scholarly journals SPECTROPHOTOMETRIC STUDY OF ACID-BASE PROPERTIES OF SPATIAL-DISTORTED DERIVATIVES OF PORPHYRINS IN ACETONITRILE

2018 ◽  
Vol 59 (6) ◽  
pp. 49 ◽  
Author(s):  
Yulia B. Ivanova ◽  
Svetlana G. Puhovskaya ◽  
Nugzar Zh. Mamardashvili ◽  
Oscar I. Koifman
Keyword(s):  
Absorption Spectra ◽  
Molecular Form ◽  
Spectral Characteristics ◽  
Reaction System ◽  
Spectrophotometric Titration ◽  
Spectrophotometric Study ◽  
Acidic Properties ◽  
Acid Base ◽  
Electron Absorption ◽  
Base Properties

Spectrophotometric titration method was used to study the acidic properties of: 5,10,15,20-tetrakis(thienyl-2-yl)-2,3,7,8,12,13,17,18-octaethylporphyrin (I), 5,10,15,20-tetrakis(4’-t-butylphenyl)-2,3,7,8,12,13,17,18-octaethylporphyrin (II), 5,10,15,20-tetrakis(3,5-di-t-butylphe-nyl)-2,3,7,8,12,13,17,18-octaethylporphyrin (III), 5,10,15,20-tetraphenyl-2,3,7,8,12,13,17,18-octaethylporphyrin (IV), 5,15-bis(4’-methoxyphenyl)-10,20-bis(4-nitro-phenyl)-2,8,12,18-tetrame-thyl-3,7,13,17-tetraarylporphyrin (V), 5,15-bis(4’-methoxyphenyl)-10,20-diphenyl-2,3,7,8,12,13, 17,18-octaethylporphyrin (VI), 5,15-bis(4’-methoxyphenyl)-2,8,12,18-tetramethyl-3,7,10,13,17,20-hexaethylporphin (VII), 5,10,15,20-tetrakis(4’-methoxyphenyl)-2,3,7,8,12,13,17,18-octaethylpor-phyrin (VIII) in the presence of a deprotonated agent, 1,8-diazabicyclo[5.4.0] undec-7-ene, in acetonitrile. Under deprotonation two families of spectral curves in the absorption spectra, having its own system of isobestic points, are formed. Electron absorption spectrum of molecular form transforms gradually into the spectrum of the final form of dianion with titrant concentration increase. Determination of the coordinates of the inflection (and the corresponding concentration of DBU) on the titration curve  allowed us to distinguish two areas in the electron absorption spectra of the reaction system, which are likely belong to the first and second steps of deprotonation, namely, to the formation of mono- and dianionic forms (HP–  and P2–) of the compound. Spectral characteristics of the ionized forms and combined ionization constant for the first and second steps (lgКа1 and lgКа2) were revealed. At the first step in the order of decreasing acidic properties of the ligands the compounds form a series of: III< V< VIII< VI < VII< II< IV < I; at the second step in decreasing order of the acidic properties of the ligands the compounds form a series of:.III < V < VI < II <VIII< VII < IV < I. The effect of structural and electronic properties of substituents on acid-base properties of porphyrins is analyzed. Thus, chemical modification of the macrocycle can lead to direct changes in acid-base properties of supramolecular macroheterocyclic ligands and can be a powerful tool to control the reactivity of compounds of the porphyrins class.

scholarly journals SYNTHESIS, COORDINATION AND ACID-BASE PROPERTIES OF MESO-DINITROSUBSTITUTED DERIVATIVES OF 5,15-DIPHENYL-β-OCTAALKYLPORPHINE

2018 ◽  
Vol 61 (6) ◽  
pp. 17
Author(s):  
Svetlana G. Pukhovskaya ◽  
Yulia B. Ivanova ◽  
Dmitry A. Erzunov ◽  
Aleksander S. Semeykin ◽  
Sergei A. Syrbu
Keyword(s):  
Spectral Characteristics ◽  
Spectrophotometric Titration ◽  
Basicity Constant ◽  
Acidity Constant ◽  
Electronic Effects ◽  
Acid Base ◽  
Electronic Effects Of Substituents ◽  
Derivatives Of ◽  
Base Properties

Presented work shows results of synthesis and spectrophotometric researches on properties of meso-dinitrosubstituted derivatives of 5,15-diphenyl-β-octaalkylporphyrin nitroderivatives in comparison with 2,8,12,18,3,7,13,17-octaethylporphyrin and 2,3,7,8,12,13,17,18-octaethyl-5,15-dinitroporphyrin. The method of spectrophotometric titration with perchloric acid (for determining the basicity constant) and 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) was used in order to study the acid-base properties of porphyrins, namely to determine the acidity constant. The spectral characteristics of the ionized forms of 5,15-dinitro-10,20-diphenyl-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporfin-F (I) and 5,15-dinitro-10,20-bis(4-nitrophenyl)-2,8,12,18-tetramethyl-3,7,13,17-tetraethylporphyrin (II) and the corresponding total constants of the acidic (pKa (I) = 6.00 and pKa (II) = 5.27) and the basic (pKb (I) = 19.78 and pKb (II) = 19.83) ionization were provided. The reaction of complexation of porphyrins with zinc acetate was studied by spectrophotometric method in pure acetonitrile and in mixed AN + DBU solvent. The influence of the degree of deformation of the tetrapyrrole macroring, the electronic effects of substituents and the acidity of the medium on the coordination and acid-base properties of porphyrins was analyzed. It was shown that the reactions of formation of metalloporphyrins with anionic porphyrin forms proceed with much higher rates compared to molecular ones, that is accompanied with a decrease in the energy parameters of the reaction. This is evidently due to the absence of energy costs for the deformation and cleaving N-H bonds of the reaction center, as well as the stronger polarization of the molecule, and as a consequence, the higher degree of solvation of anionic forms of porphyrins in the transition state. Thus, the determination of the conditions for the existence of dianionic forms of porphyrins gives grounds for the development of new sensor systems for the recognition and determination of the concentration of metal cations in liquid media due to a sharp increase in the rate of formation of metalloporphyrins in the presence of an organic base.Forcitation:Pukhovskaya S.G., Ivanova Yu.B., Erzunov D.A., Semeykin A.S., Syrbu S.A. Synthesis, coordination and acid-base properties of meso-dinitrosubstituted derivatives of 5,15-diphenyl-β-octaalkylporphine. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 6. P. 17-28

INSTRUMENTAL STUDY OF THE PROPERTIES OF REGIONAL WINES FROM MERLOT GRAPES

2020 ◽  
Author(s):  
Н.К. Стрижов ◽  
О.Н. Шелудько ◽  
А.А. Охрименко ◽  
Т.С. Ткачева
Keyword(s):  
Absorption Spectra ◽  
Raw Materials ◽  
Spectral Characteristics ◽  
Climatic Conditions ◽  
Grape Variety ◽  
Acid Base ◽  
High Quality ◽  
Data Set ◽  
Titration Curves ◽  
Base Properties

Для обеспечения внутреннего рынка высококачественными эксклюзивными винами из отечественного виноградного сырья необходимо производство российских вин защищенных наименований, что требует применения достоверных способов идентификации происхождения, основанных на фундаментальных знаниях о формировании отличительных признаков качественных вин в зависимости от сорта винограда и природно-климатических условий его произрастания. В статье дан анализ изменений интегральных характеристик вин, полученных из винограда сорта Мерло, выращенного в различных регионах. Проведен сравнительный анализ вида кривых титрования и спектров поглощения образцов вин с расчетом идентификационных критериев, характеризующих кислотно-основные свойства и фенольный комплекс данных вин. Построена зависимость связи спектральных характеристик и кислотно-основных свойств изученных образцов вин, установлена корреляция (R 0,82), что доказало влияние на форму кривых титрования образцов вин наличия фенольных и красящих компонентов. Установлено, что некоторые спектры поглощения и формы кривых титрования образцов вин близки, что подтверждает один сорт винограда, а другие имеют значительные различия, что свидетельствует о подмене сорта винограда или значительных технологических отличиях. To ensure the domestic market of the country with high quality exclusive wines from domestic grape raw materials it is necessary to produce Russian wines of protected names. This requires the use of reliable methods of identification of origin, based on fundamental knowledge about the formation of distinctive features of high-quality wines, depending on the grape variety and natural and climatic conditions of its growth. The article analyzes changes in the integral characteristics of wines obtained from Merlot grapes grown in different regions. A comparative analysis of the titration curves and absorption spectra of the samples studied wine with the calculation criteria characterizing the acid-base properties and phenol data set of wines. The relationship between the spectral characteristics and the acid-base properties of the studied wines was constructed, and a correlation was established (R 0,82), which proved the influence of the presence of phenolic and coloring components on the shape of the titration curves of wine samples. It was found that some absorption spectra and the shape of the titration curves of the studied wines are close, which confirms one grape variety, while others have significant differences from each other, which indicates a substitution of the grape variety or significant technological differences.

UV and IR Spectral Characteristics of Chloramben in Selected Environments

Weed Science ◽  
1976 ◽  
Vol 24 (1) ◽  
pp. 107-114 ◽  
Author(s):  
V. E. Berkheiser ◽  
J. L. Ahlrichs
Keyword(s):  
Ir Spectra ◽  
Water Content ◽  
Absorption Spectra ◽  
Spectral Characteristics ◽  
Uv Absorption ◽  
Hydration Water ◽  
Carboxyl Group ◽  
Amino Group ◽  
Acid Base ◽  
Uv Absorption Spectra

Ultraviolet (UV) absorption spectra were recorded of chloramben (3-amino-2,5-dichlorobenzoic acid) and selected relatives in solutions of different pH's. From these spectra, the Broensted acid-base properties of chloramben were deduced. Interpretations of solution spectra were applied to UV absorption spectra of chloramben adsorbed onto Ca-montmorillonite at low water content. Infrared (IR) transmittance spectra were recorded of chloramben and selected derivatives in KBr pellets and band assignments were made. Interpretations of these spectra were also applied to IR spectra of chloramben adsorbed onto Ca-montmorillonite at low water content. Both UV and IR measurements indicated that protonation of the amino group occurs and that the carboxyl group of chloramben is strongly hydrogen-bonded to the hydration water of the interlayer cations.

Electrochemical Study of Acid-Base Properties of Some 2,5-Dihydro-1,3,4-thiadiazoles in Aqueous-Ethanolic Solutions

1998 ◽  
Vol 63 (1) ◽  
pp. 31-41
Author(s):  
Maria Turowska ◽  
Grzegorz Mloston ◽  
Pawel Krzyczmonik ◽  
Jacek Raczak ◽  
Jaroslaw Romanski
Keyword(s):  
Ionic Strength ◽  
Dissociation Constants ◽  
Mndo Method ◽  
Electrochemical Study ◽  
Acidic Properties ◽  
Acid Base ◽  
Weak Bases ◽  
Formation Enthalpies ◽  
Protonated Forms ◽  
Base Properties

The dissociation constants Ka for spherically crowded 2'- and 2,5-substituted thiadiazolines and their protonated forms in 45% (v/v) aqueous-ethanolic solutions (ionic strength m = 0.1) were determined using the pH-metric method. All the thiadiazoles are weak bases. Some of them showed also weak acidic properties. The formation enthalpies have been calculated using the MNDO method. On the basis of the obtained results the mechanism of the protonation process is discussed.

Acid-base properties of 1,3-diphenyl-5-(1H-tetrazol-2-yl)formazan and 1,3-diphenyl-5-(2H-1,2,4-triazol-3-yl)formazan

1982 ◽  
Vol 47 (11) ◽  
pp. 2882-2889
Author(s):  
Nadezhda Likhareva ◽  
Ladislav Šůcha ◽  
Miloslav Suchánek
Keyword(s):  
Computer Program ◽  
Dissociation Constants ◽  
Acid Base ◽  
New Compounds ◽  
Base Properties

Two new compounds from the formazan series, viz. 1,3-diphenyl-5-(1H-tetrazol-2-yl)formazan and 1,3-diphenyl-5-(2H-1,2,4-triazol-3-yl)formazan, were prepared, and the dissociation constants and molar absorptivities of all of their acid-base species were determined spectrophotometrically employing the SPEKTFOT computer program.

Spectrophotometric study of the reactions of lanthanoids with bromopyrogallol red in the presence of cation active tensides

1982 ◽  
Vol 47 (2) ◽  
pp. 503-508 ◽  
Author(s):  
Irena Němcová ◽  
Pavla Plocková ◽  
Tran Hong Con
Keyword(s):  
Absorption Spectra ◽  
Photometric Determination ◽  
Spectrophotometric Study ◽  
Ternary Complexes ◽  
Optimal Conditions ◽  
Bromopyrogallol Red ◽  
Binary Complexes

The absorption spectra of the binary complexes of lanthanoids with bromopyrogallol red were measured and the formation of ternary complexes with cation active tenside, Septonex, was studied. Optimal conditions were found for the formation of these complexes and the possibility of their use in the photometric determination of lanthanoids was demonstrated on several examples.

Sign in / Sign up

Export Citation Format

Share Document