Anion-π Interactions in Direct Amination of Core-Unsubstituted Perylene Monoimides

Area of Science:

• Organic Chemistry
• Materials Science
• Photochemistry

Background:

• Perylene monoimides (PMIs) are versatile chromophores with tunable optoelectronic properties.
• Incorporating amino substituents at peri-positions creates push-pull systems with absorption/emission in UV-vis and Near-IR regions.
• Efficient synthesis of these functionalized PMIs is crucial for their application.

Purpose of the Study:

• To explore and compare various direct amination methods for synthesizing 9-alkylamino and 9-arylamino PMIs.
• To identify the most efficient and versatile method for introducing amino substituents onto the PMI core.
• To elucidate the mechanism of the most successful amination strategy.

Main Methods:

• Survey of five direct amination strategies: neat amines, PCC/AgNO3 oxidant, KMnO4/AgNO3 oxidant, Cu(II) catalysis, and anion-mediated amination.
• Synthesis of a series of 9-alkylamino and 9-arylamino PMIs.
• Spectroscopic and synthetic studies to characterize products and investigate reaction mechanisms.

Main Results:

• Direct amination in neat amines was only successful with pyrrolidine.
• PCC/AgNO3 and KMnO4/AgNO3 systems showed varying yields with different amines, with KMnO4/AgNO3 enabling diamino PMI synthesis.
• Cu(II) catalysis was effective for cyclic amines.
• Anion-mediated direct amination using TBAF or TBAOH provided high yields for a wide range of cyclic, alkyl, and aryl amines.
• Mechanism involves single-electron transfer from the anion, generating PMI radical anions and proceeding via a radical pathway.

Conclusions:

• Anion-mediated direct amination is the most versatile and high-yielding method for synthesizing diverse 9-amino-PMIs.
• This method facilitates the creation of novel push-pull systems with potential applications in optoelectronics.
• Understanding the radical mechanism opens avenues for further synthetic development.