7‐Oxy‐3,4‐cyclohexenecoumarin Carrying Novel Zinc(II) and Indium(III) Acetate Phthalocyanines: Synthesis, Characterization, Photophysical and Photochemical Properties

Abstract

In this study, 7‐hydroxy‐3,4‐cyclohexenecoumarin (1), two new phthalonitriles, 7‐(2,3‐dicyanophenoxy)‐3,4‐cyclohexene‐coumarin (2), 7‐(3,4‐dicyanophenoxy)‐3,4‐cyclohexenecoumarin (3), were prepared. The phthalonitrile derivatives 2 and 3 were converted to the respective non‐peripheral tetra, peripheral tetra 7‐oxy‐3,4‐cyclohexenecoumarin substituted zinc(II) (4,6) and indium(III)acetate phthalocyanine (5,7) derivatives. All novel purified compounds (2‐7) were characterized by elemental analysis, FT‐IR, UV‐vis, 1H NMR, 13C NMR, MALDI‐TOF mass data. The spectral, photophysical (fluorescence quantum yields and lifetimes), and photochemical (singlet oxygen generation and photodegradation under light irradiation) properties of the synthesized Pcs (4‐7) were studied in DMF, and the results were compared to determine the effects of the locations of substituents and the diversity of the central metal atom on these properties. The 7‐oxy‐3,4‐cyclohexenecoumarin bearing phthalocyaninatozinc(II) and indium(III)acetate complexes showed good solubility in organic solvents such as chloroform, dichloromethane, tetrahydrofuran, acetone, DMF and DMSO. The fluorescence quenching behavior were investigated using 1,4‐benzoquinone as a quencher. They have an acceptable level of singlet oxygen production, which determines the usability of phthalocyanines in photodynamic therapy applications and demonstrated appropriate photodegradation. The thermal properties of Pcs (4‐7) were also investigated.

Synthesis, characterization, and determination of photophysicochemical properties of peripheral and nonperipheral tetra‐7‐oxy‐3,4‐dimethylcoumarin substituted zinc, indium phthalocyanines

“…The coumarin compound (1) was prepared via Pechmann condensation, compounds 2 and 3 were prepared via nucleophilic aromatic substitution, and phthalocyanine compounds (4-7) were prepared via phthalonitrile derivatives' cyclotetramerization according to the literature. [46][47][48]…”

“…Fluorescence quantum yield (Φ F ) is the amount of molecules in the excited state that do return ground state by fluorescence, and it is an important parameter for PDT applications. [43,46] Fluorescence quantum yield (Φ F ) was measured in DMF for the synthesized phthalocyanine compounds (4-7). The phthalocyanines' fluorescence quantum yield (Φ F ) values were determined in DMF, and results were given in Table 2.…”

“…And also, the Φ F values for 4-7 were found lower than their counterparts containing different substituents on coumarin in the literature. [16,29,46,50] This can be due to more quenching of fluorescence via the substitution of the phthalocyanine compounds with two methyl groups located at 3 and 4 position on coumarin. It was observed that the Φ F values of zinc phthalocyanines (4 and 6) were higher than the indium phthalocyanines (5 and 7).…”

“…The indium phthalocyanines (5 and 7) showed higher singlet oxygen production than the similar coumarin-containing phthalocyanines in the literature. [46,50] UV-vis spectra of 4 for the investigation of singlet oxygen quantum yield (Φ Δ ) by chemical method using DPBF was given in Figure 9a as an example. Also, the decrease of DPBF absorbance at 417 nm for all compounds (4-7) during the singlet oxygen studies was given in Figure 9b.…”

“…The solubility of these compounds in organic solvents can be increased by attaching some groups on the phthalocyanine skeleton. [43][44][45][46] In this study, we combined these two functional materials (coumarin and phthalocyanine) into a single compound, and this time, coumarin skeleton is substituted with two methyl groups at lactone ring. For this purpose, we synthesized 7-oxy-3,4-dimethylcoumarin substituted zinc (II) phthalocyanines (4,6) and indium (III) Cl phthalocyanines (5,7) and investigated their photophysical and photochemical properties as potential PDT agents and compared them with the similar earlier reported analogues.…”