Effects of metal ion in cationic Pd(II) and Ni(II) phthalocyanines on physicochemical and photodynamic inactivation properties

•Novel nonperipheral 2-hydroxypyridine tetrasubstituted palladium(II) and nickel(II) phthalocyanines and their quarternized derivatives.•Photophysicochemical studies of the two new quarterner phthalocyanines.•Antibacterial efficiency of novel phthalocyanines against Gram (+) Methicillin-resistant Staphylococcus aureus (MRSA) and Gram (-) Aeromonas hydrophila through photodynamic therapy (PDT). Four novel tetra non-peripheral 2-hydroxypyridine substituted palladium (II) and nickel (II) phthalocyanines and their quaternized derivatives were synthesized. The phthalocyanines were fully characterized by different spectroscopic methods such as UV-Vis, FT-IR, 1H NMR and MALDI-TOF mass spectrometry. The quaternized phthalocyanines showed solubility in DMSO and water within a wide concentration range and with lack of aggregation behavior. The singlet oxygen generation properties were determined for quaternized phthalocyanine complexes in DMSO, water, and water + TritonX 100 solutions. The uptake capability and in vitro photodynamic activity studies performed on two pathogenic bacteria namely Gram (+) Methicillin-resistant Staphylococcus aureus (MRSA) and Gram (-) Aeromonas hydrophila suggested good potential of palladium (II) phthalocyanine complex (5) for the uptake and inactivation of planktonic cultured bacteria. Significant localization of water-soluble Pd(II) phthalocyanine complex was observed for MRSA biofilms. However, this resulted in low efficiency of pathogen inactivation. The newly synthesized nickel (II) phthalocyanine (6) showed lack of inactivation towards both bacterial strains under the applied mild treatment conditions.