Inversion of circularly polarized luminescence by electric current flow during transition

Area of Science:

• Organic Chemistry
• Photophysics
• Materials Science

Background:

• Chiral compounds with circularly polarized luminescence (CPL) are crucial for advanced optical applications.
• Designing CPL-active molecules necessitates understanding excited-state electric (μ) and magnetic (m) transition dipole moments.
• Predicting the magnetic transition dipole moment (m) from molecular structure remains a significant challenge.

Purpose of the Study:

• To investigate the influence of substituent positions on CPL properties in chiral binaphthol derivatives.
• To elucidate the relationship between molecular structure, current flow, and the magnetic transition dipole moment (m).
• To establish a predictive framework for designing CPL-active molecules.

Main Methods:

• Synthesis of binaphthol derivatives with varying phenylethynyl (PE) group substitution patterns.
• Experimental characterization of CPL properties, including sign inversion.
• Theoretical calculations to analyze excited-state properties and current flow dynamics during S1 → S0 transitions.

Main Results:

• Achieved CPL-sign inversion in binaphthol derivatives by strategically modifying PE group positions while maintaining axial chirality.
• Theoretical analysis revealed that PE group substitution significantly alters the orientation of the magnetic transition dipole moment (m).
• Proposed that CPL-sign inversion arises from a reversed current flow path during the S1 → S0 transition, impacting m's orientation.

Conclusions:

• The orientation of the magnetic transition dipole moment (m) and CPL sign can be controlled by the substitution pattern of functional groups.
• Predicting current flow from chemical structure offers a pathway to anticipate magnetic transition dipole moment (m) and CPL characteristics.
• This study provides a new strategy for designing CPL-active molecules, especially C2-symmetric compounds involving LUMO → HOMO transitions.