Calcium complexes phthalocyanines

Calcium-binding proteins, 6, 564, 572, 596 intestinal, 6, 576 structure, 6, 573 Calcium carbonate calcium deposition as, 6, 597 Calcium complexes acetylacetone, 2, 372 amides, 2,164 amino acids, 3, 33 arsine oxides, 3, 9 biology, 6, 549 bipyridyl, 3, 13 crown ethers, 3, 39 dimethylphthalate, 3, 16 enzyme stabilization, 6, 549 hydrates, 3, 7 ionophores, 3, 66 malonic acid, 2, 444 peptides, 3, 33 phosphines, 3, 9 phthalocyanines, 2,863 porphyrins, 2, 820 proteins, 2, 770 pyridine oxide, 3,9 Schiff bases, 3, 29 urea, 3, 9... 

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. 

This complex may be prepared from quicklime and phthalonitrile (10, 88) or from dilithium phthalocyanine and calcium chloride in ethanol (11). It does not sublime. 

By far the most detailed thermodynamic studies have been made by Berezin, who has looked at the equilibria existing in concentrated sulfuric acid. Linstead s group were the first to observe that some of the metal phthalocyanines were demetallated in concentrated sulfuric acid, whereas others appeared indefinitely stable (10). It was shown that all phthalocyanines which resisted attack were of metals whose radii were of the right size to fit nicely into the space available at the center of the ligand. Berezin has since put these observations on a more quantitative basis (19, 21, 26). Labile complexes (i.e., those which are demetallated instantly or fairly rapidly in concentrated sulfuric acid) include those of the alkali metals, alkaline earth metals, Be, Mg, Cd, Hg, Sb(III), Pb, Sn(II), Mn(II), and Fe(III). Stable complexes (demetallated very slowly in acid) include those of Zn, Al, Cl2Sn(IV), OV(IV), Co(II), Rh(II), Os(IV), Ni(II), Pd(II), Pt(II), and Cu(II). The actual rates of decomposition vary widely thus, while calcium and magnesium phthalocyanines are demetallated very rapidly, silver and lead phthalocyanines react fairly slowly (19). The rates of decomposition in 1 M sulfuric acid increase in the sequence (19) Fe(III)... 

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