Browsing by Author "Vernekar, Beena K."
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Item Bis(4-aminopyridinium) and bis(2-amino-6-methylpyridinium) cations stabilised by [MS4]2− anions: Synthesis, crystal structures, Hirshfeld surface analysis and sulfur transfer reactions(Elsevier, 2025) D’Souza, Milagrina; Harmalkar, Nikita N.; Chari, Vishnu R.; Vernekar, Beena K.; Dhuri, Sunder N.Four new organic ammonium tetrasulfidometallates: (4-aminopyridinium)2[MoS4]·H2O 1, (4-aminopyridinium)2[WS4]·H2O 2, (2-amino-6-methylpyridinium)2[MoS4] 3, and (2-amino-6-methylpyridinium)2[WS4] 4 have been synthesized by a well-known base promoted cation exchange method. All compounds were characterized by elemental analysis, IR/Raman/UV–Vis spectroscopy, thermogravimetric analysis, and X-ray crystallography. The structures of 1 and 2 consist of unique tetrahedral [MoS4]2− and [WS4]2− dianions, which are charge-balanced by crystallographically independent 4-aminopyridinium monocations. Additionally, both have a lattice water molecule, which contributes to the overall stability of their structures. In compounds 3 and 4, 4-aminopyridinium of 1 and 2 are replaced by 2-amino-6-methylpyridinium cation and lack lattice water. The different H-bonding interactions viz Nsingle bondH⋯S, Csingle bondH⋯S, Nsingle bondH⋯O and Osingle bondH⋯O are observed in 1 and 2, which are reduced to two viz. Nsingle bondH⋯S and Csingle bondH⋯S in 3 and 4. The weak interactions (Nsingle bondH⋯O and Osingle bondH⋯O) originating from lattice water further interlink cations with [MoS4]2− and [WS4]2− anions forming extended networks in 1 and 2. To understand the importance of intermolecular interactions in the structures of 1–4, the Hirshfeld surface analyses were performed. The enrichment ratio (E) in the structures of compounds 1–4 was obtained. Compounds 1–4 were tested for their sulfur transfer ability. Only compound 1 showed a predominant disulfide product formation in reaction with 1,3-dibromopropane.Item Crystal structure, biological and docking studies of solvothermally isolated novel Schiff base(Elsevier, 2023) Vernekar, Beena K.; Kotkar, Gayatri D.; D'souza, Luann R.; Hathwar, Venkatesha R.; Dhuri, Sunder N.Solvothermal condensation of 4-hydroxy-3-methoxy benzaldehyde and ethylenediamine resulted in single crystals of the novel Schiff base N,N'-Bis(4-hydroxyl-3-methoxybenzylidene)ethane-1,2-diamine (H2L) while the conventional method yielded microcrystalline H2L. Single crystals of H2L were characterized by various techniques, including single crystal X-ray diffraction. The structural analysis revealed crystallization of H2L in the monoclinic P21 space group with z = 4 and z′ = 2 indicating the presence of two independent H2L molecules in the asymmetric unit of the crystal structure connected by O6-H6…N2 weak contacts involving H and N atoms of the hydroxyl and amine groups respectively. The biological activities, namely DNA binding and cell viability studies of H2L, were performed. H2L exhibited potent activity against mushroom tyrosinase enzyme. In this work, in-silico docking studies have been conducted to evaluate the effective binding modes of H2L with 2y9x mushroom tyrosinase protein. The docking studies revealed minimum binding energy of -6.43 kcal mol−1 for H2L compared to the value of -3.64 kcal mol−1 for standard Kojic acid. The antibacterial performance of H2L was tested, and the results are presented.Item ESR Spectral Characterisation of Mn doped Zn (II) Trisethylenediamine Sulfidometalate Complexes(Blue Eyes Intelligence Engineering and Sciences Publication, 2019) Vernekar, Beena K.Aqueous reaction of Zn(II) and Mn(II) salts with ammonium tetrasulfidometalate (NH4)2[MS4] (M = Mo, W) in the presence of ammonia or ethane 1,2-diamine (en) or propane 1,2-diamine (1,2-pn) results in the formation of [M'(L)n][MS4] (M’ = Zn or Mn; L = NH3 or en or 1,2-pn). Using this strategy, Mn doped Zn complex of formula [Zn0.99Mn0.01(en)3][MS4], which exhibits characteristic hyperfine ESR spectra have been synthesized. The synthetic aspects, spectral and thermal characterization are described.Item Interaction of metal ions with Schiff bases having N2O2 donor sites: Perspectives on synthesis, structural features, and applications(Elsevier, 2023) Vernekar, Beena K.; Sawant, Pradnya S.Metal Schiff base complexes are versatile platforms for the development of potential catalysts, potent biomaterials, or luminescent compounds. Transition metals possess a diverse array of properties that can be manipulated to yield promising candidates for the future in various industrial applications. Metal Schiff base complexes represent a class of compounds that have become a field of immense interest because of their intriguing chemical and physical properties and their wide range of applications in several scientific fields. The reaction of transition metal elements with a polydentate Schiff base ligand to form metal complexes offers a good platform for combining the chemical, electronic, magnetic, optical, and redox properties of metal complexes with those of the organic materials, generating new functional materials with useful mechanical, catalytic, thermal and chemical, optoelectronic, structural and magnetic properties. The transition metal complexes can often mimic biological sites; they are, therefore, of great interest as enzyme models. This review discusses the structural features of metal complexes of the first series of transition metals with Schiff bases as ligands having N2O2 coordination sites. Further perspectives concerning the synthesis, structural aspects, characterization, and applications are presented.Item Invitro cytotoxicity and DNA interaction studies of nickel(II) mefenamato compounds with substituted α-diimines(Elsevier, 2025) Vernekar, Beena K.; Harmalkar, Nikita N.; Gaonkar, Sanket K.; Barretto, Delicia A.; Maliwal, Deepika; Pissurlenkar, Raghuvir R.; Bhowmik, Pradip K.; Dhuri, Sunder N.Two bioactive nickel(II) compounds of mefenamic acid (Hmef) with substituted α-diimines as co-ligands have been characterised using various spectroscopic methods and evaluated for cytotoxicity, DNA interaction and antioxidant studies, molecular docking and dynamics studies. Single crystal structures of [Ni(Mef-O)2(etobpy)(H2O)] 1 and [Ni(Mef-O)2(dmbpy)(H2O)(DMF)] 2, (etobpy = 4,4′-diethoxy 2,2′-bipyridine, dbmbpy = 4,4′-dimethyl-2,2′-bipyridine and DMF = N, N′-dimethylformamide) have been determined using single crystal X-ray diffraction technique. The mefenamato ligand adopts two types of coordination modes (mono- and bidentate) in 1, while in compound 2 both mef ligands display monodentate behaviour. The Ni(II) ion in both compounds shows a distorted octahedral geometry binding to two N and four O atoms. The cytotoxicity results revealed the activity of 1 and 2 against cancerous HepG2 in a dose-dependent manner. % DPPH free radical scavenging activity of 1 and 2 when performed, they exhibited IC50 values of 17.02±0.85 μM and 19.89±0.73 μM respectively, depicting their antioxidant nature. DNA binding properties of 1 and 2 were assessed by UV absorption spectroscopy, which suggested an intercalating binding between the complexes and the DNA. Both complexes act as potential agents towards DNA cleavage with the dose-dependent rise of Form II and III DNA. Further, Their interactions with DNA were studied using molecular docking and molecular dynamics simulations. Both 1 and 2 are intercalating in the major groove of DNA fragment, destabilizing the double helix strand during simulation, proving as potential candidates for cytotoxicity.Item New diclofenac salts with the dense hydrogen bond donor propane-1,3-diaminium(Royal Society of Chemistry, 2024) Breckell, Jaxon R.; Conte, Luke; Potts, Michael W.; Sawant, Pradnya S.; Butcher, Raymond J.; Vernekar, Beena K.; Richardson, ChristopherA series of solvatomorphic structures of the anti-inflammatory drug diclofenac (dcfn−) and the dense hydrogen bond donor propane-1,3-diaminium (H2pn2+) are reported. Single crystal X-ray diffraction shows each structure contains a dcfn2·H2pn formula unit (1) with solvent of crystallisation [1·2H2O, 1·3H2O, 1·2MeOH, 1·EtOH·2H2O, 1·iPrOH, 1·2DMSO]. The propane-1,3-diaminium molecules evoke extensive networks of hydrogen-bonded interactions with the solvates and the dcfn carboxylate groups. All structures are lamellar with hydrophilic solvate-containing sheets separating hydrophobic layers of aromatic dcfn moieties. Supporting characterisations by powder X-ray diffraction, Fourier transform infrared and 1H NMR spectroscopies, thermal analysis (TG–DSC) and elemental microanalysis were used to reveal the sometimes delicate phase distributions amongst this set of compounds. TG–DSC showed a consistent pattern across the water and alcohol-containing compounds with desolvation occurring before melting to an anhydrous ionic liquid form around 140–150 °C. Heating to approximately 200 °C induces a minor dehydration reaction that covalently links diclofenac and propan-1,3-diaminium molecules via amide bond formation. A mechanochemical synthetic route to 1·3H2O was determined and this compound was selected for study by gravimetric water vapour adsorption. These studies showed the lamellar structure of 1·3H2O displays reversible but imperfect water adsorption between 0% and 50% relative humidity, which is ascribed to some crystal fatigue. This work expands crystal engineering strategies for new and existing active pharmaceutical ingredients to low molecular weight diamines.Item Weakly antiferromagnetic vanillin and acetate bridged dinuclear Ni(II) compound exhibiting catecholase-like activity and biological properties(Royal Society of Chemistry, 2024) Vernekar, Beena K.; Harmalkar, Nikita N.; Gaonkar, Sanket K.; Sannigrahi, Jhuma; Dhuri, Sunder N.A dinuclear nickel compound that features vanillin (van) and acetate (OAc) bridging ligands, [Ni sub(2)(Mu-van) sub(2)(Mu-OAc)(NCS) sub(3)(H sub(2)O)].5H sub(2)O 1, was synthesized and characterized using various techniques. Crystal structure analysis revealed a pair of Ni(II) ions bridged by an acetate anion through a Mu sub(2)-Eta sup(1):Eta sup(1) coordination mode. At the same time, vanillin bridges both nickel(II) centers through phenolic oxygen, separating the two Ni ions by a distance of 3.001(7) angstrom. The temperature-dependent magnetism indicates weak antiferromagnetic behaviour in compound 1, following the Curie-Weiss law with Curie constant C = 1.0145 cm sup(3) K mol sup(-1) and Weiss constant Theta = -4.1 K. Compound 1 was evaluated for its ability to mimic the catechol oxidase enzyme using 3,5-di-tert-butylcatechol as a model substrate with a K sub(cat) value of 157.1 x 102 h sup(-1). Furthermore, compound 1 was tested for its cytotoxicity against HepG2 cancer cells and DNA cleavage properties.