This study presents the preparation of a novel tetra-substituted phthalonitrile (1), namely, 3,6-bis(hexyloxy)-4,5-bis(4-(trifluoromethoxy)phenoxy)phthalonitrile (1) and its metal-free (2)/metal {M = Zn (3), Cu (4), Co (5), Lu(CH₃COO) (6), Lu (7)} phthalocyanines. A series of various spectroscopic methods (UV-vis, FT-IR, mass, and ¹H NMR spectroscopy) were performed for the characterization of the newly synthesized compounds. The potential of compounds 2, 3, and 6 as photosensitizing materials for photodynamic and sonophotodynamic therapies was evaluated by photophysical, photochemical, and sonochemical methods. The highest singlet quantum yields were obtained for the zinc phthalocyanine derivative 3 by performing photochemical and sonochemical methods. In addition, several biological activities of the new compounds 1–7 were investigated. The newly synthesized phthalocyanines exhibited excellent DPPH scavenging activity and also DNA nuclease activity. The antimicrobial activity of the new compounds was evaluated by the disc diffusion assay. Effective microbial cell viability inhibition was observed with phthalocyanine macromolecules. The photodynamic antimicrobial therapy of the phthalocyanines showed 100% bacterial inhibition when compared to the control. They also exhibited significant biofilm inhibition activity against S. aureus and P. aeruginosa. These results indicate that new phthalocyanines are promising photodynamic antimicrobial therapies for the treatment of infectious diseases.

The emergence of nanoscience and its effect on the development of diverse scientific fields, particularly materials chemistry, are well known today. In this study, a new di-substituted phthalonitrile derivative, namely 4,5-bis((4-(dimethylamino)phenyl)ethynyl)phthalonitrile (1), and its octa-substituted metal phthalocyanines {M = Co (2), Zn (3)} were prepared. All the newly synthesized compounds were characterized using a number of spectroscopic approaches, including FT-IR, mass, NMR, and UV–vis spectroscopy. The resultant compounds modified the surface of the gold nanoparticles (NG-1–3). Characterization of the newly synthesized conjugates was carried out by transmission electron microscopy. The antioxidant activity of compounds 1–3, NG-1–3, and NG was evaluated using the DPPH scavenging process and the highest radical scavenging activity was obtained with compounds 1, NG-1, 2, and NG-2 (100%). The antimicrobial activity of compounds 1–3, NG-1–3, and NG was studied using a microdilution assay and the most effective antimicrobial activity was obtained for NG-3 against all the tested microorganisms. The newly synthesized compounds demonstrated high DNA cleavage activity. Compounds 1–3, NG-1–3, and NG significantly inhibited the microbial cell viability of E. coli and exhibited perfect antimicrobial photodynamic therapeutic activity with 100% inhibition after 20 min LED irradiation. Besides, the biofilm inhibition activity of compounds 1–3, NG-1–3, and NG on the growth of S. aureus and P. aeruginosa were examined and compounds 1–3 and NG-1–3, especially NG-1–3, displayed high biofilm inhibition activities.