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V I Kovalenko

Publications and source records attributed to V I Kovalenko.

At least 19 recordsLinked to original sources
PubMed2006

DFT analysis of structure and IR spectra of phosphorus G1v generation dendron.

FT-IR spectra of phosphorus dendron G(1v) generation with terminal P-Cl groups have been recorded. Density functional theory is used for analyzing the properties of each structural part (core, branches, surface). It is found that the repeating branching units of G(1v) exist in a single stable conformation with planar -O-C(6)H(4)-CH=N-N(CH(3))-P fragments. DFT results for the structure of G(1v) are in good agreement with recent X-ray diffraction measurements. A complete vibrational assignment is proposed for different parts of G(1v). The global and local reactivity descriptors have been used to characterize the reactivity pattern of the core function and terminal group. Our study reveals that the most reactive site of G(1v) is the core function and =CH(2) side of vinyl group is preferred for nucleophilic attack. In the dendrimer G(1) the most reactive are the terminal groups. IR spectroscopy combined with ab initio DFT computation provides unique detailed information about the structure and reactivity of the technologically relevant materials, which could not be obtained before with any other technique.

Anthracenes↗
PubMed2006

DFT calculations of structure and IR spectra of the phoshorus-containing G'0v generation dendron.

FT-IR spectra of the phosphorus-containing dendron G'(0v) generation with terminal aldehyde groups have been recorded. The structural optimization and normal mode analysis are performed for the G'(0v) on the basis of the ab initio density functional theory. This calculations gave vibrational frequencies and infrared intensities for the t,g,g- and t,-g,g-conformers of the G'(0v). The t,-g,g-conformer is 0.71 kcal/mol less stable compared to t,g,g-conformer. Relying on DFT calculations a complete vibrational assignment is proposed for different parts of the dendron. The influence of encirclement on band frequencies and intensity is studied and the information usually inaccessible is obtained. The global and local reactivity descriptors have been used to characterize the reactivity pattern of the core function and terminal groups. Our study reveals that the most reactive site in the dendron is the core function and the CH(2) side of the vinyl group is preferred for nucleophilic attack. In the dendrimer the most reactive are the terminal groups.

Aldehydes↗
PubMed2005

DFT and IR spectroscopic analysis of p-tert-butylthiacalix[4]arene.

Vibrational analysis of p-tert-butylthiacalix[4]arene based on an experimental mid and far IR spectra is described here. Density functional calculations of a most stable cone conformer related to crystalline solid FT-IR spectra in the temperature range up to 180 degrees C as well spectra of dilute solution have been used to obtain a better understanding of conformational state and a hydrogen bonding of p-tert-butylthiacalix[4]arene. Complete assignments were made for experimental FT-IR spectra of the cone conformer. Heating (up to 180 degrees C) of crystalline p-tert-butylthiacalix[4]arene did not change both conformational and cooperative H-bonding state of its molecules. A temperature spectral effect seems to be due to some relaxation of crystal packing mostly viewed on the OH bands.

Models, Molecular↗
PubMed2005

Band intensity in the IR spectra and conformations of calix[4]arene and thiacalix[4]arene.

The experimental IR and Far IR spectra of the calix[4]arene, p-tert-butylcalix[4]arene, thialcalix[4]arene and p-tert-butylthiacalix[4]arene were examined at different temperatures and interpreted. The band frequencies and intensities in the IR spectra of the calix[4]arene and thialcalix[4]arene were calculated. The absorption curves of the four possible calix[4]arene conformations: cone, partial cone, 1,2- and 1,3-alternate were computed. The bands characteristic for each conformation are defined and assigned. The obtained spectra-structure correlation can be used for the characteristic of calixarenes conformation.

Calixarenes↗
PubMed2005

The hydrogen bonding and conformations of p-tert-butylcalix[4]arene as studied by IR spectroscopy and by DFT calculations.

IR and far IR spectra of p-tert-butylcalix[4]arene were recorded at various temperatures between 16 and 180 degrees C and spectra of solutions and crystalline solids were obtained. Ab initio density functional calculations gave vibrational frequencies and infrared intensities for four conformers: cone, partial cone, 1,2- and 1,3-alternate. Complete assignments were made for experimental IR spectra of the cone conformer. The bands characteristic for each conformation were defined. It was revealed that O--H stretching low-frequency shift Deltanu in the cone conformation exceeds Deltanu shifts for other conformers. The effect was stipulated by a cooperative interaction of cyclic hydrogen bonds. The obtained spectra-structure correlation can be used for characteristic of calixarenes conformation.

Calixarenes↗
PubMed2004

Fourier-transform infrared and Raman difference spectroscopy studies of the phosphorus-containing dendrimers.

FT IR and Raman spectra of 12 generations of the phosphorus-containing starburst dendrimers containing P=S and P=O bonds with terminal aldehyde and P-Cl groups were compared. The influence of the encirclement on the band frequencies and intensity is studied and due to the predictable, controlled and reproducible structure of the dendrimers the information usually inaccessible is obtained. Bands in the IR difference (G2'(P=O)-G2'(P=S)) spectra have characteristic EPR-like form. The strong band at 1600 cm(-1) show marked changes of the optical density in dependence of the aldehyde (-CH=O) or azomethyne (-CH=N-) substituents in the aromatic ring. The analysis of difference spectra enables one to assign the characteristic bands nu(P=S) and nu(P=O) for the bonds in the core, in the repeating unit and in the terminal groups of the dendrimers. This assignment is supported by the calculation of the absorption curves of the different fragments of dendrimer with the force constants and electro-optical parameters. The IR and Raman spectra of dendrimers are depended on the ratio of number terminal groups to a number of repeating units, which in its turn is strictly determined by the generation number. Thus, the marked differences in the vibrational spectra of the first successive generations aspire to zero for the higher ones. The rather rigid repeated units with little conformational flexibility define the perfect microstructure of the studied phosphorus-containing dendrimers up to the eleventh generation.

Molecular Structure↗
PubMed2002

Calculation of IR spectra of the elementoorganic dendrimers.

Various approximations to the analysis of the dendrimer vibrational spectra are introduced. The merits and demerits of the fragment method, calculation of the first generation and linear chains containing different number of the repeated units are discussed. The experimental spectra of two series of the phosphorus-containing starburst dendrimer generations are interpreted on the basis of the calculation of the frequencies of the normal vibrations and the band intensities in their IR spectra. The analysis of spectra enables one to assign the characteristic bands for the groups in the core, in the repeating unit and the terminal groups of the dendrimers. This assignment is supported by the calculation of the absorption curves with the force constants and electro-optical parameters (EOP). The vibrational spectra of studied starburst dendrimers (SD) (up to 11 generations) are in general identical to begin with four generation. The most marked changes of band position and their intensities are seen in spectra of the first generations, when all fragments of molecule contribute appreciably to the spectral pattern. The comparative study of vibrational spectra of SD and linear polymers reveal their main characteristic features, which are determined by their structural peculiarities.

Phosphorus Compounds↗
PubMed1991

[The specificity of the peripheral blood changes in patients with gastric peptic ulcer].

Leucocytes were studied in 112 patients with ulcer disease of the stomach in comparison with periods of existence of an ulcer defect of the gastric mucosa. Methods of statistical analysis allowed to establish that the peripheral blood shows phasic changes in the absolute content of the leucocytes and their forms, pathogenetically related to the course of the reparative process.

Adult↗
PubMed1989

[Coronary circulation in patients with ischemic heart disease with various degrees of arteriosclerosis obliterans of the leg during selection surgical treatment].

First in the literature, the relationship between the coronary and lower limb circulation is detailed on the basis of objective findings. Comparison of the two patient groups (the patients categorized according to the degree of lower limb ischemia revealed by Doppler ultrasound echocardiography) in respect to the clinicomorphofunctional characteristics of the coronary flow in IHD patients suggested the absence of a significant correlation between them. Varying severity of lower limb ischemia does not influence the gravity of IHD manifestation in the same patients.

Adult↗
PubMed1985

[Blood supply to the heart and coronary vasodilation reserves in experimental myocardial hypertrophy].

The effects of pressure overload left ventricular hypertrophy (LVH) on heart performance and coronary circulation were investigated in dog experiments. The data obtained clearly demonstrate that left ventricular systolic and end-diastolic pressures were increased in LVH dogs. The heart rate and cardiac output were unchanged. However, there was a tendency toward lowering in the maximal rate of myocardial contractility and relaxation (+dP/dtmax and--dP/dtmax). It has been shown that in LVH dogs, the coronary blood flow was higher and coronary artery resistance was lower than in control ones. The peak reactive hyperemic flow was higher in LVH dogs but the coronary artery resistance calculated at the height of reactive hyperemia was similar both in control and LVH dogs, evidence of a reduction in the total coronary vasodilator reserves in the latter ones. The diastolic pressure-time index-tension time index (DPTI/TTI) ratio in LVH dogs decreased so that the value was sufficiently low to predict a reduction in endocardial perfusion even in experimental increased coronary perfusion pressure.

Animals↗
PubMed1985

[Changes in the blood surface-active properties during the correction of hemorheological disorders in patients with occlusive lesions of the abdominal aorta and arteries of the extremities].

Significant hemorheologic disorders were demonstrated in 68 patients with Leriche's syndrome and 50 patients with Raynaud's disease, as compared to 42 normal controls. Plasma and erythrocyte membrane surface tension (ST) was measured, using a surface balance, in 29 patients with Leriche's syndrome, 26 patients with Raynaud's disease and 24 normal subjects. In both kinds of vascular abnormality, major parameters of erythrocyte membrane adsorption film ST remained unchanged, yet the areas of their adsorption hysteresis loops increased. In patients with Raynaud's disease, the minimal plasma ST increased, while the stability index and the hysteresis loop area declined. In patients with Leriche's syndrome, those were unchanged. The control of hemorheologic disorders by moderate hemodilution using albumin, rheopolyglucin, antiaggregants and fibrinolytic agents resulted in the normalization of plasma ST parameters in Raynaud's disease, and a greater hysteresis loop area in both kinds of vascular disease. Major parameters of erythrocyte membrane adsorption film ST remained unchanged, while the area of their hysteresis loops decreased.

Adult↗