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Photooxidative Generation of Dodecaborate-Based Weakly Coordinating Anions
Jonathan C Axtell1, Marco S Messina1,2, Ji-Yuan Liu3
1Department of Chemistry and Biochemistry , University of California, Los Angeles , 607 Charles E. Young Drive East , Los Angeles , California 90095-1569 , United States.
Inorganic Chemistry
|June 29, 2019
Summary
New redox-active proanions initiate visible-light polymerization of styrenes. These compounds act as photoinitiators and weakly coordinating anions, with reaction conditions influencing polymer length.
Area of Science:
- Polymer Chemistry
- Photochemistry
- Organometallic Chemistry
Background:
- Visible-light-initiated polymerization offers a sustainable and efficient method for polymer synthesis.
- Developing novel photoinitiators that are stable, efficient, and versatile is crucial for advancing polymerization techniques.
- The role of counterions in controlling polymerization outcomes, such as polymer molecular weight and dispersity, is a key area of research.
Purpose of the Study:
- To introduce and investigate novel redox-active proanions as photoinitiators for visible-light-initiated styrene polymerization.
- To explore the influence of these proanions on polymer properties, particularly molecular weight.
- To elucidate the mechanism of initiation and the role of the proanions as weakly coordinating anions (WCAs).
Main Methods:
- Experimental polymerization studies using blue-light irradiation.
- Synthesis and characterization of dodecaborate-based proanions B12(OCH2Ar)12.
- Computational studies to understand the electronic properties and interactions of the proanions.
Main Results:
- Neutral, air-stable proanions initiated styrene polymerization via single-electron oxidation under blue light.
- Polymers with molecular weights ranging from approximately 6 to 100 kDa were obtained.
- Specific reaction conditions, particularly the presence of 4-X substituents on styrene and the use of proanion 1 in CH2Cl2, led to longer polymers (>100 kDa), indicating modulation of ion pairing.
Conclusions:
- The studied proanions function as effective photoinitiators and subsequently as weakly coordinating anions (WCAs) in polymerization.
- Reaction conditions significantly influence the degree of ion pairing, thereby controlling polymer chain growth.
- This work demonstrates a single reagent capable of acting as a strong photooxidant and forming a WCA, offering a versatile tool for polymer synthesis.
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