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Conformation- and Coordination Mode-Dependent Stimuli-Responsive Salicylaldehyde Hydrazone Zn(II) Complexes
Han-Wen Zheng1,2, Dong-Dong Yang1, Yong-Sheng Shi1
1Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University, Beijing 100875, China.
Inorganic Chemistry
|April 12, 2023
Summary
Three new zinc(II) complexes display unique stimuli-responsive luminescence. Complex 1 shows reversible photochromism, while complexes 2a and 2b exhibit mechanochromism and delayed fluorescence, offering insights for novel material design.
Area of Science:
- Coordination Chemistry
- Materials Science
- Photophysics
Background:
- Luminescent zinc(II) complexes are valuable for applications requiring responsiveness to external stimuli.
- Schiff base ligands, specifically O,N,O-hydrazones, offer versatile coordination and excellent luminescence.
- Understanding stimuli-responsive mechanisms is key to designing advanced functional materials.
Purpose of the Study:
- To synthesize and investigate the stimuli-responsive behaviors of three novel salicylaldehyde hydrazone zinc(II) complexes.
- To explore the underlying mechanisms of photochromic, mechanochromic, and delayed fluorescence properties.
- To correlate structural features and coordination modes with observed multi-stimuli-responsive characteristics.
Main Methods:
- Synthesis of three salicylaldehyde hydrazone zinc(II) complexes (1, 2a, 2b).
- Characterization of their photoluminescence, photochromism, and mechanochromism in solution and solid states.
- Analysis of crystal-phase transformations and the role of intermolecular interactions (e.g., halogen bonding).
Main Results:
- Complex 1 exhibits reversible photochromic and photoluminescent properties in solution, attributed to configuration eversion and excited-state intramolecular proton transfer (ESIPT).
- Complex 2a shows solid-state mechanochromic luminescence due to crystalline-to-amorphous transformation and possesses delayed fluorescence from halogen bonding.
- Complex 2b displays photochromism via UV-induced electron transfer and radical generation, and can be formed from 2a via crystal-phase transformation.
Conclusions:
- The synthesized zinc(II) complexes demonstrate diverse stimuli-responsive behaviors dependent on their state, conformation, and coordination.
- Mechanisms involving ESIPT, intermolecular interactions, and crystal-phase transformations are crucial for their responsiveness.
- This study provides valuable insights for designing multi-stimuli-responsive materials based on salicylaldehyde hydrazone zinc(II) complexes.
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