Probing intermetallic coupling in dinuclear N-heterocyclic carbene ruthenium(II) complexes

A series of bimetallic N-heterocyclic carbene (NHC) ruthenium(II) complexes were synthesized, which comprise two [RuCl₂(cymene)(NHC)] units that are interlinked via the NHC nitrogens by alkyl chains of different length. Electrochemical characterization revealed two mutually dependent oxidation processes for the complex with a methylene linker, indicating moderate intramolecular electronic coupling of the two metal centers (class II system). The degree of coupling decreases rapidly upon increasing the number of CH₂ units in the linker and provides essentially decoupled class I species when propylene or butylene linkers are used. Electrochemical analyses combined with structural investigations suggest a through-bond electronic coupling. Replacement of the alkyl linker with a p-phenylene group afforded cyclometalated complexes, which were considerably less stable. The electronic coupling in the methylene-linked complex and the relatively robust NHC–ruthenium bond may provide access to species that are switchable on the molecular scale

The Place of the History of Chemistry in the Teaching and Learning of Chemistry

To those of us who are sold on history it may seem non-controversial to suggest that the learning and teaching of chemistry should give cognisance to the historical development of the subject. However, this suggestion is proving controversial amongst some in the chemistry profession. For example, in the October 2010 edition of Chemistry in Australia Rami Ibo takes issue with the emphasis on the history of science in the HSC chemistry curriculum (Year 12) in New South Wales. He studied chemistry, physics and biology for his HSC in NSW and concluded that, because the primary focus of these three sciences was History of Science, “There was hardly any content that challenged our minds, and calculations barely involved plugging in numbers into an equation…..We were required to recall Antoine Lavoisier’s experiments that led to the theories of acids and bases… while my friends in Lebanon were studying ideal gas laws, chemical kinetics, acids and bases, organic chemistry, soaps and detergents, medicinal chemistry and new materials” (Ibo 2010). What does the literature have to say in response to such arguments? Does the presence of the history of chemistry in a curriculum necessarily reduce important content and problem solving skills? A study of the literature suggests at least three reasons for persisting with aspects of the history of chemistry in the learning and teaching of chemistry. 1. The fact that student conceptions sometimes recapitulate early ideas found in the history of chemistry is seen as offering teachers a means of a deeper understanding of student ideas with the potential for more positive learning outcomes. 2. Conceptual clarity is more easily achieved within an historical context. Often conceptual usefulness is pursued at the expense of conceptual depth (de Berg 2008a). 3. The history of chemistry directly gives us some idea of the epistemological status of chemistry within science and knowledge in general and therefore gives a student access to aspects of the Nature of Science. This review chapter also examines different ways the history of chemistry has been incorporated into chemistry curricula and looks at the purported advantages, disadvantages, and limitations of such attempts. Some directions for future research in this area are included in the chapter