Alexander A. Ksenofontov

Comparative analysis of physicochemical properties of dinuclear zinc(II) helicates with 2,2′-, 2,3′-, and 3,3′-bis(dipyrromethenes)

The effect of the attachment position of a methylene spacer in 2,2′-, 2,3′-, and 3,3′-bis(dipyrromethene) N4-ligands (H2L) on physicochemical properties of their dinuclear homoleptic helicates [Zn2L2], such as specific features of their molecular structure, luminescence spectral characteristics, lability in acid solutions, and thermal stability in an argon atmosphere, has been examined. It has been shown that the substitution of the biladiene-type helicand by its 2,3- and especially 3,3′-analogues leads to a considerable enhancement of the chromophoric properties, an increase (up to 30-fold) of the fluorescence quantum yield, and an increase in the stability of corresponding dinuclear helicates [Zn2L2].

Molecular structure of bis (dipyrrolylmethanates) of d -metals according to the quantum chemical calculations by the PM6 method

Quantum chemical calculations of the molecular structure of bis(dipyrrolylmethanates) of cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), and mercury(II) of the composition [M2L2] are performed using the PM6 method within the Gaussian 09W program package. The lengths of M-N coordination bonds, the values of dihedral angles formed by N-M-N bonds, the distances lM⋯M between the M⋯M atoms are optimized. It is noted that the regularities obtained from the analysis of the results of quantum chemical calculations of the molecular structure of [M2L2] helicates reliably reflect the main trends of changes in their physicochemical properties depending on the nature of a complexing agent and the features of the ligand structure.

A quantum chemical study of the molecular structure of zinc(II) and boron(II) complexes with monoiodo and dibromo substituted dipyrrines

The geometric parameters of the molecular structures of 4-monoiododipyrrine, 4,4′- and 5,5′-dibromodipyrrine complexes with zinc(II) and boron(III) of the composition [ZnL2] and [BF2L] respectively are determined at the M06 and B3LYP levels of density functional theory with the Def2-SVP basis set. The lengths of Zn–N, B–N, and B–F coordination bonds, N–X–N, F–B–F, C–C–C bond angles, the dihedral angles between the planes of pyrrole rings in the dipyrrine ligand, dipyrrine planes in [ZnL2], dipyrrine core and the plane passing through the atoms of the BF2 group are optimized. The effect of structural factors on the geometric parameters and the widths of the HOMO–LUMO energy gap in halogen substituted dipyrrinates is analyzed.

Crystal solvates of zinc(II) bis(dipyrrinates) with triethylamine: composition, stability and spectral-luminescent properties

Abstract Crystal solvates of 2,2′-, 2,3′- and 3,3′-bis(dipyrrinato)zinc(II) with triethylamine (TEA) were obtained by slow crystallization. Composition, structural organization, stability, and spectral-luminescent properties of the crystal solvates were studied by FTIR, Powder X-ray Diffraction, thermal, mass spectral, absorption and fluorescence analyses. The thermal dissociation processes of crystal solvates in an argon atmosphere have been investigated. It is shown that zinc(II) helicates with decamethylsubstituted 2,2′-, 2,3′-, and 3,3′-bis(dipyrrin)s with TEA form stable supramolecular complexes of the composition [Zn2L2(TEA)4] and [Zn2L2TEA]. Spectroscopic studies showed that the quantum yield (φ) of [Zn2L2(TEA)n] crystal solvates in cyclohexane is noticeably (3–4.5 times) lower than φ of [Zn2L2] complexes. Quantum chemical study indicated the most likely mechanism for the coordination of solvent molecules on the coordinating centers of [Zn2L2]. Thermal and energy stability of [Zn2L2(TEA)n] solvates reduced when replacing the 2,2′- on 2,3′-, and 3,3′-isomer. The obtained results are of interest for the development of [Zn2L2] fluorescent sensors of the electron donor molecules.

Theoretical studies on the electronic structure and spectroscopic properties of transition metals bis(dipyrrinate)s

ABSTRACT Density functional theory (DFT) and Time-dependent density functional theory (TD– DFT) computations have been used to reveal structural, molecular, electronic and spectral–luminescent parameters and features of several homoleptic transition metals bis(dipyrrine) complexes. The influence of complexing agent and ligand nature on the regularities in geometric, spectral–luminescent properties, kinetic and thermal stability changes in the [M2L2] complexes series were studied. Special attention is paid to the influence of the solvating media (PCM/TD–B3LYP/Def2–SVP) on changing spectral–luminescent properties of d-metals bis(dipyrrinate)s. The interpretation of the dependence between spectral–luminescent properties of the complexes and HOMO–LUMO (highest occupied molecular orbital and lowest unoccupied molecular orbital) energy gaps width was given. It was shown that the regularities in changing the helicates’ quantum yield depending on the nature of complexing agent, ligand and solvent properties, obtained from quantum-chemical calculations, are in the agreement with our previously obtained experimental data. Thus, structural and spectral–luminescent characteristics of new [M2L2] luminophors can be evaluated with high reliability, and good forecast prospects for their use as fluorescent dyes for optical devices can be made in terms of the results of theoretical studies (B3LYP/Def2–SVP and TD–B3LYP/Def2–SVP).

Influence of Solvation and Structural Contributions on Fluorescence of Dipyrrine Dyes

AbstractThe results of quantum-chemical and spectral researches of zinc(II) complexes with alkylated dipyrrine and 3,3′-, 2,3′- and 2,2′-bis(dipyrrine)s in non-polar and polar solvents and their binary mixtures are presented. It was investigated the efficiency of the fluorescence quenching of fluorophores depending on of the solvation and structural contributions. Found that 3,3′-bis(dipyrrinato)zinc(II) demonstrates the highest sensitivity of the fluorescence to the presence of the electron-donor component compared with the studied complexes. The obtained results allow to offer dipyrrine and bis(dipyrrine) zinc(II) complexes as new, highly sensitive and selective fluorescent sensors of the N- and O-containing toxicants. Graphical AbstractInfluence of solvation and structural contributions on fluorescence of dipyrrine dyes

Kinetic model and mechanism of the acid dissociation of d-metal bis(dipyrrolylmethenates)

A kinetic model and a mechanism have been developed by quantum chemical simulation for the protolytic dissociation of dinuclear homoleptic bis(dipyrrolylmethenates) of d-metals (M) with the general formula [M2L2] and a double-helix structure. The reaction is described by a third-order equation that is first-order with respect to the complex and second-order with respect to the acid. The main contribution to the total dissociation rate is made by the rate-determining step, specifically, attack of the second acetic acid molecule on the nitrogen atom of one of the coordination sites of the helicate. The dinuclear helicates of 3,3′-bis(dipyrrolylmethenes) are more inert in an acidic medium than 2,3′- and 2,2′-bis(dipyrrolylmethenes).

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.

ZINC(II) BIS(DIPYRROMETENATES) AS NEW FLUORESCENT CHEMOSENSORS OF N- AND O-CONTAINING ANALYTES

22 Изв. вузов. Химия и хим. технология. 2016. Т. 59. Вып. 6 Для цитирования: Антина Е.В., Березин М.Б., Гусева Г.Б., Ксенофонтов А.А., Вьюгин А.И. Бис(дипиррометенаты) цинка(II) как новые флуоресцентные хемосенсоры Nи О-содержащих аналитов. Изв. вузов. Химия и хим. технология. 2016. Т. 59. Вып. 6. С. 22-27. For citation: Antina E.V., Berezin M.B., Guseva G.B., Ksenofontov A.A., V’yugin A.I. Zinc(II) bis(dipyrrometenate)s as new fluorescent chemosensors of Nand O-containing analytes. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2016. V. 59. N 6. P. 22-27.