Constructing heterometallic frameworks with highly connected topology based on edge-to-edge hexanuclear lanthanide clusters

Abstract

Hydrothermal reactions of Sm₂O₃ and CuI with 4-pyridin-4-ylbenzoic acid afford two heterometallic frameworks, namely, [Sm₃Cu₅I₄L₆(μ₃-OH)₂(OAc)(H₂O)₃]·ClO₄·2H₂O (1) (OAc = acetate) and [Sm₆Cu₁₄I₁₂L₁₄(μ₃-OH)₄(H₂O)₅]·2ClO₄·8H₂O (2). X-ray crystal structure analyses reveal that these two 3D pillared-layer heterometallic frameworks are both constructed from similar ribbon-like edge-to-edge hexanuclear Ln clusters. Interestingly, the {Sm₆}¹ cores in 1 and {Sm₆}² clusters in 2 are both connected by carboxyls of L ligands into 1D Ln-cluster organic chains along the a axis. In 1, such chains are linked by [CuL]⁻ pillars and 1D stair-like [Cu₄I₄]_n chains to give a pillared-layer 3D framework. Whereas in 2, these chains are extended by the [CuL]⁻ pillars and [Cu₁₂I₁₂]_n layers to form a 3D framework. Remarkably, to further stabilize the framework of 2, the [CuL]⁻ pillars connect the {Sm₆}² clusters of neighbouring 1D Ln-cluster organic chains interpenetrating through the 11-ring windows of [Cu₁₂I₁₂]_n layers. Topological analyses indicate that 1 and 2 possess a highly (6,14)-connected and a rare odd 11-connected topology, respectively. Furthermore, the IR, TGA, PXRD, UV-Vis spectra of 1 and 2 have also been studied.