Construction of six new luminescent Ln(iii)–Zn(ii) heterometallic coordination polymers based on heterometallic secondary building units

Abstract

Six new d–f heterometallic Ln(III)–Zn(II) coordination polymers (CPs), namely, {[EuZn(NIPH)1.5(INC)(H2O)(OH)]·0.5H2O}n (1), [LnZn(NIPH)2(INC)(H2O)]n [Ln = Eu (2), Tb (3)], [EuZn2(NIPH)2.5(INC)2]n (4) and [LnZn(NIPH)2(NC)(H2O)]n [Ln = Eu (5), Tb (6)] [H2NIPH = 5-nitroisophthalate, HINC = isonicotinate, and HNC = nicotinate], were obtained under hydrothermal conditions. All the compounds are based on well-defined heterometallic secondary building units (SBUs). Compound 1 is a 3D network with pcu topology, which was generated from tetragonal tetranuclear heterometallic [Eu2Zn2(NIPH)4(INC)2(OH)2] SBUs connected by NIPH2− and INC− ligands. Compounds 2 and 3 are isostructural and exhibit 3D heterometallic frameworks with bcu topology constructed by the linkage of 2D layers containing linear tetranuclear heterometallic [Eu2Zn2(NIPH)6(INC)2] SBUs and INC− anions. Compound 4 possesses 7-connected 3D frameworks with the Schläfli symbol of (33·411·56·6) constructed by the interconnection of linear trinuclear heterometallic [EuZn2(NIPH)4(INC)4] SBUs, NIPH2− ligands and INC− anions. In compounds 5 and 6, 3D networks are formed through the linkage among linear tetranuclear [Ln2Zn2(NIPH)8(NC)2] SBUs, NIPH2− ligands and NC− anions. All the compounds represent examples of 3D lanthanide–transition heterometallic–organic coordination polymers with two types of metal ions and two organic carboxylates. Furthermore, their solid-state fluorescence properties have been investigated at room temperature.