B. T. Thaker

Synthesis, spectral, crystallography and thermal investigations of novel Schiff base complexes of manganese (III) derived from heterocyclic β-diketone with aromatic and aliphatic diamine

The Schiff base tetradentate ligands N,N-bis-(3,5-dimethyl-1-p-tolyl-1H-pyrazol-4-ylmethylene)-ethane-1,2-diamine (H(2)L(1)), N,N-bis-(3,5-dimethyl-1-p-sulfonyl-1H-pyrazol-4-ylmethylene)-ethane-1,2-diamine (H(2)L(2)), N,N-bis-(3,5-dimethyl-1-p-tolyl-1H-pyrazol-4-ylmethylene)-benzene-1,2-diamine (H(2)L(3)) and N,N-bis-(3,5-dimethyl-1-p-sulfonyl-1H-pyrazol-4-ylmethylene)-benzene-1,2-diamine (H(2)L(4)) were prepared from the reaction between 5-oxo-3-methyl-1-p-tolyl-1H-pyrazole-4-carbaldehyde or 4-(4-formyl-5-oxo-3-methyl-pyrazol-1-yl)-benzenesulfonic acid and o-phenylenediamine or ethylenediamine. And these are characterized by elemental analysis, FT-IR, (1)H NMR and GC-MS. The corresponding Schiff base complexes of Mn(III) were prepared by condensation of [Mn(3)(mu(3)-O)(OAc)(6)(H(2)O)(3)].3H(2)O with ligands H(2)L(1), H(2)L(2), H(2)L(3) and H(2)L(4). All these complexes have been characterized by elemental analysis, magnetic susceptibility, X-ray crystallography, conductometry measurement, FT-IR, electronic spectra and mass (FAB) spectrometry. Thermal behaviour of the complexes has been studied by TGA, DTA and DSC. Electronic spectra and magnetic susceptibility measurements indicate octahedral stereochemistry of manganese (III) complexes, while non-electrolytic behaviour complexes indicate the absence of counter ion.

Synthesis, spectroscopic and thermal investigation of Schiff-base complexes of Cu(II) derived from heterocyclic β-diketone with various primary amines

The mononuclear complex [Cu(PMFP)(bipy)]ClO4 was prepared by reaction of Cu(NO3)2·5H2O with ligand PMFP and 2,2′-bipyridine. The corresponding Schiff bases were prepared by condensation of [Cu(PMFP)(bipy)]ClO4 with ethylenediamine, ethanolamine and glycine with general formula [Cu(PMFP-SB)(bipy)]ClO4 (where PMFP = 1-phenyl-3-methyl-4-formyl-2-pyrazolin-5one; bipy = 2,2′-bipyridine). All the compounds have been characterized by elemental analysis, magnetic susceptibility, conductometry measurements and 1H-NMR, FT-IR, ESR, electronic spectra and mass spectrometry. Electronic spectra and magnetic susceptibility measurements indicate square planar stereochemistry. Thermal stability, order of kinetics, heat capacity and activation energy of thermal degradation for these complexes were determined by TGA and DSC. Hamiltonian and bonding parameters from ESR spectra indicate the metal ligand bonding is partially covalent.

Determination of pregabalin in human plasma by electrospray ionisation tandem mass spectroscopy

A rapid, precise, specific, and accurate Electrospray Ionisation Tandem Mass Spectrometry (ESI-MS / MS) method has been developed and subsequently validated, for the determination of pregabalin (PB) in human plasma. Gabapentin (GB) was used as the internal standard. PB and GB were extracted from the plasma using a combination of deproteinization, using 0.1% formic acid and liquid–liquid extraction, using methylene chloride. PB and GB were separated using the Hypurity advance column (50 mm × 4.6 mm, 5 μm) and mobile phase, consisting of methanol : 0.1% formic acid (80:20 v / v). PB was determined by using ESI-MS / MS in positive ion mode, with the help of the API 2000 spectrophotometer, operated in a multiple reaction monitoring mode. The parent-to-product ion combination of m / z 160.2→55.1 and 172.2→95.0 was used to quantify PB and GB, respectively. The assay was validated in the concentration range of 99.79 – 4019.90 ng / mL for PB. The limit of quantification (LOQ) was identifiable and reproducible at 99.79 ng / mL. The method has been successfully applied to study the pharmacokinetics of PB in healthy male volunteers.

Synthesis, spectral, thermal, and antibacterial investigation of mixed ligand complexes of oxovanadium(IV)

Novel mononuclear mixed-ligand oxovanadium(IV) complex [VO(PMFP)(Bipy)]ClO4 was prepared by the condensation of VOSO4 · 5H2O with ligands 1-phenyl-3-methyl-4-formyl-2-pyrazolin-5one (PMFP) and 2,2′-bipyridyl (Bipy). The corresponding Schiff bases were prepared by the condensation of [VO(PMFP)(Bipy)]ClO4 with ethylenediamine, ethanolamine, and glycine. All the compounds have been characterized by elemental analysis, magnetic susceptibility, X-ray crystallography, conductometry measurement, 1H NMR, FT-IR, ESR, electronic spectra, and mass spectrometry. Electronic spectra and magnetic susceptibility measurements indicate distorted octahedral stereochemistry of the oxovanadium(IV) complexes. Thermal stability, kinetic order, heat capacity, and activation energy of thermal degradation of these complexes were determined by TGA and DSC. The presence of one coordinate water molecule is suggested from the IR and TGA studies. Hamiltonian and bonding parameters were found from ESR spectra, indicating that the metal-ligand bonding is partial covalent. Antibacterial screening is reported for the ligand and complexes of oxovanadium(IV).

Manganese(III) Schiff-base complexes involving heterocyclic β-diketone and diethylene triamine

Synthesis, spectral, thermal and coordination aspects of pentadentate Schiff-base complexes of the type [Mn(L)(X)] · H2O [where H2L = N,N′–diethylamine bis(1-phenyl-3-methyl-4-acetylimino-2-pyrazoline-5-ol) and X=NCS, NO3, ClO4, CN or N3] are reported. The Schiff-base ligand (H2L) and metal complexes have been characterized by elemental analysis, FT-IR, 1H-NMR, magnetic measurements, molar conductivity measurements, electronic spectra, cyclic voltammetric and thermal studies. Magnetic moment values are close to 4.9 B.M. indicating high spin complexes lacking exchange interaction. Infrared spectral data suggest coordination of the secondary amino group making the ligand pentadentate. All complexes are electrochemically inactive, indicating high stability. Thermal decomposition of the Schiff-base complexes indicates loss of water of hydration and decomposition of the ligand. Kinetic parameters such as order of reaction (n) and the energy of activation (E a) are reported using the Horowitz–Metzger method, indicating first order kinetics and giving the activation entropy (ΔS*), the activation enthalpy (ΔH*) and the free energy of activation (ΔG*).

Mononuclear and long-range single-bridged binuclear complexes of oxovanadium(IV) involving conjugated heterocyclic nitrogen base and heterocyclic β-diketones

SummaryBinuclear complexes of OVIV have been prepared by reacting aromatic diamines with mixed-ligand (mononuclear) complexes of the type [(diamine), VO(PmAcp or PmbzP)], where (diamine) = 2,2′-bipyridine or 1,10-phenanthroline, and PmAcp or PmbzP heterocyclic β-diketone ligands = 1-phenyl-3-methyl-4-acetyl or 4-benzoyl-2-pyrazolin-5-one. 2,6-Diaminopyridine orm-phenylenediamine condenses with the MeCO or PhCO groups of PmAcp and PmbzP on two complex molecules, thus bridging the two VOII centres. The complexes have been characterized by electronic, i.r. and e.s.r. spectra, magnetic measurements, thermogravimetry, conductometry and microanalysis. The magnetic moments and the order of antiferromagnetism are explained on the basis of delocalized π-orbitals, orientation of the metal orbitals and the bridging Schiff base. The metal-ligand bond is covalent.

Synthesis, spectral, and thermal studies of oxomolybdenum(V) Schiff-base complexes derived from heterocyclic β-diketone

Six mononuclear Mo(V) Schiff-base complexes were prepared by the reaction of MoCl5 with Schiff bases, namely HL1–HL3 and HL4–HL6, such as 5-hydroxy-3-methyl-1(2-chloro)phenyl-1H-pyrazolone-4-carbaldehyde (I), 5-hydroxy-3-methyl-1(3-chloro)phenyl-1H-pyrazolone-4-carbaldehyde (II), and 5-hydroxy-3-methyl-1(3-sulfoamido)phenyl-1H-pyrazolone-4-carbaldehyde (III) with ethanolamine and propanolamine, respectively, in aqueous ethanolic medium. The resulting complexes have been characterized by elemental analyses, molar conductance, FT-IR, 1H-NMR, electronic, electron spin resonance (ESR) spectra, magnetic susceptibility, and thermal study. The molar conductivity data show them to be non-electrolytes. IR and 1H-NMR spectral data suggest that the ligand is a dibasic bidentate with ON donor toward metal ion. Electronic, magnetic, and ESR spectral data suggest that the oxomolybdenum(V) complexes have distorted octahedral geometry. One chloride coordinated to molybdenum is confirmed by thermal study.

Synthesis, Spectroscopic and Thermal Investigations of O‐Phd and P‐Phd Bridged Binuclear Manganese (III) Schiff Base Complexes Derived from Pyrazolone Base Ligands

Acyl pyrazolone and their derivatives are an important class of chelating compounds called heterocyclic β‐diketones. β‐diketones have played, and continue to play, a key role in coordination compounds that have found wide application in several fields, from new materials to catalysts, as precursors for CVD in the microelectronic industry and as potential antitumourals. Due to variety of application of this class of ligand, there are studies on metal complexes of many researchers, including ours. We herein report the structural variability of pyrazolone moiety and its chelating nature with manganese (III) ions, in mononuclear and binuclear complexes. The mononuclear complex [Mn(PMFP)(bipy)(OAc)]ClO4 and [Mn(PMFP‐Me) (bipy)(OAc)]ClO4 was prepped by reaction of Mn(OAc)3 · 2H2O with ligand PMFP or PMFP‐Me (where PMFP=5‐Hydroxy‐3‐methyl‐1‐phenyl‐1H‐pyrazole‐4‐carbaldehyde; PMFP‐Me=5‐hydroxy‐3‐methyl‐1‐p‐tolyl‐1H‐pyrazole‐4‐carbaldehyde; bipy=2,2′bipyridyl). The corresponding binuclear complexes were prepared by bridging molecule, o‐phD or p‐phD (o‐phD= where o‐phenelene diamine or p‐phD=p‐phenelen diamine). Both the ligand PMFP and PMFP‐Me were characterized by elemental analysis and 1H‐NMR, GC‐MS, FT‐IR spectroscopic study. The resulting complexes have been characterized by elemental analysis, magnetic susceptibility and conductometry measurements and spectroscopic methods FT‐IR, electronic spectra and mass spectrometry. All the complexes were electrolytic in nature and consist of 1∶2 electrolytes in solution. Electronic spectral and magnetic susceptibility measurements indicate square pyramidal geometry around manganese (III) ion. TGA and DSC determined thermal stability, heat capacity and activation energy of thermal degradation for these complexes.

Spectroscopic and ab-initio study of schiff base ligand 4-[(2-hydroxyethylamino)-methylene]-5-methyl-2-p-tolyl-2,4-dihydro-pyrazol-3-one

Pyrazolone ring systems represent an important class of compounds [1] not only for their theoretical interest but also for their number of application in diverse area [2-6].[...]

Synthesis, Spectral, Magnetic and Thermal Studies of the Complexes of CoII and NiII With Some Bidentate and Tridentate Hydrazone Ligands

The reaction of Co(NO3)2.6H2O and Ni(NO3)2.6H2O with hydrazones derived from 1-phenyl-3-methyl-4-acyl-5-pyrazolone (where acyl = acetyl, propionyl, butyryl and benzoyl) with 2-picolinic acid hydrazide have been studied and characterized on the basis of elemental analysis, magnetic moments, molar conductivity measurements, IR and electronic spectral studies and thermogravimetric analysis. Various ligand field parameters have been calculated. Electronic spectral data and the magnetic moment values suggest an octahedral structure for all cobalt(II) and nickel(II) complexes.