Synthesis and singlet oxygen generation of boron-2-(4,5-dibromo-1H-imidazole-2-yl)-3,5-dipyrazolopyridine complex for antimicrobial photodynamic therapy

Abstract

In this study, the pyridine side of a boron 2-(2'-pyridyl) imidazole (BOPIM) core, which has very few derivatives synthesized in the literature and can show fluorescence properties in solid form, was derivatized with 1-methylpyrazole, predicted to have activity against fungi or bacteria according to the literature. Additionally, its imidazole side was brominated to increase the efficiency of singlet oxygen production by increasing the intersystem crossing. The photophysical properties of the new synthesized BOPIM derivative were investigated in general organic solvents with different polarities. While the wavelength of the maximum absorbance was determined as 406 nm in CH₂Cl₂ and THF, the wavelength of the highest emission was measured at 497 nm in CH₃CN solvent. The largest Stokes shift was determined as 104 nm in CH₃CN. This value was considerably higher than those of many photosensitizers. The singlet oxygen generation potential of the BOPIM derivative was revealed using a 440-nm LED lamp in the presence of singlet oxygen scavenger 1,3-diphenylisobenzofuran (DPBF). Additionally, it was demonstrated that the BOPIM derivative had no toxic effects by measurements made in the dark.

Keywords: Antimicrobial photodynamic therapy; BOPIM; pyrazole; singlet oxygen.