Visible-Light-Triggered Photoswitching of Diphosphene Complexes.

Area of Science:

• Organometallic Chemistry
• Photochemistry
• Materials Science

Background:

• Diphosphene transition metal complexes are known for E to Z isomerization under UV light.
• Their potential for photoswitching applications remains largely unexplored.
• This study investigates novel diphosphene complexes for light-induced reversible transformations.

Purpose of the Study:

• To synthesize and characterize diphosphene complexes capable of reversible photoisomerization.
• To explore the mechanism of light-induced haptotropic rearrangements in these complexes.
• To elucidate the electronic factors governing visible-light-induced photoswitching.

Main Methods:

• Synthesis of diphosphene complexes using triflate salt precursors.
• Photoisomerization studies using blue and UV light irradiation (400-470 nm).
• Reversal studies using yellow and red light irradiation (590-630 nm) and coordinating solvents.
• Density Functional Theory (DFT) calculations to understand electronic properties and reaction pathways.

Main Results:

• Red-colored η²-diphosphene complexes (3a,b[OTf]) isomerize to blue-colored η¹-complexes (5a,b[OTf]) upon blue/UV light exposure.
• The haptotropic rearrangement is reversible, reverting to the η²-form with yellow/red light or in coordinating solvents.
• DFT calculations reveal the photochromic isomerization originates from the S₁ excited state via a conical intersection.

Conclusions:

• Demonstrated reversible visible-light-induced photoswitching in diphosphene transition metal complexes.
• Established a mechanism involving haptotropic rearrangement and electronic transitions.
• These findings highlight the potential of diphosphene complexes in developing novel photoswitchable materials.