Transition Metal Ions Regulated Structural and Catalytic Behaviors of Coordination Polymers

Abstract

Three new coordination polymers (CPs), I [Cu(L)(H2O)]·2H2O, II [Zn(L)], and III [Ag(HL)(CH3CN)], were synthesized by employing a novel pyrazole-based dicarboxylate ligand (H2L) through a solvothermal strategy. Single-crystal structural analysis established that compounds I and II exhibit two-dimensional (2D) sheet structures, while compound III possesses a one-dimensional (1D) ladder structure due to the connectivity of terminal solvent moiety. The geometries of metal ions vary from square planar (Cu2+ ion) to distorted tetrahedral (Zn2+ and Ag+ ion). Topological study showed that compound I has made a (4·62)2(42·62·82) net, while compounds II and III have exposed common (44·62) sql net and (42·6) net, respectively. The Lewis acidic nature of compounds I, II, and III has been confirmed with various heterogeneous catalytic reactions. For the first time, one-pot multicomponent synthesis of α-amino amidine has been performed by the three CPs and the reaction kinetics has been altered by the variation of Lewis acidic metal centers. The roles of metal ions for structural variations and the catalytic performances are investigated in a series of CPs.