Deformed Phthalocyanines: Synthesis and Characterization of Zinc Phthalocyanines Bearing Phenyl Substituents at the 1‐, 4‐, 8‐, 11‐, 15‐, 18‐, 22‐, and/or 25‐Positions

Abstract

The synthesis of a series of zinc phthalocyanines partially phenyl-substituted at the 1-, 4-, 8-, 11-, 15-, 18-, 22-, and/or 25-positions (the so-called alpha-positions) is reported. Macrocycle formation based on 3,6-diphenylphthalonitrile, o-phthalonitrile, and zinc acetate predominantly yielded the near-planar disubstituted complex and opposite tetrasubstituted isomer, while the lithium method yielded the sterically hindered hexasubstituted complex and adjacent tetrasubstituted isomer. All compounds have been characterized by 1H NMR, MALDI-TOF-MS, and elemental analysis methods. In addition, crystal structures have been solved for the di-, hexa-, and octasubstituted complexes and the adjacent tetrasubstituted isomer. DFT geometry optimization calculations predict more highly deformed structures than those observed in the crystals. The packing force of the crystals cannot therefore be ignored, particularly for the less phenyl-substituted derivatives. The crystal structures have revealed that overlap of the phenyl groups causes substantial deformation of the phthalocyanine (Pc) ligands within the crystals, while strong pi-pi stacking in the remainder of the Pc moiety lacking phenyl substituents can suppress the impact of the deformation. Absorption spectra show sizable red shifts of the Q-band with increasing number of phenyl groups. Analysis of the results of absorption spectra and electrochemical measurements reveals that a substantial portion of the red shift is attributable to the ring deformations. Molecular orbital calculations lend further support to this conclusion. A moderately intense absorption band emerging at around 430 nm for highly deformed octaphenyl-substituted zinc Pc can be assigned to the HOMO-->LUMO+3 transition, which is parity-forbidden for planar Pcs, but becomes allowed since the ring deformations remove the center of symmetry.

Pegylated phthalocyanines: synthesis and spectroscopic properties

“…12,24,29–32 Such compounds are often observed to absorb and emit at longer wavelengths compared with their β-substituted analogs. This property could favor their application as photosensitizers for PDT due to the deeper penetration of long wavelength light into most human tissues.…”

A Discrete Supramolecular Conglomerate Composed of Two Saddle‐Distorted Zinc(II)‐Phthalocyanine Complexes and a Doubly Protonated Porphyrin with Saddle Distortion Undergoing Efficient Photoinduced Electron Transfer

“…[11][12][13] The saddle distortion facilitates protonation of pyrrole nitrogen atoms to allow access to a stable diprotonated porphyrin, which can act as an electron acceptor. [14] To construct supramolecular conglomerates composed of both porphyrin and phthalocyanine in a well-defined manner, we have taken advantage of saddle distortion of both components. [12] In contrast, the Zn II complex of the saddle-distorted phthalocyanine 1,4, 8,11,15,18,22,25-octaphenylphthalocyanine (H 2 OPPc) exhibits a lower oxidation potential relative to the corresponding porphyrin complex.…”

Electronic structures of azulene-fused porphyrins as seen by magnetic circular dichroism and TD-DFT calculations

“…It should be noted that the MCD spectra of cone-shaped subporphyrin [11], subphthalocyanine and subnaphthalocyanine [12] compounds also contain similar B term envelopes at slightly higher energy than the Q00 band. Although the possibility that this arises from a z-polarized transition has not been pointed out previously, the intense positive B term intensity in this region may be an indication of the presence of a z-polarized transition [11][12][13][14][15][16].…”