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Guest Exchange Mechanisms in Mono‐Metallic Pd II /Pt II ‐Cages Based on a Tetra‐Pyridyl Calix[4]pyrrole Ligand
Author(s) -
Escobar Luis,
EscuderoAdán Eduardo C.,
Ballester Pablo
Publication year - 2019
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201909685
Subject(s) - chemistry , quinuclidine , tetra , crystallography , metal , ligand (biochemistry) , selectivity , dissociation (chemistry) , steric effects , oxide , stereochemistry , medicinal chemistry , catalysis , organic chemistry , biochemistry , receptor
Planar pyridyl N ‐oxides are encapsulated in mono‐metallic Pd II /Pt II ‐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 II ‐cage, and does not take place in the Pt II counterpart. A modification of the encapsulation mechanism for the quinuclidine N ‐oxide is postulated that requires the partial dissociation of the Pd II ‐cage. The substrate binding selectivity featured by the cages is related to their different guest uptake/release mechanisms.