Tri-nuclear phthalocyanine complexes carrying N/O donor ligands as hydrogen peroxide catalysts, and their bleaching activity measurements by an online spectrophotometric method

A phthalocyanine (4) with four salicylhydrazone ligating groups that are directly linked through oxygen bridges to the macrocyclic core has been synthesized by condensation of tetrakis(4-formylphenoxy)phthalocyaninato zinc(II) (3) with salicylhydrazine. Salicylhydrazine was crystallized in methanol during the synthetic procedure. The crystal structure has triclinic space group P-1 with a = 5.8292(6) Å, b = 7.3039(7) Å, c = 17.9798(18) Å, α = 84.272(8)°, β = 89.184(8)°, γ = 81.469(8)°, and Z = 4. Intramolecular O–H⋯O and intermolecular O–H⋯O, N–H⋯N, N–H⋯O hydrogen bonds were determined in the crystal structure. In addition, there is a weak C–H⋯π interaction. Complexation on the periphery to yield tri-nuclear Zn(II)Pcs (5–7) was performed through the reaction of a Schiff base-substituted phthalocyanine (4) with MnCl₂·4H₂O, CoCl₂·6H₂O, or Ni(OAc)₂ salts. Fourier transform infrared, ¹H NMR, ¹³C NMR, UV–Vis, ICP-OES (inductively coupled plasma optical emission spectroscopy), mass spectroscopies, and elemental analyses were applied to characterize the prepared compounds. Bleach catalyst activity of the prepared phthalocyanine complexes (5–7) was examined by the degradation of morin and curcumin, respectively. The catalysts had better activity for color removing in solutions at ambient temperature than to that of tetraacetylethylenediamine (TAED).