Phthalocyanines alkali metal complexes

The protons released are presumably available to compensate for the loss of the charge balancing cations within the zeolite. In conventional syntheses, the phtha-lonitrile condensation normally requires the nucleophilic attack of a strong base on the phthalonitrile cyano group [176, 177]. This function is presumably accommodated by the Si-O-Al (cation) basic sites within the ion-exchanged faujasite zeolites [178, 179]. The importance of this role is perhaps emphasized by the widespread use of alkali metal exchanged faujasites, particularly the more basic NaX materials of higher aluminium content [180, 181] as hosts for encapsulated phthalocyanine complexes. 

The alkali metal phthalocyanines are, with the exception of the dilithium derivative, fairly insoluble in most organic solvents. The dilithium complex is unique in being soluble in a wide range of organic solvents including alcohol and acetone 11). All the complexes are readily demetallated by dilute aqueous acid. Dilithium phthalocyanine is rapidly demetallated by cold water 11), while disodium phthalocyanine is more resistant to hydrolysis, reacting slowly with hot water. The dipotassium derivative is said to be more readily demetallated than the sodium complex, perhaps because of its larger size 10). 

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)... 

Catalysts for ammonia synthesis consisting of donor-acceptor complexes of alkali metals and transition metal phthalocyanines. (Tokyo University). US 3658721 (1972). 

Figure 15.15 schematically shows a cyano-bridged intrinsic semiconductive phthalocyanine complex that can be synthesized by the displacement of the axial anion X by CN" in a coordinatively unsaturated compound PcMX. This synthesis has been used for the preparation of [PcMn(CN)L [184], [PcFe(CN)], [185], and [2,3-NcFe(CN)], [186]. The starting materials were synthesized by oxidative chlorination of the appropriate phthalocyanines with thionyl chloride or oxygen and concentrated aqueous hydrochloric acid. The chlorides PcMCI (M = Fe, Mn) were converted into the bridged complexes [PcM(CN)] in aqueous or ethanolic alkali metal cyanide solutions. 

The alkali metal dicyano(phthalocyaninato)cobalt-(III) complexes M [PcM(CN)2] were characterized by infrared spectroscopy and in the case of peripherally substituted phthalocyanines also by UV-vis and H NMR spectroscopy. The H NMR spectra of the complexes recorded in acetone-c/ft show the expected number and intensities of signals that confirm the proposed structures. The fact that H NMR spectra are obtained supports the proposed oxidation state -1- 3 and the octahedral ligand field of the Co atom. Otherwise a paramagnetic substance would result. 

History. Braun and Tschemak [23] obtained phthalocyanine for the first time in 1907 as a byproduct of the preparation of o-cyanobenzamide from phthalimide and acetic anhydride. However, this discovery was of no special interest at the time. In 1927, de Diesbach and von der Weid prepared CuPc in 23 % yield by treating o-dibromobenzene with copper cyanide in pyridine [24], Instead of the colorless dinitriles, they obtained deep blue CuPc and observed the exceptional stability of their product to sulfuric acid, alkalis, and heat. The third observation of a phthalocyanine was made at Scottish Dyes, in 1929 [25], During the preparation of phthalimide from phthalic anhydride and ammonia in an enamel vessel, a greenish blue impurity appeared. Dunsworth and Drescher carried out a preliminary examination of the compound, which was analyzed as an iron complex. It was formed in a chipped region of the enamel with iron from the vessel. Further experiments yielded FePc, CuPc, and NiPc. It was soon realized that these products could be used as pigments or textile colorants. Linstead et al. at the University of London discovered the structure of phthalocyanines and developed improved synthetic methods for several metal phthalocyanines from 1929 to 1934 [1-11]. The important CuPc could not be protected by a patent, because it had been described earlier in the literature [23], Based on Linstead s work the structure of phthalocyanines was confirmed by several physicochemical measurements [26-32], Methods such as X-ray diffraction or electron microscopy verified the planarity of this macrocyclic system. Properties such as polymorphism, absorption spectra, magnetic and catalytic characteristics, oxidation and reduc-... 

Radiochromatographic techniques have been used to determine the rates of oxidation of cysteine by pertechnate ion, Tc04. The technetium(vu) is reduced by the thiol (and cysteine ethyl ester) to form a Tc complex which involves both S- and 7V-co-ordination of the amino-acid. The rate law is first order with respect to both [Tc ] and [RSH]. A hydrogen-ion dependence observed is attributed to the formation of pertechnic acid, the rate-determining step being the nucleophilic attack by the thiol at the metal centre of HTCO4. The oxidation of RSH (R=Et, Pr, or Bu) has been studied over the range 20—40 °C in aqueous alkaline solutions in the presence of metal phthalo-cyanines. The reaction is zero order with respect to [thiol], first order in phthalocyanin and decreases in the order M = Co>Mn> V>Feii. No effects are observed from the nature of the alkali cation. 

---