Quantum chemical determination of molecular geometries and spectral investigation of 4-ethoxy-2, 3-difluoro benzamide

Synthesis, characterization, optical properties, biological activity and theoretical studies of a 4 nitrobenzylidene) amino) phenyl)imino)methyl)naphthalen-2-ol -based fluorescent Schiff base

A new Schiff base, 1-(E)-(4-((E) 4nitrobenzylidene) amino) phenyl)imino) methyl)naphthalen-2-ol (4NMN), was prepared from the reaction of p-phenylenediamine with 2-hydroxy-1-naphthaldehyde and 4-nitrobenzaldehyde and characterized with spectroscopic analysis. UV-VIS and NMR. Frontier molecular orbitals, molecular electrostatic potential, and chemical reactivity descriptors of the synthesized compound were studied using molecular modeling methods. The antibacterial and antifungal activities of the Schiff base were studied for its minimum inhibitory concentration. The compound showed a higher effect on yeast than against bacteria. Density functional theory (DFT) calculations were performed to study the mechanism of reaction for the synthesis of 4NMN, and the results were consistent with the experimental findings. 4NMN exhibited moderate antibacterial and antifungal activities and demonstrated higher inhibition potential against different resistant strains compared to the reference drug gentamycin. The absorption and fluorescence spectra of 4NMN were measured in different solvents, and the effect of relative polarity and acidity on the medium was observed. An inner filter effect was observed at high concentrations, and the compound showed considerable fluorescence enhancement with increasing medium viscosity and fluorescence quenching by the addition of traces of Cr1+ and Cu2+. Additionally, molecular docking studies were conducted to investigate the efficiency of antibacterial and antifungal targets.

New inorganic inhibitors derived from cefotaxime to enhance corrosion resistance of mild steel in 3% NaCl

To overcome the threat of corrosion and its cost, a new Schiff base was prepared and utilized to synthesize inorganic inhibitors to enhance corrosion resistance and reduce current density. The Schiff base was obtained from the interaction of cefotaxime with acetylacetone, while 1H NMR and IR spectra were used to confirm the preparation. Moreover, FeIII, CoII, NiII and CuII metal salts were reacted with the Schiff base to give the corresponding complexes. Meanwhile, the non-ionic behavior of the observed complexes in solutions was proved from the conductance results. In addition, the octahedral geometry and the postulated structure of complexes were determined from CHNM%, IR spectroscopy, UV-visible spectra, and TGA analysis. Also, the energy of molecular orbitals (HOMO and LUMO) and other quantum mechanics parameters were calculated using the DFT method. The observed results indicated the reactivity of metal complexes and their ability to donate electrons more than the Schiff base. Furthermore, the corrosion rate of a steel sample under various concentrations of inhibitors was calculated by a potentiodynamic polarization test. The obtained data displayed that metal complexes declined the corrosion rate more than the Schiff base; therefore, the binding between the metal ion and the Schiff base improved the inhibition efficiency.

Experimental and Quantum Chemical Studies of Nicotinamide-Oxalic Acid Salt: Hydrogen Bonding, AIM and NBO Analysis

The computational modeling supported with experimental results can explain the overall structural packing by predicting the hydrogen bond interactions present in any cocrystals (active pharmaceutical ingredients + coformer) as well as salts. In this context, the hydrogen bonding synthons, physiochemical properties (chemical reactivity and stability), and drug-likeliness behavior of proposed nicotinamide–oxalic acid (NIC–OXA) salt have been reported by using vibrational spectroscopic signatures (IR and Raman spectra) and quantum chemical calculations. The NIC–OXA salt was prepared by reactive crystallization method. X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) techniques were used for the characterization and validation of NIC–OXA salt. The spectroscopic signatures revealed that (N7–H8)/(N23–H24) of the pyridine ring of NIC, (C═O), and (C–O) groups of OXA were forming the intermolecular hydrogen bonding (N–H⋯O–C), (C–H⋯O═C), and (N–H⋯O═C), respectively, in NIC–OXA salt. Additionally, the quantum theory of atoms in molecules (QTAIM) showed that (C10–H22⋯O1) and (C26–H38⋯O4) are two unconventional hydrogen bonds present in NIC–OXA salt. Also, the natural bond orbital analysis was performed to find the charge transfer interactions and revealed the strongest hydrogen bonds (N7–H8⋯O5)/(N23–H24⋯O2) in NIC–OXA salt. The frontier molecular orbital (FMO) analysis suggested more reactivity and less stability of NIC–OXA salt in comparison to NIC–CA cocrystal and NIC. The global and local reactivity descriptors calculated and predicted that NIC–OXA salt is softer than NIC–CA cocrystal and NIC. From MESP of NIC–OXA salt, it is clear that electrophilic (N7–H8)/(N23–H24), (C6═O4)/(C3═O1) and nucleophilic (C10–H22)/(C26–H38), (C6–O5)/(C3–O2) reactive groups in NIC and OXA, respectively, neutralize after the formation of NIC–OXA salt, confirming the presence of hydrogen bonding interactions (N7–H8⋯O5–C6) and (N23–H24⋯O2–C3). Lipinski’s rule was applied to check the activeness of salt as an orally active form. The results shed light on several features of NIC–OXA salt that can further lead to the improvement in the physicochemical properties of NIC.

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.

Exploration of physicochemical properties of 4-methoxy acetanilide: A nonlinear optical crystal

The single crystal XRD analysis has been used to examine the structure of the centrosymmetric crystal 4-Methoxy acetanilide. The material delineated in orthorhombic system with the space group of Pbca. FTIR and Raman spectrum analysis have been executed to comprehend the molecular interactions and to study the vibrational nature of the functional groups presented in the title molecule. Characteristic studies like optical, dielectric and thermal stability have also been carried out. Detailed explorations have been conducted on the optical properties of the crystal using both quantum chemical calculations and experimental data.