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Bent N,Nâ˛âdiphenylâdihydrodibenzo[a,c]phenazine amphiphiles are introduced as mechanosensitive membrane probes that operate by an unprecedented mechanism, namely, unbending in the excited state as opposed to the previously reported untwisting in the ground and twisting in the excited state. Their dual emission from bent or âclosedâ and planarized or âopenâ excited states is shown to discriminate between micelles in water and monomers in solidâordered (So), liquidâdisordered (Ld) and bulk membranes. The dualâemission spectra cover enough of the visible range to produce vesicles that emit white light with ratiometrically encoded information. Strategies to improve the bent mechanophores with expanded Ď systems and auxochromes are reported, and compatibility with imaging of membrane domains in giant unilamellar vesicles by twoâphoton excitation fluorescence (TPEF) microscopy is demonstrated. |
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We show that the coherent manipulation of molecular wavepackets in the excited states of trp-containing dipeptides allows efficient discrimination among them. Optimal dynamic discrimination fails, however, for some dipeptide couples. When considering the limited spectral resources at play (3 nm bandwidth at 266 nm), we discuss the concept of discriminability, which appears uncorrelated to both static spectra and relaxation lifetimes. |