EFFECT OF EXCITATION WAVELENGTH ON PHOTOREDUCTION OF METAL-FREE AND COPPER(II) 1,4,8,11,15,18,22,25-OCTABUTOXYPHTHALOCYANINES WITH TRIETHANOLAMINE

Irradiation of 1,4,8,11,15,18,22,25-octabutoxyphthalocyanine (H(2)Pc(O Bu)(8)) and its copper derivative (CuPc(OBu)(8)) in degassed ethanol s olutions containing triethanolamine with red light at 656 nm exciting their Q band did not induce any reaction but the irradiation with UV-v iolet light at 313-425 nm exciting their Soret band led to their reduc tion. The reciprocal quantum yields for photoreduction of H(2)Pc(OBu)( 8) and CuPc(OBu)(8) on 365 nm excitation increased with increasing rec iprocal concentration of triethanolamine. Among the excitation light w avelengths, 360 nm light was the most effective for photoreduction. On the basis of these and other findings, the mechanism of the reaction is discussed and the participation of a higher excited state of the ph thalocyanines is suggested.