Lokesh Kumar Gupta

Synthesis and EPR Spectral Studies of Mono- and Binuclear Cobalt(II) and Nickel(II) Complexes with New 20‐Membered Dithiatetraazamacrocyclic [N4S2] Ligand

Abstract A new ligand, 6,10,16,20‐tetraketo‐8,18‐dithia‐1,5,11,15‐tetraazacycloeicosane [N4S2] (L), and its complexes with cobalt(II) and nickel(II), have been synthesized and characterized by elemental analyses, molar conductance, magnetic susceptibility measurements, EPR and electronic spectral studies. The complexes were found to have the general composition [ML]X2 and [M2LX2]X2 for mono and binuclear complexes (M = Co, Ni; X = Cl, NO3, and SCN; and L = macrocyclic ligand). The mononuclear complexes of Co(II) and Ni(II) were found to have six‐coordinated octahedral geometry. However, the binuclear complexes of Co(II) and Ni(II) are square‐planar.

Spectroscopic studies on chromium(III), manganese(II), cobalt(II), nickel(II) and copper(II) complexes with hexadentate nitrogen–sulfur donor [N2S4] macrocyclic ligand

Complexes of transition metals have been synthesized with hexadentate ligand (2,6-bis(((2-mercaptophenyl)thio)methyl)pyridinato)metal(II). These complexes have been synthesized via the two step template reaction by using the benzene dithiol, 2,6-bis(chloro)methyl pyridine and corresponding metal salt as key raw materials. The structures of the complexes have been elucidated on the basis of elemental analysis, molar conductance measurements, magnetic susceptibility measurements, IR, electronic and EPR spectral studies. All of the complexes were found to possess six-coordinated geometry and are of high spin type.

Synthesis, Physicochemical and Electrochemical Studies on Mn(II), Co(II), Ni(II), and Cu(II) Complexes with an N‐Donor Tetradentate (N4) Macrocycle Ligand Derived from Ethyl Cinnamate

Abstract Manganese(II), cobalt(II), nickel(II), and copper(II) complexes with a new tetradentate ligand, 1,3,7,9‐tetraaza‐4,10‐diketo‐6,12‐diphenyl‐2,8‐dithiocyclododecane (L), were synthesized and characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, mass, 1H NMR, IR, electronic, EPR spectral and cyclic voltammetric studies. On the basis of the IR, electronic, and EPR spectral studies, an octahedral geometry has been assigned for the Mn(II) and Co(II) complexes, a square‐planar one for the Ni(II) and a tetragonal one for the Cu(II) complexes.

Spectroscopic characterization and quantitative determination of atorvastatin calcium impurities by novel HPLC method

Seven process related impurities were identified by LC-MS in the atorvastatin calcium drug substance. These impurities were identified by LC-MS. The structure of impurities was confirmed by modern spectroscopic techniques like (1)H NMR and IR and physicochemical studies conducted by using synthesized authentic reference compounds. The synthesized reference samples of the impurity compounds were used for the quantitative HPLC determination. These impurities were detected by newly developed gradient, reverse phase high performance liquid chromatographic (HPLC) method. The system suitability of HPLC analysis established the validity of the separation. The analytical method was validated according to International Conference of Harmonization (ICH) with respect to specificity, precision, accuracy, linearity, robustness and stability of analytical solutions to demonstrate the power of newly developed HPLC method.

Variation of the ground state properties of trapped Bose-Einstein condensate due to localized impurity

Bose-Einstein condensates have been, by now, observed in as many as nine different atomic assemblies of bosons. Such a condensate is quantum mechanical interacting system whose ground state properties can be studied theoretically by solving the appropriate non-linear Gross-Pitaevskii-Ginzburg GPG equation. One can now study the change in the behavior of Bose-Einstein condensate by introducing a localized impurity which interacts with the condensate as a function of position of impurity in the condensate. The introduction of such an impurity can be mimicked by simply allowing an intensely focused laser beam to interact with the condensate. This would lead to alteration of ground state properties of the condensate as it would now interact with a potential of type V Sech2(r/w) where, V and w are amplitude and width of the impurity potential, respectively. The modified GPG equation in the presence of localized impurity potential as function of position in the condensate, has been numerically solved to obtain its various ground state properties as function of position, such as total energy per particle, chemical potential, kinetic, harmonic trap potential and two-body interaction energies per particle in addition to energy associated with impurity potential, correlation length, healing length etc. We have studied the behavior of the above-mentioned ground state properties as the position of localized impurity is changed in the condensate from core to peripheral position. While the total, harmonic oscillator potential and impurity energies decrease as the position of localized impurity is displaced from core of the condensate to its periphery, the value of two-body inter-particle interaction energy increases. Further, the values of chemical potential and total energy per particle shows decrease by ~ 9% and ~ 17% respectively, leading to the inference that the stability of condensate increases as the localized impurity is moved away from the core of the condensate.