We designed and synthesized self-assembled bis-PtII dimer 1⋅4 BF4 with quino[8,7-b][1,10]phenanthroline as an extended π-face contact area, which acts as the first artificial receptor with high affinity toward iodinated aromatic compounds significantly based on noncovalent iodine⋅⋅⋅aromatic-plane interactions in a “side-on” fashion. Despite their structural similarity to a previously reported metallohost 24+ that bears 2,2′:6′,2′′-terpyridine units, a dramatic change in selectivity toward substituted benzene derivatives was observed for 14+. 1H NMR spectroscopic titration revealed a high affinity of 14+ towards haloarenes, with exceptionally large association constants for 2-iodophenol (Ka=16 000 M−1) and 1,2-diiodobenzene (Ka=21 000 M−1), which are 93- and 140-fold higher, respectively, than the values obtained for 24+. In addition, 14+ showed a remarkably high affinity and selectivity toward 2,6-diiodophenol (Ka=35 000 M−1), which is an important substructure of the thyroid hormone T4. X-ray crystallography and theoretical calculations strongly suggest that “side-on” iodine⋅⋅⋅aromatic-plane interactions and π–π stacking contribute to the strong 1,2-diiodobenzene and 2,6-diiodophenol binding. The results obtained here give unique and valuable insight into the nature of halogen atom interactions in their “side-on” region with an electropositive aromatic plane, which may provide useful guidance for designing artificial receptors for iodinated biomolecules.
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