meso-Tetrapyridylporphins and Their Metal Complexes. Syntheses and Physico-Chemical Properties

Three isomers of meso-tetrapyridylporphins, i.e. tetra(2-pyridyl)- (2), (3-pyridyl)-(3), and (4-pyridyl)- (4), porphin have been synthesized. They were soluble in acetic acid, chloroform and acidic aqueous solvents. Solubilities in chloroform, dimethylform-amide and pyridine were in the order 3>2>4. Comparison of the visible spectra indicated that the intensities of the bands due to 0–0 transitions decreased (3>4>2) with an increase of the electron-withdrawing character of the pyridyl substituent. The copper(II) and zinc(II) complexes of 2 and 3 have been prepared. Infrared and nuclear magnetic resonance spectra and their assignments of the porphins and/or the metal complexes were described.