyanine or naphthalocyanine ring.

[6,6]‐Open and [6,6]‐Closed Isomers of C70(CF2): Synthesis, Electrochemical and Quantum Chemical Investigation

Novel difluoromethylenated [70]fullerene derivatives, C70(CF2 )n (n=1-3), were obtained by the reaction of C70 with sodium difluorochloroacetate. Two major products, isomeric C70(CF2 ) mono-adducts with [6,6]-open and [6,6]-closed configurations, were isolated and their homofullerene and methanofullerene structures were reliably determined by a variety of methods that included X-ray analysis and high-level spectroscopic techniques. The [6,6]-open isomer of C70(CF2 ) constitutes the first homofullerene example of a non-hetero [70]fullerene derivative in which functionalisation involves the most reactive bond in the polar region of the cage. Voltammetric estimation of the electron affinity of the C70(CF2 ) isomers showed that it is substantially higher for the [6,6]-open isomer (the 70-electron π-conjugated system is retained) than the [6,6]-closed form, the latter being similar to the electron affinity of pristine C70. In situ ESR spectroelectrochemical investigation of the C70(CF2 ) radical anions and DFT calculations of the hyperfine coupling constants provide evidence for the first example of an inter-conversion between the [6,6]-closed and [6,6]-open forms of a cage-modified fullerene driven by an electrochemical one-electron transfer. Thus, [6,6]-closed C70(CF2 ) constitutes an interesting example of a redox-switchable fullerene derivative.

Study of the catalytic activity of electrochemically reduced forms of phthalocyanines in the reaction of CO2 with epoxides

Catalytic activity of electrochemically reduced forms of mono- and diphthalocyanine complexes of transition and rare-earth elements in the reaction of carbon dioxide with epoxides is considerably higher than that of corresponding neutral forms. The catalytic efficiency depends on the nature of the phthalocyanine complex, the method of the catalyst immobilization, and the electrophilicity of epoxide.

Electrochemical investigation of lanthanide octa-tert-butylsubstituted diphthalocyanine complexes in solutions. Approximation of their redox transitions by semiempirical calculations for yttrium diphthalocyanine

The electrochemical potentials of seven redox transitions for green forms and eight redox transitions for blue forms of neutral octa-tert-butylsubstituted diphthalocyanine cornplexes of lanthanides Pct2Ln (Ln=Pr, Sm, Dy, and Lu) in solutions were measured by cyclic voltammetry and rotating disc electrode techniques. The spectroelectrochemical investigation of the products of two-electron oxidation and reduction of the green form of Pct2Lu was performed. The frontier molecular orbitals, total charge densities, total spin densities, electrostatic potentials, and heats of ion formation for (Pc2Y)m+,n− (m=0, 1, 2 and 3;n=1, 2, 3 and 4), which can model the products of the redox transitions of the diphthalocyanines under study, were calculated using the semiempirical ZINDO/1 method. The calculations for (Pc2Y)m+,n− and absorption spectra show that the electron changes in all redox transitions of the green forms of Pct2Ln are mainly localized on the ligands.

Interaction of xenon diflouride with organomercury compounds

Abstract XeF2 is shown to react with organomercury compounds, R2Hg (R = PhCC,p-MeOC6H4, p-Me2NC6H4, p-EtO2CC6H4 and PhCH2), with cleavage of the CHg bond. The products of the reaction are the following: Xe, RHgF (or RHgF/HgF2 mixture; for R = benzyl RHgF undergoes fast demercurization), RF (excluding R = PhCC), R2, and the products of radical, R·, reactions with solvents (dry CCl4 or CHCl3). The ease of reaction, about which one can judge from the temperature of the beginning of Xe evolution (given in brackets in °C), was found to decrease in the following sequence: R = PhCH2 (—45) p-Me2NC6H4, (—40), PhCC (—5), p-MeOC6H4 (5), p-EtO2CC6H4 (25). This sequence indicates XeF2 to be an electron acceptor and R2Hg an electron donor. It follows from the reaction mixture composition that the reaction goes via free radicals. The absence of fluorinated organomercury products in the reaction mixtures may be considered as evidence that XeF2 reacts more easily with the CHg bond than with CH or CC bonds. XeF2 reacts also with HgX2 (X = Cl, Br, I) under mild conditions to give X2, HgF2, and Xe in quantitative yields.

Electrochemical and electrochromic properties of rare-earth metal diphthalocyanine complexes

The electrochemical and spectroelectrochemical properties of several new rare-earth metal diphthalocyanine complexes with different substituents containing both electron-withdrawing and -donating substituents in the phthalocyanine rings were studied. The influence of structural modification of the phthalocyanine complexes (viz., the nature of the central metal atom and substituents in the phthalocyanine rings and the number of phthalocyanine rings in the complexes) on the total number of redox transitions, their potentials, and spectral characteristics of anionic and cationic forms of the complexes was examined. The potentials of the first anodic and cathodic redox transitions of the diphthalocyanine complexes are in a good linear correlation with the ionic radii of lanthanides. The potentials of the observed redox transitions of the complexes under study correlate well with the sums of Hammett constants for the substituents and the minimum molecular electrostatic potential of the benzene rings in the phthalocyanine moiety, which serves as a measure of electron perturbations introduced by the substituents. The revealed regularities allow the prediction of the redox properties and structure of rare-earth element diphthalocyanine complexes, which are redox-active in a specified potential range.

Electrochemically induced aromatic nucleophilic substitution with [(η5-C5H5)Fe(CO)2]− and [(η5-C5H5Mo(CO)3]− anions

Abstract The reaction of low S N (Ar)-active and non-active aryl halides p -XC 6 H 4 Hal (X  CH 3 , H, Cl, COCH 3 , CN or NO 2 ; Hal  I or Br) with [(η 5 -C 5 H 5 )Fe(CO) 2 ] − and [(η 5 -C 5 H 5 )Mo(CO) 3 ] − is studied using a number of electrochemical methods (cyclic voltammetry, rotating-ring-disk-electrode technique and preparative-scale electrolysis). It is shown that the electrode catalysis enables one to carry out aromatic nucleophilic substitution which generally leads to σ-aryl derivatives of (η 5 -cyclopentadienyl) irondicarbonyl. Nevertheless, a detailed study of the mechanism of the reduction and oxidation of [(η 5 -C 5 H 5 )Fe(CO) 2 C 6 H 4 X- p ] at a Pt electrode reveals that the irreversibility of their reduction processes imposes certain restrictions on performing electrode-initiated aromatic nucleophilic substitution. This results in the occurrence of the “electrochemical activation window”, i.e. . limitation of the potential region where electrochemically induced aromatic nucleophilic substitution is possible. For the [(η 5 -C 5 H 5 )Mo(CO) 3 ] − anion, we failed to obtain its σ-aryl derivatives using electrochemical activation of aryl halides. The main product of the reaction is (η 5 -C 5 H 5 )Mo(CO) 3 Hal.