Antiprotozoal agents as water soluble singlet oxygen photosensitizers: Imidazo[1,2-a]pyridine and 5,6,7,8-tetrahydro-imidazo[1,2-a]pyridine derivatives

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• 作者：Ayman A. Abdel-Shafi^a ; ^{aaashafi@sci.asu.edu.eg" class="auth_mail" title="E-mail the corresponding author} ; Ahlam M. Fathi^b ; Mohamed A. Ismail^c ; David W. Boykin^d
• 关键词：Antiprotozoal agents ; Photophysical properties ; Dual fluorescence ; Quantum yield ; Singlet oxygen
• 刊名：Journal of Luminescence
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：181
• 期：Complete
• 页码：164-170
• 全文大小：1110 K

文摘

In this study we report on the photophysical properties of some imidazo[1,2-a]pyridine and 5,6,7,8-tetrahydroimidazo[1,2-a]pyridine derivatives and their efficiency as singlet oxygen photosensitizers in aqueous media. In aqueous solution, the wavelengths of maximum absorption are in the range of 269–307 nm, while the wavelengths of maximum emission cover the range of 357–462 nm. It has been found that the fluorescence decay of these derivatives were fitted very well with mono-exponential function for one of the compounds and with bi- exponential function for the other compounds with χ² of about 1.0±0.1 in all cases and show solvent isotope effect. It has also been found that excited singlet state relaxation is dominated by non-radiative relaxation pathways. Rate constants for oxygen quenching of the excited singlet states of these compounds are close to the diffusion rate constant in H₂O and D₂O. Singlet oxygen quantum yields photosensitized by imidazo[1,2-a]pyridine and 5,6,7,8-tetrahydroimidazo[1,2-a]pyridine derivatives were reported in D₂O and found to be in the range 0.01-0.1 relative to phenalenone as a standard. The rate constants, k_q^Δ, for quenching of singlet oxygen by ground state sensitizers in D₂O are also reported and found to be in the range (0.82–6.74)×10⁹ M⁻¹ s⁻¹.