Ferrocene-Bearing Dodecylphthalocyanines: Synthesis, Spectroscopic and Electrochemical Behavior

Ferrocenylbutoxy-bearing dodecylated phthalocya-nines, MPc(C12H25)x(OC4H8Fc)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 Qy-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 D4h 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 (Nmeso), 397.8 (Ncore), 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, Epa, 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.

Automated summary

In this study, a series of phthalocyanine compounds with different functional groups were synthesized, and their spectroscopic and electrochemical properties were investigated.