Structural, Spectral, Biological and Electrochemical Studies Of Some 3d Transition Metal Complexes of O-N-S and N-N-S Donor Ligands

The primary aim of these investigations was to probe the spectroscopic, electrochemical, biological and single crystal X-ray diffraction studies of some selected transition metal complexes of 4N-monosubstituted thiosemicarbazones. Transition metal complexes with thiosemicarbazones exhibit a wide range of stereochemistries and possess potential biological activity. Metal complexes of thiosemicarbazones are proved to have improved pharmacological and therapeutic effects. The studies are conducted to bring about a fair understanding of the structure activity relationship and to develop certain effective and economical metal-based antimicrobial agents. Study showed that the thiosemicarbazones have antibacterial, antiviral and antiproliferative properties and hence used against tuberculosis, leprosy, psoriasis, rheumatism, trypanosomiasis and coccidiosis. Certain thiosemicarbazones showed a selective inhibition of HSV and HIV infections. The insolubility of most thiosemicarbazones in water causes difficulty in the oral administration in clinical practice. Transition metal complexes are found to have more activity than uncombined thiosemicarbazones. They exhibit a variety of denticity and can be varied by proper substitution. The stereochemistry assumed by the thiosemicarbazones during the coordination with transition metal ions depends on the factors such as preparative conditions and availability of additional bonding site in the ligand moiety and charge of the ligand. The resulting complexes exhibited a wide range of stereochemistries and have biomimic activity and potential application as sensors

Electrical and Optical Properties of Znga2o4 Thin Films Deposited By Pulsed Laser Deposition

ZnGa2O4 spinel is a promising new UV transparent electronic conductor. Enhancing the electrical conductivity of this potential oxide phosphor can make it a promising transparent conducting oxide. In this paper, we have investigated the effects of processing and doping on the conductivity of semiconducting ZnGa2O4, particularly thin films. Crystalline zinc gallate thin films have been deposited on fused quartz substrates employing the pulsed laser deposition (PLD) technique at room temperature for an oxygen partial pressure of 0.1 Pa (0.001mbar). The films were found to be UV transparent, the band gap of which shifted to 4.75eV on hydrogen annealing. The band gap of the oxygen stoichiometric bulk powder samples (4.55eV) determined from diffuse reflection spectrum (DRS) shifted to 4.81eV on reduction in a hydrogen atmosphere. The electrical conductivity improved when Sn was incorporated into the ZnGa2O4 spinel. The conductivity of ZnGa2O4:Sn thin films was further improved on reduction.

Growth of zinc oxide thin films for optoelectronic application by pulsed laser deposition

Zinc oxide (ZnO) thin films were deposited on quartz, silicon, and polymer substrates by pulsed laser deposition (PLD) technique at different oxygen partial pressures (0.007 mbar to 0.003 mbar). Polycrystalline ZnO films were obtained at room temperature when the oxygen pressure was between 0.003 mbar and .007 mbar, above and below this pressure the films were amorphous as indicated by the X-ray diffraction (XRD). ZnO films were deposited on Al2O3 (0001) at different substrate temperatures varying from 400oC to 600oC and full width half maximum (FWHM) of XRD peak is observed to decrease as substrate temperature increases. The optical band gaps of these films were nearly 3.3 eV. A cylindrical Langmuir probe is used for the investigation of plasma plume arising from the ZnO target. The spatial and temporal variations in electron density and electron temperature are studied. Optical emission spectroscopy is used to identify the different ionic species in the plume. Strong emission lines of neutral Zn, Zn+ and neutral oxygen are observed. No electronically excited O+ cations are identified, which is in agreement with previous studies of ZnO plasma plume.

Transparent p-AgCoO2/n-ZnO diode heterojunction fabricated by pulsed laser deposition

Transparent diode heterojunction on ITO coated glass substrates was fabricated using p-type AgCoO2 and n-type ZnO films by pulsed laser deposition (PLD). The PLD of AgCoO2 thin films was carried out using the pelletized sintered target of AgCoO2 powder, which was synthesized in-house by the hydrothermal process. The band gap of these thin films was found to be ~3.89 eV and they had transmission of~55% in the visible spectral region. Although Hall measurements could only indicate mixed carrier type conduction but thermoelectric power measurements of Seebeck coefficient confirmed the p-type conductivity of the grown AgCoO2 films. The PLD grown ZnO films showed a band gap of ~3.28 eV, an average optical transmission of ~85% and n-type carrier density of~4.6×1019 cm− 3. The junction between p-AgCoO2 and n-ZnO was found to be rectifying. The ratio of forward current to the reverse current was about 7 at 1.5 V. The diode ideality factor was much greater than 2.

Studies on Some Simple and Zeolite-Y Encapsulated 3d-Transition Metal Complexes of Schiff Bases Derived From 2-Aminobenzothiazole

In this regard Schiff base complexes have attracted wide attention. Furthermore, such complexes are found to play important role in analytical chemistry, organic synthesis, metallurgy, refining of metals, electroplating and photography. Many Schiff base complexes are reported in literature. Their properties depend on the nature of the metal ion as well as on the nature of the ligand. By altering the ligands it is possible to obtain desired electronic environment around the metal ion. Thus there is a continuing interest in the synthesis of simple and zeolite encapsulated Schiff base complexes of metal ions. Zeolites have a number of striking structural similarities to the protein portion of natural enzymes. Zeolite based catalysts are known for their remarkable ability of mimicking the chemistry of biological systems. In view of the importance of catalysts in all the areas of modern chemical industries, an effort has been made to synthesize some simple Schiff base complexes, heterogenize them by encapsulating within the supercages of zeoliteY cavities and to study their applications. The thesis deals with studies on the synthesis and characterization of some simple and zeoliteY encapsulated Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) complexes and on the catalytic activity of these complexes on some oxidation reactions. Simple complexes were prepared from the Schiff base ligands SBT derived from 2-aminobenzothiazole and salicylaldehyde and the ligand VBT derived from 2-aminobenzothiazole and vanillin (4-hydroxy-3- methoxybenzaldehyde). ZeoliteY encapsulated Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) complexes of Schiff base ligands SBT and VBT and also of 2-aminobenzothiazole were synthesized. All the prepared complexes were characterized using the physico-chemical techniques such as chemical analysis (employing AAS and CHN analyses), magnetic moment studies, conductance measurements and electronic and FTIR spectra. EPR spectra of the Cu(II) complexes were also carried out to know the probable structures and nature of Cu(II) complexes. Thermogravimetric analyses were carried out to obtain the information regarding the thermal stability of various complexes. The successful encapsulations of the complexes within the cavities of zeoliteY were ascertained by XRD, surface area and pore volume analysis. Assignments of geometries of simple and zeoliteY encapsulated complexes are given in all the cases. Both simple and zeoliteY encapsulated complexes were screened for catalytic activity towards oxidation reactions such as decomposition of hydrogen peroxide, oxidation of benzaldehyde, benzyl alcohol, 1-propanol, 2-propanol and cyclohexanol.

Studies on Some Transition Metal Complexes of Schiff Bases Derived from Quinoxaline-2-carboxaldehyde

Two series of transition metal complexes of Schiff bases derived from quinoxaline-2-carboxaldehyde with semicarbazide (QSC) and furfurylamine (QFA) were synthesised and characterised by elemental analyses, molar conductance and magnetic susceptibility measurements, IR, electronic and EPR spectral studies. The QSC complexes have the general formula [M(QSC)Cl2]. A tetrahedral structure has been assigned for the Mn(II), Co(II) and Ni(II) complexes and a square-planar structure for the Cu(II) complex. The QFA complexes have the formula [M(QFA)2Cl2]. An octahedral structure has been assigned for these complexes. All of the complexes exhibit catalytic activity towards the oxidation of 3,5-di-tert-butylcatechol (DTBC) to 3,5-di-tert-butylquinone (DTBQ) using atmospheric oxygen. The cobalt(II) complex of the ligand QFA was found to be the most active catalyst.

Synthesis and Characterization of Some New Transition Metal Complexes of the Schiff Base Derived from Quinoxaline-2-Carboxaldehyde and 2- Aminophenol

Some new transition metal complexes of the Schiff base quinoxaline-2-car boxalidene-2-aminophenol (HQAP) have been synthesized and characterized by elemental analyses, conductance and magnetic measurements and IR and UV-Visible spectral studies. The complexes have the following empirical formulae: [Mn(QAP121, [Fe(QAPl2C1I, [Co(QAPl21, [Ni(QAP121 and [Cu(QAP121. A tetrahedral structure has been assigned for the manganese(=), cobalt(II1, nickel(II1 and copper(II1 complexes. For the iron(IIIl complex an octahedral dimeric structure has been suggested