Donor-acceptor Stenhouse adducts (DASAs) are visible-light-responsive photoswitches with avariety of emerging applications in photoresponsive materials.T heir two-step modular synthesis,centered on the nucleophilic ring opening of an activated furan, makes DASAs readily accessible.However, the use of less reactive donors or acceptors renders the process slow and low yielding,which has limited their development. We demonstrate here that 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) promotes the ring-opening reaction and stabilizes the open isomer,a llowing greatly reduced reaction times and increased yields for knownderivatives.Inaddition, it provides access to previously unattainable DASA-based photoswitches and DASA-polymer conjugates.T he role of HFIP and the photochromic properties of as et of new DASAs is probed using ac ombination of 1 HNMR and UV/Vis spectroscopy. The use of sterically hindered, electron-poor amines enabled the dark equilibrium to be decoupled from closed-isomer halflives for the first time.

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Donor-acceptor Stenhouse adducts (DASAs) are a rapidly emerging class of visible light-activated photochromes and DASA-functionalized polymers hold great promise as biocompatible photoresponsive materials. However, the photoswitching performance of DASAs in solid polymer matrices is often low, particularly in materials below their glass transition temperature. To overcome this limitation, DASAs are conjugated to polydimethylsiloxanes which have a glass transition temperature far below room temperature and which can create a mobile molecular environment around the DASAs for achieving more solution-like photoswitching kinetics in bulk polymers. The dispersion of DASAs conjugated to such flexible oligomers into solid polymer matrices allows for more effective and tunable DASA photoswitching in stiff polymers, such as poly(methyl methacrylate), without requiring modifications of the matrix. The photoswitching of conjugates with varying polymer molecular weight, linker type, and architecture is characterized via time-dependent UV-vis spectroscopy in organic solvents and blended into polymethacrylate films. In addition, DASA-functionalized polydimethylsiloxane networks, accessible via the same synthetic route, provide an alternative solution for achieving fast and efficient DASA photoswitching in the bulk owing to their intrinsic softness and flexibility. These findings may contribute to the development of DASA-functionalized materials with better tunable, more effective, and more reversible modulation of their optical properties.

The development of viable photodynamic therapy protocols is often hindered by photosensitizers that require high-energy UV irradiation that has limited potential for clinical use due to its low tissue penetration. Herein, we report a strategy for extending the excitation wavelength of potential photosensitizers via the covalent attachment of a terbium(III)-1,4,7,10-tetraazacyclododecane-1,4,7-triacetate complex (DO3A-Tb). The method was systematically demonstrated with a series of polycyclic aromatic hydrocarbons (naphthalene, phenanthrene, anthracene, pyrene, and fluoranthene) to prepare six new complexes (Tb1-Tb6) with bathochromic shifts that extended into the visible region. Determination of their quantum yields for singlet oxygen (O) production at 350 and 420 nm showed significant enhancements from the parent molecule in all cases. Cell viability studies on cervical cancer cells (HeLa) and noncancerous MRC-5 cells showed no measurable cytotoxicity for all complexes prior to light irradiation. However, after irradiation at 420 nm (20 min, 9.27 J cm), Tb3-Tb6 were phototoxic to HeLa cells with IC values between 14.3-32.3 μM. Cell morphological studies and fluorescence microscopy with live/dead cell stains confirmed these findings. In addition, these complexes were highly stable in human blood plasma, with no significant degradation observed after 96 h at 37 °C. This excellent phototoxicity profile and high stability in blood plasma, coupled with the moderately lipophilic nature of the complexes, favorably indicate the potential of DO3A-Tb as a heavy atom-bearing moiety for modification of potential photosensitizers into ideal phototherapeutic drug candidates with longer excitation wavelengths for in vivo application.

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A bimacrocyclic luminescent terbium(III) sensor is reported for the selective 'turn-off' detection of Cu 2+ ions in aqueous solutions. The current sensor differentiates from previous sensors in that it offers the use of 1) time-gated luminescence detection to remove background signal, 2) a longer excitation wavelength of up to 350 nm for increased biocompatibility, and 3) a practically irreversible detection as a form of probing Cu 2+ ions with an extremely low limit of detection of about 1.7 nM. Synopsis: The detection of copper ions in aqueous solutions is an active and growing research field relevant to bioanalyses and environmental sampling. There is a high demand for sensitive and selective probes for copper in biological environment including intracellular monitoring. This would allow for a better understanding of the bivalent role of copper in the human body. Herein, we report a bimacrocyclic luminescent terbium(III) sensor for the selective 'turn-off' detection of Cu 2+ ions in aqueous solutions.

Donor-acceptor Stenhouse adducts (DASAs) are visible-light-responsive photoswitches with avariety of emerging applications in photoresponsive materials.T heir two-step modular synthesis,centered on the nucleophilic ring opening of an activated furan, makes DASAs readily accessible.However, the use of less reactive donors or acceptors renders the process slow and low yielding,which has limited their development. We demonstrate here that 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) promotes the ring-opening reaction and stabilizes the open isomer,a llowing greatly reduced reaction times and increased yields for knownderivatives.Inaddition, it provides access to previously unattainable DASA-based photoswitches and DASA-polymer conjugates.T he role of HFIP and the photochromic properties of as et of new DASAs is probed using ac ombination of 1 HNMR and UV/Vis spectroscopy. The use of sterically hindered, electron-poor amines enabled the dark equilibrium to be decoupled from closed-isomer halflives for the first time.