Aminopolycarboxylate Bismuth(III)-Based Heterometallic Compounds as Single-Source Molecular Precursors for Bi4V2O11 and Bi2CuO4 Mixed Oxides

Abstract

Five heterometallic complexes of general formula M(L)y{Bi(APC)}2·nH2O [M = VO2+, Cu2+; APC = aminopolycarboxylate, in this work ethylenediaminetetraacetate (edta4–) or 1,2 cyclohexanediaminetetraacetate (cdta4–); L = 2,2′-bipyridine; y = 0, 1, or 2; n = 5–16] have been synthesized. The crystal structures of four of them have been determined from single-crystal X-ray diffraction data. The compounds have been probed as single-source molecular precursors for Bi4V2O11 and Bi2CuO4 mixed oxides. Temperature-controlled X-ray powder diffraction was used to monitor the phase transitions during the thermolysis of the precursors. The influence of the ligand type and intermetallic distances in the precursors, heating rate, and the atmosphere have been investigated. The best candidates to yield pure Bi4V2O11 and Bi2CuO4 are complexes with separations between heterometals of ∼4 Å containing ∼29–30% of carbon. The optimal working conditions under which the precursors can be smoothly converted to the corresponding heterometallic oxides are heating at low rates under air flow. The precursors containing ∼29–30% of carbon yield smaller grains and more homogeneous morphology of the residues than the analogues with lower or higher carbon amount. The advantage of the APC-based molecular precursor method is compared to previously reported procedures to produce bimetallic oxides.