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Manipulating the Through‐Space Spin–Spin Interaction of Organic Radicals in the Confined Cavity of a Self‐Assembled Cage
Author(s) -
Nakabayashi Koji,
Kawano Masaki,
Kato Tatsuhisa,
Furukawa Ko,
Ohkoshi Shinichi,
Hozumi Toshiya,
Fujita Makoto
Publication year - 2007
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.200600293
Subject(s) - radical , cage , chemistry , confined space , electron paramagnetic resonance , photochemistry , crystallography , nuclear magnetic resonance , organic chemistry , physics , combinatorics , mathematics
We show a new approach to manipulating the through‐space spin–spin interaction by utilizing the confined cavity of a self‐assembled M 6 L 4 coordination cage. The coordination cage readily encapsulates stable organic radicals in solution, which brings the spin centers of the radicals closer to each other. In sharp contrast to the fact that the radical in solution in the absence of the cage is in a doublet state, in the presence of the cage through‐space spin–spin interaction is induced through cage‐encapsulation effects in solution as well as in the solid state, resulting in the triplet state of the complex. These results were confirmed by ESR spectroscopy and X‐ray crystallography. The quantity of triplet species generated by encapsulation in the cage increases with increasing affinity of the radicals to the cage. We estimated the affinity between several types of guests and the cage in solution by cyclic voltammetry. We also demonstrate that the through‐space interaction of organic radicals within the self‐assembled coordination cage can be controlled by external stimuli such as heat or pH.