Aggregation induced phosphorescent N-oxyde-2,2'-bipyridine bismuth complexes and polymorphism-dependent emission

Area of Science:

• Inorganic Chemistry
• Materials Science
• Photochemistry

Background:

• Bismuth complexes are explored for their unique electronic and photophysical properties.
• Ditopic ligands like N-oxide-2,2'-bipyridine (bp2mo) are less common in coordination chemistry.
• Understanding solid-state luminescence in metal complexes is crucial for developing new optical materials.

Purpose of the Study:

• To synthesize and characterize unprecedented bismuth complexes using the ditopic ligand bp2mo.
• To investigate the luminescence properties, specifically phosphorescence, of these bismuth complexes in different phases.
• To elucidate the mechanism behind the observed luminescence, including aggregation-induced effects.

Main Methods:

• Synthesis and crystallization of bismuth complexes with bp2mo.
• Polymorph characterization (α, β, γ phases).
• Photoluminescence spectroscopy (emission spectra, quantum yield measurements).
• Density Functional Theory (DFT) and Time-Dependent DFT (TDDFT) calculations.

Main Results:

• Three polymorphs of [BiBr3(bp2mo)2] were successfully synthesized and crystallized.
• The crystal phases exhibited significant phosphorescence with quantum yields up to 17%.
• The complex showed weak fluorescence in solution, indicating a solid-state effect.
• DFT/TDDFT calculations supported aggregation-induced phosphorescence linked to weak intermolecular interactions.

Conclusions:

• The synthesized bismuth complexes demonstrate aggregation-induced phosphorescence (AIP) in the solid state.
• The ligand bp2mo facilitates unique intermolecular interactions leading to AIP in bismuth systems.
• These findings open avenues for designing novel bismuth-based luminescent materials with tunable solid-state emission.