Two novel metal complexes based on 2,2′-bipyridine and 2,4-dihydroxybenzoic acid: Synthesis, crystal structure and catalytic performance

Abstract

To further enhance the catalytic performance of copper/lead 2,4-dihydroxybenzoate salt, two novel ternary complexes, Cu(C10H8N2)2(C7H5O4)·3H2O (complex 1) and [Pb(C10H8N2)(C7H5O4)2]·H2O (complex 2) were designed by introducing carbon framework ligand. The molecular structures of complexes 1 and 2 were determined by single crystal X-ray diffraction analysis. Both complex 1 and complex 2 were crystallized in the monoclinic crystal system. The difference is that the central Cu ion in complex 1 is connected to one oxygen atom of the carboxyl group of 2,4-dihydroxybenzoic acid, while the other 2,4-dihydroxybenzoic acid anion only acts as a counterion to balance the charge. But the central Pb ion in complex 2 is connected to four oxygen atoms of the carboxyl groups of two 2,4-dihydroxybenzoic acid and forms a six-coordinated structure. The Hirshfeld surface and associated 2D fingerprint analysis offer valuable insights into the intermolecular interactions within the crystal structure. Importantly, the thermal analysis results show that the thermal decomposition temperature of complex 1 is 204.1 °C, which has better thermal stability than complex 2. Furthermore, complex 1 showed remarkable catalytic activity on RDX compared to complex 2, and changed the thermal decomposition of RDX from melting decomposition to solid phase decomposition. This study will provide a new insight into development of combustion catalysts.