S. M. Shaaban

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.

Electrical and spectral studies of solid organic semiconductors. I, Structural interpretation of promoted conductivity of salicylaldazine

Abstract Salicylaldazine possesses semiconducting properties, being enhanced by chelation with the d-block elements Mn2+, Fe2+, Co2+, Ni2+ Cu2+ and Zn2+ but not affected by salt formation with Mg2+. Promoted conduction could be a consequence of enhanced electron decocalization where the d-shell electrons appear to contribute as charge carrier. Salicylaldazine shows also a phase transition phenomenon, probably associated with two molecular systems which exchange conduction at different thermal stabilities. Chelation or salt formation assists in merging these phases.

Temperature dependence of the electrical conductivity of selenous acid and its transition metal selenites

The electric conductivity has been measured over a wide range of temperatures including phase transition temperatures of selenous acid and its transition metal selenites. The effect of hydrogen bonding formation of the crystal structure, as well as, the ion pair formation on the conduction mechanism in the low and high temperature regions was visualized using infrared spectra. The values of thermal activation energies obtained from the electrical conductivity measurements indicate that selenous acid at measuring temperatures and the transition metal selenites at high temperatures behave like semiconducting materials. The transfer of protons along the lines of hydrogen bonds via removal of water molecules during dehydration, and ion pair formation was considered to be the main source participating in the conduction processes.

Temperature dependence of the electrical conductivity of urea and thiourea

Abstract Correlation of the molecular structure with the thermal study of the electrical conductivity of urea and thiourea was carried out. The values of the thermal activation energies, as well as the energy gaps corresponding to the maximum absorption bands of ultraviolet (UV) and visibfe spectra in the solid state indicate that the two compounds behave like semiconductors. The semiconducting properties arise as a result of electron delocalization via n-bond formation (&NH, C=NH: ) and the generation of highly polar resonance hybrid structures. 1. Introduction The possibility of electrical conductivity process in organic crystals specially for aromatic hydrocarbons has been studied by many authors [ l-51. As a part of a continuing study in our laboratory, the present work was taken up to investigate the relationship be- tween electrical conductivity and chemical structure ofurea CO(NH*)* and thiourea CS(NH2)2. Urea is one of the few simple organic compounds having high c~stallo~aphic symmet~. It crystallizes in the te- tragonal scalenol hydra1 division of the tetragonal system

Electrical and spectrophotometric properties of charge transfer complexes of picric acid and some aniline derivatives

The charge transfer complexes produced by the reaction between picric acid and some aniline derivatives were prepared. The prepared charge transfer complexes (CTC) were investigated using infrared and nuclear magnetic resonance spectroscopy aiming to throw more light on their molecular structure. It was proved that a proton transfer interaction takes place between PiOH and x-Ph.NH2 leading to the formation of PiO} and x-Ph.NH3+ ions. The normal π-π1 electronic interaction takes place by transferring an electron from the aniline ring to the picric acid. The semiconducting properties of the CTC were investigated. All the prepared complexes were proved to have a semiconducting character within the temperature range investigated.

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 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.