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The electronic absorption spectral characteristics of cycloimmonium ylids with a zwitterionic structure have been analyzed in forty-three solvents with different hydrogen bonding abilities. The two ylids lack fluorescence emission but are very dynamic in electronic absorption spectra. Using the maximum of the ICT band, the goal was to establish an accurate relationship between the shift of the ICT visible band and the solvent parameters and to estimate two of the descriptors of the first (the) excited state: the dipole moment and the polarizability. Two procedures were involved: the variational method and the relationships of the Abe model. The results indicate that the excited state dipole moment of the two methylids decreases in the absorption process in comparison with the ground state. The introduction of a correction term in the Abe model that neglects the intermolecular H-bonding interactions leads to a more accurate determination of the two descriptors. The strong solvatochromic response of both ylids has been further applied in distinguishing the solvents as a function of their specific parameters. Principal component analysis was applied to five selected properties, including the maximum of the charge transfer band. The results were further applied to discriminate several binary solvent mixtures. [ABSTRACT FROM AUTHOR]

Fluorescein sodium is a very important compound for a wide spectrum of applications, from which medical applications prevail. Despite this, there are very few studies in the literature related to the structure and fundamental properties of fluorescein sodium and its solutions, with most of the studies dealing with fluorescein. The purpose of the present article is to determine some parameters of the fluorescein sodium molecule approaching the quantum-mechanical modeling and experimental solvatochromism in both binary and ternary solutions. For data analysis, several theoretical models were applied. The results highlight the intermolecular interactions involved in the spectral shift of the electronic absorption band of fluorescein sodium when dissolved in different solvents or binary solvents and allowed the estimation of the difference between the interaction energy in molecular pairs of the type of fluorescein sodium − solvent 1 and fluorescein sodium − solvent 2. By applying a variational method, the dipole moment in the first excited state of the fluorescein sodium molecule and the angle between the dipole moments in the ground and excited states, respectively, were estimated. These results are useful for a better understanding of the behavior of fluorescein sodium when dissolved in different solvents or combinations of solvents, to develop new practical applications. [ABSTRACT FROM AUTHOR]

The 1-dithiocarboxy-2-ethoxy-1-(isoquinolin-2-yl)-2-oxoethan-1-ylid (iQTCY) zwitterionic molecule has been studied by computational and spectral means in order to establish some of its structural parameters in the ground electronic state as well as the nature and the strength of its universal and specific interactions with different solvents. The prevalence of the orientation–induction interactions in the diluted solutions of iQTCY in aprotic solvents and the additional specific interactions by hydrogen bonds (HB) in the protic solvents were demonstrated. Three theoretical models were comparatively used to estimate the composition of the first solvation shell of the iQTCY molecule in ternary solutions. The difference between the interaction energies in molecular pairs solute–solvent was computed based on the statistical cell model of ternary solutions of iQTCY in mixtures of water–ethanol and water–methanol. Using the electro-optical parameters computed by the quantum-mechanical technique and the results of the solvatochromic study, the excited state dipole moment of iQTCY was estimated within the limit of the variational method applicable to molecules that show only an absorption electronic spectrum. [ABSTRACT FROM AUTHOR]

8-hydroxyquinoline is a plant natural compound, but it can be also obtained by synthesis, with a wide range of applications. An extensive theoretical investigation of 8-hydroxyquinoline, performed by quantum-mechanical modeling, give important information on the physical properties of this molecule. A solvatochromic study of 8-hydroxyquinoline was also performed, the results of which allowed to estimate the contribution of each type of intermolecular interactions to the total spectral shift of the absorption band. Also, the electric dipole moment in the excited state of this molecule was estimated by the variational method and by Abe's model. [ABSTRACT FROM AUTHOR]

The spectrally active molecules in very small quantities are used as probes which measure the local field in liquids by the modifications induced in their electronic spectra. The energy levels of the molecules participating in the electronic transitions are stabilized in solvation process. When the solvation energy differs in the two states of the electronic transition, the spectral shifts of the electronic bands yield information about the strength of the solute-solvent interactions. The multi-linear dependences between the spectral shifts of the electronic bands and the solvent parameters are used to compute the contributions of each type of intermolecular interactions at the solvation energy. Both non-polar and polar spectrally active molecules are used in this study to evidence the intermolecular interactions in various solvents. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

Abstract: Compounds with basic character, N-ylids can be involved in specific interactions with protic solvents. Consequently, “long range” (universal) and “short range” (specific) forces act simultaneously in the protic solutions of N-ylids. The contributions of these interactions to the total spectral shift measured in the Electronic Absorption Spectra (EAS) were separated on the basis of solvatochromic effects. Supplemental spectral shifts measured in protic solvents compared with aprotic ones increases with the chemical shift of –OH signal from the 1H Nuclear Magnetic Resonance (NMR) spectra of the protic solvents. Important information about the strength of the specific interactions was obtained from the spectral study of N-ylids ternary solutions in binary solvents with protic and non-protic molecules. The model of ternary solutions was used to estimate the potential energy in the molecular pairs of the type N-ylid-protic solvent. [Copyright &y& Elsevier]

Four carbanion monosubstituted p-aryl-1,2,4-triazol-1-ium methylids are subjected to a comparative study between their spectral and quantum-mechanical parameters in order to obtain more information about their structural features in hydroxyl solvents as water and ethanol and also on the nature of electronic absorption transitions from the visible range. The quantum mechanical analysis, made by the Spartan'14 program, established a series of molecular parameters of the studied ylids important for their reactivity and for intermolecular interactions with hydroxyl liquids. An extensive solvatochromic study of 1,2,4-triazol-1-ium ylids is impossible due to their limited solubility in liquids. Binary solvent mixtures of water and ethanol with known solvent parameters from the literature were used for this study. The electronic absorption spectra in binary solvents water and ethanol were used to establish the influence of intermolecular interactions on the spectral characteristics of the studied methylids and also on the composition of their first solvation shell in ternary solutions. The difference between the interaction energies in molecular pairs ylid–water and ylid–ethanol was determined based on the statistical cell model applied to the ternary solutions of the type of ylid + water + ethanol. The obtained values are very small due to the hydroxylic nature of the two solvents. [ABSTRACT FROM AUTHOR]

The results obtained both in quantum chemical computation and in solvatochromic study of pyridinium di-carbethoxy methylid (PCCM) are correlated in order to estimate the electric dipole moment in the excited state of this molecule. This estimation is made by a variational method in the hypothesis that the molecular polarizability does not change in time of the absorption process. Ternary solutions of PCCM in protic binary solvents are used here, both establishing the contribution of each type of interaction to the spectral shift and to characterize the composition of the first solvation shell of PCCM. Results are compared with those obtained before for other binary solvents. The difference between the interaction energies in molecular pairs of PCCM-active solvent and PCCM-less active solvent was also estimated based on the cell statistical model of the ternary solutions. [ABSTRACT FROM AUTHOR]

Highlights: [•] A schema of electronic levels of the two studied ylids was proposed. [•] Supplies of universal and specific interactions in protic solvents were estimated. [•] Excited state dipole moment of ylids was estimated by spectral methods. [•] Hydrogen bond energy in molecular pair ylids – octanol was also estimated. [ABSTRACT FROM AUTHOR]

Abstract Three azo-derivatives: 2, 2′-Dihydroxyazobenzene (DHAB), Sudan Orange G (SOG) and 4-(Phenylazo) diphenylamine (PDA) were studied in this paper from quantum-mechanical and spectral point of view. The nature and the contribution of the intermolecular interactions to the spectral shifts in the solutions of the studied azo-derivatives were established based on the existent theories. Some electro-optical parameters of the studied molecules were calculated with Spartan 14 software using Density Functional Theory (DFT) employing the B3LYP model and the standard 6-31G* basis set. The polarizability and dipole moment in the excited states were estimated considering the variation of the angle between dipole moments in electronic states giving the visible absorption band. Graphical abstract Unlabelled Image Highlights • Visible absorption bands appear through the same mechanism. • The dispersion interactions are predominant in the studied solutions. • The dipole moment of the studied azo-derivatives increases by excitation. [ABSTRACT FROM AUTHOR]

Pyridinium-acetyl-benzoyl-methylid is a cycloimmonium ylid studied here from structural and spectral point of view. Quantum mechanical analysis offers information about the most stable spatial structure, the electro-optical properties in the ground electronic state as well as the QSAR parameters of PABM. The solvatochromic study of the visible absorption band of PABM was made in order to establish the electro-optical features of the ylid in the excited electronic state and also to approximate the contribution of different types of intermolecular interactions in solutions with different solvents. The ternary solutions of PABM were used to estimate the difference between the interaction energies in molecular pairs of the types: ylid-inactive solvent and ylid-active solvent from interaction point of view. [ABSTRACT FROM AUTHOR]

The nature and strength of the intermolecular interactions in the solutions of three azo-benzene derivatives (AD i , i = 1, 2, 3) were established by solvatochromic effects in solvents with different electric permittivities, refractive indices and Kamlet–Taft constants. A quantum mechanical analysis corroborated with spectral data offered information about the excited state dipole moments and polarizabilities of the studied compounds. The separation of the supply of universal and specific interactions to the total spectral shift was made based on the regression coefficients from the equations describing the solvatochromic effect. Supplementary information about the composition of the first solvation shell and the energy in the solute–solvent molecular pairs were obtained analyzing the ternary solutions of AD i , i = 1, 2, 3 compounds in solvent mixture Methanol (M) + n -Hexane (H). [ABSTRACT FROM AUTHOR]

• Pyridinium acetyl benzoyl methylid (PABM) is a basic, nucleophilic dipolar molecule. • Solvatochromism of PABM is realized in binary solvents. • Contributions of various PABM interactions with hydroxyl solvents were established. • Potential energy in pairs of molecules PABM – hydroxyl solvents was estimated. A solvatochromic study is made for ternary solutions of pyridinium acetyl-benzoyl methylid in the binary solvents mixtures water (1) + ethanol (2) and water (1) + methanol (2), based on the solvatochromic Kamlet-Taft parameters and on the statistical cell model of ternary solutions, in order to obtain new information on the nature and strength of intermolecular PABM-solvent interactions in these ternary solutions. The binary solvent mixtures chosen in this study consists of two protic liquids, transparent in the visible range and able to participate in specific interactions with the ylid molecules. The contribution of non-specific and specific interactions is estimated for each binary solvent mixture (using the correlation coefficients in multi-parametric linear correlation equations based on the empirical Kamlet-Taft solvent parameters). The difference between the energies in the molecular solute-solvent pairs of the type ylid-protic solvent in the two types of binary solvent mixtures is also estimated. Image, graphical abstract [ABSTRACT FROM AUTHOR]