Ferrocene-Bearing Dodecylphthalocyanines: Synthesis, Spectroscopic and Electrochemical Behavior.

Ferrocenylbutoxy-bearing dodecylated phthalocyanines, MPc(C 12 H 25 ) x (OC 4 H 8 Fc) y with M = 2H (compound series 6 and 8 ) or Zn (compound series 5 , 7 and 9 ), x ≤ 8 and y ≤ 4, were synthesized through either metal-free statistical condensation between 3,6-bis(dodecyl)phthalonitrile, 2 , and 4- ( 1 ), or 3-(4'-ferrocenylbutoxy)phthalonitrile, 4 , or a zinc template statistical condensation between 4,5-bis(dodecyl)phthalonitrile, 3 , and 1 in the presence of anhydrous zinc acetate, or by zinc insertion into metal-free phthalocyanines. Compounds were designed to have eight nonperipheral dodecyl substituents, six nonperipheral dodecyl, either one peripheral or one nonperipheral 4'-ferrocenylbutoxy substituent, four nonperipheral dodecyl and two peripheral 4'-ferrocenylbutoxy substituents, or four peripheral 4'-ferrocenylbutoxy substituents. The compound having six peripheral dodecyl and one peripheral 4'-ferrocenylbutoxy substituents was also synthesized. Metal-free and zinc complex Q-band maximum absorption wavelengths increased nonlinearly from 704 to 725 nm for the Q y -band of metal-free compounds, or from 676 to 699 nm for the Q-band of zinc complexes in moving from all peripheral-substituted to all non-peripheral-substituted complexes. A rare case of accidental Q-band degeneracy where only one electronic Q-band is observed for asymmetrical zinc complexes NOT having D 4 h symmetry, compounds 5 , 7b - e , and 9b , is also described. X-ray photoelectron spectroscopy (XPS) differentiated between four types of phthalocyanine nitrogen atoms; binding energies were ca . 399.8 ( N -H), 398.1 (N meso ), 397.8 (N core ), and 398.7 eV ( N -Zn), respectively. An electrochemical study of these compounds revealed up to five different redox processes in dichloromethane but only three in tetrahydrofuran (THF). The first ring-based oxidation of both metal-free compounds 6a - e and zinc phthalocyanines 7a - e exhibited a near-linear increase in peak anodic potentials, E pa , with the systematic replacement of two nonperipheral dodecyl substituents with one peripheral 4'-ferrocenylbutoxy group. When four 4'-ferrocenylbutoxy groups were substituted on the phthalocyanine macrocycle, aggregation of the first oxidized species was observed. Zinc insertion into metal-free phthalocyanines lowered formal redox potentials. An electrochemical scheme consistent with electrochemical results is provided.