ZIRCONIUM AND HAFNIUM DIHYDROXY­PHTHALO­CYANINATES: METHODS OF SYNTHESIS AND REACTIVITY

Abstract

Usually in order to obtain out-of-plane sub­stituted phthalocyanine complexes of zirconium and hafnium (PcML2), the reaction of substitution of chlorine atoms in dichloridophthalocyaninates PcMCl2 is used. How­ever, this method has some limitations because during this reaction, hydrogen chloride is released, which can initiate the hydrolysis of starting compounds sensitive to an acidic environment, in particular, β-ketoesters, which, in turn, can lead to the formation of by-pro­ducts and, accordingly, to a decrease purity and yield of target complexes. At the same time, in similar reactions in which the initial phthalocyanine compounds are dihydroxyphthalocyaninates of zirconium and hafnium  (PcM(OH)2), as a result of interaction with dicarbonyl compounds or carboxylic acids, water is formed, which does not have a negative effect on the starting substances or on the course of the reaction as a whole. Methods of obtaining zirconium and hafnium dihydroxyphthalocyaninates based on metal alkoxides and by hydrolysis of the corresponding PcMCl2 were investigated in the work. It was established that the synthesis of PcM(OH)2 based on the corresponding alkoxides occurs with low yields (25–40%), increasing the reaction temperature from 140 to 220oC does not lead to their significant increase. It was found that the hydrolysis of PcMCl2 should be carried out under more stringent conditions than previously described, which makes it possible to obtain PcM(OH)2 with high yields. The reactivity of PcM(OH)2 was investigated when interacting with β-diketones and aliphatic carboxylic acids and compared with the reactivity of PcMCl2. It was established that the reactivity of PcM(OH)2 is similar to PcMCl2.  However, it should be noted that in the case of the synthesis of β-ketoesterphthalocyanine complexes, the use of the corresponding  PcM(OH)2 leads to a significant increase in the yield of the final products of the reaction compared to PcMCl2. This effect can be explained by the fact that hydrogen chloride is not released during the reaction with PcM(OH)2 and, accordingly, hydrolysis of the ester group does not occur.