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 Pd^II 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 MPc(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.