Synthesis of a NbO Type Homochiral Cu(II) Metal Organic Framework: Ferroelectric Behavior and Heterogeneous Catalysis of Three-Component Coupling and Pechmann Reactions

A chiral tetracarboxylic acid ligand, H4L, incorporating the (S)-(+)-2-methylpiperazine moiety in its middle, solvothermally forms a homochiral Cu(II) framework, {[Cu-2(L)(H2O)(2)].(4DMF)(4H(2)O)}(n) (LCu). It forms a non interpenetrated structure consisting of [Cu-2(COO)(4)] paddle-wheel secondary bonding units (SBUs) with NbO topology. Interestingly, the framework LCu exhibits excellent ferroelectric properties. It shows a remnant polarization (Pr) of similar to 3.5 mu C cm(-2) and a coercive field (E-c) of similar to 12 kV cm(-1) with a distinct electric hysteresis loop. Dielectric studies of LCu reveal almost frequency-independent behavior with a dielectric constant (epsilon(r)) of similar to 42 and a low dielectric loss (tan delta) of similar to 0.04 up to 10(6) Hz, for potential use in high-frequency applications. In addition, activated framework LCu' having uncoordinated metal sites acts as an efficient heterogeneous catalyst in the three-component coupling of amines, aldehydes, and alkynes, as well as in Pechmann reactions of phenols with beta-ketoesters.