Hyperconjugative Aromaticity-Based Circularly Polarized Luminescence Enhancement in Polyaurated Heterocycles

Area of Science:

• Organometallic chemistry
• Photophysics
• Aromaticity studies

Background:

• Hyperconjugative aromaticity (HA) is common in metalla-aromatics but its influence on photophysical properties is largely unknown.
• Investigating HA's role is crucial for designing novel functional materials.

Purpose of the Study:

• To explore the impact of different HA scenarios on the photophysical properties of triaurated indolium and benzofuranylium compounds.
• To correlate structural features influenced by HA with chiroptical responses in gold clusters.

Main Methods:

• Synthesis of nearly isostructural triaurated indolium and benzofuranylium compounds.
• Theoretical calculations and structural analyses to understand electronic structures and bonding.
• Synthesis of chiral bibenzofuran-centered gold clusters.
• Photoluminescence and chiroptical spectroscopy (Circular Dichroism and Circularly Polarized Luminescence).

Main Results:

• Biased HA influences metal atom arrangement, frontier orbital parentage, and HOMO-LUMO gaps.
• HA affects electron delocalization, π-coordination, and aurophilic interactions.
• Triaurated benzofuranylium complexes exhibit superior photoluminescence (up to 49.7% quantum yield) compared to indolium analogues.
• Hexanuclear gold clusters show strong Circular Dichroism and intense Circularly Polarized Luminescence (g_lum up to 10^-3) in aggregated and solid states.
• Chiroptical response is linked to HA-driven aggregation and intermolecular exciton couplings.

Conclusions:

• HA significantly tailors photophysical and chiroptical properties in gold complexes.
• Benzofuranylium derivatives offer enhanced luminescence.
• HA-mediated aggregation in hexanuclear clusters amplifies chiroptical signals, enabling applications in chiral sensing and optoelectronics.