Syntheses, crystal structures, thermal stabilities and luminescence of six M(II)-hydroxyphosphonoacetate materials

Abstract

Hydrothermal reactions of Zn II, Ba II or Co II ion with 2-hydroxyphosphonoacetic acid (H 3L) afforded six metal phosphonates, namely, [Zn 5(O 3PCH(OH)CO 2) 4(C 6H 9N 2) 2] ( 1), [(C 4H 12N 2)Zn 5(O 3PCH(OH)CO 2) 4(H 2O) 2] ( 2), [(C 3H 12N 2) 0.5Zn 5(HO 3PCH(OH)CO 2)(O 3PCH(OH)CO 2) 3(H 2O) 2]·0.75H 2O ( 3), [BaZn 2(O 3P CH(OH)CO 2) 2] ( 4), [Ba(HO 3PCH(OH)CO 2)] ( 5) and [(NH 4) 2Co 7(HO 3PCH(OH) CO 2) 6(HPO 4) 2(H 2O) 6]·4H 2O ( 6). In 1, zinc tetrahedra ([ZnO 4]) and octahedra ([ZnO 5N], [ZnO 6]) are bridged by 2-hydroxyphosphonoacetate with penta- and hexadendate modes into a hybrid layer, which is further pillared by the 3-picolylamines to form a 3D structure through Zn–N bonds and hydrogen bondings. Both 2 and 3 are 3D framework encapsulating piperazine and 1,2-propanediamine cations, respectively. In solids 4– 6, the cross-linkages of [ZnO 4], [BaO 10] and [CoO 6] polyhedral with 2-hydroxyphosphonoacetate form 3D frameworks. Solids 3 and 4 behave thermally stable up to 250 and 300 °C under air atmosphere, respectively. It is interesting that the peak emission of solid 3 displays a 10 nm red-shift after simple heat-treatment.