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(H_2Pyzha) in H_2O/Me0 H led to three new heterobimetallic 15-metallacrown-5 complexes.In a MeOH/H_2O 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:metallacrownSm(H_2O)_3 {Cu(pyzha)}_5(H_2O)_2(MeOH)(HSO_4)_2]·(H_2O)_2(HSO_4)(1);Nd(H_2O)_2(MeOH) {Cu(pyzha)}_5(ClO_4)_2(H_2O)_5(NO_3)](2);Eu(H_2O)_2(MeOH) {Cu(pyzha)}_5(ClO_4)_2(H_2O)_5(NO_3)](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 2and 3 show that of copper(Ⅱ) and ligand.