pH variation induced construction of a series of entangled frameworks based on bi- and tri-metallic cores as nodes

Abstract

Reactions of 1,4-bis(pyridin-4-ylmethoxy)benzene (L) and zinc acetate salts with different multi-caboxylate acids: 1,4-benzenedicarboxylic (p-H₂BDC), isophthalic acid (m-H₂BDC) and benzene-1,3,5-tricarboxylic acid (H₃BTC) yield four entangled structures and one 3D supramolecular framework depending on pH variation. The structures of compounds 1–5 were elucidated by single crystal X-ray diffraction. Topology analysis revealed that the entangled structures of compounds 1–4 covered a range of poly-threading, self-penetrating and interpenetrating coordination. Interestingly, the poly-threaded arrays with cyclohexane-like windows in chair conformation in compound 2 was firstly observed. What's more, compound 4 exhibited a rare eight-connected self-penetrating network based on trinuclear zinc clusters as nodes with 4²⁴6⁴ topology. Photoluminescent properties and thermogravimetric analyses for 1–5, were also investigated in detail.