Mechanically Interlocked Radicals for Air-Stable Redox States
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Solution Overview
Problem
The synthesis and isolation of persistent organic radicals in crystalline forms remain challenging due to their fleeting existence and tendency to undergo dimerization or oxidation, and achieving molecular systems with adjustable redox states is difficult.
Innovation Solution
Mechanically interlocked air-stable persistent organic radicals are developed, comprising a first ring with a 4,4′-bipyridinium subunit or derivative and a diazapyrenium subunit, allowing access to multiple radical and cationic redox states, with specific compositions and methods for their preparation, including crystalline forms with defined molecular packing arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional organic radicals are synthesized and isolated, then their fleeting existence and tendency to undergo dimerization and oxidation are observed, but achieving persistent air-stable radicals in crystalline forms remains challenging
Solution Approach 1:
The radical system is segmented into multiple redox states through the incorporation of both 4,4'-bipyridinium and 2,7-diazapyrenium subunits within the mechanically interlocked catenane structure. This segmentation allows the radical to access discrete redox states (0, 2+, 4+, 6+, 7+, and 8+) rather than existing as a single unstable state, thereby improving reliability and resistance to degradation
Solution Approach 2:
The patent creates a composite molecular system by integrating two different redox-active subunits (4,4'-bipyridinium and 2,7-diazapyrenium) into a single mechanically interlocked catenane structure. This composite approach enables the radical to exhibit multiple accessible redox states and enhanced stability, resolving the contradiction between reliability and compositional stability
2Adaptability or versatility
If molecular systems with adjustable redox states are designed, then the complexity of synthesis and isolation increases, but achieving air-stable persistent radicals with multiple redox states remains difficult
Solution Approach 1:
The mechanically interlocked catenane structure serves multiple functions simultaneously: it provides mechanical bonding for stability, incorporates multiple redox-active subunits for adjustable redox states, and enables air-stability for persistent radical existence. This multi-functionality achieves adaptability with multiple redox states while managing synthesis complexity through a unified structural platform
3Manufacturing precision
If crystalline forms of persistent radicals are synthesized, then the molecular packing arrangement must be precisely controlled, but achieving defined crystal structures with specific lattice parameters remains challenging
Solution Approach 1:
The patent achieves precise molecular packing in the crystalline state by optimizing local interactions within the catenane structure, including the arrangement of 4,4'-bipyridinium and 2,7-diazapyrenium subunits. This local quality control enables defined crystal structures with specific lattice parameters (a=13.5±0.1 Å, b=16.5±0.1 Å, c=22.5±0.1 Å) while managing the overall complexity of crystal engineering
Data Source
AI summary
Provided herein are mechanically interlocked air-stable persistent organic radicals. The radical compositions may access a multiplicity of radical, cationic redox states as well as a fully cationic redox state. A composition comprises a first ring mechanically interlocked with a second ring or a salt thereof, wherein the first ring comprises a 4,4′-bipyridinium subunit or a derivative thereof and a diazapyrenium subunit or a derivative thereof and the second ring comprises a 4,4′-bipyridinium subunit or a derivative thereof. In some embodiments, the second ring further comprises a diazapyrenium subunit or a derivative thereof. Methods of preparing the compositions are also provided.