Using hinged ligands to target structurally flexible copper(II) MOFs

Here we report two new flexible MOFs based on a bis-pyrazolylmethane 'hinged' link design that favours the formation of two distinct structural nodes within the resulting 2-D and 3-D structures. The less sterically demanding ligand H(2)bcppm affords a 2-D layered MOF, {Cu-2[Cu-II(NO3)(2)(bcppm)(2)](DMF)(2)}center dot 2DMF (1), constructed from copper(II) paddlewheel and mononuclear octahedral copper(II) nodes. The use of a more sterically encumbered tetramethyl analogue H(2)bcpdmpm induces a dramatic twisting of the ligand backbone that yields a 3-D MOF{Cu-4[Cu-I(bcpdmpm)(2)](2)(EtOH)(2)(H2O)(2)}(NO3)(2)center dot 12DMF (2) formed from a very similar mix of nodes, specifically copper(II) paddlewheel clusters and mononuclear tetrahedrally coordinated copper(I) centres. Herein we describe the crystal structures, solid-state flexibility, and gas adsorption properties of both materials.