Growth and characterization of hydroxyethylammonium picrate single crystals for third-order nonlinear optical applications

Spectroscopic investigation, hirshfeld surface analysis and molecular docking studies on anti-viral drug entecavir

Four 4-[[(4-nitrophenyl)methylene]imino]phenols (2a-d) were synthesized. After deprotonation in solution, they formed the solvatochromic phenolates 3a-d, which revealed a reversal in solvatochromism. Their UV-vis spectroscopic behavior was explained on the basis of the interaction of the dyes with the medium through combined effects, such as nonspecific solute-solvent interactions and hydrogen bonding between the solvents and the nitro and phenolate groups. Dyes 3a-c were used as probes to investigate binary solvent mixtures, and the synergistic behavior observed was attributed to solvent-solvent and solute-solvent interactions. A very unusual UV-vis spectroscopic behavior occurred with dye 3d, which has in its molecular structure two nitro substituents as acceptor groups and two phenyl groups on the phenolate moiety. In alcohol/water mixtures, the E(T)(3d) values increase from pure alcohol (methanol, ethanol, and propan-2-ol) until the addition of up to 80-96% water. Subsequently, the addition of a small amount of water causes a very sharp reduction in the E(T)(3d) value (for methanol, this corresponds to a bathochromic shift from 543 to 732 nm). This represents the first example of a solvatochromic switch triggered by a subtle change in the polarity of the medium, the color of the solutions being easily reversed by adding small amounts of the required cosolvent.

Nitro-Substituted 4-[(Phenylmethylene)imino]phenolates: Solvatochromism and Their Use as Solvatochromic Switches and as Probes for the Investigation of Preferential Solvation in Solvent Mixtures

4-(Nitrostyryl)phenols 2a–9a were synthesized, and by deprotonation in solution, the solvatochromic phenolates 2b–9b were formed. Their absorption bands in the vis region of the spectra are due to π–π* electronic transitions, of an intramolecular charge-transfer nature, from the electron-donor phenolate toward the electron-acceptor nitroarene moiety. The frontier molecular orbitals and natural bond orbitals were analyzed for the protonated and deprotonated forms. The calculated geometries are in agreement with X-ray structures observed for 4a, 6a, and 8a. The HOMO–LUMO energy gaps suggest that, after their deprotonation, an increase in the electron delocalization is observed. In the protonated compounds, the HOMO is primarily localized over the phenol ring and the C═C bridge. After deprotonation, it extends toward the entire molecule, including the NO2 groups. The solvatochromism of each dye was studied in 28 organic solvents, and it was found that all compounds exhibit a reversal in solvatochromism, whic...

Synthesis and Solvatochromism of Substituted 4-(Nitrostyryl)phenolate Dyes.

Second and third-order nonlinear optical and DFT calculations on 2-amino-5-chloro pyridinium-L-tartrate: A phasematchable organic single crystal

Physiochemical properties of organic nonlinear optical crystal from combined experimental and theoretical studies.

Computational studies of 1,2-disubstituted benzimidazole derivatives

Some novel Y-shaped imidazole derivatives were developed and characterized by NMR and mass spectral techniques. The photophysical properties of these imidazole derivatives were studied in several solvents. The Kamlet-Taft and Catalan’s solvent scales were found to be the most suitable for describing the solvatochromic shifts of the absorption and fluorescence emission. The adjusted coefficient representing the electron releasing ability or basicity of the solvent, C
 β
 or C
 SB has a negative value, suggesting that the absorption and fluorescence bands shift to lower energies with the increasing electron-donating ability of the solvent. This effect can be interpreted in terms of the stabilization of the resonance structures of the chromophore. The observed lower fluorescence quantum yield may be due to an increase in the non-radiative deactivation rate constant. This is attributed to the loss of planarity in the excited state provided by the non co-planarity of the cinnamaldehyde ring attached to C(2) atom of the imidazole ring. Such a geometrical change in the excited state leads to an important Stokes shift, reducing the reabsorption and reemission effects in the detected emission in highly concentrated solutions.

Kamlet-Taft and Catalan Studies of Some Novel Y-Shaped Imidazole Derivatives

In the title compound, C25H16N4, the fused ring system is essentially planar [maximum deviation = 0.1012 (15) A]. The imidazole ring makes dihedral angles of 77.41 (8) and 56.26 (8)° with the phenyl rings attached to nitro­gen and carbon, respectively. The dihedral angle between the two phenyl rings is 65.50 (8)°. Weak C—H⋯π inter­actions are found in the crystal structure.

https://journals.iucr.org/e/issues/2011/04/00/hg5009/hg5009.pdf

1,2-Diphenyl-1H-imidazo[4,5-f][1,10]phenanthroline.

In the title compound, C25H15FN4·H2O, the fused ring system is essentially planar [maximum deviation of 0.0822 (14) A]. The imidazole ring makes dihedral angles of 76.83 (7) and 32.22 (7)° with the phenyl group attached to nitro­gen and the fluoro­benzene group to carbon, respectively. The dihedral angle between the two phenyl rings is 72.13 (7)°. Inter­molecular O—H⋯N, O—H⋯F, C—H⋯F, C—H⋯O and C—H⋯N hydrogen bonds are found in the crystal structure.

https://journals.iucr.org/e/issues/2011/08/00/hg5061/hg5061.pdf

M. Venkatesh Perumal

Papers

Physiochemical properties of organic nonlinear optical crystal from combined experimental and theoretical studies.

Computational studies of 1,2-disubstituted benzimidazole derivatives

Kamlet-Taft and Catalan Studies of Some Novel Y-Shaped Imidazole Derivatives

1,2-Diphenyl-1H-imidazo[4,5-f][1,10]phenanthroline.

2-(4-Fluoro-phen-yl)-1-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline monohydrate.