Daniela Babusca

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.

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.

Spectral study of specific interactions between zwitterionic compounds and protic solvents.

The zwitterionic compounds, like ylids, can interact both by universal and specific forces with the protic solvents. Ylids have a visible electronic absorption band with intramolecular charge transfer (ICT), very sensitive to the solvent nature and considered as an indicator of their stability. Two zwitterionic compounds: pyridinium dicarbethoxy methylid and iso-quinolinium dicarbethoxy methylid were studied from solvatochromic point of view and the contribution of solute-solvent specific interactions to the total spectral shift of the visible ICT band was established. Ternary solutions of the studied ylids were used to estimate the difference of interaction energies in molecular pairs ylid-protic solvent and ylid-aprotic solvent in the limits of the cell model of three component solutions.

Quantum Mechanical and Absorption Spectral Characterization of Rhodamine B in Ternary Solution

ABSTRACT Geometrically optimized structure and quantum mechanical properties of rhodamine B were calculated. Electronic absorption spectra of rhodamine B were studied in a ternary solution of methanol and water. Kamlet–Taft empirical scales were utilized to characterize intermolecular interactions and their contributions to total spectral shifts.

Spectral and Quantum Mechanical Characterization of 3-(2-Benzothiazolyl)-7-(Diethylamino) Coumarin (Coumarin 6) in Binary Solution

ABSTRACT Absorption and fluorescence spectra of 3-(2-benzothiazolyl)-7-(diethylamino) coumarin in various solvents were recorded to characterize intermolecular interactions. The contributions of each interaction to the total spectral shifts were estimated. The properties of coumarin 6 were calculated using density function theory with the hybrid functional B3LYP level theory combined with 6-311 + G basis set. The excited state dipole moment was calculated from the variation of spectral shifts in absorption and fluorescence with solvent permittivity and refractive index using the Lippert–Mataga, Bakhshiev, and Kawski–Chamma–Viallet equations.

Solvent scales used to study the intermolecular interactions in binary solutions of two p-aryl-pyridazinium methylids.

The visible electronic absorption band with intramolecular charge transfer of two pyridazinium ylids having common carbanion and different heterocycles is recorded in solutions and its position is correlated to parameters of some empirical scales of solvents. The nature of the intermolecular interactions in pyridazinium ylid solutions is discussed and the supply of each type of interaction is established based on solvatochromic study.

Excited state molecular polarizability estimated by solvatochromic means

There are few methods for determining the electro-optical parameters in excited molecular states. Between them, the solvent influence on the electronic (absorption or fluorescence) spectra of organic molecules offer the possibility to estimate the excited state dipole moment and/or polarizability by multiple linear regression between the spectral shifts and solvent macroscopic parameters. A comparative study of the polarizability values determined by spectral means for some benzene derivatives in excited states is made in this paper.There are few methods for determining the electro-optical parameters in excited molecular states. Between them, the solvent influence on the electronic (absorption or fluorescence) spectra of organic molecules offer the possibility to estimate the excited state dipole moment and/or polarizability by multiple linear regression between the spectral shifts and solvent macroscopic parameters. A comparative study of the polarizability values determined by spectral means for some benzene derivatives in excited states is made in this paper.

Solvent empirical scales and their importance for the study of intermolecular interactions

The solvent empirical scales were developed in order to classify the solvents regarding their influence on the absorption or fluorescence spectra of different spectrally active molecules. The intermolecular interactions in binary solutions of three molecule having an intramolecular charge transfer visible absorption band are studied in this paper: 5-[2-(1,2,2,4-tetramethyl-1,2,3,4-tetrahydroquinolin-6-yl)-vinyl]-thiophene-2-carbaldehyde (QTC), 1-cyano-2-{5-[2-(1,2,2,4-tetramethyl-1,2,3,4-tetrahydroquinolin-6-yl)-vinyl]-thiophen-2-yl}-vinyl)-phosphonic acid diethyl ester (QTCP) and p-phenyl pyridazinium-p-nitro-phenacylid (PPNP). The solvent empirical scales with a single parameter (Z scale of Kosower, ET (30) or ETN scale of Reichardt and Dimroth) can be used to describe the strength of intermolecular interactions. The contributions of each type of interactions to the total spectral shift are evaluated using the solvent multiple parameters empirical scales defined by Kamlet and Taft and by Catalan et al.

Quantum-Mechanical and Solvatochromic Characterization of Quercetin

ABSTRACT Quercetin was subjected to a quantum-mechanical analysis and energetic and electro-optic parameters were evaluated. A solvatochromic study was used to estimate the dipole moment of quercetin in the excited state and to determine the angle between the dipole moments of this molecule in the electronic states responsible for the visible absorption band. The contribution of each type of intermolecular interactions to the total spectral shift experimentally recorded in quercetin solution was also established in this study.

Solvatochromic and Quantum-Mechanical Characterization of Methyl Red

ABSTRACT Quantum-mechanical characterization for methyl red was performed using density function theory. The dipole moment and polarizability in the ground state of methyl red were theoretically calculated. The contribution of intermolecular interactions to spectral shifts in solution and the limits in which the excited states’ dipole moment vary in the neutral form were established by a solvatochromic study. The solvatochromism of the acid and alkaline forms of methyl red was experimentally measured and compared with calculated spectra.