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.