Adjacent versus Opposite Type Di-Aromatic Ring-Fused Phthalocyanine Derivatives:  Synthesis, Spectroscopy, Electrochemistry, and Molecular Orbital Calculations

Abstract

A series of adjacent and opposite type di-aromatic ring-fused phthalocyanines (Pc's) of varying size have been prepared and characterized spectroscopically and electrochemically, and most of their properties have been reasonably reproduced by molecular orbital (MO) calculations. The adjacent isomers alone were obtained preferentially by using a diphthalonitrile unit linked via a short aryl chain. The main results are summarized as follows. (i) The Q-band shifts to longer wavelength and its intensity increases, but the degree of change decreases, with increasing molecular size. On the bases of the experiments and MO calculations, setting the size of the effect of benzene directly fused to the tetraazaporphyrin (TAP) skeleton at unity, the effect of the second and third benzene units is roughly about 0.75-0.80 and 0.48 +/- 0.06, respectively. As a result of this, among compounds having an isomeric pi-system, the Q-band of a D(4h) type species lies at longer wavelength than those of adjacently and oppositely di-aromatic ring-fused species. (ii) The Q-band of adjacently substituted species does not split appreciably, while that of the oppositely substituted species splits substantially, the extent having a parallel relationship with the ratio of long to short axes in the molecule. In general, the larger the ratio, the larger the splitting. (iii) The Q-band of oppositely dibenzo-fused and bis(dialkyl)-substituted TAP does not show explicit splitting because of the large coefficients of the carbons substituted with alkyl groups in the MOs. (iv) Interestingly, the first oxidation in adjacently and oppositely dibenzo-fused CoTAP occurs at the cobalt and ligand, respectively, although they are isomers to each other.

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

“…[22,23] We have therefore performed mixed condensations using o-phthalonitrile and 3,6-diphenylphthalonitrile, employing both methods. In the case of the lithium method, ZnPh 2 Pc (2) was obtained in 16.5 % yield (based on the total mixed nitrile), along with sterically hindered 4 and 5 in yields of 2.7 and 7.1 %, respectively, while little of the opposite isomer, 3, could be isolated.…”

“…[6] Reports on nonplanar substituted Pcs have begun to appear only recently. Cooks group reported the crystal structure of a conformationally stressed 1,4,8,11,15,18,22,25-octaisopentyl H 2 Pc, [7] while we independently reported a highly deformed a-octaphenylated H 2 Pc (H 2 PcPh 8 ). [8] Gorun and co-workers have since characterized the first dome-shaped metal-free Pc in the solid state.…”

Electronic Structures of Zinc and Palladium Tetraazaporphyrin Derivatives Controlled by Fused Benzo Rings

“…[1][2][3] Furthermore, Pcs and tetraazaporphyrins (TAPs) are analogous to porphyrins, which play important roles in biological systems such as photosynthetic reaction centers, heme, and vitamin B 12 .…”

Synthetic approaches to asymmetric phthalocyanines and their analogues

“…Although formation of the other asymmetric and symmetric by-products in this reaction is unavoidable and thus purification of the target adjacent AABB phthalocyanines requires extensive chromatography steps, this method allows formation of rare AABB type compounds in a reasonably selective way. [156][157][158][159][160][161] Moreover, the key advantage of the use of the bis(phthalonitriles) with short rigid bridging groups similar to, for instance, 2,2′-dihydroxy-1.1′-binaphthyl, is suppressed formation of oligomeric phthalocyanines by the self-condensation reaction of such building blocks. …”