Sensitization-initiated electron transfer via upconversion: mechanism and photocatalytic applications

Abstract

A full picture of a new multi-photon excitation mechanism relying on sTTA upconversion is provided, together with selected photocatalytic applications. All mechanistic steps are investigated and the catalytically active species is observed directly.

Modulating TTA efficiency through control of high energy triplet states

“…[1][2][3] Environmental and economic benefits of maximising upconversion quantum yields are evident, as TTA-UC has been identified as a method to increase solar cell efficiencies beyond that of the Shockley-Queisser limit. [4][5][6] Furthermore, TTA-UC has been successfully demonstrated in many photovoltaic, [6][7][8][9][10][11][12][13][14][15][16] photocatalytic, [17][18][19] and biosensing [20][21][22] applications, often where achieving maximum upconversion quantum yield (QY) is a figure of merit. A second figure of merit is the threshold intensity (I th ).…”

Purely organic Vis-to-UV upconversion with an excited annihilator singlet beyond 4 eV

“…24 This field is experiencing a revival as a result of recent upconversion-driven applications for challenging chemical transformations in the greater context of photocatalysis. 1,4,7,25 So far, only five different types of UV annihilators have been identified: PPO, 24,26,27 terphenyl, 28 quarterphenyl, 28 pyrene [29][30][31][32] and naphthalene 3,4,[33][34][35][36] (and their derivatives). 2,36 The energies of these excited annihilator singlets (S 1 ) produced through sTTA with visible (blue or violet) light as energy input have typical values on the order of 3.6 eV.…”

Photophysics of Perylene Diimide Dianions and Their Application in Photoredox Catalysis

“…This can be an advantage because biphotonic processes require typically much higher excitation densities to achieve comparable efficiencies than monophotonic processes. [18] c) Molecular structures of the PDI compounds investigated in this work (dipp = 2,6-diisopropylphenyl, PEG = polyethylene glycol chain comprised of an average of seven repeat units).…”

“…[7a, 9a, 13a] The S 1 lifetime of PDI 2À is 40 times longer and is anticipated to be more reducing than the D 1 state of *PDIC À ,[7c] and furthermore is accessible via excitationw ith asingle green photon instead of requiring the consecutivea bsorption of two blue photons. This can be an advantage because biphotonic processes require typically much higher excitation densities to achieve comparable efficiencies than monophotonic processes [18]. c) Molecular structures of the PDI compounds investigated in this work (dipp = 2,6-diisopropylphenyl, PEG = polyethylene glycol chain comprised of an average of seven repeat units).…”