Ionothermal synthesis, crystal structure, topology and catalytic properties of heterometallic coordination polymers constructed from N-(phosphonomethyl) iminodiacetic acid

Abstract

Reactions of rare earth chlorides, N-(phosphonomethyl)iminodiacetic acid (H₄pmida) and ferrous oxalate dihydrate under ionothermal conditions result in four new isostructural 3d–4f heterometal coordination polymers, [LnFe^IIIFe^II₆(Hpmida)₆]·2H₂O {Ln = Eu (1), Dy (2), Ho (3) and Y (4)}. All compounds were characterized by infrared spectroscopy, elemental analysis, thermogravimetric analysis, and X-ray diffraction. The compounds feature a very interesting three dimensional (3-D) structure built up from a secondary building unit, [Fe₂(Hpmida)₂]²⁻ and possess a new topology type and complicated unique tilings. The catalytic properties of compounds 1–4 were investigated showing that these types of compounds are heterogeneous catalysts in the Knöevenagel condensation with high selectivity.