Metal-to-ligand ratio-controlled assembly of two Ca(II) complexes: Synthesis, structures, reactant-induced reversible transformation, and catalytic properties

Hydrothermal reactions of Ca(NO3)2 center dot 4H2O and topiroxostat with different metal-to-ligand ratios yielded two new complexes {[Ca2(L)2(H2O)6]center dot H2O}n (1) and Ca(HL)2(H2O)4 (2) [H2L = 4-(3-(pyridine-4-yl)-1H-1,2,4-triazol-5-yl)picolinic acid], involving ligand in situ formation by hydrolysis of topiroxostat. X-ray structural analysis revealed that complex 1 has a 1D coordination polymeric structure while complex 2 displays a 0D discrete molecule. Both complexes exhibit interesting reactant-induced reversible structural transformation properties. Thermogravimetric analysis and temperature-dependent PXRD patterns indicated that the network of 1 keep high thermal stability up to 400 degrees C. The catalytic performance of the complexes for the solvent-free ring-opening polymerization of epsilon-caprolactone has been investigated.

Automated summary

Two new complexes with different structures and thermal stabilities were successfully synthesized through hydrothermal reactions, and they showed reversible structural transformation properties. The ligand in the complexes was also formed in situ through hydrolysis reaction. The catalytic performance of the complexes in the solvent-free ring-opening polymerization of epsilon-caprolactone was significant.