Influence of reaction conditions on the channel shape of 3d-4f heterometallic metal-organic framework

Three structural kinds of 3d-4f metal-organic-frameworks (MOFs), {[Ln(4)(ox)(3)(Ni(IDA)(2))(3)(H2O)(6)]}(n)center dot xnH(2)O (Type I: Ln=La, Nd, Eu, Gd; IDA = iminodiacetate, ox = oxalate), {[Ln(2) (ox)(Ni(IDA) (2))(2)(H2O)(2)]}(n)center dot 2nH(2)O (Type II: Ln=La, Pr, Nd, Eu) and {[Dy-2(ox)(2)Ni(IDA)(2)(H2O)(2)]}(n)center dot 2nH(2)O (Type III), have been synthesized under hydrothermal condition. The crystal structures consist of Ln-oxalate tetramers for Type I, dimers for Type II and one-dimensional polymers for Type III bridged by the metalloligand [Ni(IDA)(2)](2-). While Type I contains a mixture of Ln(6)Ni(4)-parallelogram (A-Type) and Ln(6)Ni(2)-parallelogram (B-Type) channels, Type II and Type III contain only A-type and B-type channels, respectively. A fairly high stability of the MOFs is indicated by thermogravimetric analyses and reversible dehydration and rehydration of guest water molecules, which is confirmed by single crystal-to-single crystal transformation of 1 and 5.