One-Dimensional Single-Chain Molecular Magnet with a Cross-Linked π–π Coordination Network [{Co^II(Δ)Co^II(Λ)}(ox)₂(phen)₂]_n

Abstract

A one-dimensional single-chain molecular magnet [{Co II (Δ)Co II (Λ)}(ox) 2 (phen) 2 ] n with a cross-linked π−π coordination network has been synthesized hydrothermally and investigated for its structural and magnetic properties. Oxalate (ox) ligands bridge the paramagnetic Co II metal ions, whereas phenanthroline (phen) ligands exhibit π−π coordination networks. The compound has been thoroughly investigated using room-temperature X-ray and neutron diffraction, infrared spectroscopy, dc magnetization, and reverse Monte Carlo (RMC) simulation methods. Rietveld refinement of the powder X-ray and neutron diffraction patterns at room temperature confirms the single-phase formation of the compound in the monoclinic structure with a space group P2 1 . Structural analysis reveals that the compound assembles in the form of a one-dimensional zigzag chainlike structure. Chains consist of two asymmetric Δand Λ-Co II ions and a π−π coordinating network bridged by ox and phen ligands, respectively. The chain lies in the crystallographic ac plane, infinite in length with the absence of interchain π−π overlap. dc magnetization data fitted over the high-temperature regime (T > 5 K) using the Ising chain model reveals the one-dimensional magnetic nature of the compound with alternately spaced magnetic Co II sites with two different Landég factors and exchange coupling constant values. Different Landég factors (2.5 and 2.1) and negative exchange coupling constant values (−108 and −20 K) at two alternating Co II sites indicate a ferrimagnetic behavior of this chain compound. In the low-temperature regime (T < 5 K) the compound exhibits spontaneous magnetization and hysteresis at 1.6 K, due to the occurrence of long-range threedimensional (3-D) magnetic ordering. A prominent clustering of the C atoms around the Co atoms is ascertained by RMC analysis of diffuse scattering in the neutron diffraction pattern. The pair correlations distances between Co−Co, Co−C, Co−N, and Co−O atoms are found to be 5.0, 2.2, 2.5, and 2.4 Å, respectively, for the compound.

Two cobalt complexes containing different nitronyl nitroxide radicals: Structure and magnetic properties

“…The nitronyl nitroxide is a stable spin system which can be linked with the metal center through the O-N groups to produce metal-radical complexes [8][9][10]. Metal-radical complexes which have definite geometry are in favor of the fundamental studies of magneto-structural correlation, especially the way how structural factors affect the metal-organic radical interaction [11][12][13][14]. These investigations are necessary not only for understanding the spin-coupling behaviors between the metal ion and the organic radical but also for the development of new molecular magnetic materials [15,16].…”

“…A large number of transition metal-radical complexes with various structures and magnetic properties were synthesized and characterized [1,7,9,13,19,20]. A series of zero, one dimensional and multidimensional complexes based on transition metal were reported [6,11,17,18,[21][22][23]. Cobalt (II) complexes have been researched rarely because of large spin-orbital * Corresponding author.…”

Pyrene-Enhanced Ferromagnetic Interaction in a FeCl4–-Based Poly(ionic liquid)s Organic Magnet

“…The magnetic interaction in the organic magnet is weakened to show a low Curie temperature ( T c ) − or even paramagnetism and antiferromagnetism. , In order to improve the ferromagnetic interaction of the organic magnet, intermolecular interaction was introduced into the molecules to enhance the ferromagnetic interaction with a short- or long-range correlation. The molecular magnet with intermolecular interaction forms single chain (1D), 2D network, and 3D-ordered network structures, which result in ferromagnetic ordering, antiferromagnetic ordering, and spin glass states, respectively. − Whether the molecular interaction is ferromagnetic or antiferromagnetic is based on the strength and correlation of the intermolecular interaction, which is very important in the design of organic magnets.…”

Octahedral Lattice Distortion-Driven Ferroelectricity and Canted Antiferromagnetism in Oxalate and Phenanthrolin Ligand-Based Chain Molecular Magnets [{Fe(Δ)Fe(Λ)}1–x{Cr(Δ)Cr(Λ)}x(ox)2(phen)2]n (x = 0, 0.1, and 0.5)

“…There has been an increasing attraction toward the synthesis and characterization of SCMs ,,− with new functionalities making such compounds multifunctional as well. , Recent incorporation of π-functional organic molecules in SCMs seems interesting because of the observation of spontaneous magnetization in such compounds, which is a rather rare phenomenon in the series of π-functional magnetic materials. − The π–π interaction may give rise to a short-range or a long-range magnetic ordering, and consequently, new materials with distinct magnetic properties may emerge . For example, the oxalate and phenanthroline-based π–π molecular magnet, [{Fe­(Δ)­Fe­(Λ)}­(ox) 2 (phen) 2 ] n exhibits spontaneous magnetization below ∼10 K as reported by Li et al , Further, spontaneous magnetization above room temperature has been observed in a coordination π–π framework of 1D polymeric Cu­(II) chains with 2,2′-bipyridine ligands .…”