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The crystal structure of the salt produced by the reaction of pyrimethamine (an antimalarial drug) with 2-hydroxy-3,5-dinitrobenzoic acid [systematic name: 2,4-diamino-5-(4-chlorophenyl)-6-ethylpyrimidin-1-ium 2-hydroxy-3,5-dinitrobenzoate] has been investigated using X-rays diffraction data collected at room temperature. The results showed that there are strong intermolecular C–H⋯O, N–H⋯N, O–H⋯O types of hydrogen bonding interactions that play a key role in the crystal structure stabilization while C–H⋯O and C–H … π interaction further stabilize the structure. In addition, theoretical calculations were done to compute the binding free energies and the electron densities associated to heterodimeric, heterotrimeric and heterotetrameric salt assemblies of the pyrimethamine-2-hydroxy-3,5-dinitrobenzoate salt. The molecular electron densities, electrostatic potential and the regions of electron density accumulation as well as depletion were explored for these assemblies. These analyses not only suggest the high salt stability but also appropriate electrostatic properties of the pyrimethamine drug for the interaction with a carboxylic group that is attached to the side chains of glutamate and aspartate residues in proteins.

Four new 3-(2-(3-Phenyl-5-substituted phenyl-4,5-dihydropyrazol-1-yl)thiazol-4-yl)-2H-chromen-2-one derivatives (1–4) were synthesized and fully characterized by spectroscopic techniques. The final structures of all chromenone analogues (1–4) were confirmed by single crystal X-ray diffraction analysis. Quantum chemical studies were performed to compare the results from the theoretical studies with the experimental (X-ray as well as spectroscopic) ones. The theoretically simulated geometric parameters and other spectroscopic properties agreed nicely with the experimental data. All compounds were evaluated for biological activity (acetyl cholinesterase inhibition potential). Compound 3 emerged as the most potent derivative in acetylcholine esterase (AChE) inhibition assay with IC50 = 27.29 μM. The IC50 of compound 3 is greater than the standard drug galantamine (IC50 = 44.02 μM). To rationalize the potencies, molecular docking studies were also carried out. These docking results revealed a good correlation between binding energies values and in vitro AChE inhibition assay.

In the present study, a series of mononuclear Ni(II), Cu(II) and Zn(II) complexes with ONNO donor salen-type Schiff base ligands, derived from different 3,5-dihalosalicylaldehyde with polymethylenediamines of varying chain length, have been prepared. All the synthesized compounds were characterized by using various spectroscopic (FT-IR and 1H NMR) and analytical (CHN etc.) techniques. Furthermore, three complexes (ZnL1, NiL3 and NiL4) were successfully characterized by single crystal X-ray diffraction. The data revealed that the geometry around Zn(II) was distorted square pyramidal for ZnL1, while NiL3 and NiL4 complexes adapted slightly distorted octahedral geometries around Ni(II). The antibacterial activities of the synthesized ligands and their respective complexes were elaborated by screening them against two strains of Gram positive (Staphylococcus aureus and Bacillus cereus) and two strains of Gram negative (Escherichia coli and Pseudomonas aeruginosa) bacteria. It was found from the measurements of zones of inhibition that metal chelates are marginally more effective than free ligands.

The current work reports the formation methodology of the co-crystal between 2-amino-6-methylpyridine and succinic acid, its single-crystal characterization, and the computational study. The single-crystal analysis showed that the co-crystal molecules are interlinked by N···H‒O and O···H‒O bonds to form R22 (8) loop and D22 (5) and D22 (8) finite pattern along with the formation of infinite 2D network in the (1 0 1 ¯ ) plane having base vectors [1 0 1] and [0 1 ¯ 0]. Moreover, the weak interactions of the π-π stacking type and C O-Cg interactions are found in the title compound helping in further strengthening of the crystal structure. The Hirshfeld surface analysis confirmed that H···H interatomic contacts are the largest contributor to entire interatomic contacts with contribution of 45.8%. The computational studies supported the presence of significantly strong hydrogen bonds within the title complex. The molecular orbital analysis suggested that both HOMO/HOMO-1 and LUMO/LUMO+1 would be able to participate in oxidative-reductive processes of the complex. The HOMO has dominating contributions from one succinate unit along with minor contributions from the H-bonded NH2-group of the neighboring 2-amino-6-methylpyridin-1-ium moiety. The calculated values of the global reactivity parameters suggest noticeable stability of the title complex. It was also shown to possess quite pronounced nonlinear optical properties.

Eight new bismuth(III) complexes (1-8) of substituted hydrazones having general formula; [Bi(RCONHNCHC5H4N)Clx] and [Bi(RCONHNCHC9H6N)Clx], where R = C10H7O (1, and 8), C4H3S (2), C6H5O (3, and 6), C7H7 (4), C5H4N (5, and 7), x = 2 or 3 have been prepared. The substituted hydrazones (I1-I8) were synthesized by reacting the stoichiometric amounts of the respective hydrazides such as p-toluic hydrazide, 4-hydroxybenzhydrazide, thiophene-2-carboxylic acid hydrazide, 3-hydroxy-2-naphthoic acid hydrazide, Isonicotic acid hydrazide and appropriate aromatic aldehydes like pridine-2-carboxaldehyde and quinoline-2-carboxyaldehyde. These hydrazones (ligands),then complexed to Bi(III) species to yield the target compounds. They were characterized by FTIR, and NMR spectroscopy to find out an explicit evidence about their structural motifs. The X-ray data for (1 & I6) further validate the chemical structures of the synthesized compounds. The molecular geometry for (1) is predominately distorted pentagonal bipyramidal where hepta-coordinated Bi(III) center is attached to the nitrogens of pyridine and of azomethine moieties along with the carbonyl oxygen, two chloro and two oxygens of the (two) DMSO molecules. The bond lengths for Bi(1)-O(1), Bi(1)-N(1) and Bi(1)-N(2) are 2.323(5), 2.539(6), 2.390(5) oA respectively indicating Bi(1)-O(1) as the strongest linkage to the metal center. The H-bonding, present in (1), contributed an extra stability to the structure. The synthesized compounds were initially screened for their possible antimicrobial, alpha-amylase, and protein kinase inhibition, some (1,2,6,8) exhibit significant activity. The experimental results are further endorsed by molecular docking studies against helicobacter pylori urease (1E9Y), epidermal growth factor receptor tyrosine kinase (1M17) and human pancreatic alpha amylase (5U3A) inhibition activity. The significant ligand-receptor interactions, observed at the binding pocket of the selected drug targets, further revealed the enzyme inhibition potential of the compounds and highlighting their possible roles as therapeutic agents in future drug discovery processes.

1,3,4-Oxadiazoles are important class of heterocyclic compounds, with diverse biological applications. In this study, the synthesis of three different 1,3,4-oxadiazoles bearing pentadecyl moiety is reported. All compounds were synthesized with significant (70–82%) yields, characterized by using different spectroanalytical techniques such as UV–vis., FT-IR, NMR ( 1 H and 13 C), and finally structures were confirmed unequivocally by single crystal X-ray diffraction analysis. Quantum chemical studies by using GAUSSIAN software at DFT/B3LYP/6-31G (d, p) level of theory have been exercised to compare and validate the spectroscopic and X-ray results. Frontier molecular orbitals (FMOs) analysis of all compounds was performed by utilizing optimized geometries and gave the idea about kinetic stability and reactivity. Molecular electrostatic potential (MEP) analysis indicated the regions for electrophilic as well as nucleophilic attack. Compounds were also screened to check their antibacterial and antifungal potential.

Beginning with 2-amino-6-methyl-pyrimidin-4-ol and 2,6-diamino-pyrimidin-4-ol, 2-amino-6-methylpyrimidin-4-yl 4-acetamidobenzenesulfonate (APABS) and 2,6-diaminopyrimidin-4-yl 4-acetamidobenzenesulfonate (DPACS) were synthesized respectively through O-4-acetylamino-benzenesulfonylation reaction. The structures of the (APABS) and (DPACS) were verified unambiguously by the single crystal X-ray diffraction technique. The X-ray diffraction inspection inferred that these chemical architectures are stabilized by intermolecular attractive forces. The quantum chemical examination of optimized geometry, vibraional analysis and natural bond orbitals (NBOs) properties for APABS and DPACS were attained by adopting B3LYP/6–311G(d,p) level. Moreover, the frontier molecular orbitals (FMOs) analysis was determined by TD-DFT/B3LYP/ 6–311G(d,p) level. The simulated structural parameters and XRD results of APABS and DPACS were found in close agreement to that of concerned experimental findings. The molecular stability owing to strongest hyperconjugative interactions in APABS and DPACS was evaluated through NBO investigation. The transfer of charge phenonmenon in the entitled compounds was evaluated by FMOs. The increasing order of energy gap for compounds is APABS˂DPACS. Frontier molecular orbital energies of entitled compounds are also used to calculate the global reativity indices. The engagement of various sites in terms of chemical reactivities were determined by molecular eletrosatic potential analysis. Moreover, hirshfeldsurfaces were studied which supported the X-ray diffraction investigation in terms of intermolecular attractive forces.

The title compound 6-benzyl-11-(p-tolyl)-6H-indolo[2,3-b]quinoline 3 was synthesized by one-pot procedure including electrophile-driven cross-amination and cyclization via Friedel-Crafts alkylation. The crystal structure of this indoloquinoline was determined by means of single-crystal X-ray diffraction method and further confirmed by 1H NMR and 13C NMR. In tetracyclic compound 3 all the C–N bonds are shorter than single bonds but longer than double bonds which show significant electrons delocalization. Furthermore, the crystal packing is stabilized by the presence of π-π stacking interaction and C–H-π interaction. In addition, the antimicrobial studies revealed that the title compound exhibits strong antimicrobial activity against Aspergillus niger, Fusarium oxysporum, P. syringe and B. subtilis.

Methyl-2-(1-benzyl-4-phenyl-1 H -1,2,3-triazol-5-yl)-2-oxoacetate (1) and ethyl-2-(1-benzyl-4-phenyl-1 H -1,2,3-triazol-5-yl)-2-oxoacetate (2) were synthesized by one pot three component strategy, and characterized by FT-IR, NMR ( 1 H and 13 C) spectroscopy and TOF-MS spectrometry. Finally, the structures were unequivocally confirmed by single crystal X-ray diffraction analyses. Both compounds, 1 and 2 exist in monoclinic crystal packing having space group P2 1 /n and P2 1 /c, respectively. Crystal structures investigations revealed that the molecular structures of the title compounds are stabilized by weak intermolecular hydrogen bonding interactions to form dimers. Density functional theory (DFT) calculations were performed not only to compare with the experimental spectroscopic results but also to probe structural properties. The molecular electrostatic potential (MEP) mapped over the entire stabilized geometries of the molecules delivered information about the electrophilic and nucleophilic sites. Furthermore, frontier molecular orbital analysis gave the idea about stability and reactivity of compounds. Both compounds were also screened for brine shrimp cytotoxicity assay.