Molecular magnets magnetic

Atomic and molecular magnetic dipoles have to obey the angular momentum laws of quantum mechanics, since they are proportional to angular momenta. Each dipole can therefore make just a number of orientations with an applied magnetic induction B. Each allowed orientation corresponds to a different potential energy, and absorption of a photon with suitable energy may cause a change in orientation. 

FIGURE 16.44 The structure of a molecular magnet. The nano-size molecular torus contains 84 manganese atoms and is approximately 4 nm in diameter. The manganese atoms are bonded to groups of carbon atoms in the form of acetate ions, water molecules, and chlorine atoms. In this molecule the manganese atoms act as terromagnets. 

Figure 5-2. In the absence of an applied magnetic field a), the molecular magnetic dipoles are randomly oriented on application of an external field b), the dipoles tend to orientate parallel to the field.

The Molecular Magnetic Shielding Field Response Graph Illustrations of the Benzene Field ... 

In the Hamiltonian conventionally used for derivations of molecular magnetic properties, the applied fields are represented by electromagnetic vector and scalar potentials [1,20] and if desired, canonical transformations are invoked to change the magnetic gauge origin and/or to introduce electric and magnetic fields explicitly into the Hamiltonian, see e.g. refs. [1,20,21]. Here we take as our point of departure the multipolar Hamiltonian derived in ref. [22] without recourse to vector and scalar potentials. 

Stability of diradicals is important for photochemical reactions. Spin multiplicity of the ground states is critical for the molecular magnetic materials. The relative stability of singlet (triplet) isomers and the spin multiplicity of the ground states (spin preference) [48] has been described to introduce the orbital phase theory in Sects. 2.1.5 and 2.1.6. Applications for the design of diradicals are reviewed by Ma and Inagaki elsewhere in this volume. Here, we briefly summarize the applications. 

The spin-Hamiltonian concept, as proposed by Van Vleck [79], was introduced to EPR spectroscopy by Pryce [50, 74] and others [75, 80, 81]. H. H. Wickmann was the first to simulate paramagnetic Mossbauer spectra [82, 83], and E. Miinck and P. Debmnner published the first computer routine for magnetically split Mossbauer spectra [84] which then became the basis of other simulation packages [85]. Concise introductions to the related modem EPR techniques can be found in the book by Schweiger and Jeschke [86]. Magnetic susceptibility is covered in textbooks on molecular magnetism [87-89]. An introduction to MCD spectroscopy is provided by [90-92]. Various aspects of the analysis of applied-field Mossbauer spectra of paramagnetic systems have been covered by a number of articles and reviews in the past [93-100]. 

Girerd, J.J., Joumaux, Y. Molecular Magnetism in Bioinorganic Chemistry. In Que, L. (ed.) Physical Methods in Bioinorganic Chemistry, p. 321. University Science Books, Sausalito (2000)... 

Nitronyl and imino nitroxide free radicals are also among the most versatile spin carriers which are widely used in the design of molecular magnets. Their delocalised unpaired electrons make them convenient building blocks and ideal magnetic bridges between magnetic metals, to achieve new compounds with particular... 

Miller, J.S. and Epstein, A.J.( 1994) Organic and organometallic molecular magnetic-materials -Designer magnets, Angew. Chem., 33, 385 115. 

Cyanide complexes have a venerable history (see CCC S )),1 and find utilization in many industrial processes including as synthetic catalysts e.g., Co cyanides on inorganic supports catalyze alkylene oxide polymerization,187 molecular magnetic materials, in electroplating, and in mining. Their pharmacology and toxicology is well explored... 

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