Highly soluble tetrasubstituted lanthanide bis-phthalocyanines; Synthesis, characterization, electrical properties and aggregation studies

We report the synthesis, characterization and electrical properties of lanthanide metal based bis-phthalocyanines, {M[Pc-(b-HHT)4]2} (HHT:1-hydroxyhexane-3-ylthio){M = Lu³⁺(2), Eu³⁺(3), and Yb³⁺(4)}. The interaction of bis-phthalocyanines with Ag⁺ and Pd²⁺ metal ions were investigated by UV-vis spectroscopy and atomic force microscopy. Thin films of bis-phthalocyanine molecules were prepared by spin-coating method. The surface morphology of thin films were performed with Atomic Force Microscopy as further investigate. The electrical transport properties of ITO/Pc/Al devices were investigated. At low voltages all the films showed an ohmic conduction, whereas at higher voltage levels the conduction is dominated by space charged limited conduction with exponential distribution of trapping levels. Measurements of current density as a function of inverse temperature at constant applied voltage yielded a hole mobility values, μ_p = 2.12 × 10^-7, 6.72 × 10^-7 and 1.58 × 10^-6 m²sn^-1.V^-1 for lanthanium phthalocyanines. From the analysis of frequency, w, dependence of electrical conductivity, s_ac. it was found that the s_ac obeys the power law given by s_ac = Aw^s, in which the frequency exponent "s" decreases with temperature.