Solvent polarizability and anisotropy effects on the photophysical behavior of oxazine 1: an appropriate polarizability indicator dye

The role of microenvironments on computed vibrationally-resolved emission spectra: The case of oxazines

Oxazine dyes act as reporters of their near environment by the response of their fluorescence spectra. At the same time, their fluorescence spectra exhibit a pronounced vibrational progression. In this work, we computationally investigate the impact of near-environment models consisting of aggregated water as well as betaine molecules on the vibrational profile of fluorescence spectra of different oxazine derivatives. For aggregated betaine and a water molecule located above the plane of the dyes, we observe a distinct modification of the vibrational profile, which is more pronounced than the effect of a continuum description of a solvent environment. Our analysis shows that this effect cannot be explained by a pure change in the electronic structure, but that also vibrational degrees of freedom of the environment can be decisive for the vibrational profile and should, hence, not generally be neglected.

Excimer Fluorescence of Acriflavine Dye in Glycerol and Ethylene Glycol

This research investigates the excimerisation of acriflavine dye in ethylene glycol and glycerol solvents. Acriflavine, a member of the acridine dye family, exhibits unique fluorescence properties with applications in various fields, including cellular nucleus observation, nucleic acid analysis, and dye laser active media etc. The study explores the impact of solvent and concentration on acriflavine's emission properties, with a focus on excimer formation, which can influence its suitability as a dye laser active medium. UV-Visible absorption spectroscopy reveals concentration-dependent absorption profiles, with distinctive monomer bands. Steady-state fluorescence studies demonstrate the emergence of red-shifted excimer fluorescence bands as concentrations increase in both solvents. Temperature-dependent fluorescence studies reveal the dynamics of excimer formation, suggesting dynamic diffusion as the excimerisation mechanism. Time-resolved fluorescence spectroscopy confirms the singlet character of both monomer and excimer states, providing insights into the excimerisation process. Critical concentration values are determined, representing the equilibrium between monomeric and excimeric forms. The study also explores pH-induced spectral shifts, highlighting the influence of acidity on fluorescence properties. Overall, this research deepens our understanding of acriflavine's excimerisation in ethylene glycol and glycerol, offering insights that can enhance its diverse applications, especially in laser technologies.

Facile synthesis of triazolo/benzazolo[2,1-b]quinazolinone derivatives catalyzed by a new deep eutectic mixture based on glucose, pregabalin and urea

In this study, a novel natural deep eutectic solvent was prepared from glucose, pregabalin, and urea. The prepared solvent was identified using a variety of techniques, including Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), differential thermal analysis (DTA), and refractive index measurements (RI). The prepared deep eutectic solvent was then utilized for the one-pot synthesis of quinazolinone derivatives. The yields of the product obtained with and without the catalyst were determined, providing insights into the catalytic efficiency of the system. This protocol offers several advantages, including mild reaction conditions, easy reagent preparation, a green process, short reaction times (2-60 min), high yields (80-99%), and a straightforward procedure with the possibility of catalyst reusability.

A study on the interaction of nile blue with Uracils: A spectroscopic and computational approach

The present work focuses the investigation on fluorescence quenching of nile blue (NB) in presence of various substituted uracil molecules. UV-Visible absorption studies signify the possibility of ground state complex formation between NB and uracil molecules. The increase in concentration of quencher molecules greatly influences the emission spectra of NB. The bimolecular quenching rate constant (k_q) were calculated and found to depend on the position and electronic properties of substituent in quencher molecules. Fluorescence quenching experiments were performed at different temperature to calculate the thermodynamic parameters. The fluorescence lifetime measurements show that the quenching process proceeds through static quenching. The mechanism of fluorescence quenching includes the possibility of proton transfer. The bond dissociation enthalpy (BDE) reveals the release of H from the quencher molecules. The quencher molecules possess antioxidant activity and identified using deoxyribose degradation assay. The position of substituent and its electronic property are key features to address the antioxidant activity of uracil molecules.

The physical significance of the Kamlet–Taft π* parameter of ionic liquids

The Kamlet–Taft dipolarity/polarizability parameters π* for various ionic liquids were determined using 4-tert-butyl-2-((dicyanomethylene)-5-[4-N,N-diethylamino)-benzylidene]-Δ3-thiazoline and 5-(N,N-dimethylamino)-5′-nitro-2,2′-bithiophene as solvatochromic probes.

Experimental and molecular dynamics studies of anthraquinone dyes in a nematic liquid-crystal host: a rationale for observed alignment trends

The experimental alignment trend of a set of anthraquinone dyes in a nematic host is rationalised by calculated molecular order parameters and transition dipole moments.

Solvent effects on the photophysical properties of poly[1,4-dihydroxyanthraquinoneimine-1,3-bis(phenylene-ester-methylene)tetramethyldisiloxane]

Absorption and fluorescence spectra of a polyquinoneimine, PQI, built on 1,4-dihydroxyanthraquinone and a siloxane diamine, 1,3-bis(amino-phenylene-ester-methylene)tetramethyldisiloxane, have been investigated in solvents of different polarities. The effect of solvents on the spectral properties was investigated using Lippert-Mataga and Bakhshiev polarity functions and Catalán's multiple linear regression approach. Absorption and fluorescence spectra in studied solvents exhibit hypsochromic and bathochromic shifts, respectively. The polarity of the solvent was the main parameter which changes the spectral properties of PQI. Also, the binary mixtures of chloroform with methanol and dimethyl sulfoxide were used to analyze the intermolecular interactions and preferential solvation. The preferential solvation parameters (local mole fraction (X₂(L)), excess function (δs₂) and preferential solvation constant (KPS)) were calculated from spectral data and discussed as a function of cosolvent content. The values of quantum yield, decreased linearly with increasing solvent polarity (for non-polar and polar solvents).

Excited state electric dipole moment of nile blue and brilliant cresyl blue: a comparative study

A solvatochromic study on the photophysical properties of two cationic oxazine dyes (brilliant cresyl blue and nile blue) was carried out. The electronic absorption and emission spectra of the dyes were recorded in various organic solvents with different polarity. The ground and the excited state dipole moments of the dyes were estimated from solvatochromic shift method. The solvent dependent spectral shifts in absorption and fluorescence spectra were analyzed by the Katritzky and Kamlet-Taft multi-parameter scales. This work is characterized by detailed quantitative studies on the nature and extent of solvent-solute interactions.

Estimation of ground- and excited-state dipole moments of oxazine 1 in liquid and liquid crystalline media

The absorption and fluorescence spectra of a laser dye, oxazine-1 (OX1), in liquid and liquid crystalline media were studied at room temperature. The solvatochromic method was used to determine the ground- and excited-state dipole moments by means of Lippert-Mataga, Bakshiev, Kawski-Chamma-Viallet polarity functions. The solvent polarity has no large and regular effect on the spectral behavior of OX1, and thus it might be considered as a poor solvatochromic indicator dye. In addition, applicability of solvatochromic method for this dye in anisotropic media was investigated. On the other hand, nature and degree of the solute-solvent interactions were characterized using correlation of multi-parameter solvent polarity scales. Due to the theoretical restrictions and the dye molecular structure, deviations from the solvatochromic correlation were observed.

Predicting the UV-vis spectra of oxazine dyes

In the current work we have investigated the ability of time-dependent density functional theory (TD-DFT) to predict the absorption spectra of a series of oxazine dyes and the effect of solvent on the accuracy of these predictions. Based on the results of this study, it is clear that for the series of oxazine dyes an accurate prediction of the excitation energy requires the inclusion of solvent. Implicit solvent included via a polarizable continuum approach was found to be sufficient in reproducing the excitation energies accurately in the majority of cases. Moreover, we found that the SMD solvent model, which is dependent on the full electron density of the solute without partitioning into partial charges, gave more reliable results for our systems relative to the conductor-like polarizable continuum model (CPCM), as implemented in Gaussian 09. In all cases the inclusion of solvent reduces the error in the predicted excitation energy to <0.3 eV and in the majority of cases to <0.1 eV.