Axially disubstituted silicon (IV) phthalocyanines containing different isoxazolyl groups: Design, syntheses, binding and in vitro phototoxic activities against SH-SY5Y cells

The axially different isoxazolyl disubstituted silicon (IV) phthalocyanines were synthesized by reaction of SiPcCl2 with 2-(5-isoxazolyl)-4-methylphenol or 4-chloro-2-(5-isoxazolyl)-5-methylphenol or 4-bromo-2-(5-isoxazolyl)phenol in the presence of NaH in toluene. Techniques used to illuminate the structure of silicon phthalocyanines included FT-IR, MALDI TOF, UV-vis, NMR spectroscopy. Then, we investigated DNA binding (ethidium bromide (EB)-competition studied by flow injection analysis) and in vitro cytotoxic/phototoxic actions on SH-SY5Y cells. The calculated Stern-Volmer constants were 3.7 × 103 M−1 (ISOX-M-SiPc), 1.3 × 105 M−1 (ISOX-Cl-SiPc), and 8.6 × 104 M−1 (ISOX-Br-SiPc), showing the stronger interaction of ISOX-Cl-SiPc with DNA than ISOX-M-SiPc and ISOX-Br-SiPc. The quenching constants (kq) values were calculated to be 1.61 × 1011M−1 s−1, 5.65 × 1012 M−1 s−1, and 3.74 × 1012 M−1 s−1 for ISOX-M-SiPc, ISOX-Cl-SiPc, and ISOX-Br-SiPc, respectively, which are larger than the maximum scatter collision quenching constant (2.0 × 1010 M−1 s−1). The results of MTT assay indicated that cell viabilities were 35 ± 7% and 10 ± 3% with light irradiation in the presence of ISOX-M-SiPc (at 30 and 100 µM). The results showed that ISOX-M-SiPc had the highest phototoxicity among the tested compounds but it had lower phototoxic effecs than methylene blue as a standard compound.