Zinc phthalocyanines

Zinc phthalocyanine [14320-04-8] M 580.9. Sublimed repeatedly in a flow of oxygen-free N2. 

Zinc phthalocyanine (PcZn) is prepared from phthalonitrile in solvents with a boiling point higher than 200 C, e.g. quinoline277,278 or 1-bromonaphthalene,137 or without solvent in a melt of phthalonitrile.83,116 The zinc compound normally used is zinc(ll) acetate or zinc powder. The reaction of zinc(II) acetate with phthalic acid anhydride, urea and ammonium mo-lybdate(VI) is also successful.262 The metal insertion into a metal-free phthalocyanine is carried out in an alcohol (e.g.. butan-l-ol).127,141,290 This reaction can be catalyzed by an alkali metal alkoxide.112,129... 

The tetrasubstituted phthalocyanines are formed as a mixture of four structural isomers (see p 736). The description of this substitution pattern is 1,8,15,22-, neglecting the existence of different isomers. Abbreviations, like 1,4-tetrasubstituted phthalocyanine, are often used. An example of the preparation of a tetrasubstituted phthalocyanine without solvent is the formation of zinc phthalocyanine 4. 

A mimic system of a photosynthetic apparatus was realized by solubihzing C-phy-cocyanin and zinc phthalocyanine in reversed micelles of tween-80 dispersed in cyclohexane [63]. 

Once again, a representative sample of zinc phthalocyanine complexes is presented highlighting particular areas of importance. 

The X-ray structure of zinc naphthalocyanate has been determined with Zn—N bond lengths of 1.983(4) A.829 Pentanuclear complexes with a zinc phthalocyanine core and four ruthenium subunits linked via a terpyridyl ligand demonstrate interaction between the photoactive and the redox active components of the molecule. The absorbance and fluorescence spectra showed considerable variation with the ruthenium subunits in place.830 Tetra-t-butylphthalocyaninato zinc coordinated by nitroxide radicals form excited-state phthalocyanine complexes and have been studied by time-resolved electron paramagnetic resonance.831... 

The photochemical formation and the analysis of the absorption and magnetic circular dichro-ism spectra of the anion radical of zinc phthalocyanine were carried out. A complete assignment of the optical spectrum of the anion radical was proposed.834 Similarly, spectroelectrochemical cells have been used to record absorption and magnetic circular dichroism spectra of zinc phthalocyanines and a band assignment scheme proposed.835... 

The redox potentials of zinc-substituted phthalocyanines are shown to be linearly dependent on the total Hammett substituent constant.837 In 1987, Stillman and co-workers used the absorption and magnetic circular dichroism spectra of the zinc phthalocyanine and its 7r-cation-radical species to assign the observed bands on the basis of theoretical calculations. The neutral and oxidized zinc phthalocyanine complexes with cyanide, imidazole, and pyridine were used with the key factor in these studies the stability of the 7r-cation-radical species.838 The structure of zinc chloro(phthalocyaninato) has been determined and conductivity investigated.839... 

Dinaphthotetraazaporphyrins are structural isomers of phthalocyanines. The zinc complex was formed and the properties compared to zinc phthalocyanines demonstrating a lower fluorescence quantum yield for the zinc-fused naphthalene porphyrin (D2h symmetry) vs. the zinc phthalocyanine (D4h)S36... 

Unsymmetrical zinc phthalocyanine analogs with three 15-crown-5 ether ligands appended at the 3,4-positions were synthesized and characterized. Introduction of alkali metal ions results in cofacial dimer formation with evidence for this dimerization from NMR.841... 

The blue aluminum phthalocyanine dye, Tinolux BBS (74), marketed by Ciba, is a commercial SOG.77,78 Zinc phthalocyanines, such as (75), which absorb in the near infrared at 725 nm, are also very good SOGs.73... 

Fingar VH, Wieman TJ, Karavolos PS, Doak KW, Ouellet R, van Lier JE (1993) The effects of photodynamic therapy using differently substituted zinc phthalocyanines on vessel constriction, vessel leakage and tumor response. Photochem Photobiol 58 251-258. 

Minnock A, Vernon DI, Schofield J, Griffiths J, Parish JH, Brown SB (1996) Photoinactivation of bacteria. Use of a cationic water-soluble zinc phthalocyanine to photoinactivate both gramnegative and gram-positive bacteria. J. Photochem. Photobiol. B 32 159-164. 

Since the electrochemical behaviour of metallophthalocyanines has been reviewed,103 we will simply demonstrate the ligand based nature of their redox processes. As a typical example, Figure 57 shows the redox aptitude of zinc-phthalocyanine [Zn(Pc)] CH2C12 in solution,96 together with its molecular structure.104... 

In activated sludge, 80.6% degraded after a 47-h time period (Pal et al., 1980). Chemical/Physical. Zhang and Rusling (1993) evaluated the bicontinuous microemulsion of surfactant/oil/water as a medium for the dechlorination of polychlorinated biphenyls by electrochemical catalytic reduction. The microemulsion (20 mL) contained didodecyldi-methylammonium bromide, dodecane, and water at 21, 57, and 22 wt %, respectively. The catalyst used was zinc phthalocyanine (2.5 nM). When PCB-1221 (72 mg), the emulsion and catalyst were subjected to a current of mA/cm on 11.2 cm lead electrode for 10 h, a dechlorination yield of 99% was achieved. Reaction products included a monochlorobiphenyl (0.9 mg), biphenyl, and reduced alkylbenzene derivatives. 

Gao W, Kahn A (2001) Controlled p-doping of zinc phthalocyanine by coevaporation with tetrafluorotetracyanoquinodimethane a direct and inverse photoemission study. Appl Phys Lett 79 4040... 

The pseudorotaxane self-assembles through hydrogen bonding, and the binding constant, calculated using steady-state fluorescence, is 1.4 x 10. The zinc phthalocyanine derivative exhibited an excited-state lifetime of approximately 3.1 ns. The fast decay of the excited state of 1 ZnPc upon complexation with the fullerene... 

C. Emission pattern from clean tungsten. Central dark region is (110) face, surrounded by four (211) faces. Two smaller dark spots are (100) faces. Two molecules of zinc phthalocyanine, one flat, the other on edge, are visible in and at the edge of the (110) face. 

Isele, U., van Hoogevest, P., Hil ker, R., Capraro, H., Schieweck, K., and Leuenberger, H. (1994). Large-scale production of liposomes containing monomeric zinc phthalocyanine by controlled dilution of organic solventsJ. Pharm. Sci., 83, 1608-1616. 

Porphyrin and its derivatives are well-known model compounds for photosynthetic processes that involve charge separation [87], A zinc porphyrin, a copper porphyrin, and a zinc phthalocyanine (Pc) are chosen and incorporated into PPV backbones. Four polymers are synthesized via the Heck polycondensation [88], The incorporation of these metal complex moieties in polymers XI to XIII is manifested by the appearance of Q bands from metalloporphyrin and zinc Pc... 

Second-generation photosensitizers include chlorins such as rnela -tctrahy-droxyphenyl chlorin (85) and A-aspartylchlorin [76], and phthalocyanines such as the zinc phthalocyanines (86) [77] and (87) [78],... 

Zhang and Rusling [66] employed a stable, conductive, bicontinuous microemulsion of surfactant/oil/water as a medium for catalytic dechlorination of PCBs at about 1 mA cm-2 on Pb cathodes. The major products were biphenyl and its reduced alkylbenzene derivatives, which are much less toxic than PCBs. Zinc phthalocyanine provided better catalysis than nickel phthalocyanine tetrasulfonate. The current efficiency was about 20% for 4,4 -DCB and about 40% for the most heavily chlorinated PCB mixture. A nearly complete dechlorination of 100 mg of Aroclor 1260 with 60% Cl was achieved in 18 hr. Electrochemical dehalogenation was thus shown to be feasible in water-based surfactant media, providing a lower-cost, safer alternative to toxic organic solvents. 

Kobayashi N, Ogata H, Nonaka N, Luk yanets EA (2003) Effect of peripheral substitution on the electronic absorption and fluorescence spectra of metal-free and zinc phthalocyanines. Chem Eur J 9(20) 5123-5134... 

Obirai J, Nyokong T (2005) Synthesis, electrochemical and electrocatalytic behaviour of thiophene-appended cobalt, manganese and zinc phthalocyanine complexes. Electrochim Acta 50(27) 5427-5434... 

Agboola B, Ozoemena KI, Nyokong T (2006) Synthesis and electrochemical characterisation of benzylmercapto and dodecylmercapto tetra substituted cobalt, iron, and zinc phthalocyanines complexes. Electrochim Acta 51(21) 4379—4387... 

Obirai J, Rodrigues Pereira N, Bedioui F, Nyokong T (2003) Synthesis, spectral and electrochemical properties of a new family of pyrrole substituted cobalt, iron, manganese, nickel and zinc phthalocyanine complexes. J Porphyrins Phthalocyanines 7(7) 508-520... 

Fukuda F, Homma S, Kobayashi N (2005) Deformed phthalocyanines synthesis and characterization of zinc phthalocyanines bearing phenyl substituents at the 1,4,8,11,15,18,22, and/or 25-positions. Chem Euro J 11(18) 5205-5216... 

Similarly, the dipyridyl perylenediimide 45 also axially binds to zinc(II) 1,8, 15,22-tetrakis(2,4-dimethyl-3-pentoxy)phthalocyanine (25) to form the corresponding 1 1 and 1 2 supramolecular complexes [48], The coordination of these two compounds has been monitored by UV-Vis, fluorescence, and 1H NMR spectroscopic methods. It has been found that the ligation of pyridyl ligand to zinc phthalocyanine is relatively weak and labile with a binding constant of 2,080 M-1 in CDCI3. The two components can mutually quench the fluorescence of their partner through an electron transfer process. 

Li X, Sinks LE, Rybtchinski B, Wasielewski MR. Ultrafast aggregate-to-aggregate energy transfer within self-assembled light-harvesting columns of zinc phthalocyanine tetrakis (perylenediimide). J Am Chem Soc 2004 126 10810-11. 

Selectivity. The selectivity of photosensitizers can be also affected by central metal ions and substituents at the macrocycle, eg tetrasulphonated chloroaluminium phthalocyanine [Al(pcS4)Cl] localizes well in the tumour, whereas tetrasulphonated zinc phthalocyanine [Zn(pcS4)] (and also disulphonated zinc phthalocyanine [Zn(pcS2)]) shows a relatively poor tumour localization [207],... 

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