Electronic absorption spectra and structure of hydroxycoumarin derivatives and their ionized forms

1997 ◽  
Vol 75 (4) ◽  
pp. 365-376 ◽  
Author(s):  
Valery F. Traven ◽  
Larisa I. Vorobjeva ◽  
Tatjana A. Chibisova ◽  
Edward Andrew Carberry ◽  
Noelle Jean Beyer
Keyword(s):  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Bathochromic Shift ◽  
Hydroxyl Group ◽  
Absorption Bands ◽  
Pyrone Ring ◽  
Tautomeric Forms ◽  
Wavelength Absorption ◽  
Carbonyl Function

Electronic absorption spectra of 18 hydroxycoumarin derivatives and their ionized forms have been studied. Close agreement between experimental and the PPP CI calculated electron absorption band energies has been found in most cases. Strong polarization of the carbonyl function of the pyrone ring in the 7-hydroxycoumarin derivatives, H-bonding between the hydroxyl group and neighboring substituent in the ortho-substituted hydroxycoumarins, as well as their tautomeric transformations, have been suggested in the discussion of the electronic absorption spectra of the hydroxycoumarin derivatives. In accord also with calculational results, ionization of the hydroxyl function leads to a bathochromic shift of the longest-wavelength absorption bands in the spectra of 7-hydroxycoumarin derivatives. The ionization has no effect on the electronic absorption of the 4-hydroxycoumarin derivatives. Relative stabilities of the tautomeric forms of hydroxycoumarin derivatives and their ionized forms have also been compared by MNDO calculations. Keywords: hydroxycoumarins, intramolecular H-bonding, ionization, electronic absorption spectra, keto–enol tautomerism.

scholarly journals Spectral and quantum chemical study of tautomeric and ion transformations of 2-(2-(2-hydroxy-5-sulfamoylphenyl)- hydrazono)-3-oxo-N-phenylbutanamide

2019 ◽  
Vol 60 (11) ◽  
pp. 106-113
Author(s):  
Anh Thi Ngoc Vu ◽  
◽  
Mikhail A. Ryabov ◽  
Olga V. Kovalchukova ◽  
Dmitry S. Gusarov ◽  
...  
Keyword(s):  
Absorption Spectra ◽  
Electronic Absorption ◽  
Quantum Chemical ◽  
Electronic Absorption Spectra ◽  
Bathochromic Shift ◽  
Stable Form ◽  
Ionic Form ◽  
Absorption Bands ◽  
Tautomeric Forms ◽  
The Stability

In this paper, using the method DFT/B3LYP of quantum chemical modeling, the stability of tautomeric, conformer, and anionic forms of 2-(2-(2-hydroxy-5-sulfamoylphenyl)hydrazone-3-oxo-N-phenylbutanamide (H2L) was studied and the geometric, electronic structure and bond lengths of molecules in various tautomeric forms were determined. It was shown that the stability of tautomeric molecules H2L as anionic forms was determined by the number of existing intermolecular hydrogen bonds (closing six-membered and five-membered cycles). The most stable tautomeric and conformal forms of an organic molecule and its dianion are proposed. The interatomic distances, angles, charges on atoms, IR and electronic absorption spectra of tautomeric forms of the molecule and dianion (H2L and L2-) were calculated. In this work, we studied the electronic absorption spectra in an aqueous-alcoholic solution and found that in an alkaline medium the molecule transforms into the ionic form with a bathochromic shift of 47 nm, corresponding to the results of the shift of the long-wavelength band electronic absorption spectra upon transition from the hydrazotautomer (form a) to the dianion form (form b’’) at 92 nm obtained by TD-DFT. The calculated results for the distance and angles between atoms are in good agreement with the experimental data of the molecule by X-ray diffraction analysis. It was shown that the IR spectrum of the stable form appears two absorption bands in the region of 1690 and 1655 cm–1, which are attributed to stretching vibrations of carbonyl groups (C=O), bound by a strong intramolecular hydrogen bond and the presence of the NH-hydrazone fragment of the 1H NMR spectrum confirmed the most stable for a neutral molecule is the hydrazone form.

Spectroelectrochemical Study of some μ3-Oxo-μ-acetato Trinuclear Rhodium(III) and Iridium(III) Complexes

1995 ◽  
Vol 50 (4) ◽  
pp. 551-557 ◽  
Author(s):  
Kenta Takahashi ◽  
Keisuke Umakoshi ◽  
Akihiro Kikuchi ◽  
Yoichi Sasaki ◽  
Masato Tominaga ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Electronic Absorption Spectrum ◽  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Visible Region ◽  
Absorption Bands ◽  
Visible Absorption ◽  
The One ◽  
Species Being

New trinuclear rhodium(III) complexes, [Rh3(μ3-O)(μ-CH3COO)6(L)3]+ (L = imidazole (Him), 1-methylimidazole (Meim), and 4-methylpyridine (Mepy)) have been prepared. The Him, Meim, and Mepy complexes show reversible one-electron oxidation waves at E1/2 = +1.12, +1.12, and +1.28 V vs Ag/AgCl, respectively, in acetonitrile. Electronic absorption spectra of the one electron oxidized species of these complexes and [Rh3(μ3-O)(μ-CH3COO)6(py)3]+ (py = pyridine) (E1/2 = +1.32 V ) were obtained by spectroelectrochemical techniques. While the Rh3(III,III,III) states show no strong visible absorption, the Rh3(III,III,IV ) species give a band at ca. 700 nm (ε = 3390-5540 mol dm-3 cm-1). [Ir3(μ3-O)(μ-CH3COO)6(py)3]+ with no strong absorption in the visible region, shows two reversible one-electron oxidation waves at +0.68 and +1.86 V in acetonitrile. The electronic absorption spectrum of the one-electron oxidized species (Ir3(III,III,IV )) also shows some absorption bands (688 nm (ε, 5119), 1093 (2325) and 1400 (ca. 1800)). It is suggested that the oxidation removes an electron from the fully occupied anti-bonding orbital based on metal-dπ-μ3-O-pπ interactions, the absorption bands of the (III,III,IV ) species being assigned to transitions to the anti-bonding orbital.

scholarly journals Electronic spectra of carbon chains of relevance to astrophysics

1997 ◽  
Vol 178 ◽  
pp. 287-294
Author(s):  
John P. Maier
Keyword(s):  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Spectra ◽  
Homologous Series ◽  
Electronic Absorption Spectra ◽  
Absorption Bands ◽  
Carbon Chains ◽  
Diffuse Interstellar Bands ◽  
Spectroscopic Characteristics

The electronic absorption spectra of a variety of carbon chains have been identified in the laboratory. The measurements were carried out in 5 K neon matrices on mass-selected species. On the basis of the trends evident in the homologous series, it can be predicted in which region absorption bands of the carbon chains are to be expected for the not yet measured longer and isoelectronic species. The spectroscopic characteristics, photostability and structural considerations point out which and what size carbon chains could be the diffuse interstellar bands absorbers.

Substitution effect in electronic absorption spectra of 2- and 2,6-substituted 4-benzhydrylidene-2,5-cyclohexadien-1-ones

1984 ◽  
Vol 49 (9) ◽  
pp. 1949-1964 ◽  
Author(s):  
Lubomír Musil ◽  
Bohumír Koutek ◽  
Jiří Velek ◽  
Milan Souček
Keyword(s):  
Absorption Spectra ◽  
Electronic Absorption ◽  
Significant Contribution ◽  
Inductive Effect ◽  
Electronic Absorption Spectra ◽  
Resonance Effect ◽  
Gaussian Function ◽  
Substitution Effect ◽  
Band Position ◽  
Wavelength Absorption

Electronic absorption spectra of the seventeen fuchsone derivatives Ia-Iq were recorded in n-hexane. The symmetric Gaussian function could be fitted to absorption profiles within the region of the lowest energy π-π* transition. Bad parameters obtained in this way were utilized in calculation of the corresponding oscillator and dipole strengths. The effect of substitution on positions and intensities of all the observed bands was also investigated. The most sensitive response to substituent change is exhibited by the longest wavelength absorption band. The relation between the substituent nature and band position or oscillator strength may be quantified as P sum from i=1 to n (ρiσi) + P0. It follows from the analysis of variance that both the inductive and steric effects are operating. On the other hand, for the non-symmetrically substituted fuchsones, the band intensity characterized by the molar absorption coefficient is a linear function of the inductive effect only. There is no statistically significant contribution of the resonance effect in any of the quantities investigated. The effect of solvent was followed by the separate evaluation of the wavenumbers related to maxima of the longest wavelength band of fuchsones Ia-Iq in the following series of solvents: n-hexane, cyclohexane, isooctane, tetrahydrofurane, acetone, acetonitrile and ethanol.

scholarly journals Luminescent determination of residues of trazodon hydrochloride and melatonin after cleaning pharmaceutical equipment

2019 ◽  
pp. 73-81
Author(s):  
O. D. Voitiuk ◽  
A. V. Yegorova ◽  
Yu. V. Scrypynets ◽  
S. N. Kashutskуy ◽  
V. P. Antonovich
Keyword(s):  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Xenon Lamp ◽  
Excitation Spectra ◽  
Absorption Bands ◽  
Limit Of Quantitation ◽  
Trazodone Hydrochloride

A prerequisite for ensuring the quality of medicines is their production in accordance with the rules of GMP (Good Manufacturing Practice for Medicinal Products), one of the most important requirements of which is equipment cleaning. In many cases, the same equipment is used in the production of various preparations. Therefore, to prevent contamination of each of the following drugs, the previous one, it is very important to carry out an effective equipment cleaning procedure with a mandatory assessment of its purity. The purpose of this study was to develop simple, express, selective methods for luminescent determination of residual quantities of APIs of trazodone hydrochloride (TG) and melatonin (MT) in washes to control the completeness of their removal when cleaning process equipment. The excitation and luminescence spectra were recorded using a Cary Eclipse "Varian" spectrofluorimeter (Australia) with a xenon lamp 150 W. Electronic absorption spectra were recorded on a UV-2401 PC spectrophotometer «Shimadzu» (Japan). The electronic absorption spectra of TG and MT have absorption bands in the UV spectral region. It was established experimentally that the excitation spectra of TG and MT are similar to their absorption spectra (λex = 318 nm (TG) and λem = 274 nm (MT)). The effect on the luminescence intensity of TG and MT of methanol, ethanol, acetonitrile, dimethylformamide, dimethylsulfoxide, propanol (50 v/v) was studied. It is established that the maximum luminescence is observed in water. The methods were validated according to the following parameters: specificity, linearity, accuracy, limit of quantitation. The degree of extraction of trazodone hydrochloride and melatonin from applicators and surfaces of pharmaceutical equipment is more than 90%. The developed methods can be recommended for determining the residual amounts of trazodone hydrochloride and melatonin while monitoring the quality of the cleaning of pharmaceutical equipment.

Dithiolate Mixed with Diimine and it's Metal Effects on Sensors

2014 ◽  
Vol 1021 ◽  
pp. 52-55
Author(s):  
Yong Hui Jia ◽  
Chao Xu
Keyword(s):  
Energy Level ◽  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Spectra ◽  
Electronic Absorption Spectra ◽  
Orbital Energy ◽  
Absorption Bands ◽  
The Relationship ◽  
Orbital Energy Level

Determination of the two Maleinitriledithiolate • phenanthroline-5 ,6-dione Lynn mixed copper (II), zinc (II) complexes MLL' (L=mnty, 1,2 twelve dicyanoethylene-1,2 - thiol ion L '= phen-5, 6-dione, l, 10 - phenanthroline-5 ,6-one o) amine in dimethy-l phthalate (DMF), acetone (Acet.) and chloroform (HCli) electronic absorption spectra corresponding to transitions studied the relationship between the absorption bands in the electronic spectra associated molecular orbital energy level diagram to explore their photographic oxidation characteristics in DMF.

scholarly journals Quantum-chemical modeling of structure and properties of nitrogen derivatives of phloroglucinol

2019 ◽  
Vol 57 (3) ◽  
pp. 51-57
Author(s):  
Mikhail A. Ryabov ◽  
◽  
Thi Ngok Anh Vu ◽  
Olga V. Kovalchukova ◽  
Dmitry S. Gusarov ◽  
...  
Keyword(s):  
Electronic Absorption ◽  
Quantum Chemical ◽  
Electronic Absorption Spectra ◽  
Bathochromic Shift ◽  
Dft Method ◽  
Chemical Modeling ◽  
Tautomeric Forms ◽  
The Stability ◽  
Intramolecular Hydrogen ◽  
L1 And L2

The DFT/B3LYP quantum-chemical method has been used to simulate the structure of 2-((2-hydroxyphenyl) diazonyl) benzene-1,3,5-triol (L1) and 2-((2-hydroxy-4-nitrophenyl) diazonyl) benzene-1,3,5-triol (L2) molecules. The spatial and electronic structure of molecules in various tautomeric forms was determined. It was shown that the stability of these compounds is primarily due to the presence of strong intramolecular hydrogen bonds (IHB), which form six-membered cycles, and the isomerism of the molecule, which assume the formation of IHB. The structures where IHB form five-membered cycles, are less stable. In general, for the L1 and L2 molecules, azo-tautomers were found to be 4 and 3 kJ/mol more stable than the hydrazo-tautomers, respectively. Such a small difference in energy of molecules for the gas phase did not allow us to conclude about the form of existence of molecules in solutions or in the crystalline state. To assess the possibility of transition between tautomers, we used the DFT method to calculate the transition states (TS) between the azo and hydrazo tautomers of the L1 and L2 molecules. The barrier of the transition from the azo form to the hydrazo form was found to be 14 kJ/mol for the molecules L1 and L2, respectively. The interatomic distances, angles, charges on atoms, IR and electronic absorption spectra of tautomeric forms of L1 and L2 molecules were calculated. It has been established that the long-wave absorption band (LB) of the electronic absorption spectrum bathochromically shifts at transition from azo to hydrazo-tautomers by 41 nm for L1 and 40 nm for L2. The introduction of a nitro group also leads to a bathochromic shift of the LB by 22 nm at transition from azo-tautomer L1 to hydrazo-L1 L2 and by 21nm at transition from azo-L2 to hydrazo-L2.

scholarly journals The main optical characteristics of UV-spectra of 5-(adamantane-1-yl)-4R-1,2,4-triazole-3-thiones derivatives

2018 ◽  
pp. 57-62
Author(s):  
V. M. Odyntsova
Keyword(s):  
Matrix Element ◽  
Absorption Band ◽  
Oscillator Strength ◽  
Absorption Spectra ◽  
Electronic Absorption ◽  
Elemental Analysis ◽  
Electronic Absorption Spectra ◽  
Uv Spectra ◽  
Optical Characteristics ◽  
Absorption Bands

The development of pharmaceutical chemistry confronts molecular spectroscopy the problem of calculating the electronic states, assumptions and explanations of the various properties of complex organic compounds. In recent years, following the basic optical characteristics of the electronic absorption spectra: the wave number of maximum absorption – νmax (in cm-1), the half-width of the absorption bands of – ∆ν1/2 (cm-1), the integral intensity of the absorption band (in l/mol·cm2), the oscillator strength of the electronic transition – f, the matrix element of the transition of electrons – Mik. began widely used. These constants allow you to determine the chromophores in the investigated substances, to establish the probability and the resolution of the electrons’ transition. Our goal was the calculation and study of the basic optical characteristics of the electronic absorption spectra of 5-(adamantane-1-yl)-4R-1,2,4-triazole-3-thione, namely 5-(adamantane-1-yl)-4-methyl-1,2,4-triazole-3-thione and 5-(adamantane-1-yl)-4-phenyl-1,2,4-triazole-3-thione derivatives. When deciding about the purity of the compounds we used melting point, thin layer chromatography and the results of elemental analysis. UV spectra of the investigated compounds was measured with a spectrophotometer Specord 200-222U214 (Germany). Elemental analyzer GmbH (Germany) was used for carrying out the elemental analysis. It is determined that the values of the half-width Δν½ and integrated intensity of the absorption bands (A), the oscillator strength (f) and matrix element of the transition (Mik) can be used as an important constants of 5-(adamantane-1-yl)-4R-1,2,4-triazole-3-thione derivatives for their identification and establishing a deep connection between spectra and structure of the molecule. For the studied compounds is the most characteristic absorption band in the medium wave spectrum with high values of A and f, which indicate about the permitted and probable transitions of electrons which give rise to the observed maxima. Based on the study of the basic optical characteristics of the electronic absorption spectra of 5-(adamantane-1-yl)-4R-1,2,4-triazole-3-thione derivatives is found that chromatofor in the studied molecules is the structure of 1,2,4-triazole and substituents (adamantane, methyl and phenyl radicals). A distinctive feature, namely 5-(adamantane-1-yl)-4-phenyl-1,2,4-triazole-3-thione 5-(adamantane-1-yl)-4-methyl-1,2,4-triazole-3-tion are the values A, f, Mik, which can be used to identify the investigated compounds.

scholarly journals Interactions in Electrodeposited Poly-3,4-Ethylenedioxythiophene—Tungsten Oxide Composite Films Studied with Spectroelectrochemistry

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1630
Author(s):  
Aleksandra O. Efremova ◽  
Elena G. Tolstopjatova ◽  
Rudolf Holze ◽  
Veniamin V. Kondratiev
Keyword(s):  
Tungsten Oxide ◽  
Absorption Spectra ◽  
Conducting Polymer ◽  
Electronic Absorption ◽  
Electrostatic Interactions ◽  
Electronic Absorption Spectra ◽  
Composite Films ◽  
Cyclic Voltammograms ◽  
Absorption Bands ◽  
Peak Separation

Cyclic voltammograms and optical absorption spectra of PEDOT/WO3 composite films were recorded in order to identify possible interactions and modes of improved performance of the composite as compared to the single materials. Changes in the shape of redox peaks related to the W(VI)/W(V) couple in the CVs of WO3 and the composite PEDOT/WO3 films indicate electrostatic interactions between the negatively charged tungsten oxide species and the positively charged conducting polymer. Smaller peak separation suggests a more reversible redox process due to the presence of the conducting polymer matrix, accelerating electron transfer between tungsten ions. Electronic absorption spectra of the materials were analyzed with respect to changes of the shapes of the spectra and characteristic band positions. There are no noticeable changes in the position of the electronic absorption bands of the main chromophores in the electronic spectra of the composite film. Obviously, the interactions accelerating the redox performance do not show up in the optical spectra. This suggests that the existing electrostatic interactions in the composite do not significantly change the opto-electronic properties of components of the composite but resulted in the redistribution of fractions of polaron and bipolaron forms in the polymer.

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