Molecular crystals, magnetism magnetic interactions, type

Apart from subtle exceptions, an isolated molecule differs from a molecule in a crystal in that the isolated molecule has no shape, whereas in a crystal it acquires shape, but loses its identity as an independent entity. This paradoxical situation is best understood through the famous Goldstone theorem, which for the present purpose is interpreted to state that any phase transition, or symmetry broken, is induced by a special interaction. When a molecule is introduced into an environment of other molecules of its own kind, a phase transition occurs as the molecule changes its ideal (gas) behaviour to suit the non-ideal conditions, created by the van der Waals interaction with its neighbours. An applied electric or magnetic field may induce another type of transformation due to polarization of the molecular charge density, which may cause alignment of the nuclei. When the field is switched off the inverse transformation happens and the structure disappears. The Faraday effect (6.2.3) is one example. 

Some examples of OD assemblies (Scheme 14) in halogen-bonded cocrystals include heteromeric isoindohne nitroxide-1,1,33 -tetramethylisoindolin-2-yloxyl (TMIO) diiodotetrafiuorobenzene (DITFB) trimers (2 1). ° These trimeric cocrystals were studied to demonstrate the ability of XB to assemble paramagnetic molecnles, such as TMIO, in supramolecular arrays. Reported crystal structures show expected N-0- I interaction consistent with n a electron donation from the nitroxide N-O moiety. Further development in this type of system could lead to potential application in the fields of molecular magnetism, spintronics, and quantum computing. 

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