Spectral and electrochemical behavior of 1-[(NO2, COOH)-substituted phenyl]-3,5-diphenylformazans

Abstract  

1-[(NO₂, COOH)-substituted phenyl]-3,5-diphenylformazans were synthesized. The compounds were characterized by infrared (IR), ultraviolet–visible (UV–vis), ¹H nuclear magnetic resonance (NMR), ¹³C NMR spectra, elemental analysis, and cyclic voltammetry. From the UV–vis spectra of substituted formazans it was seen that λ _max values were shorter than the λ _max value of unsubstituted formazan. It was observed that the shift values were dependent on the type and position of the substituents. A correlation between Hammett substituent coefficients and λ _max values was obtained. The oxidation peak potentials of substituted formazans were found more anodic than that of unsubstituted formazan. The oxidation mechanism was a single step for the NO₂-substituted formazans, and two steps for COOH-substituted formazans.     

Cobalt(II), copper(II), nickel(II) and zinc(II) complexes of two novel Schiff base ligands and their antimicrobial activity

Two new, Schiff base ligands containing cyclobutane and thiazole rings, 4-(1-methyl-1-mesitylcyclobutane-3-yl)-2-(2,4-dihydroxybenzylidenehydrazino)thiazole (L¹H) and 4-(1-methyl-1-mesitycyclobutane-3-yl)-2-(2-hydroxy-3-methoxybenzylidenehydrazino)thiazole (L²H) and their mononuclear complexes with a 1:2 metal-ligand ratio have been prepared with acetate salts of Co^II, Cu^II, Ni^II and Zn^II in EtOH. The structures of the ligands and their complexes have been established by microanalyses, i.r., u.v.–vis., ¹³C- and ¹H-n.m.r. spectra, and by magnetic susceptibility measurements. The complexes are mononuclear. Thermal properties of the ligands and complexes have been studied by t.g.a. and d.s.c. techniques. Antimicrobial activities of the ligands and their complexes have been tested against eight different microorganisms. Some of the complexes and L¹H were found to be active against some of the microorganisms studied.     

Molecular weight distribution by stirring-induced fractional precipitation

Ultrahigh molecular weight polyethylenes GUR, UTEC 2540, and UTEC 3540 were fractionated by precipitation from cooling of solutions with stirring [stirring-induced fractional precipitation (SIFP)]. The samples were dissolved in decalin and precipitated over the temperature range of 100-78°C. Three types of procedures were investigated. From fractionation data, the integral and differential molecular weight distribution (MWD) of the polymer were calculated. The MWD and average molecular weights, and , by size exclusion chromatography (SEC) and the limiting viscosity number of the fractions and whole polymer were determined. From these data, the Mark-Houwink constants were calculated. The ‘K’ and ‘a_η’ values obtained were 6.70 × 10^?4 and 0.69, respectively. The MWD curves calculated from SIFP technique by using these constants are in accordance with the MWD by SEC. Fractionation depended on the chemical nature of the stirrer and the cooling rate of the solution during precipitation. The methodology is reproducible. Faster fractionation was observed compared with other methods. © 1995 John Wiley & Sons, Inc.     

N‐(4‐Nitro­benzyl­idene)‐N′‐phenyl­hydrazine

Molecules of the title compound (alternative name: p‐nitro­benz­aldehyde phenyl­hydrazone), C₁₃H₁₁N₃O₂, adopt an E configuration about the azomethine C=N double bond. Molecules are approximately planar and the dihedral angle between the planes of the phenyl rings is 11.62 (9)°. Hydro­gen bonding links mol­ecules related by 4₂ screw axes to form helices with a pitch of 7.7186 (8) Å.     

A new mesitylenic cyclobutane substituted Schiff base ligand and its Co(II), Cu(II), Ni(II), and Zn(II) complexes

A new ligand, 4‐(1‐methyl‐1‐mesityl‐3‐cyclobutanyl)‐2‐(2‐hydroxy‐1‐naphthylideneimino)thiazole (LH), has been synthesized starting from 1‐methyl‐1‐mesityl‐3‐(2‐chloro‐1‐oxoethyl)cyclobutane and thiourea and subsequently 2‐hydroxy‐1‐napthalaldehyde. Mononuclear complexes with a metal‐ligand ratio of 1:2 have been prepared with Co(II), Cu(II), Ni(II), and Zn(II) metals. The authenticity of the ligand and its complexes are proposed based on elemental analyses, IR, UV‐vis, ¹³C and ¹H NMR spectra, magnetic susceptibility measurements, thermogravimetric analyses, and differential scanning calorimetry. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:42–46, 2001     

The effect of gamma irradiation on electrical and dielectric properties of organic-based Schottky barrier diodes (SBDs) at room temperature

The effect of ⁶⁰Co (γ-ray) irradiation on the electrical and dielectric properties of Au/Polyvinyl Alcohol (Ni,Zn-doped)/n-Si Schottky barrier diodes (SBDs) has been investigated by using capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements at room temperature and 1 MHz. The real capacitance and conductance values were obtained by eliminating series resistance (R_s) effect in the measured capacitance (C_m) and conductance (G_m) values through correction. The experimental values of the dielectric constant (ε′), dielectric loss (ε″), loss tangent (tanδ), ac electrical conductivity (σ_ac) and the real (M′) and imaginary (M″) parts of the electrical modulus were found to be strong functions of radiation and applied bias voltage, especially in the depletion and accumulation regions. In addition, the density distribution of interface states (N_ss) profile was obtained using the high-low frequency capacitance (C_HF-C_LF) method for before and after irradiation. The N_ss-V plots give two distinct peaks for both cases, namely before radiation and after radiation, and those peaks correspond to two different localized interface states regions at M/S interface. The changes in the dielectric properties in the depletion and accumulation regions stem especially from the restructuring and reordering of the charges at interface states and surface polarization whereas those in the accumulation region are caused by series resistance effect.     

Synthesis,spectroscopy, and quantum-chemical calculations on 1-substituted phenyl-3,5-diphenylformazans

In this study 1-substituted phenyl-3,5-diphenylformazans were synthesized from benzaldehyde-N-phenylhydrazone and appropriate phenyldiazonium salts having CH₃, Br, and Cl at the o-, m-, and p-positions of 1-phenyl ring. Their structures were determined by infrared and ultraviolet–visible spectra. Bathochromic effect in accordance with the electron-donating effect of CH₃, Br, and Cl group and its magnitude were dependent upon type and position of substituent on the ring. The ground-state geometries and absorption wavelengths for 1-phenyl substituted formazans were studied with density functional theory and time-dependent density functional theory. The calculations were carried out by using PBE1PBE functional with 6-311G(2d,2p) basis set for λ_max of the UV–vis spectra for the studied formazans. A good agreement was obtained between the experimental and computed values.     

Antimicrobial activity studies of the metal complexes derived from substituted cyclobutane substituted thiazole Schiff base ligands

Two novel bidentate Schiff base ligands derived from 4-(1-methyl-1-mesitylcyclobutane-3-yl)-2-aminothiazole (LH) have been prepared and characterized by elemental analyses, i.r., ¹³C- and ¹H-n.m.r. spectra, u.v.–vis. and magnetic susceptibility measurements. The complexes are mononuclear. Antimicrobial activities of the ligands and their complexes have been tested: Bacillus megaterium DSM 32, Candida albicans FMC 17, Enterobacter aeroginosa CCM 2531, Escherichia coli ATCC 25922, Listeria monocytogenes SCOTTA, Micrococcus luteus LA 2971, Proteus vulgaris FMC 11, Pseudomonas aeruginosa DSM 50071, Saccharomyces cerevisiae FMC 16 and Staphylococcus aureus COWAN I. The thermal properties of the ligands and their complexes have been studied by t.g.a.