Narrow Results

Amino-substituted tetraphenylporphyrins (5,10,15,20-tetrakis(4′-aminophenyl)porphyrin, 5-(4′-aminophenyl)–10,15,20-triphenylporphyrin) and their copper complexes in dichloromethane and ethanol were electropolymerized by the cyclic voltammetry method and their electrochemical properties were studied. The polyporphyrin films obtained by electro-oxidation transmit electricity and possess semiconductor properties of different types. The poly-5,10,15,20-tetrakis(4′-aminophenyl)porphyrin films obtained from different solvents are similar to each other in chemical composition but different in morphology. The polyporphyrin film surface morphology was studied by AFM microscopy.

Fe(III)-complexes of amino-substituted tetraphenylporphyrins obtained from solutions in organic solvents: dichloromethane, ethanol, and dimethyl sulfoxide have been electropolymerized. The solvents’ effects on deposition and surface morphology of the obtained polyporphyrin film have been determined. It is only possible to obtain a polyporphyrin film from DMSO solutions through electrochemical activation of electropolymerization by a superoxide anion radical (O${}_2^{•-})$. The activation effect of the dissolved oxygen becomes evident in porphyrin interaction with the superoxide anion radical (O${}_2^{•}-)$ that is synthesized in DMSO thanks to the quasi-reversible redox process. The size of particles forming the film is lowest when the film is deposited from DMSO and highest when it is deposited from dichloromethane. Therefore, the ratio of polyporphyrin phase grain growth rate to the nucleation rate has the highest value when the film is deposited from dichloromethane. Such films have the most developed surfaces, while those deposited from ethanol are the smoothest. If the film is deposited on an ITO-electrode, the particles forming the surface are a little larger than in the case of deposition on Pt, which is explained by a slower nucleation on the ITO surface. FeClT($m$-NH₂Ph)P-based films obtained from ethanol and dichloromethane have negative photo-EMF values, which indicates that the $n$-type films have semiconductor properties.

The influence of solvent, supporting electrolyte and electrolysis modes on poly-5,10,15,20-tetrakis($p$-aminophenyl)porphyrin film growth were studied by the quartz crystal microbalance method. Electropolymerization was carried out in potentiostatic and potentiodynamic modes from dichloromethane and ethanol solutions. Tetrabutylammonium perchlorate (TBAP) and tetrabutylammonium hexafluorophosphate (TBAHFP) were used as supporting electrolytes. Surface micrographs of films electrodeposited over a different number of cycles of potential variation were obtained. The specific surface area, the pore size, and the thickness of the obtained polyporphyrin films were determined. The number of electrons participating in 5,10,15,20-tetrakis($p$-aminophenyl)porphyrin electropolymerization was determined by the quartz crystal microbalance method. Based on the electronic absorption spectroscopy results, it was established that porphyrin macroheterocycles were preserved in an oxidized state in polyporphyrin.

The process of electrodeposition of polyporphyrin films based on amino-substituted tetraphenylporphyrins and their metal complexes (CuT($p$-NH${}_{\mathrm{\text{2}}}$Ph)P, FeClT($m$-NH${}_{\mathrm{\text{2}}}$Ph)P, MnClT($m$-NH${}_{\mathrm{\text{2}}}$Ph)P) has been studied by the quartz crystal microbalance method. The surfaces of the films have been characterized by the scanning electron microscopy method and the number of electrons taking part in porphyrin electropolymerization has been determined. It has been established that the most intensive film growth is observed for the metal-free porphyrin ligand. The obtained polyporphyrin films have been analyzed for the catalytic ability in oxygen electroreduction reactions.

The process of 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin electropolymerization has been studied by the quartz crystal microbalance method in different electrodeposition conditions. The films were deposited in two modes: in potentiostatic conditions (at the potential of $+$2 V) and in potentiodynamic conditions (CV with the potential scan rate of 20 mV/s). The effect of electrolysis parameters on 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin electropolymerization has been studied by obtaining films in two modes and using two supporting electrolytes: tetrabutylammonium perchlorate or tetrabutylammonium hexafluorophosphate. The biggest film mass gain was observed on a clean electrode surface. At further film deposition on the polyporphyrin-coated electrode, the film mass growth stopped. The electrodeposition effectiveness was somewhat higher in the potentiodynamic conditions, with the formation of a looser film. The nature of the supporting electrolyte did not have a significant effect on the electrodeposition process. A significant contribution to the deposition was made by the electrode material. The film thickness was 25–80 nm. The films possessed $p$-type conductivity; and the flat-band potential for poly-H${}_{\mathrm{\text{2}}}$T(4-OHPh)P obtained in potentiodynamic conditions was 0.33 V, for poly-H${}_{\mathrm{\text{2}}}$T(4-OHPh)P obtained in potentiostatic conditions it was 0.16 V.

Poly-5,10,15,20-tetrakis($p$-aminophenyl)porphyrin films were obtained by interfacial polymerization and electropolymerization. According to the results of electron spectroscopy and IR spectroscopy it has been determined that oxidative polymerization of 5,10,15,20-tetrakis($p$-aminophenyl)porphyrin, regardless of its type (chemical/electrochemical), proceeds through the formation of phenazine and dihydrophenazine fragments. It has been established that the film obtained by the electrochemical method is in the oxidized state, the supporting electrolyte anions are included in the film. The polyporphyrin films obtained by interfacial polymerization are non-conductive. As a result of doping the films obtained by the chemical method, due to the oxidation in the anodic potential region, the polymer acquires $p$-type semiconductor properties. It has been shown that electrochemical doping of poly-5,10,15,20-tetrakis($p$-aminophenyl)porphyrin films can make them electroconductive. The obtained films can be recommended as elements of photovoltaic devices, the operation of which is based on the excitation of excitons under the action of light radiation, the redistribution of which leads to a change in the potential of the working electrode.

Polyporphyrin films based on 5,10,15,20-tetrakis(4-pyridyl)porphyrin and 5,10,15,20-tetrakis(4-aminophenyl)porphyrin were obtained by electrochemical polymerization during the electrooxidation of the respective monomers. The polyporphyrin formation involved the side substituents, with the $\pi$-conjugated porphyrin platform being preserved. The obtained polyporphyrins form uniform electroconductive coatings, tightly adhered to the electrode surface. The electrochromic properties were studied by the spectroelectrochemical method. Electronic absorption spectra of the films were recorded under the action of electric current at the stepwise potential changes within several intervals. The obtained polyporphyrin films were shown to possess electrochromic properties. The films were oxidized when exposed to anodic potentials and reduced when exposed to cathodic potentials. The electronic absorption spectra were used to calculate the optical band gap of the initial, oxidized and reduced films and to evaluate their conductivity. The highest conductivity was found in the electrochemically oxidized poly-5,10,15,20-tetrakis(4-aminophenyl)porphyrin film.

The process of 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin electropolymerization has been studied by the quartz crystal microbalance method in different electrodeposition conditions. The films were deposited in two modes: in potentiostatic conditions (at the potential of +2 V) and in potentiodynamic conditions (CV with the potential scan rate of 20 mV/s). The effect of electrolysis parameters on 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin electropolymerization has been studied by obtaining films in two modes and using two supporting electrolytes: tetrabutylammonium perchlorate or tetrabutylammonium hexafluorophosphate. The biggest film mass gain was observed on a clean electrode surface. At further film deposition on the polyporphyrin-coated electrode, the film mass growth stopped. The electrodeposition effectiveness was somewhat higher in the potentiodynamic conditions, with the formation of a looser film. The nature of the supporting electrolyte did not have a significant effect on the electrodeposition process. A significant contribution to the deposition was made by the electrode material. The film thickness was 25–80 nm. The films possessed p-type conductivity; and the flat-band potential for poly-H₂T(4-OHPh)P obtained in potentiodynamic conditions was 0.33 V, for poly-H₂T(4-OHPh)P obtained in potentiostatic conditions it was ‑0.16 V.