Tunable Aggregation‐Induced Emission of Imidazole Hydrazones by pH and Anions

Abstract

Aggregation-induced emission (AIE) materials have drawn great attention for applicationsa so rganic light-emitting diodes (OLED) and probes. The applications are, however,r estricted by the complexs yntheses and hydrophobic properties. Herein, ao ne-step synthesis of an AIE materialb ased on imidazole hydrazone is assessed. Protonation of the imidazole-H leads to emission color changef rom yellow to green in the solid state. The emission color is recovered upon imidazole-H + deprotonation. Moreover,t he emission wavelength shifts from 532 to 572 nm by anion exchange. In addition, an enhanced emission (F F up to 22.6 %) was obtained with the Br À anion compared with NTf 2 À ,S bCl 5 À ,P F 6 À ,a nd OTf À anions.X -ray crystallography studies togetherw ith theoretical calculations show that the enhanced emissiono f hydrazone salts arises from strong hydrogen bondingb etween the hydrazone proton andt he halide ion (Cl À or Br À ).

Optical Sensing and Imaging of pH Values: Spectroscopies, Materials, and Applications

“…The sensor undergoes a fluorescence color change from orange to green, and the intensity ratio at 516 and 559 nm is enhanced when the pH value is increased from 5.0 to 7.0 (p K a value 4.8). The same is true for other Schiff bases, , salicylaldehyde azines, and of some hydrazones . Some show dual emission and therefore enable ratiometric intracellular sensing .…”

“…The same is true for other Schiff bases, 906 , 907 salicylaldehyde azines, 908 and of some hydrazones. 909 Some show dual emission and therefore enable ratiometric intracellular sensing. 910 Other AIE-based sensors for determination of pHi make use of smartly functionalized anthracenes, 911 of BF 2 chelates 912 , 913 or of E / Z isomers of N -methylpyrrole-benzohydrazide-based BF 2 complexes, these also containing >C=N– bonds of the Schiff base type and undergoing pH-induced AIE.…”

Low-Dimensional Organic Lead Halides with Organic–Inorganic Collaborative Luminescence Regulated by Anion in Dimension

“…Most of Cl forms the Pb–Cl octahedrons with Pb, and the rest of Cl exists in the form of free ions. The 1 H NMR signal of −N–H 3 protons in 2 is 7.93 ppm, and the signal shifts to 8.13 ppm in 3 , indicating that −N–H 3 protons form stronger hydrogen bonds in 3 (−N–H···Br – , −N–H···Cl – , −N–H···Cl–Pb = 2.496 Å, 2.159 Å, 2.395 Å) . In addition, there are multiple hydrogen bonds between −C–H protons of organic cations and Cl–Pb in 3 (C–H···Cl–Pb = 2.748, 2.788, and 2.840 Å), and the free Br – also forms strong hydrogen bonds with the −N–H proton of the adjacent organic cations, which allows for an orderly connection of the organic cations.…”

Cleancap-Regulated Aggregation-Induced Emission Strategy for Highly Specific Analysis of Enzyme

“…2,3 The aggregation of AIE building blocks could be triggered by solubility change, 4 electrostatic interaction, 5 target-site reaction, 6 and environmental stimuli. 7 Most of the AIE-based aggregations are driven by hydrophobic or electrostatic interactions without regular patterns. Controlled assembly of AIE system not only demonstrates excellent signal transduction efficiency but also provides editable aggregate structures for design of further recognition sites.…”

“…Aggregation-induced emission (AIE) exhibits fascinating fluorescence enhancement by the restriction of intramolecular motions in the aggregate state . AIE phenomenon is widely applied in light emitting devices, biosensors, cell imaging, and drug-delivery due to the enhanced signal responses and excellent photostability. , The aggregation of AIE building blocks could be triggered by solubility change, electrostatic interaction, target-site reaction, and environmental stimuli . Most of the AIE-based aggregations are driven by hydrophobic or electrostatic interactions without regular patterns.…”