Direct Guest Exchange Induced Single-Crystal to Single-Crystal Transformation Accompanying Irreversible Crystal Expansion in Soft Porous Coordination Polymers

Two flexible porous coordination
materials, [Mn­(pybimc)2]­·2H2O·G
(G = toluene, 1tol; THF, 1thf), where pybimc = 2-(2′-pyridyl)-benzimidazole-5-carboxylate,
featuring identical one-dimensional chain structure have been characterized.
Guest exchange studies have exhibited that 1tol cannot be converted to 1thf through direct replacement of guest toluene molecules
by THF molecules, but, of particular interest, 1thf is actually converted to 1tol and 1aromatic (where aromatic = o-, m-, p-xylene) upon the exchange of THF to toluene and other
aromatic molecules, respectively. This signifies a single-crystal
to single-crystal transformation accompanied irreversible crystal
expansion. In-depth analyses reveal that the nature of the weak yet
sufficiently strong framework–guest C–H···π
interactions, rather than the guest size, observed in this system
plays a key role in guiding the adsorption of liquid-phase aromatics
in the soft crystalline materials.