Preparation, QTAIM and Single‐Crystal Exploration of the Pyrimethamine‐Based Co‐Crystal Salts with Substituted Benzoic Acids

A synthetic approach towards drug modification: 2-hydroxy-1-naphthaldehyde based imine-zwitterion preparation, single-crystal study, Hirshfeld surface analysis, and computational investigation

The current work is about the modification of primary amine functionalized drugs, pyrimethamine and 4-amino-N-(2,3-dihydrothiazol-2-yl)benzenesulfonamide, via condensation reaction with 2-hydroxy-1-naphthaldehyde to produce new organic zwitterionic compounds (E)-1-(((4-(N-(2,3-dihydrothiazol-2-yl)sulfamoyl)phenyl)iminio)methyl)naphthalen-2-olate (DSPIN) and (E)-1-(((4-amino-5-(4-chlorophenyl)-6-ethylpyrimidin-2-yl)iminio)methyl)naphthalen-2-olate (ACPIN) in methanol as a solvent. The crystal structures of both compounds were confirmed to be imine-based zwitterionic products via single-crystal X-ray diffraction (SC-XRD) analysis which indicated that the stabilization of both crystalline compounds is achieved via various noncovalent interactions. The supramolecular assembly in terms of noncovalent interactions was explored by the Hirshfeld surface analysis. Void analysis was carried out to predict the crystal mechanical response. Compound geometries calculated in the DFT (Density Functional Theory) study showed reasonably good agreement with the experimentally determined structural parameters. Frontier molecular orbital (FMO) analysis showed that the DSPIN HOMO/LUMO gap is by 0.15 eV smaller than the ACPIN HOMO/LUMO gap due to some destabilization of the DSPIN HOMO and some stabilization of its LUMO. The results of the charge analysis implied formation of intramolecular hydrogen bonds and suggested formation of intermolecular hydrogen bonding and dipole-dipole and dispersion interactions.

Linear and Nonlinear Optical Responses of Nitrobenzofurazan-Sulfide Derivatives: DFT-QTAIM Investigation on Twisted Intramolecular Charge Transfer

In this study, we report on the green fluorescence exhibited by nitrobenzofurazan-sulfide derivatives (NBD-Si, i = 1-4). The optical responses of these studied compounds in a polar methanol solvent were simulated by the use of time-dependent density functional theory (TD-DFT) employing the Becke-3-Parameter-Lee-Yang-Parr (B3LYP) functional along with the 6-31G(d,p) basis set. The computed energy and oscillator strength (f) results complement the experimental results. The band gap was calculated as the difference between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO). Additionally, the density of states (DOS) was computed, providing a comprehensive understanding of the fundamental properties of these materials and further corroborating the experimental data. When the experimental data derived from ultraviolet/visible (UV/visible) and fluorescence spectroscopic techniques and those from simulated spectra are analyzed, the extracted values match up adequately. In addition, the NBD-sulfide compounds exhibit a large Stokes shift up to 85 nm in a polar methanol solvent. They are hypothesized to represent a novel paradigm of excited-state intramolecular charge transfer (ICT). To understand the intrinsic optical properties of NBD-Si materials, an ICT was identified, and its direction within the molecule was evaluated using the ratio of βvect and βtotal, values extracted from the computed nonlinear optical (NLO) properties. Moreover, the reduced density gradient (RDG)-based noncovalent interactions (NCIs) were employed to characterize the strength and type of NBD-Si interactions. Furthermore, noncovalent interactions were identified and categorized using the Quantum Theory of Atoms in Molecules (QTAIM) analysis. Ultimately, the combination of Hirshfeld surface analysis and DFT calculations was utilized to enhance the characterization and rationalization of these NCIs.

Polymorphs of Substituted p-Toluenesulfonanilide: Synthesis, Single-Crystal Analysis, Hirshfeld Surface Exploration, and Theoretical Investigation

Polymorphism is an exciting feature of chemical systems where a compound can exist in different crystal forms. The present investigation is focused on the two polymorphic forms, triclinic (MSBT) and monoclinic (MSBM), of ethyl 3-iodo-4-((4-methylphenyl)sulfonamido)benzoate prepared from ethyl 4-amino-3-iodobenzoate. The prepared polymorphs were unambiguously confirmed by single-crystal X-ray diffraction (SC-XRD) analysis. According to the SC-XRD results, the molecular configurations of both structures are stabilized by intramolecular N-H···I and C-H···O bonding. The crystal packing of MSBT is different as compared to the crystal packing of MSBM because MSBT is crystallized in the triclinic crystal system with the space group P1̅, whereas MSBM is crystallized in the monoclinic crystal system with the space group P21/c. The molecules of MSBT are interlinked in the form of dimers through N-H···O bonding to form R22(8) loops, while the MSBM molecules are connected with each other in the form of an infinite chain through C-H···O bonding. The crystal packing of both compounds is further stabilized by off-set π···π stacking interactions between phenyl rings, which is found stronger in MSBM as compared to in MSBT. Moreover, Hirshfeld surface exploration of the polymorphs was carried out, and the results were compared with the closely related literature structure. Accordingly, the supramolecular assembly of these polymorphs is mainly stabilized by noncovalent interactions or intermolecular interactions. Furthermore, a density functional theory (DFT) study was also carried out, which provided good support for the SC-XRD and Hirshfeld studies, suggesting the formation of both intramolecular and intermolecular interactions for both compounds.

Spectroscopic, Biological, and Topological Insights on Lemonol as a Potential Anticancer Agent

A monoterpene alcohol known as lemonol was investigated experimentally as well as theoretically in order to gain insights into its geometrical structure, vibrational frequencies, solvent effects on electronic properties, molecular electrostatic potential, Mulliken atomic charge distribution, natural bond orbital, and Nonlinear Optical properties. The frontier molecular orbital energy gap values of 5.9084 eV (gas), 5.9261 eV (ethanol), 5.9185 eV (chloroform), 5.9253 eV (acetone), and 5.9176 eV (diethyl ether) were predicted, and it shows the kinetic stability and chemical reactivity of lemonol. Topological studies were conducted using Multiwfn software to understand the binding sites and weak interactions in lemonol. The antiproliferative effect of lemonol against the breast cancer cell line Michigan Cancer Foundation (MCF-7) was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, while nuclear damage, condensation, and reactive oxygen species generation were identified using acridine orange/ethidium bromide, propidium iodide, and dichlorodihydrofluorescein diacetate staining. The theoretical and experimental findings are highly correlated, confirming the structure, and the results of in vitro studies suggest that lemonol acts as a potent inhibitor against the human breast cancer cell line MCF-7, highlighting its strong antiproliferative activity.

New cocrystals of heterocyclic drugs: structural, antileishmanial, larvicidal and urease inhibition studies

Many heterocycles have been developed as drugs due to their capacity to interact productively with biological systems. The present study aimed to synthesize cocrystals of the heterocyclic antitubercular agent pyrazinamide (PYZ, 1, BCS III) and the commercially available anticonvulsant drug carbamazepine (CBZ, 2, BCS class II) to study the effect of cocrystallization on the stability and biological activities of these drugs. Two new cocrystals, namely, pyrazinamide-homophthalic acid (1/1) (PYZ:HMA, 3) and carbamazepine-5-chlorosalicylic acid (1/1) (CBZ:5-SA, 4), were synthesized. The single-crystal X-ray diffraction-based structure of carbamazepine-trans-cinnamic acid (1/1) (CBZ:TCA, 5) was also studied for the first time, along with the known cocrystal carbamazepine-nicotinamide (1/1) (CBZ:NA, 6). From a combination drug perspective, these are interesting pharmaceutical cocrystals to overcome the known side effects of PYZ (1) therapy, and the poor biopharmaceutical properties of CBZ (2). The purity and homogeneity of all the synthesized cocrystals were confirmed by single-crystal X-ray diffraction, powder X-ray diffraction and FT-IR analysis, followed by thermal stability studies based on differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Detailed intermolecular interactions and the role of hydrogen bonding towards crystal stability were evaluated quantitatively via Hirshfeld surface analysis. The solubility of CBZ at pH 6.8 and 7.4 in 0.1 N HCl and H2O were compared with the values of cocrystal CBZ:5-SA (4). The solubility of CBZ:5-SA was found to be significantly improved at pH 6.8 and 7.4 in H2O. All the synthesized cocrystals 3-6 exhibited a potent urease inhibition (IC50 values range from 17.32 ± 0.89 to 12.3 ± 0.8 µM), several times more potent than standard acetohydroxamic acid (IC50 = 20.34 ± 0.43 µM). PYZ:HMA (3) also exhibited potent larvicidal activity against Aedes aegypti. Among the synthesized cocrystals, PYZ:HMA (3) and CBZ:TCA (5) were found to possess antileishmanial activity against the miltefosine-induced resistant strain of Leishmania major, with IC50 values of 111.98 ± 0.99 and 111.90 ± 1.44 µM, respectively, in comparison with miltefosine (IC50 = 169.55 ± 0.20 µM).

Exploring Probenecid Derived 1,3,4-Oxadiazole-Phthalimide Hybrid as α-Amylase Inhibitor: Synthesis, Structural Investigation, and Molecular Modeling

1,3,4-Oxadiazole moiety is a crucial pharmacophore in many biologically active compounds. In a typical synthesis, probenecid was subjected to a sequence of reactions to obtain a 1,3,4-oxadiazole–phthalimide hybrid (PESMP) in high yields. The NMR (1H and 13C) spectroscopic analysis initially confirmed the structure of PESMP. Further spectral aspects were validated based on a single-crystal XRD analysis. Experimental findings were confirmed afterwards by executing a Hirshfeld surface (HS) analysis and quantum mechanical computations. The HS analysis showed the role of the π⋯π stacking interactions in PESMP. PESMP was found to have a high stability and lower reactivity in terms of global reactivity parameters. α-Amylase inhibition studies revealed that the PESMP was a good inhibitor of α-amylase with an s value of 10.60 ± 0.16 μg/mL compared with that of standard acarbose (IC50 = 8.80 ± 0.21 μg/mL). Molecular docking was also utilized to reveal the binding pose and features of PESMP against the α-amylase enzyme. Via docking computations, the high potency of PESMP and acarbose towards the α-amylase enzyme was unveiled and confirmed by docking scores of −7.4 and −9.4 kcal/mol, respectively. These findings shine a new light on the potential of PESMP compounds as α-amylase inhibitors.

Synthesis, Characterization, Crystal Structures, and Supramolecular Assembly of Copper Complexes Derived from Nitroterephthalic Acid along with Hirshfeld Surface Analysis and Quantum Chemical Studies

Two new Cu(II) carboxylate complexes, Cu-NTA and Cu-DNTA, were prepared by treating 2-nitroterephthalic acid with CuSO₄·5H₂O at room temperature. The synthesized complexes were characterized by elemental (CHN), FT-IR, and thermogravimetric analysis. The crystal structures of both complexes were explored by single crystal X-ray diffraction analysis, which inferred that the coordination geometry is slightly distorted octahedral and square pyramidal in Cu-NTA and Cu-DNTA, respectively. The non-covalent interactions that are the main feature of the supramolecular assembly were investigated by Hirshfeld surface analysis for both complexes. The propensity of each pair of chemical moieties involved in crystal-packing interactions was determined by the enrichment ratio. Quantum chemical computations were performed to optimize the molecular geometry of complex Cu-NTA and compared it with the experimental single crystal structure, which was found to be in sensible agreement with the experimental structure of the complex. The DFT method was used to see the potential of the selected Cu-NTA complex for linear and nonlinear optical properties. The static NLO polarizability <γ> of complex Cu-NTA was calculated to be 86.28 × 10^-36 esu at M06 functional and 6-31G*/LANL2DZ basis set, which was rationally large to look for NLO applications of complex Cu-NTA. Additionally, the molecular electrostatic potential and frontier molecular orbitals were also computed with the same methodology to see electronic characteristics and ground-state electronic charge distributions.

A coumarin based Schiff Base: An effective colorimetric sensor for selective detection of F- ion in real samples and DFT studies

Chemosensors are molecular devices which react with target and give a visible signal, which is a degree of its sensitivity. Herein, a novel coumarin based Schiff Base has been synthesized for F^- ions detection. The chemosensor showed an intense color change upon the addition of F^- ions (light yellow to purple). The chemosensor has fewer effects of competing anions. The limit of detection is calculated as low as 1.1 × 10^-6 and the binding constant was determined as 1.61 × 10⁴. The job's plot confirmed 1:1 stoichiometry between chemosensor and F^- ion. The reverse reaction of chemosensor with MeOH is useful to construct a combinatorial logic circuit gates. The interaction mechanism of chemosensor was deliberated by ¹H NMR, FTIR, and DFT studies. Finally, the chemosensor was useful to detect F^- ions in tooth-paste sample and test strip is prepared for F^- ions detection.