Paramagnetic materials properties

Radicals have been known for many years to form organic paramagnetic materials with numerous magnetic properties (ferro- or ferri-magnetism, spin Peierls transition, spin frustration, spin ladder systems) (see [51-60] for verdazyl radicals, [61-68] for thiazyl radicals, [69] for nitronyl nitroxide and [70-78] for Tempo radicals) (Fig. 6). When they are in their cationic form, they are valuable candidates for an association with the M(dmit)2 systems they will then provide the magnetic properties thanks to their free electron(s), whereas the M(dmit)2 moieties will provide the electrical properties. 

Depending upon its properties, the paramagnetic material can be encapsulated into the aqueous core of the liposome (if hydrophilic), incorporated or intercalated in the membrane (if lipophilic or amphiphatic), or directly attached by chemical bond to the surface membrane (107-109). 

The synthesis of paramagnetic materials that have specifically tailored magnetic properties is gaining considerable interest (see Magnetism of Extended Arrays in Inorganic Solids and Magnetism of Transition Metal Ions). For example, metallocenes and their derivatives are known to... 

Paramagnetic materials become magnetic under an external field and are then attracted by the field. This mechanism is reversible, meaning that when the external field is turned off, the material loses its magnetic properties. 

Electron spin resonance (ESR) spectroscopy a technique used for the study of substances that are paramagnetic, a property caused by the presence of unpaired electrons. In biological materials paramagnetism is principally found in two main types of molecular species, free radicals and those that contain a transition metal ion. Some spectroscopists confine the term ESR spectroscopy to the study of free radicals, because they have an identifiable electron spin, and use the term electron paramagnetic resonance (EPR) spectroscopy for the study of transition metals, where paramagnetism arises from the distribution of electrons in the d orbitals. However the spectra are taken with the same instrumentation and most authors use the terms ESR- and EPR spectroscopy either interchangeably or according to personal preference. 

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