Subcomponent Exchange Transforms an Fe(II)4L4 Cage from High- to Low-Spin, Switching Guest Release in a Two-Cage System

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McConnell, AJ 
Aitchison, CM 
Grommet, AB 
Nitschke, JR 

Subcomponent exchange transformed new high-spin Fe(II)4L4 cage 1 into previously-reported low-spin Fe(II)4L4 cage 2: 2-formyl-6-methylpyridine was ejected in favor of the less sterically hindered 2-formylpyridine, with concomitant high- to low-spin transition of the cage's Fe(II) centers. High-spin 1 also reacted more readily with electron-rich anilines than 2, enabling the design of a system consisting of two cages that could release their guests in response to combinations of different stimuli. The addition of p-anisidine to a mixture of high-spin 1 and previously-reported low-spin Fe(II)4L6 cage 3 resulted in the destruction of 1 and the release of its guest. However, initial addition of 2-formylpyridine to an identical mixture of 1 and 3 resulted in the transformation of 1 into 2; added p-anisidine then reacted preferentially with 3 releasing its guest. The addition of 2-formylpyridine thus modulated the system's behavior, fundamentally altering its response to the subsequent signal p-anisidine.

3402 Inorganic Chemistry, 34 Chemical Sciences
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Journal of the American Chemical Society
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American Chemical Society
Engineering and Physical Sciences Research Council (EP/M01083X/1)
European Research Council (695009)
Engineering and Physical Sciences Research Council (EP/K039520/1)
This work was funded by the European Research Council (695009) and EPSRC (EP/M01083X/1)