Dynamic Induction of Optical Activity in Triarylmethanols and Their Carbocations

Area of Science:

• Organic Chemistry
• Chiroptical Spectroscopy
• Supramolecular Chemistry

Background:

• Triarylmethanols are known for their unique electronic and structural properties.
• Investigating induced optical activity in synthetic molecules is crucial for developing new chiral materials.
• Understanding the factors controlling chirality transfer is essential for molecular design.

Purpose of the Study:

• To synthesize and study artificial triarylmethanols for induced optical activity.
• To elucidate the mechanisms of chirality induction in the triarylmethyl core.
• To explore the influence of substituents and carbocation formation on chiroptical properties.

Main Methods:

• Synthesis of artificial triarylmethanols with varying substituents.
• Chiroptical response measurement, including electronic circular dichroism (ECD) spectroscopy.
• Investigation of hydrogen bonding (e.g., OH···O, HO···HC) and C-H···π interactions.
• Study of carbocation formation and stability under different pH conditions.

Main Results:

• Observed chiroptical response attributed to chiral conformation of the triarylmethyl core.
• Chirality induction occurs via a cooperative and cascade process influenced by hydrogen bonding and C-H···π interactions.
• Substitution patterns (ortho, para) significantly affect Cotton effect intensity and carbocation stability.
• Ortho-substituted derivatives show intense Cotton effects but decompose rapidly upon acidification.
• Two stable carbocations exhibit intense Cotton effects around 450 nm; carbocation formation is reversible.
• Para-substituted triarylmethanol demonstrates solid-state sorting in the crystal.

Conclusions:

• Artificial triarylmethanols can exhibit significant induced optical activity.
• Non-covalent interactions, particularly hydrogen bonding, play a critical role in efficient chirality induction.
• The stability and chiroptical properties of triarylmethyl carbocations are tunable via structural modifications.
• These findings offer insights into the design of novel chiral molecules and materials.