B. A. El-Sayed

Temperature dependence of the electrical conductivity of 4-(2-OH-4-CH3 phenyl azo)-antipyrine and its copper solid complex

Abstract Correlation of the molecular structure with the current-voltage and temperature dependence of the electrical conductivity of 4-(2-OH-4-CH 3 phenyl azo)-antipyrine and its copper solid complex was carried out. The values of the thermal activation energies and the energy gaps representing the maximum absorption bands of ultraviolet (UV) and visible spectra in the solid state indicate the semiconducting behaviour of the two compounds. The semiconducting properties of the ligand arise as a result of electron-delocalization via double bonds conjugation (NN, CC), tautomerization and hydrogen bond formation and altered by the copper ion in copper complex.

Temperature dependence of the electrical conductivity of Salicylaldazinate metal chelates

A study of the temperature dependence of the electrical conductivity of Salicylaldazine and its metal complexes with the d-block elements Ni2+, Cu2+ and Zn2+, is correlated with molecular spectral data. The values of the activation energies obtained from the electrical conductivity measurements, as well as the energy gaps corresponding to the maximum absorption wavelengths in the region of ultraviolet and visible spectra, indicate the important role of chelation in producing the Salicylaldazine semiconducting properties.

The electrical conductivity of some azine compounds

Correlation of the molecular structure and thermal study of the electrical conductivity of benzaldazine (BA) and its NO2-derivatives were carried out. The values of the activation energies, obtained from the electrical conductivity measurements, as well as the energy gaps calculated from ultra violet (u.v.) and visible spectra obtained either in liquid or in solid forms indicate that all compounds behave like a semiconducting material. Both nπ*′s and ππ*′s were found to be the main sources participatiog in the cooduction processes.

Temperature and frequency dependent electrical transport in thiourea and tris (thiourea) copper (l) sulphate

The d.c. conductivity of thiourea and tris (thiourea) copper sulphate have been measured as a function of temperature, including their phase transition temperatures. The thermal activation energy values obtained showed that the two compounds behaved as semiconducting materials. The mechanism of the conductivity was interpreted in the light of their molecular spectroscopic data in the infrared, ultraviolet and visible regions. The semiconducting properties of the ligand (TU) arise as a result of electron-delocalization via π-bond formation (C=NH, C=NH2+), the hydrogen transfer and the highly polar resonance hybride structural formation, and are altered by the copper ion in copper (TU) complex. The a.c. conductivity was measured at room temperature.

Phase transition study of some selected azine compounds

Abstract The dielectric constants (real and imaginary) of benzaldazine and its hydroxy derivatives have been measured at different frequencies up to 100 kHz. The measurements were also carried out at different temperatures up to near the melting point of each sample. Two phase transitions were obtained during measurements at 320 and 370 K. The rotation of the benzene ring around the -CN- axis was responsible for these transitions. The effect of variation of the OH substituent between o -, p - and w -positions on the dielectric loss was discussed. The a.c. conductivities for the different samples were measured and explained.

Electrical transport as a function of temperature in hexacyanoferrate complexes

The electrical conductivity as a function of temperature and the current–voltage dependences of potassium and nickel hexacyanoferro and ferri complexes, have been determined. Charge transfer via the electron delocalization along overlapping dz2 orbitals of the iron to π* orbitals of the ligands (–C≡N) as well as the ionic conduction via Fe2+, Fe3+, K+, and Ni2+ cations are considered as the main sources participating in the conduction processes. The energy gaps, as calculated from the observed maximal absorption wavelengths of ultraviolet and visible spectra, and the activation energies for the free carriers, from the temperature dependence of the electrical conductivity measurements, are consistent with those of semiconductor materials.

Electrical transport as a function of temperature in urea and cobalt (III)-urea complex

The temperature dependence of the electrical conductivity, and the voltage–current dependence of urea and its cobalt solid complex were determined. The values of the thermal activation energies indicate that the two compounds behave like semiconductors. The semiconducting properties of the ligand ‘urea’ are due to the electron delocalization via π-bond formation (C=NH,C=2+) as well as the lone pair of electrons on the oxygen atoms of urea molecules. The high conductivity values of urea compared with those of its cobalt solid complex was suggested to be due to the ease of releasing the lone pair electrons on the oxygen atom as well as the hydrogen transfer during enol formation of urea molecules. The infrared, ultraviolet and visible absorption measurements were carried out to rationalize the mechanism of the conduction process in the investigated compounds.

Temperature dependence of the electrical conductivity of oxamide, dithio-oxamide and biuret

Abstract A correlation of the molecular structure with the temperature dependence of the electrical conductivity of oxamide, dithio-oxamide and biuret was carried out. The values of the thermal activation energies, as well as the electrical conductivities indicate the semiconductor behaviour of the three compounds. Intra- and intermolecular hydrogen bondings occurring in the solid phases of the investigated compounds are considered as an important reason for their semiconducting properties.

The photoconductivity of benzaldazine and its o- and p-hydroxy substituents

The photoconductivity of benzaldazine (BA) and its o-, m- and p-hydroxy substituents has been measured. The voltage dependence is described by a linear term (ohmic) and a saturation term, the former of which dominates at low field strengths (up to 300 V). The temperature dependence of the photocurrent has been studied. The m-OH-BA has not shown any photoconductivity response.

Temperature dependence of the phase transitions of benzaldazine and its o-, m-, and p-nitro derivatives

Abstract The dielectric constants of benzaldazine (BA) and its nitro derivatives have been measured at different frequencies up to 200 kHz. The measurements were carried out at temperatures up to and near the melting point of each sample. Two phase transitions were obtained during measurements at 310 and 480 K. Inversion NN rotation and inversion CN rotation mechanisms may be responsible for these transitions. The effect of interaction between the strongly polar NO 2 group of o -, m - or p -nitrobenzaldazine and the central aldimino (CHN) groups on the dielectric constant is discussed. The electric dipole moments of the samples were calculated at the peak positions, and are discussed.