Ferrocene-Bearing Dodecylphthalocyanines: Synthesis, Spectroscopic and Electrochemical Behavior

Ferrocenylbutoxy-bearing dodecylated phthalocyanines, 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 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_4h 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.

Mechanism of the Zn(II)Phthalocyanines' Photochemical Reactions Depending on the Number of Substituents and Geometry

In this work, the synthesis and the nonlinear absorption and population dynamics investigation of a series of zinc phthalocyanines (ZnPcs) dissolved in chloroform are reported. In order to determine the relevant spectroscopic parameters, such as absorption cross-sections of singlet and triplet excited states, fluorescence relaxation times, intersystem crossing, radiative decay and internal conversion, different optical and spectroscopic techniques were used. By single pulse and pulse train Z-scan techniques, respectively, singlet and triplet excited states‘ absorption cross-section were determined at 532 nm. Furthermore, the intersystem crossing time was obtained by using both techniques combined with the fluorescence lifetime determined by time-resolved fluorescence. The radiative and internal conversion rates were determined from the fluorescence quantum yield of the samples. Such spectroscopy parameters are fundamental for selecting photosensitizers used in photodynamic therapy, as well as for many other applications.

Synthesis, DFT calculations, linear and nonlinear optical properties of binuclear phthalocyanine gallium chloride

The axially substituted binuclear GaCl/GaCl phthalocyanine 1 with an unsymmetrical pattern of substitution has been prepared and its nonlinear optical (NLO) properties determined. The resulting binuclear complex retains approximately the same transition energies of monomeric (RO)8PcGaCl as far as the linear optical spectrum is concerned, although 1 has a double concentration of central atoms per molecule and an enlarged conjugated ligand. The lack of significant spectral shifts in passing from mononuclear to binuclear complexes has been rationalized theoretically by means of density functional theory calculations. The purpose of the present study is to determine whether binuclearity affects the optical limiting behavior of 1 with respect to monomeric (RO)8PcGaCl in the NLO regime determined by nanosecond laser pulses.