Light emission, from chemically generated

To our surprise and satisfaction, the general approach worked the CBI derivatives did chemiluminescence, and the sensitivity enhancement was 30- to 50-fold over fluorescence With this success, we embarked on a more thorough study of chemiluminescence with the goal of optimizing the method. Identifiable parameters that affected the efficiency of light emission from a chemically generated fluorescent molecule included ... 

Thermal electron transfer reactions of transition metal complexes can result in the product complex being formed in its excited state rather than its ground state. If this product is emissive, light is emitted from this excited state and the reaction is defined as chemiluminescent. Chemiluminescence occurs both in the oxidation of Ru(bpyH and in the reduction of Ru(bpy). The oxidation and reduction steps can be carried out by either a chemical or an electrochemical experiment. If the emissive ions are generated electrochemically on an electrode surface, the reaction is termed electrogenerated chemiluminescence. 

A second way to overcome the high reactivity of carbenes and so permit their direct observation is to conduct an experiment on a very short timescale. In the past five years this approach has been applied to a number of aromatic carbenes. These experiments rely on the rapid photochemical generation of the carbene with a short pulse of light (the pump beam), and the detection of the optical absorption (or emission) of the carbene with a probe beam. These pump-probe experiments can be performed on timescales ranging from picoseconds to milliseconds. They provide an important opportunity absent from the low temperature experiments, namely, the capability of studying chemical reactions of the carbene under normal conditions. Before proceeding to discuss the application of these techniques to aromatic carbenes, a few details illuminating the nature of the data obtained and the limitations of the experiment need to be introduced. 

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