Photochemically Produced Singlet Oxygen: Applications and Perspectives

Abstract

This Review aims to provide early stage researchers with an updated guide to applications of photochemically produced singlet oxygen and, at the same time, widen the experienced researcher's perspectives in a holistic approach to singlet oxygen chemistry. Without being exhaustive, literature between 2010 and early 2018 has been surveyed by focusing on a critical evaluation of new knowledge and applications. After an introductory section concerning singlet oxygen production, detection, and interactions with biological systems, subsequent sections describe current applications of singlet‐oxygen‐enabled technology. Besides strictly chemical synthesis applications, attention has been given to the usage of singlet oxygen in photochemically assisted therapies as well as in environmental remediation. Additionally, the potential of expanding singlet oxygen chemistry to unexplored fields has been discussed.

ortho‐Oxygenative 1,2‐Difunctionalization of Diarylalkynes under Merged Gold/Organophotoredox Relay Catalysis

“…[12] Mechanistically,a ni ntriguingp athway involving aF e-assisted oxygen radical addition to in situ generated vinyl-gold intermediates was found to be operating. [13] Banking on these reports along with our ongoing interest in the field of merged gold/ photoredox catalysis; [14] we questioned the possibility of a [4+ +2] cycloaddition reaction of photocatalytically generated 1 O 2 with the vinyl-gold species or enol-ethers generated in situ via hydroalkoxylation of diarylalkynes with alcohols (Scheme 1b). [13] Banking on these reports along with our ongoing interest in the field of merged gold/ photoredox catalysis; [14] we questioned the possibility of a [4+ +2] cycloaddition reaction of photocatalytically generated 1 O 2 with the vinyl-gold species or enol-ethers generated in situ via hydroalkoxylation of diarylalkynes with alcohols (Scheme 1b).…”

Rose Bengal Immobilized on Supported Ionic‐Liquid‐like Phases: An Efficient Photocatalyst for Batch and Flow Processes

“…The obtained organic phase was dried over Na 2 SO 4 , and the solvent was removed under vacuum to afford the desired 1-(4-vinylbenzyl)-1 H-imidazole (6.55 g, 71 %y ield). FTIR: ñ = 3005, 1570, 1505, 1408, 1320, 1285, 1231, 1017, 825, 745, 622 cm À1 ; Raman: ñ = 3059, 1622, 1571, 1409, 1347, 1205, 1182, 1075, 831, 639 cm À1 ; 1 HNMR (CD 3 The reaction mixture was cooled to RT and transferred to a1 00 mL round-bottomed flask. The product was precipitated with Et 2 O (50 mL) and sonicated for 10 min, and the white solid was then left to settle.…”

“…[1] It can be considered as ag reen reagent, generated in situ from oxygen throughirradiation with visible light of ap hotosensitizer. [3] In this context,d ifferent approaches have been designed for the immobilization of photosensitizers into ad ifferent phase than the reactants and products, facilitating itsr ecovery and reuse for further catalytic cycles. [3] In this context,d ifferent approaches have been designed for the immobilization of photosensitizers into ad ifferent phase than the reactants and products, facilitating itsr ecovery and reuse for further catalytic cycles.…”

“…[2] The use of singlet oxygen does not produce any waste or residue, othert han the photocatalyst, at the end of the process. [3] In this context,d ifferent approaches have been designed for the immobilization of photosensitizers into ad ifferent phase than the reactants and products, facilitating itsr ecovery and reuse for further catalytic cycles. [4,5] However,i n some cases, this immobilization can lead to ar eduction of the photocatalytic efficiency throughq uenching of the excited states by the polymericm atrix or by shortening the lifetime of the reactive species.…”

“…-(Ethane-1,2-diyl)bis[1-(4-vinylbenzyl)-1 H-imidazol-3-ium] chloride (1): Obtained as aw hite solid in 60 %y ield by using the above standard procedure. FTIR: ñ = 3053, 1558, 1416, 1341, 1156, 988, 908, 857, 795, 623 cm À1 ;R aman: ñ = 1620, 1601, 1414, 1316, 1195, 1174, 1016, 828, 629, 291 cm À1 ; 1 HNMR (CD3 OD, 500 MHz): d = 4.74 (s, 4H), 5.28 (d, J = 10.9 Hz, 2H), 5.41 (s, 4H), 5.84 (d, J = 17.7 Hz, 2H), 6.70-6.76 (m, 2H), 7.35 (d, J = 18.1 Hz, 4H), 7.49 (d, J = 8.1 Hz, 4H), 7.72 (d, J = 7.9 Hz, 2H), 7.82 (d, J = 7.9 Hz, 2H), 9.32 ppm (s, 2H); 13 CNMR (CD 3 OD, 300 MHz): d = 35.5, 53.0, 114.5, 122.9, 123.3, 127.0, 129.1, 133.5, 136.0, 139.1 ppm;E SI/MS (m/z):[M 2 + À2Br/2] = 198.2. 3,3'-(Butane-1,4-diyl)bis[1-(4-vinylbenzyl)-1 H-imidazol-3-ium] chloride(2):O btained as aw hite solid with 83 %y ield by using the above standard procedure.…”