E. G. Mozhzhukhina

Ruthenium(IV) and Osmium(II) Tetraphenylporphine Complexes: Synthesis and Oxidation Reactions

The Ru(IV) and Os(II) complexes (PhO)2RuTPP and OsTPP were synthesized from tetraphenylporphine (H2TPP) and K2RuO4 or K2OsO4 (taken in the molar ratio of 1 : 30) in boiling phenol. The kinetics of oxidation reactions of these complexes in solutions of HOAc (acetic), H2SO4, and HOAc–H2SO4 acids was studied. It was found that in the aerated HOAc–H2SO4 mixture heated above 340 K, these complexes are oxidized with participation of different reaction sites: the Ru(IV) complex is oxidized at macrocycle to give the π-radical-cation (PhO)2RuТPP•+, while in the Os(II) complex, the metal atom is oxidized to form the Os(III) complex. In the first case, the reaction follows the activation mechanism, whereas in the second case, the activation energy of the reaction is zero.

The magnetocaloric effect and the heat capacity of aqueous suspensions of porphyrin complexes of rare earth elements according to microcalorimetric data

The magnetocaloric effect (MCE) and heat capacity during the magnetization process of (5,10,15,20-tetraphenylporphyrinato)acetatogadolinium(III), (AcO)GdTPP, and (5,10,15,20-tetraphenylporphyrinato)chlorogadolinium(III) complexes, (Cl)GdTPP, in the form of 6%-aqeous suspensions are determined by the microcalorimetric method in a range of temperatures from 278 to 318 K and magnetic fields from 0 to 1 T. It is found that MCE for all the complexes are positive, i.e., at applying a magnetic field in the adiabatic conditions temperature of a suspension of complex increases. It is established that MCE increases with an increase in magnetic induction at all temperatures and decreases with an increase in temperature at all magnetic fields. It is shown that the substitution of chloride ligand by acetate in (X)GdTPP leads to a significant increas in MCE and its temperature dependence; in the case of (Cl)GdTPP actually MCE does not depend on temperature. Relationships between magnetothermal properties and structure of the complexes are analyzed. The conclusion is argumented that the reason of changes in magnetothermal properties after the replacement of axial ligand in gadolinium complexes and complexes of lanthanides with an unsymmetrically filled f-shell is non-planar geometry of the coordination site and specific electronic properties of the central ion. It is concluded that heat capacity of the complexes slightly increases with an increase in temperature and more noticeably in the case of (AcO)GdTPP; a magnetic component of heat capacity is revealed only in (AcO)GdTPP at temperatures above 298 K, which is connected perhaps with a temperature change in the crystal lattice of the complex and influence of the magnetic properties of gadolinium ion on this change.

Coordination of 5,10,15,20-tetraphenyl-21H,23H-porphin by rhenium in various oxidation states

A method was developed for the synthesis of three rhenium complexes, (5,10,15,20-tetraphenyl-21H,23H-porphinato)(phenoxo)rhenium(III) (PhO)ReTPP, (5,10,15,20-tetraphenyl-21H,23H-porphi-nato)(chloro)rhenium(III) (Cl)ReTPP, and μ-oxo-bis[(oxo)-(5,10,15,20-tetraphenyl-21H,23H-porphi-nato)rhenium(V)] [O=ReTPP]2O, by one reaction between porphyrin H2TPP and H2ReCl6 in boiling phenol. In the complex formation reaction accompanied by the redox process, only the metal cation is involved in the transformation. Rhenium(IV) as chlororhenic acid dispropoportionates without participation of solvent or porphyrin to give Re(III) and Re(V) complexes. The chemical structures of the products were established by spectral and elemental analysis. Characteristics of the UV, Vis, IR, and 1H NMR spectra, the chromatographic mobility, and stability of the complexes were determined.

Thiadiazoloporphyrinoids. Coordination of hexa(4-tert-butylphenyl)-substituted trithiadiazoltripyrrol macrocycle with Ni(II) in DMF

The rate constants, partial orders in the reagent concentrations and activation parameters of interaction of macroheterocyclic compound based on consecutively alternating fragments of thiazole and 3,4-bis(4-tert-butylphenyl)pyrole (3 + 3) with dehydrated Ni(OAc)2 in dry DNF depending on the reagent concentrations and temperature were determined. Within a narrow range of the salt concentrations ((1.58−1.87) × 10−4 mol/l), the third-order equation of the reaction rate was obtained i.e., the first order in a macrocyclic ligand and the second order in a salt, which was interpreted in terms of the mechanism of a stepwise coordination with three [Ni(OAc)]+ ions that is reversible only at the second step. Because of the low solubility of McH3, the monomer-dimer equilibrium also becomes kinetically significant. The constant of McH3 dimerization in DMF at 298 K equal to 1.6 × 105 mol−1 was determined by spectrophotometric titration.

Synthesis, structure, and reactions of iridium(I) complexes with 5,10,15,20-tetraphenyl-21H,23H-porphine and 5,10,15,20-tetraphenyl-21H,23H-porphine dianion

One-step joint synthesis of two iridium porphyrin complexes, a donor-acceptor SAT (sitting a top) complex μ-(5,10,15,20-tetraphenylporphine)-bis-chloroiridium(I) and the covalent complex (5,10,15,20-tetraphenylporphinato)chloroiridium(III) by the reaction of free porphyrin and chloroiridic acid (H3O)2IrCl6 in boiling phenol was studied. The structure of complexes was confirmed by spectroscopy (UV/Vis, IR, 1H NMR) and TLC. The iridium(III) SAT complex with the hydride ligand in the first coordination sphere, (acetato)hydrido(5,10,15,20-tetraphenylporphine)iridium(III), was obtained by oxidative addition reaction, which is quite rare for porphyrin complexes. The thermodynamic stability of the complexes to oxidants (aerated acids) was studied by spectrophotometric titration.

Synthesis and Reactivity of Porphyrin Complexes of Group IV p-Elements

The composition of products and the general regularities of complex formation of meso-tetraphenylporphine with Si(IV), Ge(IV), Sn(II), and Pb(II), as well as the kinetics and mechanism of dissociation of the resulting complexes under the action of proton-donor reagents were studied. The nature of chemical and steric factors that operate to stabilize mixed-ligand acido porphyrin p-metal complexes was revealed.

The kinetics of complex formation in the trithiadiazoletri[3,4-di(4-tert-butylphenyl)-pyrrole] macrocycle-copper(II) acetate-DMFA-H2O system

The paper presents the results of a study of the kinetics of coordination of a macroheterocyclic compound with an increased coordination cavity of the (3 + 3) McH3 composition consisting of sequentially alternating 1,3,4-thiadiazole and 3,4-bis(4-tert-butylphenyl)pyrrole fragments to dehydrated Cu(OAc)2 in dimethylformamide with and without H2O admixtures. The reaction could be controlled spectrophotometrically over the salt and ligand concentration ranges (0.175−0.55) × 10−4 and (0.16−0.64) × 10−5 mol/l, respectively, at temperatures of 288–303 K. A kinetic equation of an unusual form with a negative order with respect to the salt was for the first time obtained experimentally for a macrocyclic ligand by the method of excess concentrations. The kinetics of the complex formation reaction was given a theoretical interpretation. Quantitative characteristics were obtained, and the role played by water in the kinetics of complex formation was studied. These data were of importance for practical applications, for the development of optimum conditions increasing the yield of complexes when they were synthesized in complex formation reactions.

Chemical structure and reactions of axially coordinated iridium(III) porphyrins

Effect of modification of the axial (fifth and sixth) coordination sites on the physicochemical properties and reactivity of iridium(III) complexes with 5,10,15,20-tetraphenyl-21H,23H-porphine was studied. Oxidation reactions of (Cl)(H2O)IrTPP in protic solvents by atmospheric oxygen (on assistance of protons at high concentration) preceded by ligand substitution at the axial position were studied. It was found that (Cl)(H2O)IrTPP in 100% AcOH undergoes slow one-electron oxidation at the aromatic ligand to form π cation radical (CH3COO)(CH3COOH)IrTPP·+. The reaction was studied in 100% AcOH (H2O content 0.078%) at 288–308 K, its kinetic parameters were obtained. The (Cl)(H2O)IrTPP reaction product in CF3COOH was identified as complex (CF3COO)2IrIVTPP oxidized at the central metal cation. It was experimentally confirmed that the reaction in 99% CF3COOH at 298 K proceeds in two stages: the substitution of axial Cl− and H2O by excess CF3COO− (keff = (1.8 ± 0.1) × 10−3 s−1) and the oxidation of iridium to Ir(IV) (keff = (8.0 ± 0.5) × 10−5 s−1). Data on similar Re(III) complexes (PhO)ReTPP and (Cl)ReTPP are presented for comparison.

Ion-molecular interactions in the metalloporphyrin-acid system in liquid solutions

A new form of MP...Hsolv+ metalloporphyrins is found and studied in the strong acid medium, the conditions of its formation and the qualitative reaction of its determination are established. It is shown that the same form has the H4TPP2+ dication (TPP is the 5,10,15,20-tetraphenyl-21H,23H-porphyrine dianion). The stability in different acid media and in the isolated state, spectral properties and the structure of H+-associates of porphyrins are analyzed in detail by UV-visible and 1H NMR spectroscopy and quantum chemical calculations. It is shown that they have a unique two-band visible electronic spectrum with the bands near 540 nm and 700 nm, which weakly depend on the type of the central atom in the complex and noticeably change when the chromophore is functionally substituted. The proton location the ion-molecular associate and the cases of the formation of H+-associates with higher stoichiometry are revealed.

Thermodynamics of the equilibrium of the reaction between (5,10,15,20-tetra(2-methoxyphenyl)porphinato)chloroindium(III) and pyridine

The results from thermodynamic and quantum-chemical studies of the reversible reaction between (5,10,15,20-tetra(2-methoxyphenyl)porphinato)chloroindium(III) and pyridine are reported. The main physicochemical parameters of properties of its supramolecular products are obtained and analyzed. The addition of pyridine molecules to metalloporphyrin proceeds in one step to attain an equilibrium state with the formation of supramolecules with a stoichiometry of 2: 1; spectral characteristics and parameters of the stability of the latter are identified. The possibility of using substituted indium(III)porphyrin for further research in the field of hybrid solar cells is discussed.