Molecular Vises for Precisely Positioning Ligands near Catalytic Metal Centers in Metal–Organic Frameworks

We
report the construction of a molecular vise by pairing a tritopic
phenyl­phosphorus­(III) linker and a monotopic linker in opposite
positions within a metal–organic framework. The angle between
these linkers at metal sites is fixed upon changing the functionality
in the monotopic linker, while the distance between them is precisely
tuned. This distance within the molecular vise is accurately measured
by 1H–31P solid-state nuclear magnetic
resonance spectroscopy. This unveils the impact of the distance on
catalytic performance without interference from electrostatic effects
or changes in the angle of the ligand, which is unprecedented in classic
organometallic complexes.