Preparation and Electrochemical and Optical Properties of α‐Alkoxyphthalocyanines with β‐Pyridylthio Groups

Abstract

Phthalocyanines (Pcs) 5a‐Mg, 5b‐Mg, 6a‐Mg, and 6b‐Mg with eight alkoxy groups at α‐positions and 2‐ or 4‐pyridylthio groups at the β‐positions, were prepared from 3,6‐dialkoxy‐4,5‐dipyridylthiophthalonitriles. Magnesium complexes 5a‐Mg, 5b‐Mg, and 6a‐Mg were treated with trifluoroacetic acid to produce free‐base compounds 5a‐2H, 5b‐2H, and 6a‐2H. In the UV/Vis spectra, Q‐band absorption of Mg and free‐base Pcs appeared near 760 nm and 780 nm, respectively, in chloroform and 745 nm and 760 nm, respectively, in methanol. Emission spectra of these Pcs showed small Stokes shifts in chloroform and methanol. Reactions of 5a‐Mg, 5b‐Mg, and 5b‐2H with methyl iodide produced the corresponding Pcs 7a‐Mg, 7b‐Mg, and 7b‐2H with methyl pyridinium groups, respectively. After methylation of the pyridine nitrogen, the Pcs were moderately soluble in water but had little solubility in chloroform. The UV/Vis and emission spectra of methylated Pcs 7a‐Mg, 7b‐Mg, and 7b‐2H were obtained in methanol and water. Photobleaching of diphenylisobenzofuran (DPBF) was examined in methanol in the presence of Pcs 7b‐Mg and 7b‐2H, and was monitored by UV/Vis spectroscopy.