Phthalocyanine ring

Fewer articles deal with electrochemical generation of metallopolymers bearing phthalocyanine residues or differently including phtalocyanine within the conductive jr-electron system. However, proposals to use amperometric sensors based on similar modifiers are particularly interesting. Coatings similar to those formed by poly(metaUophenylporphyrine) are reasonably assumed to form (see Fig. 3.30). 

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The chemical properties of phthalocyanines depend mosdy on the nature of the central atom. Phthalocyanines are stable to atmospheric oxygen up to approximately 100°C. Mild oxidation may lead to the formation of oxidation iatermediates that can be reduced to the original products (29). In aqueous solutions of strong oxidants, the phthalocyanine ring is completely destroyed and oxidized to phthalimide. Oxidation ia the presence of ceric sulfate can be used to determine the amount of copper phthalocyanine quantitatively (30). 

Dipotassium phthalocyanine (PcK2) can be prepared analogously to the dilithium compound by refluxing phthalonitrile and potassium pentoxide in pentan-l-ol.58 With additional oxygen-donor ligands (e.g., crown ethers) it forms crystals with the potassium bulging outside of the phthalocyanine ring.133134... 

Zirconium phthalocyanine (PcZrCl2) is prepared in a high-boiling solvent like 1-chloro-naphthalene using phthalonitrile and zirconium(IV) chloride.222 If the reaction is carried out without solvent, chlorination of the phthalocyanine ring may occur as a side reaction.223,224... 

Almost every metal atom can be inserted into the center of the phthalocyanine ring. Although the chemistry of the central metal atom is sometimes influenced in an extended way by the phthalocyanine macrocycle (for example the preferred oxidation state of ruthenium is changed from + III to + II going from metal-free to ruthenium phthalocyanine) it is obvious that the chemistry of the coordinated metal of metal phthalocyanines cannot be generalized. The reactions of the central metal atom depend very much on the properties of the metal. 

What If The Phthalocyanine Rings Are Not Connected Bv A Polymer Backbone ... 

Anionic complexes can easily be prepared by the sulfonation of the aromatic rings in the complexes. Sulfonated cobalt phthalocyanine intercalated in a layered double hydroxide host was a stable catalyst for the oxidation of thiols162,163 and phenol derivatives.164 It was concluded that the complex has been intercalated with the plane of the phthalocyanine ring perpendicular to the sheet of the host (edge-on orientation) (Fig. 7.2). 

The electrochromism of the phthalocyanine ring-based redox processes of vacuum-sublimed thin films of [Lu(Pc)2] was first reported in 1970,32 and since that time this complex has received most attention, although many other (mainly lanthanide) metallophthalocyanines have been investigated for their electrochromic properties.1 Lu(Pc)2 has been studied extensively by Collins and Schiffrin33,34 and by... 

In contrast to the ionic complexes of sodium, potassium, calcium, magnesium, barium, and cadmium, the ease with which transition metal complexes are formed (high constant of complex formation) can partly be attributed to the suitably sized atomic radii of the corresponding metals. Incorporated into the space provided by the comparatively rigid phthalocyanine ring, these metals fit best. An unfavorable volume ratio between the space within the phthalocyanine ring and the inserted metal, as is the case with the manganese complex, results in a low complex stability. 

Moreover, the phthalonitrile process has the added advantage of being the more elegant of the two syntheses. This technique makes it possible to produce comparatively pure copper phthalocyanine without obtaining substantial amounts of side products, a phenomenon which is understandable in view of the fact that the phthalonitrile molecule provides the parent structure of the phthalocyanine ring. Formally, rearrangement of the bonds necessitates donation of two electrons to the system ... 

In Fig 1, IR spectra for FePc(t-Bu)4+NaY and FePc(t-Bu)4/NaY showed the bands characteristic of phthalocyanine ring(1400-1320 cm i 1280-1250 cm i for C=N and C=C stretching vibrations of Pc ring, respectively) and peripheral t-butyl groups(1510-1470 cm i). Those IR bands associated with the FePc ring are substantially shifted to lower frequencies for the intrazeolite FePc(t-Bu)4 relative to the external sample and a reference crystalline of FePc(t-Bu)4,... 

The metallophthalocyanines which have found application as elecfiochromes are mainly the rare earth derivatives, especially lutetium, and second row fiansition metals such as zirconium and molybdenum. Synthesis of these molecules follows the fiaditional routes, e.g. condensation of 1,2-dicyanobenzene with a metal acetate in a high boiling solvent (see Chapter 2). These compounds have structures in which the rare earth element is sandwiched between two phthalocyanine rings, e.g. zirconium bisphthalocyanine (1.92 M = Zr) and lutetium bisphthalocyanine (192 M = Lu), the latter protonated on one of the meso N atoms to balance the charge. 

Benzoannulation of the phthalocyanine ring is a way of extending the Jt-orbitals of the central ring system, and moving the long wavelength absorption into the near-lR. Of particular value are the naphthalocyanines (4.20) made from 2,3-naphthalonitrile,... 

Shirai et al. [71] also synthesized a novel class of polyimides containing M(II) phthalocyanine rings by solution condensation in iV-Me-2-pyrrolidone of M(II) [2,9, or 10,2,16 or 17-bis(3,4-dicarboxy benzoyl)] phthalocyanine dianhydride with 2,6-diaminopyridine followed by thermal imidation [71] (Fig. 23). 

However, all the available evidence suggests that these photoreduction reactions do not lead to oxygen formation310"312 (although small amounts of H202 may be produced),309,313 but rather hydroxyl radicals, which subsequently attack the somewhat sensitive skeletons of the porphyrin or phthalocyanine rings.311,312... 

Spectroscopy A spectrum of PtPcCP4, which is typical of these phthalocyanines is shown in Fig. 2. The most intense band is the Q band which occurs between 640 nm and 680 nm for the different metal phthalocyanines. It is the lowest allowed n - n transition of the phthalocyanine ring. In dilute solution, the Q band of the monomer typically had a molar extinction coefficient of 2 x 105 //mole-cm in agreement with previous reports. (2) Additional bands, which have been assigned to phthalocyanine aggregates (2)(3), were observed on the short wavelength side of the Q band in the relatively concentrated solutions used for the nonlinear optical studies. 

The combination of a phthalocyanine ring with crown ether moieties and redox-active tetrathiafulvalenes gave compound 117 (Scheme 64) and was described by Zou as a good candidate for a redox-active Na+ sensor [133]. 

Figure 4. Change in conductivity with time of various phthalo-cyanine-coated electrodes exposed to exponentially diluted vapors. Initial concentration was 100 ppm for ammonia and DMMP but 1000 ppm for water and ethanol. The central atom of the phthalocyanine ring is indicated near each curve.

The bonding in the excimers is covalent in nature. In polar solvents the excimers dissociate forming redox changed radicals, the unpaired electron being localized on the phthalocyanine ring, e.g. 

Thus, a redox photodisproportionation occurs either at the metal atoms or the phthalocyanine rings. 

Electronic and steric cation-anion interactions in complexes of type [L+][Ln(Pc2 )2] also affect the packing of the two staggered phthalocyanine rings, as evidenced in an unsymmetrical funnel-shape for L+ = PNP (PNP = bis(triphenylphosphine) iminium) [213c]. 

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