Synthesis, characterization, crystal structure and DFT study of two new polymorphs of a Schiff base (E)-2-((2,6-dichlorobenzylidene)amino)benzonitrile

Insights on the structural characteristics and molecular dynamic studies of methyl vanillin Schiff base bio-compounds

A new crystalline form of Schiff base, N-cyclohexyl-1-(3,4-dimethoxyphenyl)methanimine (CHADMB) was obtained from methanolic solution of cylohexylamine and (methylvanillin) 3,4dimethoxybenzaldehyde. Single crystal X-ray diffraction study reveals that the compound crystallized in monoclinic crystal system with P21/c space group having four molecules per unit cell (Z = 4). Hirshfeld surface (HS) analysis and 2D fingerprint plots reveals that weak non-covalent interactions are responsible for crystal packing. The UV-Vis spectroscopy study reveals that the optical band gap of the compound is 4.25 eV. The dielectric properties were studied as a function of frequency at room temperature and the results show that these properties can be exploited for optoelectronic applications. Thermal stability of the compound is revealed by thermogravimetric and differential thermogravimetric analysis. The in vitro antimicrobial activity against Gram negative (E. coli and P. aeruginosa and Gram positive (S. aureus ) bacterial strains and two fungal strains (C. albicans and A. niger) were studied by agar well diffusion method. It is found that the Schiff base is inhibiting the growth of the tested species to varying degrees. Molecular docking studies indicate that alkyl-pi and pi-pi weak interactions enhance the binding affinity of Schiff base-protein complexes. Molecular dynamics study reveals interaction of CHADMB complexed with bacterial protein, EC showed maximum stability which is in agreement with experimental result.Communicated by Ramaswamy H. Sarma.

Post-synthetic modification of supramolecular assemblies of β-diketonato Cu(ii) complexes: comparing and contrasting the molecular topology by crystal structure and quantum computational studies

Solvent-induced structural transformations on the metal coordination sphere in homoleptic (1 and 2) and heteroleptic (3 and 4) Cu(ii) complexes were analyzed and investigated by crystallographic and quantum computational studies.

QSAR and molecular docking studies of novel 2,5-distributed-1,3,4-thiadiazole derivatives containing 5-phenyl-2-furan as fungicides against Phythophthora infestans

Background

The 1,3,4-thiadiazoles are among the structural moieties that were found to be of utmost importance in the fields of pharmacy and agrochemicals because of their widespread biological activity that includes anti-tumor, antibacterial, anti-inflammatory, antihypertensive, anti-tuberculosis, anticonvulsant, and antimicrobial, among others.

Results

QSAR and molecular docking studies were carried out on thirty-two (32) derivatives of 2,5-disubstituted-1,3,4-thiadiazoles for their antifungal activities toward Phytophthora infestans. Using the “graphical user interface” of Spartan14 software, the structure of the compounds of the dataset is drawn and then optimized at DFT/B3LYP/6-31G* quantum mechanical method of the software. Molecular descriptors of the optimized compounds were calculated and later on divided into the training set and test sets (at a ratio of 3:1). The training set was used for model generation and the test set was for external validation of the generated model. Four models were generated by the employment of genetic function approximation (GFA) in which the optimal model (4) turned out to have the following statistical parameters: R2 = 0.798318, R2adj = 0.750864, cross-validation R2(Q2cv) = 0.662654, and external validation R2pred = 0.624008. On the molecular docking study of thiadiazole compounds with the target protein of Phytophthora infestans effector site (PDB ID: 2NAR ), compound 13 shows the highest binding affinity with − 9.3 kcal/mol docking score and composes hydrophobic as well as H-bond interactions with the target protein (2NAR).

Conclusion

The result of the QSAR study signifies the stability and robustness of the built model by considering the validation parameters and this gave an idea of template/ligand-based design while the molecular docking study revealed the binding interaction between the ligand and the protein site which gave an insight toward an “optimization method” of the structure-based design for the discovery of more potent compounds with better activity against Phytophthora infestans using the approach of computer-aided drug design (CADD) in plant pathology.

Spectroscopic and molecular docking studies on interaction of two Schiff base complexes with bovine serum albumin

This study was designed to examine interaction of two ternary copper (II) Schiff base complexes with bovine serum albumin (BSA), using spectroscopic and molecular docking techniques. The fluorescence quenching measurements revealed that the quenching mechanism was static and the binding site of both Schiff bases to BSA was singular. Förster energy transfer measurements, synchronous fluorescence spectroscopy, and docking study showed both Schiff bases bind to the Trp residues of BSA in short distances. Docking study showed that both Schiff base molecules bind with BSA by forming several hydrogen and van der Waals bonds. In addition, molecular docking study indicated that Schiff base A and Schiff base B were located within the binding pocket of subdomain IB and subdomain IIA of BSA, respectively. Results of Fourier transform-infrared spectroscopy demonstrated that bovine serum albumin interacts with both Schiff bases and the secondary structure of BSA was changed.Communicated by Ramaswamy H. Sarma.

A new crystal form and anti-microbial activity of (E)-1-[3-(2-hy-droxy-benzyl-idene-amino)-phen-yl]ethanone

The title Schiff base compound, C15H13NO2, crystallizes in a new crystal form in the space group P212121, which is different from the monoclinic P21/n space group reported previously [De et al. (2009 ▸). Indian J. Chem. Sect. B, 48, 595-598]. An intra-molecular O-H⋯N hydrogen bond occurs between the hy-droxy and azomethine moieties. In the crystal, mol-ecules are linked by weak C-H⋯O hydrogen bonds into supra-molecular chains propagating along the b-axis direction with a C(8) graph-set motif. The contribution of these two contacts in Hirshfeld surface area are around 19 and 21%, respectively. The title compound was screened for its anti-bacterial activity against two gram-negative (Escherichia coli and Salmonella typhimurium) and one gram-positive (Staphyloccus aureus) bacteria. The results of this study reveal that this Schiff base shows good activity against only one bacterium, i.e. Salmonella typhimurium.