Assembly of various reduced molybdophosphate-based cadmium complexes by controllable in situ ligand transformation

Abstract

Two novel reduced molybdophosphate-based cadmium complexes, [Cd(MoO2)12(PO4)2(HPO4)2(H2PO4)4(OH)6][Cd(H2O)2]·(H2bpp)2·bpp·7H2O (1); [Cd(MoO2)12(PO4)4(HPO4)2(H2PO4)2(OH)6]{Cd(H2O)2[K(H2O)2]2}·(H4tpc)(H2bpp)·11H2O (2) (bpp=1,3-bis-(4-pyridyl)propane, tpc=a,a-1,4-dihydroxy-e,e,e,e-1,2,4,5-tetra-(4-pyridyl)cyclohexane) have been synthesized by controlling in situ bpp transformation and characterized by IR and single crystal X-ray diffraction. Both compounds 1 and 2 are based on the [P4Mo6O28(OH)3]9− ([P4Mo6]) polyoxometalate units, which are further connected into sandwich-type [Cd(P4Mo6)2] dimers by cadmium ions. In compound 1, [Cd(P4Mo6)2] dimers are linked by cadmium ions to form one dimensional (1D) inorganic chains, which are extended into 2D supramolecular network by bpp/H2bpp through hydrogen bonding interactions. In 2, bpp molecules partially in situ transformed to tpc at the presence of Fe3+ ion and pH 4.5, and the [Cd(P4Mo6)2] dimers are linked by trinuclear {K2Cd(H2O)6} fragments to form 1D inorganic chains. Finally, the 1D chains are connected by H2bpp and in situ generated H4tpc molecules to construct a 3D supramolecular architecture through hydrogen bonding interactions. The Fe3+ ions and pH play important roles in the in situ ligand transformation, which show great effect on the assembly and structures of the title compounds. The electrochemical properties of compound 2 have been investigated.