Hydrothermal synthesis, crystal structure and heterogeneous catalytic activity of a novel inorganic–organic hybrid complex, possessing infinite La–O–La linkages

In this paper, a novel lanthanum coordination polymer formulated as {[La2(Hpdc)3(H2O)4]·2H2O}n (1, H3pdc = 3,5-pyrazoledicarboxylic acid) has been synthesized by the reaction of H3pdc with chloride salt of La(III) under hydrothermal conditions and characterized by elemental analysis, FT-IR, TGA and single-crystal X-ray diffraction. The complex crystallized in the monoclinic system Cc space group. The single-crystal X-ray structural analysis revealed that central metal La atoms are nine-coordinate and linked by bridging μ2-OCOO- groups to form [La(1)-(μ2-OCOO−)2-La(2)]n inorganic–organic chains that produce a supramolecular polymeric framework structure. The three-dimensional structure of 1 is accompanied by non-coordinating water molecules. Thermal behavior and catalytic performance of 1 have also been studied. The complex 1 showed 100% selectivity and a conversion rate of 24% on the oxidation of thymol (T) to thymoquinone (TQ).

Hydrothermal reaction of 3,5-pyrazoledicarboxylic acid in the presence of La(III). The structure of {[La2(Hpdc)3(H2O)4]·2H2O}n is shown..Figure optionsDownload as PowerPoint slideHighlights
► {[La2(Hpdc)3(H2O)4]·2H2O}n was synthesized.
► Hydrothermal method was carried out.
► The complex was monoclinic system Cc space group.
► The oxidation of thymol to thymoquinone has conversion rate of 24% with the synthesized complex.