Synthesis, Characterization and Dielectric Properties of New 5-(4-Hydroxyphenyl)-10,15,20-tri-4-[2-(3-pentadecylphenoxy)ethoxy]phenyl porphyrin and Their Ni, Co and Cu Complexes
Journal of the Brazilian Chemical Society
New asymmetric cardanol-based porphyrins, free-base and coordinated with Ni, Co and Cu, were synthesized and completely characterized as A3B type. Such porphyrins were obtained aiming improved solubility in polar solvents due insertion of an −OH phenolic group. Their thermal and dielectric properties were also evaluated. Changes in the synthetic route reduced the reaction time and improved the yields of the aldehyde precursor obtainment. Electronic absorption spectra of the new porphyrins in CH
... ew porphyrins in CH 2 Cl 2 , EtOH and acetone, indicated a decrease in the ε (molar absorptivity) values with increasing solvent polarity, except for the nickel complex which, in acetone, showed a slight increase of 2% in the ε value. The dielectric measurements showed that the conductivity (σ) and the loss tangent (tan δ) increased with frequency, but the permittivity (ε') decreased. The results showed that the coordination of the porphyrin promoted a significant change in thermal and dielectric properties, specially for to the Ni-complex compound, which presented the best dielectric properties with interesting values of permittivity and loss tangent at 100 MHz (19.46 and 0.011 a.u., respectively). Keywords: asymmetric porphyrins, cardanol, dielectric properties Synthesis, J. Braz. Chem. Soc. 1064 Scheme 1. Synthesis of asymmetric porphyrin 4a A3B type from cardanol, where (a) KOH, dibromoethane, 70 °C, 6 hours; (b) KOH, DMF, 100 °C, 6 hours; (c) 4-hydroxybenzaldehyde, CHCl 3 , BF 3 , DDQ, 1 hour; (d) acetate metal salts (Ni, 4b; Co, 4c; and Cu, 4d), chloroform/DMF, 3 hours, 90 °C.