In the crystal structure of the title compound, C(10)H(9)N(2)O(2) (+)·Cl(-)·2H(2)O, the components are linked by O-H⋯O, N-H⋯O, O-H⋯Cl and N-H⋯Cl hydrogen bonds. In the cation, the imidazole ring is oriented at a dihedral angle of 13.67 (17)° with respect to the benzene ring. In the crystal, π-π stacking occurs between nearly parallel benzene rings, which are oriented at a dihedral angle of 3.4 (1)°, the centroid-centroid distance being 3.798 (3) Å.
The advancement of ring‐strain preloaded dipolaro‐/dienophiles plays a crucial role in bioorthogonal chemistry, enabling multiple high‐precision conjugations toward biomolecules simultaneously. However, durability of these ring‐strain preloaded reagents in vivo is a concern, as the ring‐strain is not reloadable once released during delivery process. In‐situ conversion of light‐energy into ring‐strain is a promising approach to ensure both biostability and spatiotemporal control endowed by light. Herein, we advance a seven‐membered cyclic azobenzene photoswitch, dibenzo[b,f][1,4,5]thiadiazepine‐11,11‐dioxide (DBTDD), bridged by a sulphone moiety. The photoisomerization from Z‐DBTDD to ring‐strain‐loaded E‐DBTDD enables an accelerated cycloaddition with various photogenerated dipoles to establish novel photoclick reactions, featuring a dual‐λ (405 nm + 445 nm) synergistic control. In reactions with monoarylsydnones, a higher photo‐stationary ratio of E‐DBTDD, achieved by varying the power density of 445 nm laser, presented an ultrafast cycloaddition rate (kE = 6.6 × 107 M‐1 s‐1) with a 13.8‐fold acceleration compared with Z‐DBTDD, which is superior to established ring‐strain reporters (e.g., BCN‐OH, sTCO‐OH, DBTD). Then, bioorthogonal photoclick labeling of DBTDD tagged artificial phospholipid on living cell membranes was realized at subcellular resolution via an essential dual‐λ intersecting lithography with an elevated efficiency by adjusting the 445 nm power density.
A visible-light induced photo-click and release approach between monoarylsydnone and phenoxylfumarate was established to realize a precise dual fluorescence turn-on under light control.
Intracellular lipid storage and regulation occur in lipid droplets, which are of great significance to the physiological activities of cells. Herein, a lipid droplet-specific fluorescence probe (lip-YB) with a high quantum yield (QYlip-YB = 73.28%), excellent photostability, and quickly polarity sensitivity was constructed successfully. Interestingly, lip-YB exhibited remarkable two-photon (TP) characteristics, which first realized real-time monitoring of the lipid droplet multidynamics process, diagnosing nonalcoholic fatty liver disease (NAFLD) and inflammation in living mice via TP fluorescence imaging. It is found that the as-prepared lip-YB provides a new avenue to design lipid droplet-specific imaging probes, clarifies its roles and mechanisms in cell metabolism, and can timely intervene in lipid droplet-related diseases during various physiological and pathological processes.
Abstract A library of 12 N , 9 ‐Diaryl 2‐methyl‐8‐azaadenine (DAMA) compounds was designed and constructed through an aryl‐pairing combination strategy for identifying a nucleobase‐containing molecular switch that functions by the pH‐regulated Dimroth rearrangement. By utilizing 2D thin‐layer chromatography/mass spectrometry (2D‐TLC‐MS), the DAMA compounds were easily screened to identify which compounds could be used as molecular switches. The pH‐switching ability of the DAMA was achieved by incorporating the acridine group as the key structural unit, as well as dual‐modal colorimetric/fluorometric on/off properties as the probe functions. The real‐time tracing of the switching process clearly indicated that the paired aromatics on both terminals of the DAMA molecule play a key role in tuning the switching kinetics.
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