Vanadium phthalocyanine

Vanadium phthalocyanine (PcVO) is prepared from vanadium(IIl) chloride in a melt of phthalonitrile228 to which sometimes ammonium vanadate137 or molybdate229 and urea are added. Also a reaction with vanadium(V) oxide and phthalonitrile in pen tan-1-ol has been performed.230 Besides these direct syntheses, transformation of PcH2 to PcVO in refluxing dimethylformamide with vanadyl sulfate (V0S04) has been carried out.231... 

Merox [Mercaptan oxidation] A process for removing mercaptans from petroleum fractions by extracting them into aqueous sodium hydroxide and then catalytically oxidizing them to disulfides using air. The catalyst is an organometallic compound, either a vanadium phthalocyanine supported on charcoal, or a sulfonated cobalt phthalocyanine. Developed by UOP in 1958 and widely licensed by 1994, more than 1,500 units had been built, worldwide. Unzelman, G. H. and Wolf, C. J., in Petroleum Processing Handbook, Bland, W. F. and Davidson, R. L., Eds., McGraw-Hill, New York, 1967, 3-128. 

There are many dyes which fulfill the above requirements, few of which have been used until now. The first dyes used with a ruby laser were phthalocyanines the free base as well as chloro-aluminum- and vanadium-phthalocyanine in 1-chloronaphthalene or nitrobenzene 22>. While these dyes show little residual absorption 14> and good photochemical stability, the solubility is relatively low and the solvents are not well suited to operation in a laser resonator. 

Recent reviews of the phthalocyanines by Lever (57) and by Moser and Thomas 66) are available. Complexes of phthalocyanine with all of the first row transition elements, excepting scandium, have been prepared. However, titanium and vanadium phthalocyanines are known only as the oxy- or chloro-compounds and are not then strictly square planar. That phthalocyanine has considerable ability to promote the square planar configuration is further demonstrated by the existence of the chromium (III) and manganese(II) complexes (57). 

Vanadium phthalocyanine encapsulated in mesopores of SBA-15 mediated aerobic oxidation of benzene to phenol with 100% selectivity and 11.6% yield in the presence of ascorbic acid [65]. 

The redox electrochemistry of a Fe /Fe couple is easily accomplished on a phthalocyanine-coated electrode with peak separations comparable to that of platinum [141,142,163,164]. Phthalocyanine-coated electrodes are found to be efficient electrocatalysts to catalys catechol, p-benzoquinone and oxalic acid oxidations [120,150]. The electrochemical activity of these electrodes may be due to the high voltage, surface area, high electronic conductivity and redox behaviour of phthalocyanine, vanadium phthalocyanine and other phthalocyanines have been prepared by vapour deposition and show photoelectrochemical responses when dipped in aqueous electrolytes [244-249]. Polymeric phthalocyanines of Co and Fe are coated on active carbon and are shown to give catalytic properties for dioxygen reduction and thiol oxidations. Dioxygen chemisorption and ammonia absorption of metallo... 

Very unstable modifications, like the reddish, chlorine-free a-copper phthalocyanine, can be stabilized with amides or salts of copper phthalocyanine sulfonic acids (59—63). Mixture with other metal phthalocyanines, eg, tin, vanadium, aluminum, or magnesium, also inhibits crystallization change and poor performance in binders and prints (flocculation) due to the hydrophobic character of unsubstituted phthalocyanines. 

Photooxidafions are also iudustriaHy significant. A widely used treatment for removal of thiols from petroleum distillates is air iu the presence of sulfonated phthalocyanines (cobalt or vanadium complexes). Studies of this photoreaction (53) with the analogous ziuc phthalocyanine show a facile photooxidation of thiols, and the rate is enhanced further by cationic surfactants. For the perfume iudustry, rose oxide is produced iu low toimage quantifies by singlet oxygen oxidation of citroneUol (54). Rose bengal is the photosensitizer. 

Phthalocyanine 2 can be prepared from 3-phenylphthalic acid (1) and vanadium(III) chloride in the presence of urea and ammonium vanadate at high temperature in a melt.401... 

The feasibility of synthesizing oxovanadium phthalocyanine (VOPc) from vanadium oxide, dicyanobenzene, and ethylene ycol using the microwave synthesis was investigated by comparing reaction temperatures under the microwave irradiations with the same factors of conventional synthesis. The efficiency of microwave synthesis over the conventional synthesis was illustrated by the yield of crude VOPc. Polymorph of VOPc was obtained ttough the acid-treatment and recrystallization step. The VOPos synthesized in various conditions were characterized hy the means of an X-ray dif actometry (XRD), a scanning electron microscopy (SEM), and a transmission electron Microscopy (TEM). 

In an interesting study, phthalocyanine complexes containing four anthraquinone nuclei (5.34) were synthesised and evaluated as potential vat dyes and pigments [18]. Anthraquinone-1,2-dicarbonitrile or the corresponding dicarboxylic anhydride was reacted with a transition-metal salt, namely vanadium, chromium, iron, cobalt, nickel, copper, tin, platinum or lead (Scheme 5.6). Substituted analogues were also prepared from amino, chloro or nitro derivatives of anthraquinone-l,2-dicarboxylic anhydride. 

There are other metal complexes, such as tin, aluminum, magnesium, iron, cobalt, titanium, and vanadium complexes, which are similarly useful in stabilizing a particular phthalocyanine modification. Moreover, carboxy, carbonamido, sulfo, or phosphono-copper phthalocyanine may be admixed during fine dispersion of the pigment. 

The V02+ phthalocyanine [VO(pc)] has been the subject of patents as it is useful in photoelectrophoretic and xerographic imaging.887 It can exist in at least three solid phases888 and the structure of so-called phase II was determined.889 It is composed of sheets of parallel and overlapping [VO(pc)] molecules and no discrete dimer pair exists. The vanadium is five-coordinate and square pyramidal, and is 0.575 A above the plane of the four nitrogens. The V—N distances do not differ significantly with a mean of 2.026 A the V=0 distance is 1 1.580 A. 

Where the valency of a metal is not indicated, the normal valency of the metal is assumed. Beryllium probably is placed in the 0=N group because of the stability of its phthalocyanine chelate. Most often Be forms very stable bonds with oxygen as the donor element. Vanadium, nickel, and copper from the N > O group and iron from the ON group are the elements most frequently found in petroleum, chelated with porphyrin ligands. The porphyrin chelate contains four nitrogens as donor elements. 

Valinomycin metal complexes, 969 Vanadium complexes acetylacetone exchange reactions, 380 1,4-diaza-l,3-butadiene, 209 dioxygen mononuclear, 321 hydrazido(2-), 148 hydroxamic adds, 506 phthalocyanines, 865 polypyrazolylborates, 248 porphyrins, 824 dioxygen adducts, 325... 

Mitchell and Valero (1982, 1983) studied VO-phthalocyanine (VO-PC) and a Schiff base complex, VO-salen, as model vanadium compounds. The VO-PC provides a metal coordination environment comprised of four nitrogens, similar to the porphyrin. The benzo rings at the /3-pyrrolic positions contribute to enhanced aromaticity in the metal ligand. 

Vanadyl salen is readily converted at 100°C with H2S in the absence of a catalyst to a vanadium sulfide and a free organic ligand (or decomposition products). Vanadyl phthalocyanine is more stable with respect to ring attack and demetallation. Rates relative to catalytic reactions have not been measured. If VO-salen is an appropriate model of vanadium binding in asphaltenes, asphaltenic metals are more readily converted to sulfides under hydrotreating conditions than the porphyrinic metals. This suggests... 

E.p.r. studies459 indicate the formation of sandwich-type dimer complexes of V02+ and etioporphyrin (EP) in light petroleum at 77 K the e.p.r. data are consistent with an EP-EP plane distance of ca. 3.5 A. A planar ligand local environment for Vlv, possibly provided by a phthalocyanine- or porphyrin-type ligand, has been proposed460 to account for the axial microsymmetry of the V17 centre and the absence of zero-field splitting indicated by e.p.r. studies of vanadium in mineral oil. 

Mbambisa G, Nyokong T (2008) Synthesis and electrochemical characterization of a near infrared absorbing oxo vanadium(IV) octa pentyl thio-phthalocyanine. Polyhedron 27(13) 2799-2804... 

Jiang Z, Ou Z, Chen N, Wang J, Huang J, Shao J, Kadish KM (2005) Synthesis, spectral and electrochemical characterization of non-aggregating a-substituted vanadium(IV)-oxo phthalocyanines J Porphyrins Phthalocyanines 9(5) 352-360... 

Suspensions of polyacetylene were prepared as burrs or fibers (46) by using a vanadium catalyst. When the solvent was removed, films of polyacetylene were formed with densities greater than that prepared by the Shirakawa method. These suspensions were mixed with various fillers to yield composite materials. Coatings were prepared by similar techniques. Blends of polypyrrole, polyacetylene, and phthalocyanines with thermoplastics were prepared (47) by using the compounding techniques typically used to disperse colorants and stabilizers in conventional thermoplastics. Materials with useful antistatic properties were obtained with conductivities from 10" to 10" S/cm. The blends were transparent and had colors characteristic of the conducting polymer. For example, plaques containing frans-polyacetylene had the characteristic violet color exhibited by thin films of solid trans-polyacetylene. 

Preliminary results of the reaction between vanadium(iii)-tetrasulpho-phthalocyanine complex with oxygen have been reported these data were compared with those obtained for the corresponding reaction of the hexa-aquo complex ion. The oxidation of methyl ethyl ketone by oxygen in the presence of Mn"-phenanthroline complexes has been studied Mn " complexes were detected as intermediates in the reaction and the enolic form of the ketone hydroperoxide decomposed in a free-radical mechanism. In the oxidation of 1,3,5-trimethylcyclohexane, transition-metal [Cu", Co", Ni", and Fe"] laurates act as catalysts and whereas in the absence of these complexes there is pronounced hydroperoxide formation, this falls to a low stationary concentration in the presence of these species, the assumption being made that a metal-hydroperoxide complex is the initiator in the radical reaction. In the case of nickel, the presence of such hydroperoxides is considered to stabilise the Ni"02 complex. Ruthenium(i) chloride complexes in dimethylacetamide are active hydrogenation catalysts for olefinic substrates but in the presence of oxygen, the metal ion is oxidised to ruthenium(m), the reaction proceeding stoicheiometrically. Rhodium(i) carbonyl halides have also been shown to catalyse the oxidation of carbon monoxide to carbon dioxide under acidic conditions ... 

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