Photooxidation of 1,5-dihydroxynaphthalene with iridium complexes as singlet oxygen sensitizers

Abstract

Photooxidation reactions of 1,5-dihydroxynaphthalene (DHN) have been carried out in the presence of cyclometalated neutral and cationic iridium (Ir) complexes 1-6 as singlet oxygen ((1)O(2)) sensitizers in order to investigate the (1)O(2) generation quantum yield and photosensitizing durability of the complexes. The reactions allowed a successful kinetic study to provide the pseudo-first-order rate constants and the initial rates of DHN consumption, which in turn led to the (1)O(2) generation quantum yields. The results revealed that cationic Ir complexes [Ir(ppy)(2)(phen)(+) (4) and Ir(ppy)(2)(bpy)(+) (5), where ppy = 2-phenylpyridine, phen = 1,10-phenanthroline, bpy = 2,2'-bipyridyl] have high (1)O(2) generation quantum yields (Φ(Δ) = 0.93, 0.97). On the other hand, neutral complexes with lower oxidation potentials were considered to have a more efficient charge-transfer (CT) interaction with molecular oxygen, which decreased the efficiency of singlet oxygen formation. Additionally, a steric factor of the ligands was reflected in (1)O(2) generation quantum yield. High yields of the oxidized product for the photoreactions using the cationic complexes indicated their excellent photosensitizing durability, originating from the high photochemical stability upon irradiation.

Mitochondria-targeting cyclometalated iridium(III)–PEG complexes with tunable photodynamic activity

“…The triplet emissive states of many iridium(III) complexes show efficient oxygen quenching and are effective 1 O 2 sensitizers [13e15, 45,46]. In this work, the quantum yields for 1 O 2 production (F D ) of all the complexes were evaluated in aerated DMSO using a steady-state method with DPBF as a 1 O 2 scavenger [36], and the results are listed in Table 2.…”

A study of acridine and acridinium-substituted bis(terpyridine)zinc(ii) and ruthenium(ii) complexes as photosensitizers for O2 (1Δg) generation

“…Samples were withdrawn (by syringe) in 0.5 min (initial) to 5 min time intervals. Details about the procedure can be found in the reports of Murata et al 36 and Zhao et al, 43 specifically, we adopted the semi-preparative mode of operation but without the stringent use of 10 mol% photocatalyst. Experiments were performed with the absorbance maximum of the sensitizer adjusted between 0.1 and 0.3, 37c,43b preferably lower concentrated and optically matched (vide infra).…”

“…Concentrations of all reagents and the product 5-hydroxy-1,4-naphthoquinone (Juglone) were calculated from the known molar extinction coefficients (ε) at λ max (DHN and Juglone, see ref. 36; own sensitizers, see Table 2). The molar extinction coefficients of [Ru(bpy) 3 ] 2+ and MB were determined for the specific solvent mixture and found to be 15 200 M −1 cm −1 for [Ru(bpy) 3 ] 2+ , and 93 850 M −1 cm −1 for MB at λ max , respectively, which are both in good agreement with the values reported.…”

Sensing of 2,4,6‐Trinitrotoluene (TNT) and 2,4‐Dinitrotoluene (2,4‐DNT) in the Solid State with Photoluminescent RuII and IrIII Complexes

“…[29] A new, water-soluble, anionic iridium(III) bis-cyclometalated complex is reported in this work, [ + it was also possible to use dichloromethane. The use of different solvents allowed us to study the effect of polarity on the sensing of the nitroaromatics.…”