Syntheses, Structures, Luminescence, and Magnetic Properties of a Series of Novel Coordination Polymers Constructed by Nanosized [Ln₈Fe₄] Rings

Abstract

A total of five three-dimensional Ln-Fe coordination polymers (CPs) [(CH3)2NH]­[(CH3)2NH2]­[Ln2Fe­(SO4)4(L)]­·3H2O (Ln = Eu, 1; Dy, 2; Gd, 3; Sm, 4; Er, 5; H2L = tartaric acid) have been successfully synthesized under solvothermal conditions and characterized by infrared spectroscopy, thermogravimetric analysis, elemental analyses, luminescence, and magnetic properties. Structural analysis indicates that the frameworks of 1–5 are constructed from novel [Ln8Fe4] rings. In the strcutures of 1–5, LnIII and FeIII ions interconnect through O donors of sulfate anions to generate a one-dimensional chain, and the adjacent chains are joined together by ligand [L]2– to form a two-dimensional zonary plane, which is further bridged by ligand [L]2– to give a new topology and named as “ Xhd 1”. Magnetic properties of 2 and 3 were investigated using variable temperature magnetic susceptibility, and weak ferromagnetic exchange between the FeIII and LnIII ions has been established for the Gd derivative. Meanwhile, we also studied luminescence spectra and luminescence lifetimes of 1 and 4 in the solid state at room temperature. The luminescence lifetime of 1 is 0.98 ms, which is significantly longer than the values in the reported Eu3+ coordination polymers.

Magnetic Nature of the CrIII–LnIII Interactions in [CrIII2LnIII3] Clusters with Slow Magnetic Relaxation

“…Among the many lanthanide‐based complexes, 3 d –4 f coordination clusters have been considered one of the most interesting molecular systems for magnetic studies . The strategy for constructing 3 d –4 f coordination clusters is to build metal cores with organic ligands, which act not only as bridging ligands to bridge 3 d and 4 f ions, but also as peripheral ligands to separate the discrete species from each other.…”

A cuboidal [Cu4(SO4)4] structure supported by β-picoline ligands

“…Harris notation is written as [XÁYYYY] where X is the number of metals that a ligand bridges, and the Ys are the number of metals connected to each donor atom in the ligand (Papatriantafyllopoulou et al, 2009). The [3.2110] bridging motif is rare in sulfates and has only been observed in 1D coordination polymers of copper (Li et al, 2008) and lanthanide/iron mixed-metal 3D coordination polymers (He et al, 2017). There are two C-HÁ Á ÁO interactions between the ortho hydrogens of one -picoline ligand and the oxygens of two sulfate ions (Table 1).…”

“…reported structures demonstrating sulfate ions with [3.2110] bridging modes are with copper (DOHKIV, DOHKIB:Li et al, 2008) or mixtures of lanthanides with iron(He et al, 2017), including dysprosium (DADNOO), erbium…”

Generalized Heisenberg-Type Magnetic Phenomena in Coordination Polymers with Nickel–Lanthanide Dinuclear Units

“…The design and synthesis of homo- and heterometallic coordination compounds has been attracting increasing research attention, owing to their potential as new magnetic materials, as well as their relevance to bioinorganic chemistry. − Among such materials, particularly important are compounds containing multiple metallic atoms − that may be single-molecule magnets (SMMs) or single-chain magnets (SCMs) and therefore useful for high-density information storage, spintronic devices, or quantum computation applications. − Since the initial report of a {Mn 12 }-based cluster compound as the first single-molecule magnet (SMM), , much effort has been devoted to seeking compounds with improved magnetic characteristics, resulting in the documentation of numerous SMMs and SCMs. − Many discrete SMMs are based exclusively on complexes comprising only 3d transition metals − or lanthanides, − but some are based on mixed 3d–4f heterometallic entities − and double phenoxo bridges. , …”