Transformations of meso-Iminofunctionalized Pd(II) and Ni(II)-Complexes of β-Alkylsubstituted Porphyrins

The meso-imino derivatives of the palladium (II) and nickel (II) complexes of coproporphyrins I and II and beta-octaethylporphyrin were obtained by the Vilsmeier formylation followed by interaction with amines. The metal complexes of the azomethines obtained were transformed to the corresponding complexes of cyclopentane and cyclopentane-pyrrolidone fused porphyrin derivatives by thermolysis. The plausible mechanism of such transformations was suggested and substantiated with quantum chemical calculations. Meso-cyano-, meso-hydroxy-, and meso-aminocarbonyl derivatives of beta-octaethylporphyrin were obtained by treatment of the corresponding meso-imino derivatives with bases. Demetalation of the nickel complex of the meso- hydroxy-beta-octaethylporphyrin led to formation of the free base derivative. The structures of new types of the porphyrin derivatives were determined via X-ray powder diffraction analysis. The obtained types of porphyrins are promising candidates to use as photosensitizers in medicine applications due to their longer wave absorption combined with high stability.