The incorporation of supermolecular hosts design into traditional organometallic catalyst systems has been recognized, but to date, not fully realized due to the limited availability of functional artificial hosts with cavities and the compatibility of common hosts and catalysts. As a potential solution to current challenges, we examined the structural and electronic complementarities of convex 1-Zn(II), comprising functionalized tri(2-pyridylmethyl)amine (TPA) ligand, and concave basket hosts 2 and 3, having glycine and (S)-alanine amino acids at the rim. With the assistance of 1H NMR spectroscopy and mass spectrometry, we found that basket 2 would entrap 1−Zn(II) in water to give equimolar 1−Zn⊆2in complex (K = (2.0 ± 0.2) × 103 M−1) resembling Russian nesting dolls. Through ITC (Isothermal Titration Calorimetry) study, we learned hydrophobic effect was the main driven force for the nesting encapsulation. Moreover, C3 symmetric and enantiopure basket 3, containing (S)-alanine groups at the rim, was found to transfer its static chirality to entrapped 1−Zn(II) and, via intermolecular ionic contacts, twist the ligand's pyridine rings into a left-handed (M) propeller (circular dichroism spectroscopy). With molecular baskets embodying the second coordination sphere about metal-containing TPAs, the described findings should be useful for extending the catalytic function and chiral discrimination capability of TPAs, and therefore enrich the toolbox of selective C-H bonds activation/functionalization chemistry.

Russian nesting doll complexes of molecular baskets and zinc containing TPA ligands

253rd National Meeting (2017)

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