Intra-/inter-molecular interactions – Identification and evaluation by optical spectral data in solution

A Pyrazine-Based Chromophore Photophysical Properties and its Detection for Hydrazine and Acid Vapors

Designed and synthesized linear pyrazine-based D-π-A-π-A probe is investigated to study the colorimetric and emission properties with different polarity index solvents. Their molar extinction coefficients were estimated for each solvent. This TLP probe was investigated in THF/water binary solution aggregates, and a redshifted AIE was observed reaching a water fraction of 70%. Also, this TLP probe was applied to the multifunctional, rapid, sensitive and selective detection of acid-base (TFA/TEA) and hydrazine (N2H4) in colorimetric and fluorimetric sensors. The pyrazine unit probe demonstrated an acidochromic effect and explored the acid-sensing behavior. The TLP probe containing malononitrile functional groups has extensively detected hazardous hydrazine species due to nucleophilic attack of hydrazine at the α-position of dicyano. This TLP probe allowed the quick and fast-sensitive detection of hydrazine hydride with a low detection limit of 1.08 nM. According to the results, the mechanism was confirmed by UV-Vis, PL, NMR and MS spectra for the detection of hydrazine, and further evidence of the protonation-deprotonation process in added TFA/TEA was made by titration studies by 1H NMR. Therefore, this work can be used for test strip kits for multifunction applications.

Solvatochromism, Acidochromism and Photochromism of the 2,6-Bis(4-hydroxybenzylidene) Cyclohexanone Derivative

In this paper, we studied the photophysical behavior of 2,6-bis(4-hydroxybenzylidene) cyclohexanone (BZCH) under the influence of various stimuli. The photophysical properties were correlated with different solvent parameters, such as the Kamlet–Abraham–Taft (KAT), Catalán, and Laurence solvent scales, suggesting that the behavior of BZCH is influenced by both nonspecific and specific solvent-solute interactions. The Catalán solvent dipolarity/polarizability parameters were found to have a significant role in the solvatochromic behavior, which is also confirmed by the KAT and Laurence models. The acidochromism and photochromism properties of this sample in dimethylsulfoxide and chloroform solutions were also investigated. The compound showed reversible acidochromism after the addition of dilute NaOH/HCl solutions, accompanied by a change in color and the appearance of a new absorption band (514 nm). The photochemical behavior was also examined by irradiating BZCH solutions with both 254 and 365 nm light.

Blue Fluorescence of Cyano-tryptophan Predicts Local Electrostatics and Hydrogen Bonding in Biomolecules

Cyano-tryptophan is an unnatural fluorescent amino acid that emits in the visible region. Along with the structural similarity with tryptophan, the unique photophysical properties of this fluorophore make it an ideal probe for biophysical research. Herein, combining fluorescence spectroscopy, infrared spectroscopy, and molecular dynamics simulations, we show that the cyano-tryptophan's emission energy quantifies the underlying bond-specific noncovalent interactions in terms of the electric field. We further report the use of fluorophore's emission energy to predict its hydrogen bond characteristics. We demonstrate that combining experiments with molecular dynamics simulations can provide the hydrogen bonding status of the nitrile moiety. In addition, we report a method to differentiate between aqueous and nonaqueous hydrogen-bonding partners. Using a phenomenological approach, we demonstrate that the presence of the cyano-indole moiety is responsible for the distinct correlations between the fluorophore's emission and the electrostatic forces on the nitrile bond. As indole is a privileged scaffold for both native amino acids and nucleobases, cyano-indoles will have many multifaceted applications.

Experimental approach, theoretical investigation and molecular docking of 2- chloro-5-fluoro phenol antibacterial compound

The molecular structural dimerization of biologically potent 2-chloro-5-fluoro phenol (2C5FP) is optimized. A combined experimental and theoretical characteristics of vibrational spectral determinations (NMR, FT-IR and Raman) on 2-chloro-5-fluoro phenol (2C5FP) were used at DFT-B3LYP/6–31++G (d,p) level of computation. A close coherence is achieved when experimentally observed wave numbers are compared with calculated wave numbers by refinement of the scale factors. Calculated values of global chemical descriptors of the present molecule reveal significant molecular stability and chemical reactivity. Non-Linear optical (NLO) property of the present molecule is investigated by determining the second order non linear parameter of first hyperpolarizability β. Moreover, hydrogen bond and thermodynamic parameters at various temperatures are determined and discussed. Investigated compound 2C5FP possesses a better antibacterial activity against Echerichia coli, Streptococcus aureus, Pseudomonas aureus,and Staphylococcus aureus, respectively. The title molecule is subjected to molecular docking studies with two different proteins, namely Staphylococcus aureus Tyrosyl-tRNA synthetase (PDB ID: 1JIL) and human dihydroorotate dehydrogenase (hDHODH) (PDB ID: 6CJF). The results of molecular docking analysis support the antibacterial activity and demonstrate a strong interaction with the DHODH inhibitor.