Yu. S. Marfin

Sol-gel synthesis of highly effective catalyst based on cobalt tetrasulfophthalocyanine complex and silicon oxide

New hybrid materials based on silicon oxide and water soluble cobalt phthalocyanine complex were synthesized and characterized. It was shown that synthesized material exhibit pronounced catalytic activity in the R–SH type of organic compounds oxidation reaction in comparison with the individual macroheterocycle. The influence of the synthetic route of the hybrid material preparation on its catalytic efficiency was determined.

Analysis of solvation and structural contributions in spectral characteristics of dipyrrin Zn(II) complexes

Photophysical characteristics of several alkylated dipyrrin Zn(II) complexes in organic solvents were analyzed. Relations between spectral properties of complexes and physical-chemical parameters of solvents were determined with the use of linear regression analysis method. Each solvent parameter contribution in investigated spectral characteristics was estimated. Spectral properties of complexes under study depend on the specific interactions of zinc with the solvent molecules by specific axial coordination. Increasing of alkyl substitution lead to the bathochromic shifts in spectra due to the positive induction effect of alkyl groups.

Spectral and Photophysical Properties of Zinc(II) Complexes with Alkylsubstituted Derivatives of Dipyrrolylmethene and Their Resistance to Protolytic Dissociation and Photochemical Destruction

The spectral and photophysical properties of zinc(II) complexes with alkylsubstituted derivatives of dipyrrolylmethene, along with the kinetics of their protolytic dissociation and photochemical degradation in organic solvents of different natures, are studied by means of electronic absorption and fluorescence spectroscopy. It is found that protic solvents have the strongest effect on absorption spectra, while electron donors affect fluorescence spectra due to differences in the mechanisms of solvation for the ground and excited states of molecules. It is shown that the reaction product of the protolytic dissociation of complexes in benzene solutions of acetic acid is a protonated form of ligand. The observable and genuine rate constants of dissociation reactions are determined and activation parameters are calculated. A kinetic model of the process is proposed, and the regularities of the effect the nature of ligand has on the kinetics of dissociation are established. The photochemical degradation of compounds proceeds on monopyrrole products, the photolysis rate falls as the a degree of alkylation increases, and the nature of the substituent in the β-position of the ligand’s pyrrole ring has a greater effect on the stability of a compound.

Fluorescent Properties of BODIPY Sensors Based on Photoinduced Electron Transfer.

Two boron-dipyrrin (BODIPY) based dyes with dimethylaminophenyl and carboxyphenyl substituents in 8-position of dipyrrin ligand have been synthesized and characterized. Photophysical and spectral properties of the obtained compounds have been investigated in water-ethanol mixture and water-cyclohexane system with variation of pH values. The equilibria constants of the compounds were identified by classical methods of acid-base titration. BODIPY bearing dimethylaminophenyl and carboxyphenyl subunits show deprotonation/protonation dependent fluorescence off/on-switching. The change of the emission could be mechanistically explained by a PET (photoinduced electron transfer) from the 8-substituent to the fluorophore. The present study demonstrates that BODIPY-based fluorescent sensors can be used to measure the pH in the range of 2–13 extending the scope of BODIPY dyes available as pH-indicators. Investigated compounds demonstrate weak dye-dye interaction allowing their cooperative usage as indicators.

Kinetic resistance of borofluoride complexes of dipyrrolylmethenes to acids

The trends of kinetic resistance of borofluoride complexes of alkyl- and sulfo-substituted dipyrrolylmethene (Bodipy) to protolytic and solvoprotolytic dissociation in organic solvents and aqueous solutions are studied. It is established that among dipyrrolylmethene complexes with d elements, Bodipy is notable for its superresistance to acids. The rate of the dissociation reaction increases with increasing acidity of protonating mixtures or decreasing effective charge of the coordinating nitrogen atoms of the ligand. Dissociation of the complexes occurs in accordance with a second-order rate equation. A kinetic model of the process is proposed; its kinetic and activation parameters are determined. The energy profiles of the initial stages of protolytic dissociation reactions are calculated using quantum-chemical methods for two suggested variants of the transient state; the energetically preferable pathway is recognized.

Quantum-chemical study of interaction of dipyrrolylmethenes with boron trifluoride and other lewis acids

The geometric parameters and energies of the products of donor-acceptor interaction of dipyrrolylmethenes with BF3 and other inorganic Lewis acids were calculated by quantum-chemical methods. The bond nature and the energies of formation of the donor-acceptor complexes under consideration were analyzed. It was shown that the complexes with p-element fluorides are noticeably stabilized by hydrogen bonds involving the hydrogen atom of the NH group of dipyrrolylmethene and the nearest fluorine atom of a Lewis acid. Hydrogen bonding promotes further elimination of HF in the synthesis of boron fluoride complexes of dipyrrolylmethenes. The energy profile was calculated for the reaction of formation of the boron fluoride complex with dipyrrolylmethene through the intermediate donor-acceptor complex.

Spectral Properties and Possibilities of meso-Substituted BODIPY Usage in Sol–Gel Process and Materials

Hybrid materials based on organically modified silica with immobilized boron-dipyrrins (BODIPY) dyes were obtained. Spectral characteristics of the dyes were measured during the matrix formation and in obtained materials. It was stated, that immobilization does not affect the character of the absorption and fluorescence spectra of the dye, but due to the effect of fluorescent molecular rotor observed for meso-substituted BODIPY, the fluorescent quantum yields were found to increase during the matrix sealing. Quantum yield increase is linear for all of the investigated matrices except phenyl-substituted one, where the π-π interactions of the dye molecule with matrix could be observed. This effect could be used for fine control of the matrix formation process and leads to increase of the dye emission in the final material for further practical applications. All obtained hybrid materials were found to be stable upon UV light irradiation, hence immobilization enhance the stability of the dye in comparison with the BODIPY in organic solvents.