Bismuth-Based Coordination Polymers with Efficient Aggregation-Induced Phosphorescence and Reversible Mechanochromic...

Area of Science:

• Materials Science
• Inorganic Chemistry
• Luminescence

Background:

• Bismuth coordination polymers (CPs) are explored for their unique properties.
• The ditopic ligand N-oxide-4,4'-bipyridine (bp4mo) is rarely utilized in CP synthesis.
• Mechanochromic luminescence (MCL) is a phenomenon where materials change color upon mechanical stimulation.

Purpose of the Study:

• To synthesize and characterize novel bismuth coordination polymers using the bp4mo ligand.
• To investigate the mechanochromic luminescence properties of these new bismuth CPs.
• To elucidate the mechanism behind the observed luminescence changes.

Main Methods:

• Synthesis of two bismuth coordination polymers: (TBA)[BiBr4 (bp4mo)] and [BiBr3 (bp4mo)2].
• Characterization of solid-state phosphorescence quantum yields and emission wavelengths.
• Investigation of luminescence changes upon mechanical grinding and recovery via heating or water vapor exposure.
• Computational analysis using Density Functional Theory (DFT) and Time-Dependent DFT (TDDFT) calculations.

Main Results:

• Both synthesized bismuth CPs, (TBA)[BiBr4 (bp4mo)] and [BiBr3 (bp4mo)2], exhibit mechanochromic luminescence (MCL).
• (TBA)[BiBr4 (bp4mo)] shows high solid-state phosphorescence quantum yields (up to 85%) with emission at 540 nm.
• Grinding induced amorphous states and shifted luminescence from yellow to orange/red, with recovery upon heating or hydration.
• Luminescence is attributed to aggregation-induced phosphorescence (AIP).

Conclusions:

• These are the first reported examples of mechanochromic phosphors based on bismuth(III).
• The study highlights the potential of bismuth CPs with bp4mo ligand for developing responsive luminescent materials.
• The findings provide insights into the mechanism of aggregation-induced phosphorescence in bismuth-based systems.