N.K. Singh

Ni(II) and Co(III) complexes of 5-methyl-1,3,4-thiadiazole-2-thiol: syntheses, spectral, structural, thermal analysis, and DFT calculation

Two new complexes, [Ni(en)2(mtt)2] (1) and [Co(en)2(mtt)2](mtt) (2) (Hmtt = 5-methyl-1,3,4-thiadiazole-2-thiol and en = ethylenediamine), have been synthesized and characterized by various physicochemical techniques. Complexes 1 and 2 crystallize in monoclinic and orthorhombic system with space groups P 21/n and P 21 21 21, respectively. The molecular structures of 1 and 2 show that the metal ions are six-coordinate bonded through four equatorial nitrogens of two en and two axial nitrogens of mtt ligands. The crystal structures of the complexes reveal that mtt is present in thione form and bound to the metal ion through the thiadiazole nitrogen. The crystal structures of the complexes are stabilized by various intermolecular hydrogen bonding providing supramolecular architecture. Complex 2 is also stabilized by weak π···π interactions occurring between two thiadiazole rings. The bioefficacies of the ligand and complexes have been examined against the growth of bacteria to evaluate their antimicrobial potential. The biological results suggest that 2 is more active than the ligand and 1 against the tested bacteria. The geometries of the ligand and the complexes have been optimized by the DFT method and the results are compared with the X-ray diffraction data. The Co(III) complex exhibits an irreversible Co(III)/Co(II) process while the Ni(II) complex displays quasi-reversible Ni(II)/Ni(III) redox processes with large peak separation as compared to that expected for a one electron process which is thought to be coupled with some chemical reaction. Graphical abstract

NNS tridentate thiosemicarbazide and 1,3,4-thiadiazole-2-amine complexes of some transition metal ions: syntheses, structure and fluorescence properties

Abstract The reactions of Zn(II), Mn(II), and Ni(II) acetates with 1-picolinoyl-4-phenyl-3-thiosemicarbazide (Hppts) yielded [Zn(ppts)2]·CHCl3 (3), [Mn(ppts)2]·THF (4), and [Ni(ppts)2]·THF (5), respectively, but HgCl2 gave a cyclized product N-phenyl-5-(pyridin-2-yl)-1,3,4-oxadiazole-2-yl-amine (2). The treatment of Hppts with conc. H2SO4 formed N-phenyl-5-(pyridin-2-yl)-1,3,4-thiadiazole-2-yl-amine (1). Hppts is a nonfluorescent material, but 3, 4 and the cyclized products 1,3,4-oxadiazole/1,3,4-thiadiazole are fluorescent. The cyclized ligand N-phenyl-5-(pyridin-2-yl)-1,3,4-thiadiazole-2-amine (1) formed [Zn(2-Hppt)2(OAc)2] (6) and [Cd2(2-Hppt)2(OAc)2(μ-OAc)2] (7) in which Cd(II) has a binuclear acetate-bridged seven coordinate pentagonal bipyramidal geometry. Complex 7 is also a fluorescent material with maximum emission at 425 nm at an excitation wavelength of 254 nm.

Formation and spectroscopic characterization of heterobimetallic complexes containing six-coordinate iron(IV) or manganese(IV) complex anion of 1,1-dicarboethoxy-2,2-ethylene dithiolate and octahedrally coordinated complex cations of iron(II), cobalt(II), nickel(II) or zinc(II) with 1,10-phenanthroline

Abstract Novel heterobinuclear complexes ([M(o-phen)3][M′(DED)3] [M = FeII, CoII, NiII or ZnII; M′ = MnIV or FeIV; o-phen = 1,10-phenanthroline; DED = 1,1-dicarboethoxy- 2,2-ethylene dithiolate) have been prepared and characterized. The precursor complex anion [Fe(DED)3]2− has been isolated as [Bu4N)2[Fe(DED)3]. Molar conductivities of these complexes in acetonitrile indicate their 1 : 1 electrolytic behaviour. Bonding modes of the ligands, o-phen and DED have been inferred from characteristic IR absorptions suggesting their chelating nature. Room temperature magnetic moments have been measured. Electronic spectral bands suggest octahedral geometry around cobalt(II), nickel(II), iron(II), manganese(IV) and iron(IV) in these complexes. Features of ESR spectra and their g values are suggestive of manganese(IV).

Synthesis and Structural Characterization of 4-Pyridine-carboxaldehyde Nicotinoylhydrazone and its Complexes with Co(II), Ni(II), Cu(II), and Zn(II)

Abstract Pyridine-4-carboxaldehyde nicotinoylhydrazone (4-PNH) has been found to form 1:1 adducts with metal(II) halides and 1:2 complexes (metal to ligand) with metal(II) thiocyanates. Magnetic and spectral studies indicate a polymeric octahedral geometry for [M(4-PNH)X2] [M = Co(II), Cu(II), X = Cl, I; M = Ni(II), X = Cl, Br and I]. The complexes [M(4-PNH)2(NCS)2] [M = Co(II), Ni(II), Cu(II)] possess octahedral geometry around the central metal ion while [Co(4-PNH)Br2] has trigonal bipyramidal geometry around Co(II). IR and NMR spectral studies reveal that 4-PNH acts as a neutral bidentate ligand in these complexes, the bonding sites being the carbonyl oxygen and azomethine nitrogen.

Studies on Isomaleonitriledithiolato Bridged Heterobimetallic Complexes

Abstract Some new heterobimetallic complexes M[Ni(i-MNT)2] [M = Co(II), Cu(II), Zn(II), Pd(II), Cd(II), Pb(II), 2Ag(I) or 2 Tl(I); i-MNT = isomaleonitrile dithiolate dianion] have been isolated and characterized by the elemental analyses and physicochemical measurements. Infrared absorptions indicate bidentate behaviour of the ligand. Room temperature magnetic moments and electronic spectral studies suggest square planar geometry around Co(II), Ni(II) or Cu(ll) ions in their complexes. ESR parameters show square planar environment around Cu(II). Low values of molar conductance are indicative of their nonelectrolytic behaviour.

Synthetic and Physico-Chemical Studies on Co(II), Ni(II), Cu(II), and Zn(II) Complexes of Pyridine-4-carboxaldehyde Thioisonicotinoylhydrazone

Abstract Pyridine-4-carboxaldehyde thioisonicotinoylhydrazone (4-PTINH) gives 1:1 adducts with metal(II) halides, 1:2 metal to ligand complexes with metal(II) thiocyanates and a red diamagnetic complex Cu(4-PTIN)(NCS) which shows a d-d transition band at 20,000 cm−1, characteristic of dimeric Cu(II) species, and a four-line ESR spectrum at LNT, characteristic of square-planar Cu(II) complexes. Magnetic and spectral studies indicate polymeric octahedral geometry for [M(4-PTINH)X2][M = Co(II), X = Cl, M = Ni(II), X = Cl, Br or I], tetrahedral geometry for Co(4-PTINH)X2 (X = Br, I, NCS) five coordinate geometry for Cu(4-PTINH)X2 (X = Cl or Br) and octahedral geometry for Ni(4-PTINH)2(NCS)2 and Cu(4-PTINH)2(NCS)2. ESR spectral studies suggest dimeric structures for Cu(4-PTINH)Cl2 and Cu(4-PTIN)(NCS) and a monomeric structure for Cu(4-PTINH)2(NCS)2, with the unpaired electron in the dx2−y2 orbital of Cu(II). Infrared spectral studies show that 4-PTINH is a neutral bidentate ligand in all the complexes except C...

Fertility restorer (Rf) gene linked STMS marker: An efficient tool for testing the genetic purity of hybrid rice (Oryza sativa L.) seed

A fertility restorer (Rf) gene linked STMS marker, RM 6100 as well as Grow Out Test (GOT) were used for testing the genetic purity of hybrid seed of eight popular rice hybrids. The genetic purity ranging from 96.00% to 100.00%, could be determined through marker, whereas, it varied from 97.00% to 99.50% in GOT. The comparative assessment of both methods exhibited that molecular marker was more efficient than GOT, as it could detect 0.25–2.50% more impurities very precisely as compared to GOT. It suggests that a single Rf gene linked co-dominant STMS marker appeared to be a simple, precise and quick option over GOT for testing the purity of hybrid seed lots in short span of time.

Study of Assessment of Ovarian Function by Serum AMH Estimation Evaluation

Anti mullerian hormone (AMH) is a member of the transforming growth factor family of growth and differentiation factors. In the ovary, AMH has an inhibitory effect on promidial follicle recruitment as well as on the responsiveness of growing follicles to follicle-stimulating hormone (FSH). The ovary-specific expression pattern in granlosa cells of growing non-selected follicles makes AMH an ideal marker for the quantitative aspect of ovarian reserve as well as ovarian dysfunction.

Effects of Examination Stress on Blood Cell Count in First Year Medical Students

Medical students confront with significant academic, psychological, & existential stressors throughout their professional training. Studies have shown that examination stress can have a significant effect on blood cell parameters. The present study was designed to examine the effect of examination stress on different type of blood cells i.e RBC, platelets, haematocrit, TLC, eosinophil, basophil, lymphocyte, monocytes and leucocytes. The changes that occurs are increase in neutrophils and platelets, whereas lymphocytes, eosinophils and monocytes decrease in number.

Role of ADA in CSF for Diagnosis of Tubercular Meningitis

The present study was undertaken to evaluate the CSF ADA activity in patients of tubercular meningitis and efficacy of CSF ADA activity in differentiating various types of meningitis. A total of 97 patients including 18 controls were enrolled in the study. Further, total 79 study patients were divided into three groups depending upon the clinical picture and investigatory findings i.e. pyogenic meningitis (n=20), tubercular meningitis (n=35) and viral meningitis (n=24). In this study ADA level in CSF was determined in patients of tuberculous, pyogenic and viral meningitis admitted to medical wards of Subharti Hospital. This study concluded that cerebrospinal fluid (CSF) ADA activity can be reliably used for differentiating tuberculous meningitis from viral meningoencephalitis. CSF ADA activity cannot be reliably used to differentiate tuberculous meningitis from pyogenic meningitis. CSF ADA activity cannot be used in all cases for differentiating pyogenic meningitis from viral meningoencephalitis. CSF ADA activity has got prognostic value in patients of tuberculous meningitis. Duration of illness and mortality increases with progressive rise in CSF ADA activity. CSF ADA activity should be measured in all patients of meningitis, since it can differentiate those patients of TBM, whose presentation and CSF biochemical parameters are similar to patients of viral meningoencephalitis and can lead to early initiation of therapy in these patients.