Amido functional phthalocyanines as metal ion sensor; synthesis, characterization, spectroscopy, electrochemistry, in-situ spectroelectrochemistry

Tetrasubstituted metal ion sensor amido functional phthalocyanines, PyMA-MPc, {PyMA: [N1,N3-bis(pyridin-2-ylmethyl)malonamide], M = Pd(II), Cu(II) and Co(II)} bearing amido functionality on the periphery were synthesized from the corresponding tetrasubstituted diethylmalonate substituted phthalocyanines, DEM-MPc (DEM: diethylmalonate; M = Pd(II), Cu(II) and Co(II)), and 2-aminopyridine in N,N-dimethylaminoethanol (DMAE) solvent. The new complexes have been characterized by elemental analysis, FT-IR, 1H NMR and mass spectra. Peripheral malonamide groups of the phthalocyanine complexes serve as exocyclic binding sites for metal ion, such as PdII and also increase the solubility in protic solvents, i.e MeOH. Protonation of the pyridyl groups with HCl formed quaternized salts of the MPc, N1,N3-bis(pyridin-2-ylmethyl)malonamide substituted metallophthalocyanines (PyMA-PdPc×8HCl) which are freely soluble in aqueous media. Methylation of M[Pc(CH(COOC2H5)2)4] with CH3I gave the octacationic 2(3),9(10),16(17),23(24)-tetrakis-[N1,N3-bis(N-methylpyridin-2-ylmethyl)malonamide]-phthlocyaninato Cu(II) salts which are freely soluble in water. Voltammetric and spectroelectrochemical studies show that while PyMA-Pd(II)Pc and PyMA-Cu(II)Pc give ring-based reversible/quasi-reversible redox processes, PyMA-Co(II)Pc give both metal and ring-based, reversible/quasi-reversible electron transfer processes.