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JOURNAL OF MOLECULAR STRUCTURE, vol.1343, no.142751, pp.1-13, 2025 (SCI-Expanded)
In this study, novel symmetric bis(oxy)-diphthalonitrile derivatives carrying di-Schiff base groups were designed and synthesized for various applications, including pharmaceuticals and photocatalysis. The compounds, 4,4′-((((1E, 1′E)-(1,4-phenylenebis(azanilylidene) bis(methanylylidene) bis(6‑methoxy-2,1-phenylene))bis(oxy))di-phthalonitrile) (2), and their ball-type bis-metal-free (3) and lutetium(III) phthalocyanine complex derivatives (4), were characterized by elemental analysis, FTIR, 1H NMR, 13C NMR, MALDI-TOF MS, and UV–vis spectroscopy (for bis-ball-type double-decker phthalocyanines 3 and 4). The solubility and aggregation behaviors of 2 and 3, containing electron donor and acceptor groups in the symmetric di-Schiff base framework, were studied in various solvents: polar protic, aprotic, "borderline" polar aprotic, and non-polar. These bis-ball-type double-decker phthalocyanine derivatives exhibited high solubility without aggregation in all solvents studied, except hexane for 3 and 4, and water and toluene for 3. To assess their potential as photosensitizers for photocatalytic applications, their photophysical properties in DMSO and photochemical properties in DMSO and DMF were investigated. These bis-ball-type double-decker phthalocyanine derivatives exhibited absorption bands with high molar extinction coefficients in the therapeutic window, along with low but sufficient fluorescence quantum yields, lifetimes, and intersystem crossing probabilities. They also displayed adequate singlet oxygen production and high photostability. These photophysical and chemical properties make them promising candidates for various photocatalytic applications, including biological and biomedical imaging.