Ekaterina N. Ovchenkova

Cobalt(II) porphyrin axially coordinated with 2′-(pyridin-4-yl)-5′-(pyridin-2-yl)-1′-(pyridin-2-ylmethyl)-2′,4′-dihydro-1′H-pyrrolo[3′,4′ : 1,2](C60-Ih)[5,6]fullerene: formation, chemical structure, and spectroscopic properties

Abstract Construction of new effective photovoltaic devices based on organic dyes has important implications for modern and future technologies. In this article, we studied the equilibrium, the rate, and the spectral manifestation of the reaction of [(2,3,7,8,12,18-hexamethyl,13,17-diethyl,5-(2-pyridyl)porphyrinato)cobalt(II)]–[2′-(pyridin-4-yl)-5′-(pyridin-2-yl)-1′-(pyridin-2-ylmethyl)-2′,4′-dihydro-1′H-pyrrolo[3′,4′ : 1,2](C60-Ih)[5,6]fullerene] triad formation as well as its spectral properties and photo electrochemical behavior. The cobalt porphyrin–pyridyl-substituted fullerene mixtures in toluene are self-assembling systems due to axial donor–acceptor binding between Co of the porphyrin complex and N-pyridyl of the substituted fullerene. The formation rate constant, k298K, and the stability constant, K298K, of donor–acceptor triad formed by coordination of two substituted fullerene molecules to Co porphyrin are (44.4 ± 0.8) mol L−1 s−1 and (56 ± 16)×107 L2 mol−2, respectively. Modification of the titanium electrode coated with the natural oxide film was carried out using the porphyrin–fullerene triad and its individual components. Photopotential and photocurrent density of the system with modified electrode were studied. The obtained results are of interest for creating porphyrin-based donor–acceptor systems as components in organic photovoltaics.

Synthesis and properties of a new (octaethylporphyrinato)-manganese(III)–pyridinyl-substituted pyrrolidinofullerene dyad

The formation of a porphyrin–fullerene dyad from 2′-(pyridin-4-yl)-5′-(pyridin-2-yl)-1′-(pyridin-3-ylmethyl)-2′,5′-dihydro-1′H-pyrrolo[3′,4′: 1,9](C60-Ih)[5,6]fullerene and (2,3,7,8,12,13,17,18-octaethylporphyrinato) manganese(III) with axial chloride ligand has been studied on a quantitative level with the goal of obtaining supramolecules possessing biological activity. Preliminarily, the reaction of manganese(III) porphyrin with pyridine has been studied. The donor–acceptor dyads are formed either instantaneously and reversibly (pyridine) or slowly and irreversibly (substituted fullerene). In both cases, the reaction is a one-step process for which thermodynamic and kinetic parameters have been determined. The results can be used to optimize conditions for the synthesis of porphyrin–fullerene dyads. The obtained dyads have been characterized by spectral data and stability constants.

Formation Reaction and Chemical Structure of a Novel Supramolecular Triad Based on Cobalt(II) 5,10,15,20-(Tetra-4-Tert-Butylphenyl)-21Н,23Н-Porphyrin and 1-Methyl-2-(Pyridin-4′-Yl)- 3,4-Fullero[60]Pyrrolidine

Results of chemical kinetic/thermodynamic and spectroscopic studies of the reaction of cobalt(II) 5,10,15,20-(tetra-4-tert-butylphenyl)-21Н,23Н-porphyrin (CoIITBPP) with 1-methyl-2-(pyridin-4′-yl)-3,4- fullero[60]pyrrolidine (PyF) in toluene at 298 K, ending by the formation of donor-acceptor triad (PyF)2CoIITBPP, are presented. Kinetic and thermodynamic parameters of the two-way formation reaction of the triad are obtained. The chemical structure of the obtained porphyrin-fullerene triad is identified by UV, visible, fluorescent, IR, and 1H NMR spectroscopic techniques. The results are relevant for the problems of searching for supramolecular systems capable of photoinduced charge separation.

Porphyrin–Fullerene Dyad Based on Indium(III) Complex. Donor–Acceptor Complex Formation Equilibrium

Formation kinetics and spectral properties of the donor–acceptor complexes of (5,10,15,20- tetra(2-methoxyphenyl)porphinato)chloroindium(III) with 2′-(pyridin-4-yl)-5′-(pyridin-2-yl)-1′-(pyridin- 2-yl)methylpyrrolidinyl[3′,4′:1,2][60]fullerene were studied. The formation of the donor–acceptor dyad [(Py3F)InTPP(2-OCH3)4]+Cl– occurs as a two-step reaction, including fast reversible coordination of the fullerene base molecule and slow irreversible displacement of the axial chloride ion to the second coordination sphere. Quantitative characteristics for the reaction rate and equilibrium were obtained. The reaction products were identified by IR and 1H NMR spectroscopy. The most important electron optical and stability parameters of the porphyrin–fullerene dyads with inner- and outer-sphere chloride ions were determined. These results are important for studies of the photophysics of porphyrin–fullerene dyads and development of photoconverters based on them.

Self-assembled cobalt(II)porphyrin–fulleropyrrolidine triads via axial coordination with photoinduced electron transfer

Self-assembly by donor–acceptor complex formation in the (2,3,7,8,12,18-hexamethyl,13,17-diethyl,5-(2-pyridyl)porphinato)cobalt(II) (CoIIP)–1′-N-methyl-2′-(pyridin-4-yl)pyrrolidino[3′,4′:1,2][60]fullerene (PyC60) system was studied using chemical thermodynamics/kinetics, UV-vis, IR, 1H NMR spectroscopy, amperometry and quantum chemical B3LYP-D3/6-31G(d,p) methods. The results revealed the formation of a supramolecular 1 : 2 triad between CoIIP and PyC60. The equilibrium/rate constants of the donor–acceptor triad formation are observed to be (1.04 ± 0.12) × 1010 L2 mol−2 and (63.7 ± 4.5) mol−1 L s−1, respectively. The numerical values of these equilibrium/rate constants demonstrate a strong bonding between the CoIIP and fulleropyrrolidine moieties. The triad LUMO energy levels are predominantly spread on the C60 unit. However, the HOMO energy levels are mainly spread on the porphyrin ring pointing at the property of photoinduced electron transfer (PET) in the obtained triad. Modification of the covered natural oxide film titanium electrode surface in the voltammetry experiment was carried out by using the porphyrin–fullerene triad and the self-assembly components. The maximum efficiency coefficient of the incident photon energy conversion to current (IPCE) and photocurrent density values of (PyC60)2CoIIP at 365 nm are significantly larger than those of CoIIP and PyC60. The results are of interest for creating porphyrin-based donor–acceptor systems as components in organic photovoltaics.

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.

Magnetothermal properties of (octakis-trifluoromethylphenyltetraazaporphinato)manganese(III) acetate in aqueous suspension

The magnetocaloric effect (MCE), heat capacity, and magnetization thermodynamic parameters of the high-spin (octakis-trifluoromethylphenyltetraazaporphinato)manganese(III) acetate, (AcO)MnTAP(3-CF3C6H4)8, in a 1% aqueous suspension were determined by means of microcalorimetric method at 275–320 K in magnetic fields of 0.1–1.0 T. The conditions are comparable with those used with (octakis(3-tert-butylphenyl)tetraazaporphinato)manganese(III) acetate, (2,3,7,8,12,13,17,18-octaethylporphinato)manganese(III) chloride and (5,10,15,20-tetraphenylporphinato)manganese(III) chloride, acetate or bromide studied earlier. Paramagnetic properties were found in high-disperse particles of complexes, positive MCE values were obtained. As paramagnets, these complexes exhibit a big magnetocaloric effect (up to 0.85 K when the magnetic induction is changed from 0 to 1 T) at temperatures close to room, what could be employed for cooling in home and industrial refrigerators and hyperthermia in cancer diagnostics and therapy. MCE sensitivity to the nature and electronic structure of the aromatic macrocycle was discussed. The specific heat capacity of the complex depended on the temperature was obtained. Effect of magnetic field on the temperature dependence of the specific heat capacity for (AcO)MnTAP(3-CF3C6H4)8 practically is not visible.