Development of phenazine-2, 3-diol-based photosensitizers: effect of formyl groups on singlet oxygen generation. (16th June 2021)

• Record Type: Journal Article
• Authors: Ohira, Kazuki; Imato, Keiichi; Ooyama, Yousuke
• Is Part Of: Materials chemistry frontiers. Volume 5:Number 14(2021)
• Page Start: 5298
• Page End: 5304
• Publication Date: 2021-06-16
• Subjects: Materials science -- Periodicals; Chemistry -- Periodicals; 540
• DOI: 10.1039/d1qm00649e
• Languages: English
• ISSNs: 2052-1529

Abstract

Abstract : Phenazine-2, 3-diol-based photosensitizers with different numbers of formyl groups were developed, and their photosensitizing ability to generate singlet oxygen was investigated. Abstract : Phenazine-2, 3-diol derivatives KO-0–3, which have zero to three formyl groups, respectively, have been developed as photosensitizers (PSs) possessing the ability to generate singlet oxygen ( 1 O2 ). The photoabsorption bands of KO-0–3 are significantly red-shifted compared to those of phenazine-2, 3-MOM (methoxymethyl) derivatives 5–8, whose hydroxy and formyl groups are protected, and have onsets at around 600–650 nm. Furthermore, the fluorescence quantum yields ( Φ fl ) of KO-0–3 ( Φ fl = 0.024–0.097) are lower than those of 5–8 ( Φ fl = 0.34–0.46) in solution. To gain insight into the 1 O2 generation properties of KO-0–3, we evaluated the 1 O2 quantum yields ( Φ Δ ) and rate constants ( k obs ), and demonstrated that KO-1–3 possess a higher ability to generate 1 O2 under visible light irradiation than those of 5–8 . Moreover, it was found that the Φ Δ values of KO-0–3 increase in the order of KO-0 (0.036) < KO-1 (0.22) < KO-2 (0.33) < KO-3 (0.41) with increasing number of formyl groups. This result indicates that formyl groups facilitate the intersystem crossing (ISC) from the lowest singlet excited states of the PSs (S1 ) to the triplet excited states (T n ) according to El-Sayed's rule. Consequently, this work provides useful knowledge in molecular design of efficient phenazine-2, 3-diol-based PSs for photodynamic therapy (PDT).