Molecular Magnets

Abstract

The well‐known magnetic materials used in present‐day technologies, such as, Fe, Fe2O3, Cr2O3, SmCo5, Nd2Fe14B, and so on, are all atom‐based. And due to this reason the preparation/processing of these conventional magnets requires energy consuming high temperature routes. In contrast, the new emerging molecule‐based magnetic materials exploit self‐assembly methods that play with weak intermolecular interactions to produce long‐range bulk magnetic order in them. The first successful synthesis of molecular magnets was made in 1986, and since then, a large variety of them have been synthesized, which can be categorized on the basis of the chemical nature of the magnetic units involved: organic, metal‐based systems, heterobimetallic assemblies, or mixed organic–inorganic systems, single molecule magnets, single chain magnets, and so on. Solubility, low density, and biocompatibility are attractive features of molecular magnets. Being weakly colored, unlike their opaque classical magnet “cousins” listed above, possibilities of photomagnetic switching exist. There have been attempts to design and synthesize polyfunctional molecular magnets, such as those exhibiting second‐order optical nonlinearity, liquid crystallinity, or chirality simultaneously with long‐range magnetic order. Efforts also continue to design the ever‐elusive polymer magnets toward applications in industry. While providing a brief overview of the field of molecular magnetism, this chapter aims to highlight a few recent developments in it, including from the author's own lab.

A short, versatile route towards benzothiadiazinyl radicals

“…Stable molecular radical species have long been targeted as potential molecular magnets for future magnetic storage applications, and as test-beds for fundamental studies into magnetic communication. 1 Several metal-free radical families 2 have been explored which exhibit divergent properties from metal centred species. These are of particular interest because, in addition to their magnetic properties, many exhibit a unique form of bonding wherein they dimerise via π–π interactions (termed “pancake bonding”) rather than formation of simple 2c2e − bonds.…”

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)

“…Low-dimensional molecule-based magnetic materials, under the categories of single-chain magnets (SCM), − possess exotic magnetic properties, , such as spin frustration, slow magnetic relaxation, , short-range/long-range magnetic correlations, and strong easy-axis magnetic anisotropy. ,− Therefore, such molecule-based magnetic materials are, in general, very attractive for research on contemporary magnetism as well as from an application point of view. ,,,− Many such molecule-based magnetic materials with unusual magnetic properties and their possible technological applications have been reported recently in the literature. − In 2001, the first SCM [Co II (hfac) 2 (NITphOMe)], (hfac = hexafluoroacetylacetone, NITPhOMe = 4′-methoxy-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) was reported . SCMs show weak magnetic relaxations because of their large uniaxial-type magnetic anisotropy, strong intrachain magnetic interaction, and negligible interchain interactions, resulting in one-dimensional (1D) magnetic ordering .…”