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a splitting that increases with decreasing barrier width. For barrier widths below 5 nm it exceeds the thermal energy at room temperature. For a given bairier width, we find only small variations of the tunneling induced splitting demonstrating agood homogeneitywithin a molecule ensemble.The entanglement may be controlled by application of electromagnetic field. For example, using an electric field along the molecule axis we can break the entanglement. Tunneling of carriers is prevented then and emission from intra-dot and inter-dot excitons in which electron and hole are located on the same and on opposite dots, respectively, is observed. The voltage required for the entanglement breaking increases with de^ creasing barrier width reflecting the increasing 'robustness'of the entanglement for narrow barriers.

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Zinc salts are abundant, inexpensive, nontoxic, and exhibit environmentally benign properties. As a result, organic chemists have been interested in using zinc salts as catalysts in organic synthesis during the last three decades. In this chapter, the main contributions on zinc-catalyzed organic synthesis are summarized and discussed. Many name reactions with zinc as catalyst are included, as well as zinc-catalyzed reduction and oxidation reactions.

This chapter is an update to the earlier Science of Synthesis Section 1.7.8 describing methods for the synthesis of ferrocenes. The focus is on the literature published between 2000 and early 2013. The main methods discussed are direct complexation of ligands, modification of cyclopentadienyl rings by electrophilic substitution or directed lithiation, and functional-group transformations in ferrocenyl side-chains. The access to nonracemic ferrocenes and to ferrocenes with configurationally defined side-chain chirality is discussed.