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

## TL;DR

This paper describes the synthesis of a new boron complex that efficiently generates singlet oxygen for potential use in antimicrobial photodynamic therapy.

## Contribution

A novel BOPIM derivative was synthesized with enhanced singlet oxygen production and high Stokes shift for photodynamic therapy applications.

## Key findings

- The new BOPIM derivative showed a maximum absorbance at 406 nm and a high emission at 497 nm in specific solvents.
- It exhibited a large Stokes shift of 104 nm in CH3CN, higher than many photosensitizers.
- The compound generated singlet oxygen efficiently and showed no toxicity in dark conditions.

## 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.