Chapter 17
Synergetic Photon Upconversion
Realized by a Controlled Toroidal
Interaction in Hexaarylbenzene
Derivatives
Tadashi Mori
Abstract Triplet-triplet annihilation (TTA) is the most promising photon upconversion (UC) sequence, where a weak light source such as sun light can be used
to frequency upconvert the visible to near-infrared light into a photon with a more
useful wavelength, applicable in such as the solar cell devices. Although this antiStokes shift emission has long been known, and their application has been extensively
investigated, less has been explored the effect on the structural modification of the
relevant sensitizer and acceptor chromophores. Motivated by a beautiful and functional cylindrical structure of light-harvesting proteins, as well as recent investigation
on the cyclic array of nano-wires, we prepared the derivatives of hexaarylbenzene
(HAB) containing 9,10-diphenylanthracene and 2,5-diphenyloxazole units as model
acceptor systems to investigate the efficiency of TTA-UC and the relevant photophysical processes. The dynamics of propeller-shaped HAB structures as well as
toroidal interaction between the peripheral aromatic rings has been well investigated
by combined experimental and theoretical studies on their chiroptical properties.
Yet preliminary, we found that through the synergetic interaction of the peripheral
chromophores, effective energy migration and hopping become possible, to facilitate the efficient TTA-UC, that can be switched on and off by modulation of the
strength of toroidal interaction of the relevant HAB emitter. Further possibilities of
photosynergetic effects in the TTA-UC process are also discussed.
Keywords Triplet-triplet annihilation · Photon upconversion · Anti-Stokes
emission · Toroidal interaction · Exciton delocalization · Hexaarylbenzene
derivatives · Photosynergetic effect
T. Mori (B)
Department of Molecular Chemistry, Graduate School of Engineering, Osaka University, Suita,
Osaka 565-0871, Japan
e-mail: tmori@chem.eng.osaka-u.ac.jp
© Springer Nature Singapore Pte Ltd. 2020
H. Miyasaka et al. (eds.), Photosynergetic Responses in Molecules
and Molecular Aggregates, https://doi.org/10.1007/978-981-15-5451-3_17
287
Synergetic Photon Upconversion
Realized by a Controlled Toroidal
Interaction in Hexaarylbenzene
Derivatives
Tadashi Mori
Abstract Triplet-triplet annihilation (TTA) is the most promising photon upconversion (UC) sequence, where a weak light source such as sun light can be used
to frequency upconvert the visible to near-infrared light into a photon with a more
useful wavelength, applicable in such as the solar cell devices. Although this antiStokes shift emission has long been known, and their application has been extensively
investigated, less has been explored the effect on the structural modification of the
relevant sensitizer and acceptor chromophores. Motivated by a beautiful and functional cylindrical structure of light-harvesting proteins, as well as recent investigation
on the cyclic array of nano-wires, we prepared the derivatives of hexaarylbenzene
(HAB) containing 9,10-diphenylanthracene and 2,5-diphenyloxazole units as model
acceptor systems to investigate the efficiency of TTA-UC and the relevant photophysical processes. The dynamics of propeller-shaped HAB structures as well as
toroidal interaction between the peripheral aromatic rings has been well investigated
by combined experimental and theoretical studies on their chiroptical properties.
Yet preliminary, we found that through the synergetic interaction of the peripheral
chromophores, effective energy migration and hopping become possible, to facilitate the efficient TTA-UC, that can be switched on and off by modulation of the
strength of toroidal interaction of the relevant HAB emitter. Further possibilities of
photosynergetic effects in the TTA-UC process are also discussed.
Keywords Triplet-triplet annihilation · Photon upconversion · Anti-Stokes
emission · Toroidal interaction · Exciton delocalization · Hexaarylbenzene
derivatives · Photosynergetic effect
T. Mori (B)
Department of Molecular Chemistry, Graduate School of Engineering, Osaka University, Suita,
Osaka 565-0871, Japan
e-mail: tmori@chem.eng.osaka-u.ac.jp
© Springer Nature Singapore Pte Ltd. 2020
H. Miyasaka et al. (eds.), Photosynergetic Responses in Molecules
and Molecular Aggregates, https://doi.org/10.1007/978-981-15-5451-3_17
287