Three-dimensional network-structured cyanide-based magnets

Journal ArticleIntroduction Magnets based on metal oxides have been important for hundreds of years. Magnetite, Fe3O4, Co-doped (y)-Fe2O3, and CrO2 are important examples. The oxide (O2-) bridge between the magnetic metal ions has filled p orbitals (Figure 1a) that provide the pathway for strong spin coupling. Albeit with twice as many atoms, cyanide (C=(_)N(-) can bridge between two metal ions via its pair of empty antibonding orbitals (Figure 1b) and filled nonbonding orbitals. Even prior to a detailed understanding of either their composition or structure, magnetic ordering of several cyanide complexes, although at low temperature, was noted.(1

Tetracyanoethylene-based organic magnets

Journal ArticleSeveral classes of organic magnets based upon the tetracyanoethenide radical anion, [TCNE](.-), either unbound, (u), and (u4) bonded to zero, two and four metal sites have been reported. The putative (u4) bonded V(TCNE)x room temperature magnet has been extended to include M(TCNE)x(M = Mn, Fe, Co, Ni) magnets. M for this class of magnets is assigned to be in the divalent oxidation state. A (o-[TCNE](22-) dimer intermediate has been isolated. The intrachain magnetic coupling for the 1-D coordination polymers having [TCNE](.-u)-bridge bonded to [MnIIIporphyrins]+ is discussed in the context of a structure-function correlation arising from the dihedral angle between the [MnIIITPP]+'s MnN4 and [TCNE](.-) mean planes and the magnitude of magnetic coupling. This correlation is ascribed to the increasing importance of the (o-MnIII dz2/[TCNE](.-pz overlap with decreasing dihedral angle

Using fission

Journal ArticleAtoms are just like people, both are lazy. Energy is a measure of work, i.e., more work implies more energy. Atoms do not like to work, hence they try to reduce the energy in their atomic system. For different elements the energy reduction occurs by reaction, e.g., an energetic sodium atom reacts with an energetic chlorine atom to form a less energetic salt molecule

Organic and molecular ferromagnets

Journal ArticleUnlike common ferromagnets such as iron, nickel, cobalt or even cobalt-samarium and Nb-Fe-B, it is extremely rare for a discrete molecule, especially an organic or polymeric material, to have cooperative magnetic interactions. Since the mid-1980s a few such materials have been prepared which demonstrate that ferromagnetic interactions can be present in a molecular-based system. The reports have stimulated studies as to the origins as well as to the properties of molecular/organic ferromagnets. Three routes have led to highly magnetic molecular/polymeric materials: (a) chains of isolated alternating radical cations and radical anions, (b) covalently bonded chains containing alternating different metal ions, and (c) covalently bonded chains involving metal ions and nitroxide radicals

Magnetically ordered molecule-based assemblies

Journal ArticleThe development of molecules and assemblies of molecules exhibiting technologically important bulk properties, such as magnetic ordering, is an important worldwide research focus. Organic- and molecule-based magnets have been discovered and several families have been reported with magnetic ordering temperatures exceeding room temperature and as high as ?125 degrees ?C. Examples of both hard and soft magnets have been reported with coercivities as high at 27 000 Oe (and exceeding commercially available magnets) have been reported. Several examples are based on the radical anion of tetracyanoethylene, S = 1/2 [TCNE]??

Crystal engineering or crystal mysticism? A case study

Journal ArticleThe de novo design and synthesis of a crystalline motif of a substance is a holy grail for a growing number of organic and inorganic synthetic chemists. Achievement of targeted architectural arrangements is less reliable as the complexity increases. Simple substitution of, for example, alkyl pendant groups with homologues1 are most prone to success. Enthusiasts in this area have dubbed this evolving realm of research as 'crystal engineering,'2 and 'reticular chemistry,' as "...the practice of logical synthesis must begin with knowledge of the target network 'blueprint' and identification of the required building blocks for its assembly. The process is central to our ability to achieve true design of solid state materials: we refer to its implementation as reticular chemistry."3 The flurry of activity has led to a plethora of fascinating new structures and materials, many conferences, symposia, monographs, and scientific papers in all of the leading journals, not to mention a glut of new jargon

Quest for molecule-based magnets

Journal ArticleIn the past decade a new class of magnets possessing spins on organic species have been discovered and studied. These magnets can be fabricated at room temperature and may enable useful devices and/or processes. Herein we discuss several of the mechanisms that can enable the stabilization of magnetic ordering and also provide examples of molecule-based magnets

Two-dimensional molecular-based ferrimamagnets incorporating decamethylmetallocenium cations

Journal ArticleFour new molecular-based magnets have been synthesized, and their magnetic properties have been investigated in detail. Their formulae are [M'(C5Me5)2]2M2[Cu(opba)]3.(DMSO)x(H20)y with M' = Fe, M = Mn, x = 5, y = 4 (1), M' = Fe, M = Co, x = 6, y = 4 (2), M' = Co, M = Mn, x = 5.5, y = 4 (3) and M' = Co, M = Co, x = 5.5, y = 4 (4) [opba = ortfro-phenylenebis (oxamato)]. The decamethylmetallocenium cations [Fe(C5Me5)2]+ and [Co(C5Me5)2]+ are most probably located between the anionic honeycomb-like networks Mn2[Cu(opba)]3 and Co2[Cu(opba)]3

Noise in highly correlated commensurate charge transfer salts

Journal ArticleWe present the results of a study of the frequency (f) dependent noise power for commensurate charge transer salts with strong coulomb repulsion. f-1 noise is observed with increasing currents. Excess f-1 noise is measured for samples which were chemically doped to form solitons. Frequency independent shot noise is not observed

Isolation and structural determination of octacyanobutanediide, [C4(CN)8]2-; precursors to M(TCNE)x magnets(**)

Journal ArticleThe reaction of MI2.xMe3CN (M = Mn, Fe) and TCNE (tetracyanoethylene) leads to unprecedented [C4(CN)8]2-U4-metal complexes which have been crystallographically characterized and are precursors to M(TCNE)x-yS magnets