Novel metallophthalocyanines bearing 2-(2-bromophenyl)ethoxy groups: Elucidating the effect of the central atom on singlet oxygen production via photochemical and sono-photochemical processes

Abstract

Photodynamic therapy (PDT) and sonodynamic therapy (SDT) have been developed as alternatives to conventional treatment modalities in the treatment of cancer. The combination of these methods, sono-photodynamic therapy (SPDT), has a higher efficacy than the effective success rates of these two applications alone. The high singlet oxygen production potential of phthalocyanine complexes and their high sensitivity to sound and light make these compounds suitable sensitizers for SPDT and are of great interest to researchers. This study aims to investigate the effect of the central metal ion on the photochemical and sonophotochemical properties of phthalocyanine complexes and to evaluate their potential for use in SPDT, taking into account their singlet oxygen production. For this purpose, tetra-substituted zinc(II) (4), magnesium(II) (5) and biaxially substituted Si (IV) (6) phthalocyanines containing novel phthalonitrile derivatives were synthesized and characterized and the photochemical and sono-photochemical properties of these complexes in DMF were investigated. The results obtained from the excitation of the synthesized compounds by light irradiation and the synergistic effect of light and sound showed that singlet oxygen production increased with increasing heavy atom effect in the molecule. With the photochemical method using light irradiation, Phi Delta values for phthalocyanines (4, 5 and 6) were 0.58, 0.38 and 0.40, respectively, whereas with the sono-photochemical method using the synergistic effect of light and ultrasound, Phi Delta values reached 0.70 for 4, 0.54 for 5 and 0.58 for 6. The data obtained proved that the singlet oxygen production increased slightly by changing the method from light radiation to ultrasound/light. This demonstrated the sensitivity of 4, 5 and 6 to sound. These data indicate that compounds (4, 5 and 6) may be a promising agent in SPDT applications eliminating the disadvantages of PDT and SDT applications. This study will be a pioneer in understanding the sono-photochemical measurements of phthalocyanine compounds for future studies on sono-photosensitizers.