Phthalocyanines magnesium

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. 

Metal-free, chloroaluminum phthalocyanine [14154-42-8] vanadyl phthalocyanine [13930-88-6], or magnesium phthalocyanines are sufficiently soluble in organic solvents and show enough bleachable absorption at 694.3 nm to serve as repeated Q-switching elements for mby lasers (qv) (180). Phthalocyanines have been used in other lasers as weU (181). 

Magnesium phthalocyanine (PcMg) can be prepared in a melt of the phthalonitrile and elemental magnesium. Often some ammonium molybdatc(VI) is added. Remaining phthalo-nitrilc and magnesium are removed by extraction with a suitable solvent and by washings with hydrochloric acid, respectively.55-83-97 136 137... 

Similarly, the metal-free equivalent of phthalocyanine 21 was obtained in a yield of 30% by heating phthalonitrile 20 in the presence of magnesium sulfate, sodium sulfate, urea, and ammonium molybdatc(IV) as catalyst at 260-280 C for 2 hours.4 4... 

The photophysical properties of magnesium(II) tetra-(i-butyl)phthalocyanine (27) have been studied in solution, in micelles and in liposomes cation radical formation (CBr4 as electron acceptor) has been detected with UV excitation, or by a two-photon excitation using a pulsed laser in the therapeutic window at 670 nm.118 The Mg11 complex of octa(tri-z -propylsilylethy-nyl)tetra[6,7]quinoxalinoporphyrazine (28) has been prepared as a potential PDT sensitizer. The synthesis is shown in Figure 8. Compound (28) has Amax 770 nm (e = 512,000 M-1 cm-1), d>f = 0.46 and d>A = 0.19 (all in THF, under air).119... 

The phthalocyanine [1-4] system is structurally derived from the aza-[18]-annulene series, a macrocyclic hetero system comprising 18 conjugated n-electrons. Two well known derivatives of this parent structure, which is commonly referred to as porphine, are the iron(III)complex of hemoglobin and the magnesium complex of chlorophyll. Both satisfy the Htickel and Sondheimer (4n + 2)- electron rule and thus form planar aromatic systems. 

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. 

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. 

Phthalocyanine is likewise obtained by hydrolyzing a corresponding calcium or magnesium salt in an acidic medium. 

A. Wong, R. Ida, X. Mo, Z. Gan, J. Poh and G. Wu, Solid-state Mg NMR spectroscopic and computational studies of organic compounds. Square-pyramidal magnesium(ll) ions in aqua(magnesium) phthalocyanine and chlorophyll a. ]. Phys. Chem. A, 2006,110, 10084-10090. 

O. Lumpkin, Mg and N nuclear quadrupole resonances in chlorophyll-a and magnesium phthalocyanine. /. Chem. Phys., 1975, 62, 3281-3283. 

Photochemical transformations invoiving magnesium porphyrins and phthalocyanines... 

The photochemistry of true organomagnesium compounds remains almost completely unexplored. A literature search in preparation of this work found only a few scattered examples of photochemical studies, mostly in relation to Grignard reactions and 1,3-diketonate chelates Similar to the situation with organozinc compounds magnesium tetrapyrrole chelates, i.e. magnesium porphyrins 1, 5,10,15,20-tetraazaporphyrins (por-phyrazines) 2 and phthalocyanines 3 have found more interest. This is primarily related... 

Although porphyrins and especially phthalocyanines are stable compounds, both will undergo photooxidative degradation or photoexcited ET reactions . An additional problem with magnesium complexes is their low stability in aqueous solution, as they demetallate quite easily. This is one of the main reasons that many photochemical studies targeted at modeling the natural situation use the more stable zinc(II) complexes. In addition, past years have seen increasing evidence that both Mg(II) and Zn(II) chlorophylls do exist in nature. 

For example, in 1963 the photochemistry of magnesium phthalocyanine with coordinated uranium cations was studied in pyridine and ethanol and indicated the occurrence of PET to the uranium complex . A rapid photoinduced electron transfer (2-20 ps) followed by an ultrafast charge recombination was shown for various zinc and magnesium porphyrins linked to a platinum terpyridine acetylide complex . The results indicated the electronic interactions between the porphyrin subunit and the platinum complex, and underscored the potential of the linking para-phenylene bisacetylene bridge to mediate a rapid electron transfer over a long donor-acceptor distance. 

The low stability of the magnesium porphyrins has precluded most potential applications. Other metallotetrapyrroles have found industrial uses for oil desulfurization, as photoconducting agents in photocopiers, deodorants, germicides, optical computer disks, semiconductor devices, photovoltaic cells, optical and electrochemical sensing, and molecular electronic materials. A few scattered examples of the use of Mg porphyrins in nonlinear optical studies have appeared" and magnesium phthalocyanines have been used in a few studies as semiconductor or photovoltaic materials" " One of the few... 

The photosensitivity spectra of the saturated polymers containing phthalo-cyanine are shown in Fig. 49 [286]. The photosensitivity is due to the presence of the dye. The pure p form magnesium phthalocyanine has nearly the same spectra. Apparently the polymer matrix environment promotes the P-form formation. The long wavelength maximum is related to the aggregated dye form with solvent inclusion. 

Fig. 49. Photoelectromotive force spectra of the magnesium phthalocyanine in polystyrol (/), polyvinyl carbazole (2), luvican (i) [285]...

The reaction of dibromide 229 with copper(l) cyanide in DMF gave dicarbonitrile 230 in 59% yield (Scheme 28) <1995ACS658>. Template-assisted cyclization of the dicarbonitrile 230 with copper or magnesium powder gave metal phthalocyanines 92 (M = Cu) and 231a (M = Mg) containing metal-free phthalocyanine 231b (M = 2H) (3 7 mixture) in 55% and 64% yields, respectively. 

Synthesis of Magnesium Phthalocyanine from Metallic Magnesium and o-Cyanobenzamide (Classic Experiments of Linstead [2])... 

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