Dana Ortansa Dorohoi

SOLVENT INFLUENCE ON THE ELECTRONIC ABSORPTION SPECTRA OF SOME AZOAROMATIC COMPOUNDS

Solvent-induced effects on the π–π* electronic absorption band frequencies of some azobenzene derivatives are described in terms of dipole–dielectric, solute–solvent, and hydrogen bonding interactions. A multiple linear regression equation for νmax was developed based on polarizability–polarity parameters and Kamlet–Taft solvatochromic parameters. Although the polarizability is a major contributor to the interactions in solutions, parameters related to the solvent polarity, hydrogen bond acidity, and hydrogen bond basicity are also statistically significant in determining the spectral shifts.

Molecular interactions in binary solutions of 4-aminophthalimide and 3-p-cumyl-pyridazinium-acetyl-benzoyl-methylid

Abstract The solution parameters determining the shifts of the 4-aminophthalimide (4-AF) and 3- p -cumyl-pyridazinium-acetyl-benzoyl-methylid (PM) visible bands have been established by multiple regression. The characteristics are specified for the charge transitions. It has been ascertained that the chemical displacement δ H (ppm) of the hydroxil group proton can be used to express the proton transfer interactions.

Intermolecular interactions in some pyridazinium ylides solutions

Abstract The nature of intermolecular interactions in the solutions of the pyridazinium ylides has been analysed. A relation for the calculation of the visible band frequencies has been established in function of the solvent parameters.

Solvent influence on the electronic absorption spectra (EAS) of 1,6-diphenyl-1,3,5-hexatriene (DPH)

The electronic absorption spectra of 1,6-diphenyl-1,3,5-hexatriene (DPH) were recorded in a great number of solvents with various physico-chemical properties. The dependence of the wavenumber in the maximum of the DPH vibronic bands on the solvent dispersion function demonstrates the prevalence of the dispersion interactions in the studied solutions. Some electro-optical parameters of DPH molecule were computed by HyperChem and were correlated with the results obtained from the solvatochromic effects on DPH. The polarizability in the electronic excited state of DPH has been estimated from the solvatochromic effect.

Intermolecular interactions in binary and ternary solutions of two cycloimmonium-carboethoxy-anilido-methylids

Two cycloimmonium ylids with pyridinium and iso-quinolinium as heterocycle and having common carbanion were studied from the point of view of the solvent influence on electronic absorption spectra in binary and ternary solutions. The supplies of the universal and specific interactions to the spectral shifts in the electronic absorption spectra of hydroxyl solutions were separated. The strength of the specific interactions of the ylid molecules with octanol was estimated by using ternary solutions in binary solvent Octanol+Dichloroethane, in which the universal interactions have similar strengths. Quantum mechanical calculations and also the solvatochromic effect allowed us estimating the values of the molecular dipole moments in the excited state of the studied ylids. The conclusions showed that by excitation the molecular dipole moment of the studied ylids decreases or changes its sense, due to the electronic charge transport from the carbanion towards the heterocycle.

The spectroscopy of the Cycloimmonium Ylides

Abstract For the cycloimmonium ylides with heterocycle and one carbonion substitute common, we searched the lone pair electrons level position in the energetic levels diagram and its dependence on the group electronegativity of the substitutes.

Quantum-mechanical study and spectral analysis on some derivatives of Rhodamine in solutions.

Abstract Rhodamine derivatives (B and 6G) are heterocyclic compounds, related to florone. They are widely used as dyes with numerous biotechnological applications. The quantum-mechanical, electro-optical and spectral properties of the isolated molecules in the ground state were determined using molecular modeling programs. The visible electronic absorption spectra of 6G and B Rhodamine were recorded in solvents with different macroscopic parameters. Dipolar moments and polarizabilities of the studied Rhodamines in the excited state were determined by solvatochromic study.

New method to determine the optical rotatory dispersion of inorganic crystals applied to some samples of Carpathian Quartz.

A new method to determine the optical rotatory dispersion (ORD) in the visible range, based on a channeled spectrum obtained with a uniax inorganic crystal introduced between two crossed polarizers with its optical axis parallel to the light propagation direction is detailed in this paper. When the studied inorganic crystals are transparent, this method permits the estimation of the optical rotatory dispersion in the visible range, for which the cheap polarizers are available. The speed of the measurements is very high, because the estimations are made from the channeled spectrum obtained for a single arrangement of the optical components. By using a computer, ORD is quickly determined for the visible range. The results obtained by this method for some Carpathian Quartz samples are consistent with those from literature. The proposed method can be also applied in UV and IR spectral ranges, when the anisotropic layers are transparent and the linearly polarized radiations can be obtained.

Electronic Absorption Spectra of Two 3-Aryl-pyridazinium-2,4,6-picryl-benzoyl-methylids

ABSTRACT The visible electronic absorption spectra of two carbanion disubstituted cycloimmonium ylids having a 3-aryl-pyridazinium derivative as cation and a common disubstituted carbanion (-2,4,6-picryl-benzoyl) were studied in solvents with different physical and chemical properties. The visible electronic absorption band of 3-aryl-pyridazinium ylids is attributed to an electron charge transfer from the carbanion toward the heterocycle. The solvent effects on the visible electronic band of the studied ylids were described both by empirical parameters defined by Kosower and by using the theory of a dielectric homogeneous solution. Some remarks about the nature of the molecular interactions in the 3-aryl-phthalazinium-2,4,6-picryl-benzoyl methylid solutions are made in this paper on the basis of solvatochromic study.

Solvatochromic Characterization of Sudan Derivatives in Binary and Ternary Solution

ABSTRACT Sudan derivatives are widely used as dyes for foods, textiles, plastics, paper, and cosmetics. The wavenumbers in the maximum of the electronic absorption bands of two Sudan derivatives in solvents with varying physicochemical properties were correlated with microscopic and macroscopic parameters of solution components. The molecular parameters of the Sudan derivatives in the excited state were estimated using solvatochromic and quantum-mechanical calculations.