Browsing by Author "Chote Lal Yadav"

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Anti-leishmanial study of discrete tetrahedral zinc(ii) β-oxodithioester complexes
(Royal Society of Chemistry, 2024) Chote Lal Yadav; None Anamika; Rajan Singh; Akhilesh Kumar; Rakesh K. Singh; Michael G. B. Drew; Krishna K. Manar; Nanhai Singh
We have synthesized four new oxygen/sulfur(O^S) chelate complexes, [Zn(L)2], where L represents different ligands: methyl-3-hydroxy-3-(furyl)-2-propenedithioate (L1, 1), methyl-3-hydroxy-3-(p-fluorophenyl)-2-propenedithioate (L2, 2), methyl-3-hydroxy-3-(p-chlorophenyl)-2-propenedithioate (L3, 3), and methyl-3-hydroxy-3-(p-bromophenyl)-2-propenedithioate (L4, 4). These complexes have been characterized by using IR, multinuclear NMR (1H, 13C{1H}, and 19F{1H}), and UV-vis spectroscopy. The structural characterization of complexes 1, 2, and 4 was further achieved by single crystal X-ray diffraction (SCXRD). The supramolecular structures of these complexes are stabilized by non-covalent C-H⋯π (ZnOSC3, chelate), C-S⋯π (ZnOSC3, chelate), π⋯π (ZnOSC3,), C-H⋯O, C-H⋯F-C and C-H⋯H-C interactions. The luminescence properties of Zn(ii) complexes 1-4 were studied at room temperature in the solid phase. The antileishmanial activity was evaluated for all complexes. Complexes 1 and 4 exhibited significant anti-promastigote and anti-amastigote activities, with IC50 values of 2.0 and 1.33 μg mL−1, and 2.79 and 2.02 μg mL−1, respectively. Additionally, cytotoxicity assays demonstrated that these Zn(ii) β-oxodithioester complexes were toxic to promastigotes, but showed reduced toxicity towards RAW 264.7 cell lines at varying concentrations. Furthermore, the optical band gap energies of complexes 1-4 were measured and found to exhibit semiconducting behavior. © 2025 The Royal Society of Chemistry.
Catalytic activity of new heteroleptic [Cu(PPh3)2(β-oxodithioester)] complexes: Click derived triazolyl glycoconjugates
(Royal Society of Chemistry, 2019) Kavita Kumari; Anoop S. Singh; Krishna K. Manar; Chote Lal Yadav; Vinod K. Tiwari; Michael G.B. Drew; Nanhai Singh
A series of four new and two known luminescent heteroleptic Cu(i) complexes of the form [Cu(PPh3)2(β-oxodithioester)] (β-oxodithioester = methyl-3-hydroxy-3-(2-furyl)-2-propenedithioate L1 1, methyl-3-hydroxy-3-(2-thienyl)-2-propenedithioate L2 2, methyl-3-hydroxy-3-(4-methoxyphenyl)-2-propenedithioate L3 3, methyl-3-hydroxy-3-(4-bromophenyl)-2-propenedithioate L4 4, methyl-3-hydroxy-3-benzyl-2-propenedithioate L5 5 and methyl-3-hydroxy-3-(3-pyridyl)-2-propenedithioate, L6 6) have been synthesized and characterized by elemental (C, H, N) analysis, and IR, UV-visible, 1H, 13C{1H}, and 31P{1H} NMR spectroscopy and their structures have been ascertained by X-ray crystallography. These complexes were exploited as catalysts for azide-alkyne cycloaddition reactions (click chemistry) for the synthesis of triazolyl glycoconjugates, where they displayed efficient catalytic activity at room temperature. Optimization of the reaction conditions and formation of regioselective products in high yields in the absence of a base/additive are concomitant with the click protocol. The substrate scope was successfully extended by varying the types of sugar azides and alkyne scaffolds, affording the corresponding triazole products in excellent yields at low catalyst loadings (1 mol%). Furthermore, catalyst 1 showed excellent recyclability and was reused for five cycles with little decrease in efficiency. © 2019 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Cooperative metal-ligand influence on the formation of coordination polymers, and conducting and photophysical properties of Tl(i) β-oxodithioester complexes
(Royal Society of Chemistry, 2018) Chote Lal Yadav; Gunjan Rajput; Krishna K. Manar; Kavita Kumari; Michael G. B. Drew; Nanhai Singh
Eight novel Tl(i) β-oxodithioester complexes, [TlL]n (1-8), with ligands, L = methyl-3-hydroxy-3-(2-furyl)-2-propenedithioate (L1), methyl-3-hydroxy-3-(2-thienyl)-2-propenedithioate (L2), methyl-3-hydroxy-3-(3-pyridyl)-2-propenedithioate (L3), methyl-3-hydroxy-3-(4-pyridyl)-2-propenedithioate (L4), methyl-3-hydroxy-3-(9-anthracenyl)-2-propenedithioate (L5), methyl-3-hydroxy-3-(4-fluorophenyl)-2-propenedithioate (L6), methyl-3-hydroxy-3-(4-chlorophenyl)-2-propenedithioate (L7) and methyl-3-hydroxy-3-(4-bromophenyl)-2-propenedithioate (L8), were synthesized and thoroughly characterized by elemental analysis, and IR, UV-Vis, 1H and 13C{1H} NMR spectroscopy, and their structures were ascertained by X-ray crystallography. Complexes 1 and 2 crystallized in P21 and P212121 chiral space groups, respectively, and were studied using Circular Dichroism (CD) spectra. Solid state structural analyses revealed that the β-oxodithioester ligands are bonded to Tl(i) ions in (O, S) chelating and chelating-bridging modes, thereby forming different types of 1D and 2D coordination polymeric structures. By considering the metal-assisted bonding interactions, various coordination numbers of 5-8 and 10 are established around the metal centre. Except for 5 and 7a which have Tl...Tl separations at 3.724(1) and 3.767(1), 3.891(1) Å respectively, the remaining complexes have no Tl...Tl distances <4.0 Å. This indicates that the majority of structures contain only weak inter- and intramolecular thallophilic interactions. The structures of 1-8 highlight the role played by variations in substituents in the dithioester unit in the structure and properties of the complexes. The multi-dimensional assembly in these complexes rests on important non-covalent C-H...π (TlOSC3, chelate), C-H...X (X = F, Cl, O, N), C-H...π, H...H and rare Tl...H-C intermolecular anagostic interactions. The Tl...H-C anagostic interactions together with C-O...Tl and C-S...Tl interactions formed 7-, 11- and 12-membered chelate rings about the metal centers. The anagostic interactions in 1, 2 and 7b were assessed by theoretical calculations. All the complexes showed bright green luminescent emissions in solution and solid phases. Time-resolved emission spectra revealed a triexponential decay curve and short mean lifetime for fluorescence behavior. © The Royal Society of Chemistry.
Effect of Substituents on the Crystal Structures, Optical Properties, and Catalytic Activity of Homoleptic Zn(II) and Cd(II) β-oxodithioester Complexes
(American Chemical Society, 2020) Chote Lal Yadav; Anamika; Gunjan Rajput; Kamlesh Kumar; Michael G. B. Drew; Nanhai Singh
Five novel zinc(II) and cadmium(II) β-oxodithioester complexes, [Zn(L1)2] (1), [Zn(L2)2]n (2), [Zn(L3)2]n (3) [Cd(L1)2]n (4), [Cd(L2)2]n (5), with β-oxodithioester ligands, where L1 = 3-(methylthio)-1-(thiophen-2-yl)-3-thioxoprop-1-en-1-olate, L2 = 3-(methylthio)-1-(pyridin-3-yl)-3-thioxoprop-1-en-1-olate, and L3 = 3-(methylthio)-1-(pyridin-4-yl)-3-thioxoprop-1-en-1-olate, were synthesized and characterized by elemental analysis, IR, UV-vis, and NMR spectroscopy (1H and 13C{1H}). The solid-state structures of all complexes were ascertained by single-crystal X-ray crystallography. The β-oxodithioester ligands are bonded to Zn(II)/Cd(II) metal ions in an OΓS and N chelating/chelating-bridging fashion leading to the formation of 1D (in 2-4) and 2D (in 5) coordination polymeric structures, but complex 1 was obtained as a discrete tetrahedral molecule. Complex 4 crystallizes in the C2 chiral space group and has been studied using circular dichroism (CD) spectroscopy. The multidimensional assemblies in these complexes are stabilized by many important noncovalent C-H···π(ZnOSC3, chelate), π···π, C-H···π, and H···H interactions. The catalytic activities of 1-5 in reactions involving C-C and C-O bond formation have been studied, and the results indicated that complex 3 can be efficiently utilized as a heterogeneous bifunctional catalyst for the Knoevenagel condensation and multicomponent reactions to develop biologically important organic molecules. The luminescent properties of complexes were also studied. Interestingly, zinc complexes 1-3 showed strong lumniscent emission in the solid state, whereas cadmium complexes 4 and 5 exhibited bright luminescent emission in the solution phase. The semiconducting behavior of the complexes was studied by solid-state diffuse reflectance spectra (DRS), which showed optical band gaps in the range of 2.49-2.62 eV. © 2020 American Chemical Society.
Ferrocene-Functionalized Dithiocarbamate Zinc(II) Complexes as Efficient Bifunctional Catalysts for the One-Pot Synthesis of Chromene and Imidazopyrimidine Derivatives via Knoevenagel Condensation Reaction
(American Chemical Society, 2021) Anamika; Chote Lal Yadav; Michael G. B. Drew; Kamlesh Kumar; Nanhai Singh
Four new mononuclear/coordination polymeric (CP) zinc(II) complexes (1-4) of ferrocenyl/pyridyl-functionalized dithiocarbamate ligands, N-ferrocenylmethyl-N-butyl dithiocarbamate (L1), N-ferrocenylmethyl-N-ethylmorpholine dithiocarbamate (L2), N-ferrocenylmethyl-N-2-(diethylamino)ethylamine dithiocarbamate (L3), and N-4-methoxybenzyl-N-3-methylpyridyl dithiocarbamate (L4), have been synthesized and characterized by elemental analyses, IR, UV-vis, and 1H and 13C{1H} NMR spectroscopic techniques. The solid-state structures of complexes 1, 3, and 4 have been determined by single-crystal X-ray crystallography as well as powder X-ray diffraction. Single-crystal X-ray crystallography revealed a monomeric structure for complex 1 but 1D polymeric structures for complexes 3 and 4. In all complexes, dithiocarbamate ligands are bonded to the Zn(II) metal ion in a S^S chelating mode, and in the CPs, N atoms on the 2-(diethylamino)ethylamine and 3-pyridyl functionalities in the ligands on the neighboring molecules are also bonded to metal centers, leading to the formation of either a discrete tetrahedral molecule in 1 or 1D CP structures in 3 and 4. The Zn(II) metal centers in the polymeric structures exhibited either square-pyramidal or octahedral geometries. The supramolecular structures in these complexes are sustained via C-H···π(ZnCS2, chelate; 3 and 4), C-H···π, and H···H interactions. The catalytic performances of complexes have also been assessed in the Knoevenagel condensation and one-pot multicomponent reactions. Catalysis results showed that the CP 3 acts as a heterogeneous bifunctional catalyst with excellent transformation efficiency at low catalyst loading. ©
Highly efficient and recyclable pre-catalysts based on mono- and dinuclear heteroleptic Cu(I) dithio- PPh3 complexes to produce variety of glycoconjugate triazoles
(Elsevier B.V., 2019) Avadhesh K. Singh; Chote Lal Yadav; Kunj Bihari Mishra; Santosh K. Singh; Ajit N. Gupta; Vinod Kumar Tiwari; Michael G.B. Drew; Nanhai Singh
Highly efficient and reusable pre-formed mono- and dinuclear heteroleptic copper(I) dithiocarbamate and dithiocarbimate complex based catalysts, [Cu(PPh3)2(L)] and [Cu2(PPh3)4(L)] (L = N-(4-methylpyridyl)-N-(3-methylpyridyl)dithiocarbamate− L1 1, N-methylfuryl-N-methylthiophenedithiocarbamate- L2 2; 4-chlorobenzenesulfonyl dithiocarbimate2- L3 3, 4-bromobenzenesulfonyldithiocarbimate2- L4 4) have been utilized in the cycloaddition reactions of azide and alkyne to form a variety of glycoconjugate triazoles in Click chemistry. These new pre-catalysts have been characterized by elemental (C, H, N) analysis, IR, UV–vis., 1H, 13C{1H}, and 31P{1H} NMR spectroscopy and their structures have been revealed by X-ray crystallography. In the structures of (1,2)/(3,4) the copper atoms are situated within a four coordinate (P2S2)/(P2NS) distorted tetrahedral geometry. Notably in the dinuclear complexes 3 and 4, the dithiocarbimate ligands are bonded in a S, S- chelating mode to one copper atom and simultaneously bridge the other copper centre via N, S- donor atoms. 1-4 are strongly luminescent in CH2Cl2 solution at room temperature. © 2019 Elsevier B.V.
Highly efficient structurally characterised novel precatalysts: Di- and mononuclear heteroleptic Cu(i) dixanthate/xanthate-phosphine complexes for azide-alkyne cycloadditions
(Royal Society of Chemistry, 2019) Anamika; Anand K. Agrahari; Krishna K. Manar; Chote Lal Yadav; Vinod K. Tiwari; Michael G. B. Drew; Nanhai Singh
Novel heteroleptic dinuclear [Cu2(L)(PPh3)4] (L = 2,6-pyridinedimethyldixanthate L1 1, 1,4-benznedimethyldixanthate L2 2, 1,4-cyclohexanedixanthate L3 3) and mononuclear [Cu(L4)(PPh3)2] 4 (L4 = piperonylxanthate) and [Cu(L5)(dppf)] 5 (L5 = methylxanthate, dppf = 1,1′-bis(diphenylphosphino)ferrocene) complexes have been synthesised and characterised by elemental (C, H, and N) analysis, high resolution mass spectrometry, and IR, UV-vis, 1H, 13C{1H} and 31P{1H} NMR spectroscopy. Single crystal X-ray diffraction revealed S,S-bifunctional coordination of the dixanthate group in dinuclear complexes 1-3 while 4 and 5 are mononuclear. Complexes 1-5 adopt tetrahedral coordination geometry about the copper atom. These precatalysts having two and one copper(i) centres in a single molecule have been applied in copper catalysed azide-alkyne cycloaddition (CuAAC) reactions for the synthesis of a variety of glycoconjugate triazoles using the Click approach. Particularly the dinuclear catalyst 1, formed on the pyridyl linker based dixanthate ligand, displayed outstanding and reusable catalytic activity for this reaction. Full optimization of the reaction conditions demonstrated a noteworthy Click catalytic system with low catalyst loading under mild reaction conditions. © 2019 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Homoleptic Ni(ii) dithiocarbamate complexes as pre-catalysts for the electrocatalytic oxygen evolution reaction
(Royal Society of Chemistry, 2022) Sarvesh Kumar Pal; Baghendra Singh; Jitendra Kumar Yadav; Chote Lal Yadav; Michael G. B. Drew; Nanhai Singh; Arindam Indra; Kamlesh Kumar
Four new functionalized Ni(ii) dithiocarbamate complexes of the formula [Ni(Lx)2] (1-4) (L1 = N-methylthiophene-N-3-pyridylmethyl dithiocarbamate, L2 = N-methylthiophene-N-4-pyridylmethyl dithiocarbamate, L3 = N-benzyl-N-3-pyridylmethyl dithiocarbamate, and L4 = N-benzyl-N-4-pyridylmethyl dithiocarbamate) have been synthesized and characterized by IR, UV-vis, and 1H and 13C{1H} NMR spectroscopic techniques. The solid-state structure of complex 1 has also been determined by single crystal X-ray crystallography. Single crystal X-ray analysis revealed a monomeric centrosymmetric structure for complex 1 in which two dithiocarbamate ligands are bonded to the Ni(ii) metal ion in a S^S chelating mode resulting in a square planar geometry around the nickel center. These complexes are immobilized on activated carbon cloth (CC) and their electrocatalytic performances for the oxygen evolution reaction (OER) have been investigated in aqueous alkaline solution. All the complexes act as pre-catalysts for the OER and undergo electrochemical anodic activation to form Ni(O)OH active catalysts. Spectroscopic and electrochemical characterization revealed the existence of the interface of molecular complex/Ni(O)OH, which acts as the real catalyst for the OER. The active catalyst obtained from complex 2 showed the best OER activity achieving 10 mA cm−2 current density at an overpotential of 330 mV in 1.0 M aqueous KOH solution. © 2022 The Royal Society of Chemistry.
Impact of substituents on the crystal structures and anti-leishmanial activity of new homoleptic Bi(iii) dithiocarbamates
(Royal Society of Chemistry, 2019) Anamika; Rajan Singh; Krishna K. Manar; Chote Lal Yadav; Akhilesh Kumar; Rakesh K. Singh; Michael. G. B. Drew; Nanhai Singh
Six new functionalised homoleptic Bi(iii) dithiocarbamate complexes, [Bi(L1-L6)3] (L1 = (N-4-nitrobenzyl-N-furfuryl)dithiocarbamate 1, L2 = (N-4-chlorobenzyl-N-3-methylpyridyl)dithiocarbamate 2, L3 = (N-4-bromobenzyl-N-3-methylpyridyl)dithiocarbamate 3, L4 = (N-4-dimethylaminobenzyl-N-3-methylpyridyl)dithiocarbamate 4, L5 = (1-(2-pyridyl)piperazine)dithiocarbamate 5 and L6 = (N-4-methoxybenzyl-N-benzyl)dithiocarbamate 6), have been prepared and characterised by elemental analyses, powder X-ray diffraction (PXRD) and (IR, UV-Vis, 1H and 13C{1H} NMR) spectroscopy. The structures of the six complexes have been revealed in the solid state by X-ray crystallography and assessed by DFT calculations. Complexes 1 and (2, 5 and 6) are similarly dimeric in which the three dithiocarbamate ligands are bound to the seven and eight-coordinate Bi(iii) centre, respectively, in asymmetric S,S-bidentate and μ2,κ2 S,S-chelating/chelating-bridging modes. By contrast, complex 4 is monomeric with a six-co-ordinate metal atom while complex 3 forms a polymeric structure with the metal in a seven-coordinate environment. The specific geometries of all compounds are distorted by the stereochemical lone pair. In these complexes, supramolecular structures have been sustained by non-covalent C-H⋯N, C-H⋯O, C-H⋯Cl, C-H⋯Br, C-H⋯π, C-H⋯π (BiCS2, chelate) and H⋯H interactions. The anti-leishmanial activities of the complexes have been tested; 5 and 6 showed potential anti-promastigote activity with IC50 values of 7.16 and 7.44 μM, and anti-amastigote activity with IC50 values of 8.40 and 9.70 μM, respectively. Cytotoxicity assays for complexes 1-6 showed toxicity on promastigotes but lower toxicity against the RAW 264.7 cell line at different concentrations. © 2019 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
New heteroleptic [Ni(ii) 1,1-dithiolate-phosphine] complexes: Synthesis, characterization and electrocatalytic oxygen evolution studies
(Royal Society of Chemistry, 2020) Anamika; Dharmendra Kumar Yadav; Krishna K. Manar; Chote Lal Yadav; Kamlesh Kumar; Vellaichamy Ganesan; Michael G. B. Drew; Nanhai Singh
Four new heteroleptic Ni(ii) complexes with general formula [Ni(ii)(LL′)] (L = 2-(methylene-1,1′-dithiolato)-5-phenylcyclohexane-1,3-dione (L1) and 2-(methylene-1,1′-dithiolato)-5,5′-dimethylcyclohexane-1,3-dione (L2); L′ = 1,2-bis(diphenylphosphino)ethane (dppe) and bis(diphenylphosphino)monosulphide methane (dppms) have been synthesized and characterized by elemental analysis and spectroscopy (IR, UV-Vis, 1H, 13C{1H} and 31P{1H} NMR). All complexes 1-4 have also been characterized by PXRD and single crystal X-ray crystallography. The solid state molecular structures revealed distorted square planar geometry about the four-coordinate Ni(ii) metal centre together with rare Ni⋯H-C intra/intermolecular anagostic interactions in axial positions. In these complexes supramolecular structures have been sustained by non-covalent C-H⋯O, C-O⋯H-O, C-H⋯π, C-H⋯π (NiCS2, chelate), π⋯π and H⋯H interactions. Their electrocatalytic properties have been investigated for oxygen evolution reaction (OER) in which complex 2 showed the highest activity with 10 mA cm-2 at the potential of 1.58 V vs. RHE. In addition, complex 2 also exhibits an OER onset potential at 1.52 V vs. RHE. This journal is © The Royal Society of Chemistry.
Ni(ii)-Dithiocarbamate and -diphosphine coordination complexes as pre-catalysts for electrochemical OER activity
(Royal Society of Chemistry, 2024) Sarvesh Kumar Pal; Toufik Ansari; Chote Lal Yadav; Nanhai Singh; Prem Lama; Arindam Indra; Kamlesh Kumar
Electrochemical water oxidation holds immense potential for sustainable energy generation, splitting water into clean-burning hydrogen and life-giving oxygen. However, a key roadblock lies in the sluggish nature of the oxygen evolution reaction (OER). Finding stable, cost-effective, and environmentally friendly catalysts with high OER efficiency is crucial to unlock this technology's full potential. Here, we have synthesized four new cationic heteroleptic Ni(ii) complexes having the formula [Ni(S^S)(P^P)]PF6 (1-4) where S^S represents bidentate dithiocarbamate ligands (N,N-bis(benzyl)dithiocarbamate and N-benzyl-N-3-picolyldithiocarbamate) and P^P represents diphosphine ligands (1,2-bis(diphenylphosphino)ethane (dppe) and 1,1-bis(diphenylphosphino)ferrocene (dppf)). The complexes were characterized by UV-Vis, FT-IR, and multinuclear NMR spectroscopic techniques. Single crystal X-ray structures of all complexes are also reported. The molecular structures showed a distorted square planar geometry around the Ni(ii) center defined by a bidentate S^S dithiolate chelating ligand and a P^P diphosphine chelating ligand. Interestingly, the complexes exhibit weak non-covalent interactions, contributing to the overall supramolecular structures. The role of complexes in water oxidation has been investigated electrochemically in a 1.0 M KOH solution after immobilization onto the surface of activated carbon cloth (CC). Detailed analyses revealed that the complexes are promising precatalysts for generating active Ni(OH)2/NiO(OH) as a true oxygen evolution reaction (OER) catalyst at CC upon anodic activation. Notably, the catalyst derived from complex 4@CC exhibited the highest OER activity with a Tafel slope of 93 mV per decade and reaching a current density of 10 mA cm−2 at a low overpotential of 250 mV in a 1.0 M KOH solution. This study reveals the significance of dithiocarbamate and diphosphine ligands in facilitating the conversion of Ni(ii) complexes into highly active OER catalysts. © 2025 The Royal Society of Chemistry.
Spontaneous Resolution upon Crystallization and Preferential Induction of Chirality in a Discrete Tetrahedral Zinc(II) Complex Comprised of Achiral Precursors
(American Chemical Society, 2019) Chote Lal Yadav; Gunjan Rajput; Kamal Kumar Bisht; Michael G. B. Drew; Nanhai Singh
A pair of enantiomeric tetrahedral complexes (λ-[Zn(L)2] and Δ-[Zn(L)2]) comprised of the achiral ligand methyl-3-hydroxy-3-phenyl-2-propenedithioate (L) have been synthesized by spontaneous resolution. Two chiral inducers, viz., d-(-)- and l-(+)-tartaric and mandelic acids, have been employed to achieve bulk homochirality and extend the generality of the present work. The work highlights the achievement of bulk homochirality using readily available chiral inducers in the synthesis of a spontaneously resolving chiral tetrahedral zinc(II) complex using achiral starting materials. These findings are established by 30 sets of single-crystal X-ray diffraction data with refined Flack parameters and circular dichroism spectroscopy. © 2019 American Chemical Society.