Browsing by Author "Harmalkar, Nikita N."

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    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.
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    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.