Molecular Tectonics. Selective Exchange of Cations in Porous Anionic Hydrogen-Bonded Networks Built from Derivatives of Tetraphenylborate

Tetraphenylmethanes with multiple hydrogen-bonding sites are known to associate to form robust
porous supramolecular networks. Analogous anionic networks can be built from the corresponding
tetraphenylborates. Crystallization of the tetraphenylphosphonium salt of tetraphenylborate 2 produces an
anionic network in which 74% of the volume is available for including cations and neutral guests. Other
salts of anion 2 with diverse cations crystallize consistently to form the same network, whereas a neutral
analogue of anion 2, tetraphenylmethane 1, produces an uncharged network that is far less open. Cations
can be exchanged in single crystals of salts of tetraphenylborate 2 with retention of crystallinity and with
selectivities similar to those observed in typical zeolites. Together, these observations provide new strategies
for making ordered molecular materials by design, and they reveal that constructing such materials from
charged subunits offers special advantages.