Mahesh K. Singh

Synthesis and characterization of manganese(IV) and ruthenium(III) complexes derived from bis (2-hydroxy-1-naphthaldehyde)oxaloyldihydrazone

Bis(2-hydroxy-1-naphthaldehyde)oxaloyldihydrazone(naohH4) interacts with manganese(II) acetate in methanol followed by addition of KOH giving [MnIV(naoh)(H2O)2]. Activated ruthenium(III) chloride reacts with naohH4 in methanol yielding [RuIII(naohH4)Cl(H2O)Cl2]. The replacement of aquo by heterocyclic nitrogen donor in these complexes has been observed when the reaction is carried out in presence of heterocyclic nitrogen donors such as pyridine(py), 3-picoline(3-pic) or 4-picoline(4-pic). The molar conductance values in DMF for these complexes suggest non-electrolytic nature. Magnetic moment values suggest +4 oxidation state for manganese in its complexes, however, ruthenium(III) complexes are paramagnetic with one unpaired electron. Electronic spectral studies suggest six coordinate metal ions. IR spectra reveal that naohH4 coordinates in enol-form and keto-form to manganese and ruthenium, respectively. ESR and cyclic voltammetric studies of the complexes have also been reported.

Synthesis and spectral studies on heterobimetallic complexes of manganese and ruthenium derived from N-(2-hydroxynaphthalen-1-yl)methylenebenzoylhydrazide

The complex [MnIV(napbh)2] (napbhH2 = N-(2-hydroxynaphthalen-1-yl)methylenebenzoylhydrazide) reacts with activated ruthenium(III) chloride in methanol in 1 : 1.2 molar ratio under reflux, giving heterobimetallic complexes, [MnIV(napbh)2RuIIICl3(H2O)] · [RuIII(napbhH)Cl2(H2O)] reacts with Mn(OAc)2·4H2O in methanol in 1 : 1.2 molar ratio under reflux to give [RuIII(napbhH)Cl2(H2O)MnII(OAc)2]. Replacement of aquo in these heterobimetallic complexes has been observed when the reactions are carried out in the presence of pyridine (py), 3-picoline (3-pic), or 4-picoline (4-pic). The molar conductances for these complexes in DMF indicates 1 : 1 electrolytes. Magnetic moment values suggest that these heterobimetallic complexes contain MnIV and RuIII or RuIII and MnII in the same structural unit. Electronic spectral studies suggest six coordinate metal ions. IR spectra reveal that the napbhH2 ligand coordinates in its enol form to MnIV and bridges to RuIII and in the keto form to RuIII and bridging to MnII.

Synthesis and structural characterization of manganese(III, IV) and ruthenium(III) complexes derived from 2-hydroxy-1-naphthaldehydebenzoylhydrazone

Reaction of 2-hydroxy-1-naphthaldehydebenzoylhydrazone(napbhH2) with manganese(II) acetate tetrahydrate and manganese(III) acetate dihydrate in methanol followed by addition of methanolic KOH in molar ratio (2 : 1 : 10) results in [Mn(IV)(napbh)2] and [Mn(III)(napbh)(OH)(H2O)], respectively. Activated ruthenium(III) chloride reacts with napbhH2 in methanolic medium yielding [Ru(III)(napbhH)Cl(H2O)]Cl. Replacement of aquo ligand by heterocyclic nitrogen donor in this complex has been observed when the reaction is carried out in presence of pyridine(py), 3-picoline(3-pic) or 4-picoline(4-pic). The molar conductance values in DMF (N,N-dimethyl formamide) of these complexes suggest non-electrolytic and 1 : 1 electrolytic nature for manganese and ruthenium complexes, respectively. Magnetic moment values of manganese complexes suggest Mn(III) and Mn(IV), however, ruthenium complexes are paramagnetic with one unpaired electron suggesting Ru(III). Electronic spectral studies suggest six coordinate metal ions in these complexes. IR spectra reveal that napbhH2 coordinates in enol-form and keto-form to manganese and ruthenium metal ions in its complexes, respectively. ESR studies of the complexes are also reported.

Synthesis and Spectral Characterization of Dioxouranium(VI) Complexes of Disalicylaldehyde Adipoyldihydrazone

Abstract The complexes [(UO2)2(saladph)(H2O)4].2H2O (1), [(UO2)2 (saladphH)-(CH3COO)2(H2O)2].6H2O (2), [(UO2)3 (saladph) (CH3COO)2(H2O)2].4H2O (3) [(UO2)3 (saladphH2)(CH3COO)2(C2H5OH)2]3.3C2H5OH (4) and [(UO2)2 (saladph) (PY)2 (H2O)2].xH2O (where pY = pyridine, or, α-, β-or γ-picoline, × = 0, 1) (5–8) have been synthesized by the reaction of uranyl acetate dihydrate with disalicylaldehyde adipoyldihydrazone (saladphH4) in water or ethanol. The complexes have been characterized by physicochemical data, IR, 1H NMR and electronic spectral studies. It is suggested that the complexes involve 6, 7, 8 and 9-coordinated uranium atoms.

Six-coordinate cadmium(II) complex containing a bridging dithiolate ligand: synthesis, crystal structure and antifungal activity study

Abstract A mixed-ligand polymeric metal complex of Cd(II) has been prepared by reactions of Cd(NO3)2·4H2O with 1,3-diaminopropane (tn) and potassium salt of 1,1-dicyanoethylene-2,2-dithiolate and characterized on the basis of spectroscopy and single-crystal X-ray diffraction analysis. Single-crystal X-ray diffraction analysis reveals that the Cd(II) complex crystallizes in monoclinic space group P21/n with distorted octahedral coordination geometry. The Cd(II) complex was screened in vitro against fungal pathogens such as Synchytrium endobioticum, Pyricularia oryzae, Helminthosporium oryzae, Candida albicans (ATCC10231), and Trichophyton mentagrophytes by the disk diffusion method. The biological testing data of the primary ligand K2i-MNT·H2O and [Cd(tn)(i-MNT)]n indicate that the complex exhibits fungistatic antifungal activity, whereas K2i-MNT·H2O has no activity. The fungicidal properties of [Cd(tn)(i-MNT)]n showed that the cadmium complex was more bioactive than the parent ligand.

Cd(II) complexation with 1,1-dithiolate and nitrogen donors: synthesis, luminescence, crystal structure, and antifungal activity study

A new luminescent complex of Cd(II) with 1,1-dicyanoethylene-2,2-dithiolate [i-MNT2− = {S2C : C(CN)2}2−] with 1,3-diaminopropane (tn) and 4-methyl pyridine (γ-picoline) as secondary ligands has been synthesized and characterized on the basis of spectroscopy and single-crystal X-ray diffraction analysis. Single-crystal X-ray diffraction analysis reveals that cadmium(II) is five coordinate in a 1-D polymer. Biological screening effects in vitro of the synthesized complex has been tested against five fungi Synchytrium endobioticum, Pyricularia oryzae, Helminthosporium oryzae, Candida albicans (ATCC10231), and Trichophyton mentagrophytes by the disk diffusion method. A comparative study of inhibition zone values of K2i-MNT·H2O and {[Cd(tn)(iMNT)(4-MePy)]·4H2O}n (1) indicates that the complex exhibits antifungal activity, whereas K2i-MNT·H2O became silent on S. endobioticum, P. oryzae, H. oryzae, C. albicans (ATCC10231), and T. mentagrophytes. Graphical abstract A new luminescent complex of Cd(II) with 1,1-dicyanoethylene-2,2-dithiolate [i-MNT2− = {S2C:C(CN)2}2−] has been synthesized and characterized on the basis of spectroscopy and single-crystal X-ray diffraction analysis. Single-crystal X-ray diffraction analysis reveals that the cadmium(II) complex is five coordinate in a 1-D polymer. Biological screening in vitro of the complex has been tested against five fungi Synchytrium endobioticum, Pyricularia oryzae, Helminthosporium oryzae, Candida albicans (ATCC10231), and Trichophyton mentagrophytes by the disk diffusion method. The antifungal activity of the complex of Cd(II) is significant compared to K2iMNT on S. endobioticum, P. oryzae, H. oryzae, and T. mentagrophytes and proved to be crucial for the growth-inhibitor effect.

Synthesis and characterization of mixed ligand complexes of cobalt(II) with some nitrogen and sulfur donors

Mixed ligand complexes of Co(II) with nitrogen and sulfur donors, Co(OPD)(S–S) · 2H2O and Co(OPD)(S–S)L2 [OPD = o-phenylenediamine; S–S = 1,1-dicyanoethylene-2,2-dithiolate (i-MNT2−) or 1-cyano-1-carboethoxyethylene-2,2-dithiolate (CED2−); L = pyridine (py), α-picoline (α-pic), β-picoline (β-pic), or γ-picoline (γ-pic)], have been isolated and characterized by analytical data, molar conductance, magnetic susceptibility, electronic, and infrared spectral studies. The molar conductance data reveal non-electrolytes in DMF. Magnetic moment values suggest low-spin and high-spin complexes. The electronic spectral studies suggest distorted octahedral stereochemistry around Co(II) in these complexes. Infrared spectral studies suggest bidentate chelating behavior of i-MNT2−, CED2−, or OPD while other ligands are unidentate in their complexes.

Synthesis, crystal structure, and antifungal activity of a newly synthesized polymeric mixed ligand complex of Zn(II) with 1,1-dithiolate and nitrogen donors

A new mixed ligand complex of Zn(II) with 1,1-dicyanoethylene-2,2-dithiolate [i-MNT2− = {S2C:C(CN)2}2−] and 1,3-diaminopropane as ligands has been synthesized and characterized on the basis of spectroscopy and single-crystal X-ray diffraction analysis. Spectroscopic studies and single-crystal X-ray diffraction analysis reveal that the zinc(II) complex is tetrahedral and adopts a 1,3-diaminopropane-assisted linear polymeric assembly. The molar conductance data of the complex in DMF solution show non-electrolytic nature. Biological screening effects of the complex in vitro have been tested against five fungi Synchitrium endobioticum, Pyricularia oryzae, Helminthosporium oryzae, Candida albicans (ATCC10231), and Trichophyton mentagrophytes by the disk diffusion method. A comparative study of inhibition zone values of the primary ligand K2i-MNT·H2O and its synthesized complex indicates that the complex exhibits a fungistatic antifungal activity whereas K2i-MNT·H2O does not affect P. oryzae. Graphical Abstract Complex of Zn(II) with 1,1-dicyanoethylene-2,2-dithiolate [i-MNT2− = {S2C:C(CN)2}2−] and 1,3-diaminopropane.