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

• Two novel reduced molybdophosphate-based cadmium complexes 1 and 2 were obtained.
• In situ bpp transformation has been observed in 1 and 2.
• It is the first example of in situ transformation of bpp ligand to tpc in [P4Mo6] system.
• The reaction conditions play important roles in the in situ syntheses of tpb and tpc.

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.

Two novel 1D P4Mo6-based metal–organic complexes constructed from the classic sandwich-type [Cd(P4Mo6)2] dimers and Cd2+ ions or trinuclear {K2Cd(H2O)6} fragments have been synthesized. In situ bpp transformation has been observed. The reaction conditions play important roles in the in situ syntheses of different tetradentate tpb and tpc from the same precursor bpp. The electrocatalytic activity of compound 2 may make it a candidate for potential catalytic material.Figure optionsDownload as PowerPoint slide