An efficient synthesis, structural (SC-XRD) and spectroscopic (FTIR, 1HNMR, MS spectroscopic) characterization of novel benzofuran-based hydrazones: An experimental and theoretical studies

Computational investigation of pyrazinamide drugs and its transition metal complexes using a DFT approach

Pyrazinamide, an antituberculosis but documented toxic drug, is subjected to computational investigation along with the metal complexes via a DFT approach to predict the structure-activity and structure-toxicity relationship. 6-31G(d,p) basis set was used for Zn, Ni, Mn, Fe, and Co, while the SDD basis set was applied to Cu, Cr, Cd, and Hg. Several reactivity parameters and charge distribution were calculated and the reactivity profile was estimated. The complexes were found to be soft and polarizable which could be responsible for their binding with bacterial targets to inhibit their growth. In contrast, pyrazinamide which is found to be hard among all is susceptible to being toxic. Moreover, the electronegative nature of the complexes can endow them with a better antibacterial effect. Since metal complexes have been found to be less toxic and more biologically interactive by computational methods, they can be employed as potent drugs for the cure of tuberculosis.

Synthesis, Characterizations, Hirshfeld Surface Analysis, DFT, and NLO Study of a Schiff Base Derived from Trifluoromethyl Amine

We synthesized an imine-based (Schiff base) crystalline organic chromophore, i.e., (E)-2-ethoxy-6-(((3-(trifluoromethyl)phenyl)imino)methyl)phenol (ETPMP), and explored its nonlinear optical (NLO) properties. The crystalline structure of ETPMP was determined by the XRD technique and equated with the associated structures utilizing a Cambridge Structural Database search. The supramolecular assembly of ETPMP was investigated regarding intermolecular interactions and short contacts by Hirshfeld surface analysis. Void analysis was performed to check the mechanical response of the crystal. Supramolecular assembly was further inspected by interaction energy calculations that were performed with the B3LYP/6-31G(d,p) functional. Besides this, the NLO properties of ETPMP and other already reported crystal TFMOS were explored utilizing the M06/6-31G(d,p) functional of the DFT approach. An excellent agreement was observed between XRD and DFT results of geometric parameters of the above-mentioned crystals. Narrow band gap along with bathochromic shift (3.489 eV and 317.225 nm, respectively) were investigated in TFMOS than that of ETPMP. Owing to these unique properties, TFMOS possesses higher linear (⟨a⟩ = 3.835 × 10-23 esu) and nonlinear (γtot. = 1.346 × 10-34 esu) response as compared to ETPMP. The outcomes explicitly show the higher nonlinearity in TFMOS, highlighting its importance in potential NLO applications.

Efficient Synthesis of Imine-Carboxylic Acid Functionalized Compounds: Single Crystal, Hirshfeld Surface and Quantum Chemical Exploration

Two aminobenzoic acid based crystalline imines (HMBA and DHBA) were synthesized through a condensation reaction of 4-aminobenzoic acid and substituted benzaldehydes. Single-crystal X-ray diffraction was employed for the determination of structures of prepared Schiff bases. The stability of super molecular structures of both molecules was achieved by intramolecular H-bonding accompanied by strong, as well as comparatively weak, intermolecular attractive forces. The comparative analysis of the non-covalent forces in HMBA and DHBA was performed by Hirshfeld surface analysis and an interaction energy study between the molecular pairs. Along with the synthesis, quantum chemical calculations were also accomplished at M06/6-311G (d, p) functional of density functional theory (DFT). The frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP), natural bond orbitals (NBOs), global reactivity parameters (GRPs) and natural population (NPA) analyses were also carried out. The findings of FMOs found that Egap for HMBA was examined to be smaller (3.477 eV) than that of DHBA (3.7933 eV), which indicated a greater charge transference rate in HMBA. Further, the NBO analysis showed the efficient intramolecular charge transfer (ICT), as studied by Hirshfeld surface analysis.

Synthesis, crystal structure, Hirshfeld surface analysis, DFT, molecular docking and molecular dynamic simulation studies of (E)-2,6-bis(4-chlorophenyl)-3-methyl-4-(2-(2,4,6-trichlorophenyl)hydrazono)piperidine derivatives

A novel drug to treat SARS-CoV-2 infections and hydroxyl chloroquine analogue, (E)-2,6-bis(4-chlorophenyl)-3-methyl-4-(2-(2,4,6-trichlorophenyl)hydrazono)piperidine (BCMTP) compound has been synthesized in one pot reaction. The novel compound BCMTP has been characterized by FT-IR, ¹H-NMR, ¹³C-NMR and single-crystal X-ray diffraction patterns. Crystal packing is stabilized by C8-H8A•••Cl10ⁱ, C41-H41•••Cl1ⁱⁱ and N1-H1A•••Cl6ⁱⁱⁱ intermolecular hydrogen bonds. From the geometrical parameters, it is observed that the piperidine ring adopts chair conformation. Hirshfeld surface analysis was carried out to quantify the interactions and an interaction energy analysis was done to study the interactions between pairs of molecules. The geometrical structure was optimized by density functional theory (DFT) method at B3LYP/6-31G (d, p) as the basic set. The smaller binding energy value provides the higher reactivity of BCMTP compound than hydroxyl chloroquine and was corrected by high electrophilic and low nucleophilic reactions. The stability and charge delocalization of the molecule were also considered by natural bond orbital (NBO) analysis. The HOMO-LUMO energies describe the charge transfer which takes place within the molecule. Molecular electrostatic potential has also been analysed. Molecular docking studies are implemented to analyse the binding energy of the BCMTP compound against standard drugs such as the crystal structure of ADP ribose phosphatase of NSP3 from SARS-CoV-2 in complex with MES and SARS-CoV-2 main protease with an unliganded active site (2019-nCoV, corona virus disease 2019, COVID-19) and found to be considered having better antiviral agents. Molecular dynamics simulation was performed for COVID-19 main protease (Mpro: 6WCF/6Y84) to understand the elements governing the inhibitory effect and the stability of interaction under dynamic conditions.

Crystal structure of E-2-chloro-N′-(1-(5-chloro-2-hydroxyphenyl)propylidene)benzohydrazide, C16H14Cl2N2O2

C16H14Cl2N2O2, triclinic, P 1 ‾ $P\overline{1}$ (no. 2), a = 8.9215(15) Å, b = 10.0013(15) Å, c = 10.5713(15) Å, α = 62.517(2)°, β = 75.325(2)°, γ = 68.9930(10)°, V = 776.8(2) Å3, Z = 2, Rgt (F) = 0.0417, wRref (F 2) = 0.1414, T = 296(2) K.

Selection of the Effective Characteristic Spectra Based on the Chemical Structure and Its Application in Rapid Analysis of Ethanol Content in Gasoline

Near-infrared (NIR) spectroscopy analysis is one of the most rapid detection methods for determining ethanol content in gasoline. Wavelength selection is a key step in the multivariate calibration analysis of NIR spectroscopy. To improve detection accuracy of ethanol content in gasoline and provide a simpler interpretation, we established NIR spectroscopy, a rapid analysis method based on the effective characteristic spectra. Five effective characteristic spectral bands were used according to the molecular structure of ethanol, followed by the development of four modeling schemes. The four modeling schemes spectra, NIR full spectra, and variable importance projection (VIP) spectra were used for modeling and analysis. The model was established based on the effective characteristic spectra without the interference spectra of aromatic hydrocarbons, achieving the best model performance. In addition, the model was further evaluated by internal cross-validation and external validation. The model's evaluation parameters were as follows: the root mean square error of cross-validation (RMSECV) was 0.6193, the correlation coefficient of internal cross-validation (R CV 2) was 0.9995, the root mean square error of prediction (RMSEP) was 0.5572, and the correlation coefficient of external prediction validation (R P 2) was 0.9995. The effective characteristic spectra model had smaller RMSEP and RMSECV values, and larger R CV 2 and R P 2 values compared to the full spectra and VIP spectra models. In conclusion, the effective characteristic spectra model had the highest accuracy and could provide rapid analysis of the ethanol content in gasoline.

Synthesis of Crystalline Fluoro-Functionalized Imines, Single Crystal Investigation, Hirshfeld Surface Analysis, and Theoretical Exploration

This investigation is focused on the synthesis of two halo-functionalized crystalline Schiff base (imine) compounds: (E)-2-methoxy-6-(((3-(trifluoromethyl)phenyl)imino)methyl)phenol (MFIP) and (E)-1-(((2-fluorophenyl)imino)methyl)naphthalen-2-ol (FPIN) by the condensation reaction of substituted benzaldehydes and substituted aniline. The crystal structures of MFIP and FPIN were determined unambiguously by single-crystal X-ray diffraction (SC-XRD) studies. Intermolecular interactions and the role of fluorine atoms in the stabilization of the crystal packing are explored for both compounds using Hirshfeld surface analysis. Accompanied with experimental studies, quantum chemical calculations were also performed for comprehensive structure elucidation at the M06/6-311G(d,p) level of theory. A comparison of experimental and density functional theory results for geometrical parameters exhibited excellent agreement. Interestingly, Frontier molecular orbitals and natural bond orbital (NBO) findings revealed that intramolecular charge transfer and hyper-conjugation interactions had played a significant role to stabilize the molecules. Both compounds exhibited a relatively larger value of hardness with a smaller global softness, which, as proposed by the SC-XRD and NBO study, shows a higher stability. Nonlinear optical (NLO) findings showed that FPIN manifested a larger value of linear polarizability (<a> = 293.06 a.u.) and second-order hyperpolarizability (<γ> = 3.31 × 10⁵ a.u.) than MFIP (<a> = 252.42 and <γ> = 2.08 × 10⁵ a.u.) due to an extended conjugation. The above-mentioned findings of the entitled compounds may play a crucial role in NLO applications.

An Efficient Synthesis, Spectroscopic Characterization, and Optical Nonlinearity Response of Novel Salicylaldehyde Thiosemicarbazone Derivatives

In this study, seven derivatives of salicylaldehyde thiosemicarbazones (1-7) were synthesized by refluxing substituted thiosemicarbazide and salicylaldehyde in an ethanol solvent. Different spectral techniques (UV-vis, IR, and NMR) were used to analyze the prepared compounds (1-7). Accompanied by the experimental study, quantum chemical studies were also carried out at the M06/6-311G(d,p) level. A comparative analysis of the UV-visible spectra and vibrational frequencies between computational and experimental findings was also performed. These comparative data disclosed that both studies were observed to be in excellent agreement. Furthermore, natural bond orbital investigations revealed that nonbonding transitions were significant for the stability of prepared molecules. In addition, frontier molecular orbital (FMO) findings described that a promising charge transfer phenomenon was found in 1-7. The energies of FMOs were further used to determine global reactivity parameters (GRPs). These GRP factors revealed that all synthesized compounds (1-7) contain a greater hardness value (η = 2.1 eV) and a lower softness value (σ = 0.24 eV), which indicated that these compounds were less reactive and more stable. Nonlinear optical (NLO) evaluation displayed that compound 5 consisted of greater values of linear polarizability ⟨α⟩ and third-order polarizability ⟨γ⟩ of 324.93 and 1.69 × 105 a.u., respectively, while compound 3 exhibited a larger value of second-order polarizability (βtotal) of 508.41 a.u. The NLO behavior of these prepared compounds may be significant for the hi-tech NLO applications.

Synthesis, crystal growth, characterization and DFT investigation of a nonlinear optically active cuminaldehyde derivative hydrazone

Single crystals of (E)-N'-(4-isopropylbenzylidene)isonicotinohydrazide monohydrate (IBIHM) were grown from ethanol by the slow evaporation from solution growth technique at room temperature. The structure was elucidated by single-crystal X-ray diffraction analysis and crystallized in the orthorhombic system with noncentrosymmetric space group P2₁2₁2₁. Optical studies reveal that the absorption was minimum in the visible region and the band-gap energy was estimated using the Kubelka-Munk algorithm. The functional groups were identified by Fourier transform infrared spectral analysis. A scanning electron microscopy study revealed the surface morphology of the grown crystal. Investigation of the intermolecular interactions, crystal packing using Hirshfeld surface analysis and single-crystal X-ray diffraction confirm that the close contacts were associated with molecular interactions. Fingerprint plots of Hirshfeld surfaces are used to locate and analyze the percentage of hydrogen-bonding interactions. The second-harmonic generation efficiency of the grown specimen was superior to that of the reference material, potassium dihydrogen phosphate. The grown crystals were further characterized by mass spectrometry and elemental analysis. Theoretical studies using density functional theory (DFT) greatly substantiated the experimental observations. Large first-order molecular hyperpolarizability (β) of about ∼70× was observed for IBIHM. The efficiency of IBIHM in terms of nonlinear optical response was verified and the molecule displayed greater chemical stability and reactivity.