Heterometal–organic frameworks: Three novel copper(II)–lanthanide(III) 15-metallacrown-5 complexes based on pyrazinohydroxamic acid as new multiple-binding pentagonal platform

Reactions of copper(II) sulfate or copper(II) perchlorate, samarium(III), erbium(III) or neodymium(III) nitrate (5/1 equiv.) with pyrazinohydroxamic acid (H2Pyzha) in H2O/MeOH led to three new heterobimetallic 15-metallacrown-5 complexes. In a MeOH/H2O solution, when adding inorganic salts, the ligands exist as protonated metallacrowns. In the solid state, their structures are more complicated as confirmed by X-ray analysis: metallacrown [Sm (H2O)3 {Cu(pyzha)}5 (H2O)2 (MeOH) (HSO4)2]·(H2O)2·(HSO4) (1); [Nd(H2O)2 (MeOH) {Cu(pyzha)}5 (ClO4)2 (H2O)5(NO3)] (2); [Eu(H2O)2 (MeOH) {Cu(pyzha)}5 (ClO4)2 (H2O)5 (NO3)] (3). The differentiation of atomic and ionic radii between the encapsulated lanthanide(III) could be used to control the bowl-shape distortion of the metallacrowns from the planar geometry. The complex 1 clearly exhibits fluorescence behavior of samarium(III), while 2 and 3 show that of copper(II) and ligand.

Introducing of pyrazine hydroxamate into copper(II)–lanthanide(III) 15-metallacrown-5 core presents various kinds of fluorescence properties with different types of rare elements.Figure optionsDownload as PowerPoint slide