Heterometallic Cu(II)-M(II) (M = Mg, Ca and Sr) complexes with a N,O-donor ligand in situ generated from topiroxostat

By introducing alkaline-earth metal ions (Mg2+, Ca2+, and Sr2+) as structure-directing agents, three new heterometallic complexes, Mg(H2O)6·[Cu2Mg(L)4(H2O)4]·4H2O (1), [CuCa(L)2(H2O)4]n (2) and [CuSr(L)2(H2O)4]n (3) [H2L = 4-(3-(pyridine-4-yl)-1H-1,2,4-triazol-5-yl)picolinic acid], have been synthesized under hydrothermal conditions and structurally characterized. H2L was in situ generated from hydrolysis of the well-known selective xanthine oxidase inhibitor topiroxostat. Complex 1 crystallizes in the space group P21/c and exhibits a zero-dimensional (0-D) structure containing the discrete [Mg(H2O)6]2+ cationic and [Cu2Mg(L)4(H2O)4]2– dianionic moieties. Complexes 2 and 3 are isostructural and crystallize in the space group C2/c, with one-dimensional (1-D) polymeric structure with infinite Cu(II)–Ca/Sr–carboxylate chains. The results reveal the significant influence of the alkaline-earth metal ions on the molecular structure. Their spectroscopic, thermal and solid-state luminescent properties have also been investigated.