Quantifying Structural Polarization by Continuous Regulation of Lone-Pair Electron Expression in Molecular Crystals

Area of Science:

• Materials Science
• Solid-State Chemistry
• Crystallography

Background:

• Rational design of structural polarization is crucial for advanced technologies.
• Stereochemical lone-pair electrons (LPEs) are key to controlling polarization, but their quantitative relationship with polarization extent is poorly understood.

Purpose of the Study:

• To establish a quantitative relationship between LPE expression and structural polarization.
• To demonstrate precise control and quantification of structural polarization using external stimuli.
• To enhance second harmonic generation (SHG) in molecular crystals.

Main Methods:

• Utilizing pressure to continuously tune LPE expression in molecular crystals.
• Introducing the I-Sb-I angle (α̅) as a metric for LPE expression.
• Quantifying the relationship between α̅ and structural polarization.

Main Results:

• Achieved precise control and quantification of structural polarization by tuning LPE expression with pressure.
• Demonstrated that decreasing α̅ localizes LPEs, repels bonding electrons, and enhances structural polarization.
• Observed enhanced second harmonic generation (SHG) in SbI3·3S8 crystals.

Conclusions:

• Established a quantitative relationship between LPE expression (via α̅) and structural polarization.
• Validated the applicability of this relationship across various molecular crystals for tailored polarization design.
• Showcased LPE tuning as a viable strategy for optimizing functional material properties like SHG.