Photoremovable protecting groups (PPGs) have attracted much attention not only in the field of organic synthesis but also in biology and materials science because of the spatiotemporally controlled release of various functional molecules upon photolysis. In this study, a new PPG, the 2-(p-aminophenyl)-1hydroxyinden-3-ylmethyl (pAPHi) chromophore, is designed and synthesized for the efficient and fast release of functional molecules with high conversion yields. The photolysis of caged benzoic acid with the pAPHi chromophore in dimethyl sulfoxide released benzoic acid in 96 % yield, with a decomposition quantum yield of 13 %. A high quantum yield of 51 % was observed with the clean formation of benzoic acid (94 % yield) in methanol. Transient absorption spectroscopic analyses clarified the generation of an intermediate carbocation as well as its reactivity.

Compounds with high two-photon absorption (2PA) performance in the near-infrared region have attracted great attention because of their application in the material and biological science. In this study, we have developed a simple and novel octupolar chromophore, tris(4′-nitrobiphenyl)amine 1, with three nitro peripheral groups attached to a triphenylamine core via biphenyl linkers. A mono-branched analogue 2 has also been prepared to investigate the effects of octupolar and dipolar systems on photophysical and 2PA behaviors. Compound 1, despite having a much simpler structure than the previous three-branched scaffolds, exhibits comparable σ 2 values, reaching 1330 GM at 730 nm and 900 GM at 820 nm in toluene. Combined with an outstanding σ 2 /MW ratio (2.2 GM g −1 mol) and a high fluorescence quantum yield (0.51), 1 displays potential as a promising twophoton (2P) probe for bioimaging. Subsequently, the ethylene glycol tetraacetic acid-substituted derivatives featuring octupolar (3 and 5) or dipolar (4 and 6) character have been synthesized and their one-photon (1P) and 2P photochemical reactions have been examined. Finally, 1P-and 2P-triggered uncaging of Ca 2+ from these calcium chelators has been confirmed.