“…Triplet Photosensitizers (PSs) are compounds showing strong absorption of UV or visible light, efficient intersystem crossing (ISC), appropriate excited state redox potential, and long triplet-state lifetimes. These compounds are widely used for photo-driven energy transfer or electron transfer processes, which are the fundamental photophysical processes in photocatalysis, such as catalytic H 2 evolution by water splitting (DiSalle and Bernhard, 2011;Gärtner et al, 2011Gärtner et al, , 2012, photocatalytic redox synthetic organic reactions (Shi and Xia, 2012;Xuan and Xiao, 2012;Hari and König, 2013), photoreduction of CO 2 (Sato et al, 2013), photodynamic therapy (PDT) (Awuah and You, 2012;Kamkaew et al, 2013;Stacey and Pope, 2013;Jiang et al, 2016;Li et al, 2017), photon upconversion (triplet-triplet annihilation upconversion) (Singh- Rachford and Castellano, 2010;Ceroni, 2011;Zhao et al, 2011;Monguzzi et al, 2012;Simon and Weder, 2012;Zhou et al, 2015), photovoltaics (Guo et al, 2006;Dai et al, 2012;Bittner et al, 2014;Cheema et al, 2014;Etzold et al, 2015), and photo-initiated polymerizations (Goessl et al, 2001;Ho et al, 2010;Rivard, 2012;Cengiz et al, 2017). It is highly desired to find a chromophore to develop a series of triplet PSs to meet these requirements.…”