Synthesis, characterization and dielectric properties of novel phthalocyanines bearing octa-peripherally substituted mercaptoquinoline moiety

The compounds which were called phthalocyanines discovered as an accident in 1907, by Braun and Tcherniac during preparation of o-cyanobenzamide from phthalimide and acetic acid. After the investigations of Linstead and X-ray studies of Robertson the structure of phthalocyanines were elucitated between 1933 and 1940. Phthalocyanines'stability to light, heat, acids and alkalies have been outstanding peculiarity. They are extensively used in printing inks, coatings, paints and plastics as blues and greens pigments. The phthalocyanines find use also in catalylts for control of sulfur effluents, lasers, lubricants, photodynamic reagents for cancer therapy, optical information storage systems, photography and xerography, high energy density batteries, chemical sensors, electrochoromic display devices and liquid crystal colour display applications. The synthesis, characterization, spectral and dielectric properties of peripherally (α) octamercaptoquinoline substituted Zn(II), Lu(III), Fe(III) and In(III) phthalocyanines are described for the first time. These complexes (2 to 5) and their precursor are characterized by elemental analysis, FT-IR, 1H NMR, electronic spectroscopy as well as mass spectroscopy. Complexes 2, 3, 4 and 5 have good solubility in organic solvents such as CHCl3, DCM, DMSO, DMF, THF and toluene and are not aggregated in all solvents within a wide concentration range. The dielectric properties and the dc conduction properties of 2-5 were investigated as a function of frequency and temperature. The dielectric properties were studied in the frequency range of 400-1x106 Hz. and in the temperature range of 300–500 K. It has been observed that both dielectric constant (ε'(ω) ) and dielectric loss (ε''(ω)) decrease with the rise in frequency as they increase with the rise in temperature. From the analysis of the dc conductivity (dc) dependence on temperature, a weak temperature dependence in low temperature region and strong temperature dependence at higher temperature region was observed for the films of 2-5, which is indicating the involvement of two conduction mechanisms.