Chiral building blocks for the construction of hybrid organic-inorganic functional materials
Homochiral MOFs with nanometer-sized cavities or channels are important emerging subclass of such materials that are potentially suited for asymmetric catalysis and enantioselective processes.1 Our interest in this area evolved from previous investigations on the structure and stability of ZnR2(L)n (L = pyridine or bipyridine) adducts which led us to the discovery of the achiral coordination polymer [(bpe)ZntBu2]n (bpe = 1,2-bis(4-pyridyl)-ethane) exhibiting unprecedented 2D fabric structure.2 It should be emphasized that achiral bipyridines such as bpe are one of the most-widely used linkers for the synthesis of MOFs. Thus, we made a step into chiral systems by developing an original synthetic strategy for easy access to chiral bipyridines. It has been demonstrated that the mononuclear and dinuclear organometallic complexes of cinchonine of the type (CN)2AlX and [R2Al(μ‑CN)]2 (CN = cinchonine) can act as chiral semi-rigid building blocks with inherent capability to self-assemble into chiral non-covalent porous materials or into heterometallic coordination polymers of helical topology.3 Moreover, the resulting new flexible non-covalent microporous material showed unique gas sorption and separation properties with an initial enthalpy of adsorption of H2 and CO2 being significantly larger than those of classical MOFs.
Cyclodextrins as a building block of novel supramolecular inorganic-organic materials