Excited-state species, transition metal

The spectral properties of this excited state species are of great interest since they represent the effects of the (d 2) (d 2 y2), d 2 metal centered transition upon... 

A novel ECL assay for the determination of 2,4- and 3,4- diaminotoluene (DAT) isomers is based on reaction of these molecules with Au" and Cu +, respectively, in aqueous solution under oxidizing conditions in buffer-containing tripropylamine [72]. Luminescence is observed upon potential ramping from 0 to -1-2.8 V. The nature of the emitting species was not specified, but could involve a charge-transfer excited state of the metal complex with DAT or an oxidized form of DAT. DAT isomers were screened for ECL enhancement against 32 metals the apparent specificity of Au+ for 2,4-DAT and Cu + for 3,4-DAT is believed to be linked to the radii of each ion. This ECL approach could lead to applications in the determination of some aminoaromatics from degradation of explosives (e.g., TNT) as well as detection and quantifiation of various transition metals in water supplies. 

The photo-excited states of some inorganic complexes are able to abstract an H atom from alkanes. Finally, high-oxidation-state late transition-metal oxo complexes snch as the active Fe =0 or Fe -0 species of cytochrome P450 methane mono-oxygenase enzyme, are also able to abstract an H atom from alkanes, which then leads to their hydroxylation (see Chap. 18). It is also possible, in some cases, to remove an H atom from Hj (see Chap. 15) ... 

There is another compensating effect at a metal electrode as a consequence of such an electron transfer in the excited state. The species D+ and D which are generated have acceptor or donor levels below or above the Fermi level of the metal where a reverse electron transfer is now possible. In the steady state reached within the lifetime of the products D+ and D at the electrode the photocurrents are compensated by the reverse electron transition from the products. Only if a feist consecutive reaction brings one of the products to an energy state where no reverse electron transfer is possible a net photocurrent can be observed at a metal electrode. It is not clear whether up to now any reaction has been found which... 

---