Conformational Control Governs Photoswitching Efficiency in Diazocines

Area of Science:

• Photochemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Diazocines are promising photoswitchable molecules, outperforming traditional azobenzenes.
• The trans isomer of diazocines can exist in multiple conformations, affecting their performance.
• Understanding these conformations is crucial for designing efficient photoswitches.

Purpose of the Study:

• To investigate the distinct conformations of diazocine trans isomers.
• To determine how these conformations influence photoswitching efficiency.
• To establish design principles for improved diazocine-based photoswitches.

Main Methods:

• Matrix isolation spectroscopy at cryogenic temperatures (4 K) in solid argon and nitrogen.
• Photochemical studies on parent diazocine, 2,9-diiododiazocine, and S-diazocine.
• Combined experimental and computational explorations.

Main Results:

• Two distinct trans isomer conformations, twist (E-t) and chair (E-c), were identified.
• The twist conformation shows superior photoswitching behavior compared to the chair conformation.
• S-diazocine exemplifies reduced performance when both conformations are similarly stable.

Conclusions:

• A key structure-function relationship exists between diazocine conformation and photoswitching efficiency.
• Cryogenic temperature observations provide valuable design parameters for room/physiological temperatures.
• To maximize photoswitch performance, stabilization of the chair conformation in the trans state should be avoided.