Nature of π-Electronic Transitions in UV Spectra of Deoxyvasicinone and Its Derivatives

Кристаллович, Э. Л.; Eshimbetov, A. G.; Чувылкин, Н. Д.; Беленький, Л. И.; Shakhidoyatov, Kh. M.

doi:10.1023/b:conc.0000011127.28348.ca

Cited by 8 publications

(5 citation statements)

References 3 publications

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“…The energies of, and electron-density distributions in, selected molecular orbitals of deoxyvasicinone 202 and its 6-amino and 6-nitro derivatives have been determined by means of ZINDO/S quantum chemical calculations. 91 The information was used in elucidating the nature of the p-electronic transitions responsible for the complex bands in the UV spectra of these compounds. Similar calculations were performed on the tetramethylene and pentamethylene analogues 203 and 204, as well as on the partially reduced compound 205, deoxyvasicine 206 and the simple bicyclic alkaloid 207, in order to identify the p-electronic transitions in their UV spectra.…”

Section: Structural and Synthetic Studiesmentioning

confidence: 99%

Quinoline, quinazoline and acridone alkaloids

2005

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Section: Structural and Synthetic Studiesmentioning

confidence: 99%

Quinoline, quinazoline and acridone alkaloids

2005

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“…The first band is located at 198 nm wavelength, while the second one has a maximum at 330 nm. According to the literature data the first absorption band is as a result of π→π * electron transitions, mainly in the aromatic structure of the molecules [33]. The second absorption band (330 nm) is probably due to the n→π * electron transitions [34].…”

Section: Spectral Behavior Of P-nitro-p-substituted Benzoylhydrazonesmentioning

confidence: 95%

UV Spectrophotometric Determination of Thermodynamic Dissociation Constants of Some Aromatic Hydrazones in Acid Media

et al. 2019

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The spectral behavior of some p-nitro-p-substituted benzoylhydrazones in the perchloric acid media was followed, applying the UV spectroscopy. The position of the absorption maximum in the spectra was defined in acidic media and the electronic transitions were discussed, as well (7<pH<1). The equilibrium between neutral and protonated form was investigated in the ethanol-water (V/V, 1:1) solutions. The observed changes in the UV spectra suggested that protonation process took place in one step. The pH region of protonation ranges between 1.4 and 2.9. Using the changes in the UV spectra which appear as a result of the protonation reaction the stoichiometric dissociation constants were determined numerically (pKBH+ = n·pH + logI) and graphically (intercept of the dependence of logI on pH). Thermodynamic dissociation constants were estimated as an intercept of dependence of pKBH+ on square root of the ionic strength. In order to achieve that, measurements were performed at different ionic strengths: 0.1, 0.25 and 0.5 mol/dm3, adjusted with sodium perchlorate. The obtained thermodynamic pKBH+ values ranged between 2.07 and 2.58. In order to predict proton transfer at a given pH, semiempirical methods AM1 and PM3 were applied. The influence of the substituents present in the p-position of the benzene ring on pKBH+ values of investigated hydrazones was discussed, too. Total energy, binding energy, enthalpy of formation, Gibbs energies of formation, atomic charge and proton affinity values were used to predict protonation site in hydrazone molecule. Furthermore, the stability and the proton affinity of the isomers (E and Z) in which hydrazones exist and their protonated forms were defined.

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“…The investigated hydrazones were synthesized in our laboratory and structurally characterized by UV spectroscopy, infrared spectroscopy (IR), nuclear magnetic resonance ( 1 H NMR and 13 C NMR), as well as by the elemental analysis [16]. Table 1.…”

Section: Structure Of Investigated Hydrazonesmentioning

confidence: 99%

Investigation Od Acid-Base Properties of Aromatic Hydrazones in Basic Media at Constant Ionic Strength

Jankulovska¹,

Dimova²,

Spirevska³

2017

RAD Conference Proceedings

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Abstract. UV spectroscopic methods were used in order to determine dissociation constants of some aromatic hydrazones. The acid-base properties of investigated hydrazones were followed in sodium hydroxide media at constant ionic strength of 0.5 mol/dm 3 adjusted with sodium perchlorate. Absorption band with the maximum of 330 nm was noticed in neutral media. A batochromic shift of this band was observed in basic media, probably due to the dissociation process. The dissociation process took place in one step for four investigated hydrazones and in two steps for the hydrazone with a phenol group in its molecule. The absorbance data from the UV spectra were used for the calculation of dissociation constants. The obtained pKHA values were between 2.11 and 2.62 which suggested that the influence of the substituents is not significant. At the same time, pKHA values were determined graphically from the intercept of the dependence of logI on pH. There are no important differences between calculated and graphically determined dissociation constant values.

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Nature of π-Electronic Transitions in UV Spectra of Deoxyvasicinone and Its Derivatives

Cited by 8 publications

References 3 publications

Quinoline, quinazoline and acridone alkaloids

Quinoline, quinazoline and acridone alkaloids

UV Spectrophotometric Determination of Thermodynamic Dissociation Constants of Some Aromatic Hydrazones in Acid Media

Investigation Od Acid-Base Properties of Aromatic Hydrazones in Basic Media at Constant Ionic Strength

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