Estimation of Singlet Oxygen Quantum Yield Using Novel Green‐Absorbing Baird‐type Aromatic Photosensitizers^†

Abstract

We report two new organic green‐absorbing singlet oxygen (1O2) photosensitizers: Quinoidal naphthyl thioamide (QDM) and bis‐iodol‐dipyrrolonaphthyridine‐dione (I2–DPND), with triplet energies of 40.8 and 47.5 kcal mol−1(at 77 K in a glassy matrix) , respectively. The UV–vis absorption and emission characteristics of QDM and I2–DPND are similar to other commercially available organic 1O2 photosensitizers such as Rose Bengal, which was used as standard/reference to estimate the 1O2 quantum yield (Φ∆) of the chromophores under study. Using 9,10‐diphenylanthracene (DPA) as an 1O2 quencher, we estimated the Φ∆ ≈ 67–85% for QDM and Φ∆ ≈ 25–32% for I2–DPND. The discrepancy in the Φ∆ values could be explained by the apparent photo‐decomposition of the later dye. Nevertheless, the high Φ∆ value for QDM is unprecedented, as this chromophore exhibits relatively low structural complexity and could further be derivatized to create novel photodynamic agents.

Triplet photodynamic and up-conversion luminescence in donor–acceptor dyads with slip-stacked vs. co-facial arrangement

“…The present investigation complements a recent work 22 (from our group), where a triptycene-based dyad 3 (Fig. 1) -synthesized from a quinoidal naphthylthioamide (QDN) triplet energy donor and 3-ethynyl perylene (Per) -underwent essentially photo-induced charge transfer (CT) [31][32][33][34] in place of the desired QDN -Per triplet energy flow (TnET) (ESI, † Fig. S13).…”

Photophysical Insights of Halogenated Dipyrrolonaphthyridine‐Diones as Potential Photodynamic Therapy Agents†

“… § Singlet oxygen quantum yields were estimated in oxygen‐saturated toluene through the relative methods using QDM as standard: Φ ∆ , QDM = 0.67 (8) in DCM (Figures S7 and S8) for more information. …”

“…The quantum yield (Φ Δ ) of 1 O 2 was calculated using the relative method (Eq. ) and using our previously reported quinodimethyl thioamide chromophore ( QDM ) as the standard (8). The Φ Δ value of Cl 2 –DPND was the lowest at 28%, whereas Br 2 –DPND and I 2 –DPND were measured at 31% and 52%, respectively (Table 1).…”

“…A Xenon lamp source equipped with a monochromator was used to excite samples of X 2 -DPNDs at λ Exc = 510 nm in toluene. The relative Φ Δ values were measured using QDM as a standard (Φ Δ,QDM = 0.67 (8) in DCM) (Figures S7 and S8). A series of solution with OD = 0.05, 0.1, 0.2, and 0.3 at λ Exc = 510 nm were prepared in oxygen-saturated toluene for QDM and the X 2 -DPNDs.…”

“…Inspired by these seminal reports, our group also investigated the iodination of DPNDs (8), with the expectation to rely on heavy atom-induced spin-orbit coupling (SOC) dynamics (9)(10)(11) to increase the triplet state population in this chromophore (I 2 -DPND). Subsequently, I 2 -DPND was employed as a photosensitizer (PS) to produce reactive oxygen species (ROS) 1 O 2 via the type II mechanism (12).…”