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/Me0 H 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 2and 3 show that of copper（Ⅱ） and ligand.