Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology (BIST), Av. Països Catalans, 16, 43007, Tarragona, Spain.
Universitat Rovira i Virgili, Departament de Química Analítica i Química Orgánica, c/Marcel⋅lí Domingo, 1, 43007, Tarragona, Spain.
Angew Chem Int Ed Engl. 2019 Nov 4;58(45):16105-16109. doi: 10.1002/anie.201909685. Epub 2019 Sep 24.
Planar pyridyl N-oxides are encapsulated in mono-metallic Pd /Pt -cages based on a tetra-pyridyl calix[4]pyrrole ligand. The exchange dynamics of the cage complexes are slow on both the NMR chemical shift and EXSY timescales, but encapsulation of the guests by the cages is fast on the human timescale. A "French doors" mechanism, involving the rotation of the meso-phenyl walls of the cages, allows the passage of the planar guests. The encapsulation of quinuclidine N-oxide, a sterically more demanding guest, is slower than pyridyl N-oxides in the Pd -cage, and does not take place in the Pt counterpart. A modification of the encapsulation mechanism for the quinuclidine N-oxide is postulated that requires the partial dissociation of the Pd -cage. The substrate binding selectivity featured by the cages is related to their different guest uptake/release mechanisms.
平面吡啶 N-氧化物被包裹在基于四吡啶杯[4]吡咯配体的单金属 Pd /Pt -笼中。笼配合物的交换动力学在 NMR 化学位移和 EXSY 时间尺度上都很慢，但笼对客体的封装在人类时间尺度上很快。一种“法式门”机制，涉及笼中间苯壁的旋转，允许平面客体通过。具有更大空间位阻的客体喹啉 N-氧化物的包封速度比 Pd -笼中的吡啶 N-氧化物慢，并且在 Pt 对应物中不会发生。提出了一种针对喹啉 N-氧化物的封装机制的修改，该修改需要部分解离 Pd -笼。笼的底物结合选择性与其不同的客体摄取/释放机制有关。
