Metal ions in the brain are a necessity as well as a poison. The presence of metal ions in the active sites of biological catalysts or metalloproteins and in the biological functioning of nucleic acids is very well documented and they are required for brain activity. On the other hand, metals are very effective in generating oxidative stress. This effect does not only play a role in immunology but also is the root of practically all neurodegenerative disorders by inducing disease via the death of neurons. Managing metal ions in the brain could therefore be an important strategy in the search for therapeutic agents used in the treatment of neurodegenerative diseases. This new title gives an overview to key topics in the area of metal ions in the brain. It focuses on the role of metal ions in neurological systems by describing their advantageous functions as well as their poisonous features. It is therefore of interest for scientists in biochemistry and biophysics, physiology, toxicology as well as for physicians focused on this topic.

'Why are atoms so small?' asks 'naive physicist' in Erwin Schrodinger's book 'What is Life? The Physical Aspect of the Living Cell'. 'The question is wrong' answers the author, 'the actual problem is why we are built of such an enormous number of these particles'. The idea that everything is built of atoms is quite an old one. It seems that l Democritus himself borrowed it from some obscure Phoenician source . The arguments for the existence of small indivisible units of matter were quite simple. 2 According to Lucretius observable matter would disappear by 'wear and tear' (the world exists for a sufficiently long, if not infinitely long time) unless there are some units which cannot be further split into parts. th However, in the middle of the 19 century any reference to the atomic structure of matter was considered among European physicists as a sign of extremely bad taste and provinciality. The hypothesis of the ancient Greeks (for Lucretius had translated Epicurean philosophy into Latin hexameters) was at that time seen as bringing nothing positive to exact science. The properties of gaseous, liquid and solid bodies, as well as the behaviour of heat and energy, were successfully described by the rapidly developing science of thermodynamics.

Most organic molecules retain their integrity when dissolved, and even though in such cases the effects exerted by solvents are, in the language of the coordination chemist, of the "outer sphere" kind, the choice of solvent can be critical to the successful outcome of an operation or preparation. Solubilities of reactants and products must be taken into account, and even if the organic principals in the reactions retain their integrity, many of the reagents are electrolytes, and their state of aggregation will affect their reactivity. In testifying to the importance of understanding solute-solvent interactions I draw attention to a large class of inorganic species for which the involvement in the chemical and physical properties by the solvent is even more deeply seated. It is comprised by the large body of metal atoms in low oxidation states for which solvent molecules intervene as reagents. At the same time, because the ions carry charges, the effects arising from outer sphere interactions are usually greater than they are for neutral molecules. To cite an example: when FeCb(s) is dissolved in water to form a dilute - say O. OlO- solution there is a complete reorganization of the coordination sphere of the cation. Whereas in the solid each cation is surrounded by six chloride ions, in the solution the dominant form is [Fe(H20)6]3+ followed by [Fe(H20)sCI]2+, [Fe(H20)4CI2]+, etc. in rapidly decreasing abundance.

The book deals with recent scientific highlights on molecular magnetism in Europe. Molecular magnetism is a new interdisciplinary discipline gathering together chemists and physicists, theoreticians and experimentalists. The book intends to provide the reader with documented answers to some current questions. How chemists can use soft conditions to transform molecules in light and transparent magnets? How a molecular system can behave as a single molecule magnet? How to combine several functions in the same molecular system? How light can be used to switch molecular magnetic properties? How can molecules be used for ultimate high density information storage or in quantum computing? What kind of methods do physicists develop and use to explore these new properties of matter? What kind of concepts and calculations can be provided for theoreticians to design new objects and to better understand the field and to enlarge its exciting developments?

The theoretical basis of this book is developed ab ovo. This requires dealing with several problems arising in physical chemistry including the concept of entropy as a thermodynamic coordinate and its relation to probability. Thus Maxwell Boltzmann and Gibbs statistical thermodynamics, and quantum statistics are made considerable use of. A statistical mechanical derivation of the law of mass action for gases and solids is presented, and the problems arising in the application of the law of mass action to the liquid state are addressed. Molecular interactions and how to take them into account when deriving the law of mass action is discussed in some detail sketching a way alternativ to the use of activities. Finally, attention is drawn to the statistical mechanical background to Linear Free Energy Relationships (LFER's) and of Isokinetic Relationships (IKR's) and their connections with molecular interactions.