Excited states in metal oxides

EXCITED STATES IN METAL OXIDES BY CONFIGURATION INTERACTION AND MULTIREFERENCE PERTURBATION THEORY... 

Excited states in metal oxides by configuration interaction and multireference perturbation theory 227... 

Three classes of polynuclear complexes containing metal-metal bonds possess emissive excited states that undergo oxidation-reduction reactions in solution the prototypes are Re2Cl T(dlt d lt),... 

The inherent electronic nature of semiconductor metal oxides can direcdy interact with molecular excited states in a manner not energetically possible with insulators. More specifically, an excited sensitizer, S, may transfer an electron to the semiconductor forming a charge separated pair [Eq. (1)] ... 

When desorption takes place from a metal surface, many hot charge carriers are generated in the substrate by laser irradiation and are extended over the substrate. Then, the desorption occurs through substrate-mediated excitation. In the case of semiconductor surfaces, the excitation occurs in the substrate because of the narrow band gap. However, the desorption is caused by a local excitation, since the chemisorption bond is made of a localized electron of a substrate surface atom. When the substrate is an oxide, on the other hand, little or no substrate electronic-excitation occurs due to the wide band gap and the excitation relevant to the desorption is local. Thus, the desorption mechanism for adsorbed molecules is quite different at metal and oxide surfaces. Furthermore, the multi-dimensional potential energy surface (PES) of the electronic excited state in the adsorbed system has been obtained theoretically on oxide surfaces [19, 20] due to a localized system, but has scarcely been calculated on metal surfaces [21, 22] because of the delocalized and extended nature of the system. We describe desorption processes undergoing a single excitation for NO and CO desorption from both metal and oxide surfaces. 

The blue precipitates obtained on mixing Fe3+ with [Fen(CN)6]4 or Fe2+ and [Fem(CN)6]3 have long been known both products are Fe4n[Fen(CN)6]3T5H20. This compound presents an intense absorption band at 700 nm due to transition from the ground state to an excited state in which an electron is transferred from an Fe11 to an Fem site. Prussian blue may be considered as the archetype of mixed valence compounds it contains two identical metals in different oxidation states. These compounds have played, and continue to play, a crucial role in the study of electron transfer phenomena.51... 

Alkaline earth metal atoms have fairly low ionization potentials, as have alkali metal atoms (e.g., 5.21 and 5.14 eV for barium and sodium, respectively [89]). Hence the reactions of alkaline earth metal atoms with oxidizing molecules are also expected to be initiated by an electron transfer and should follow the harpoon mechanism. However, alkali metal atoms are monovalent species, whereas alkaline earth metal atoms have two valence electrons. Hence peculiarities are to be expected in the alkaline earth metal reaction dynamics, especially when doubly charged products such as BaO are to be formed [90]. The second valence electron also opens up the possibility of chemiluminescent reactions, which are largely absent in alkali metal atom reactions [91, 92]. The second electron causes the existence of low-lying excited states in the product. 

E21.22 Since the intermediate is believed to be [W(CO)5], the properties of the entering group (triethylamine versus triphcnylphosphine) should not aflfect the quantum yield of the reaction, which is a measure of the rate of formation of [W(CO)5] from the excited state of [W(CO)j(py)]. The product of the photolysis of [W(CO)5(py)J in the presence of excess triethylamine will be [W(CO)5( t3)], and the quantum yield will 0.4. This photosubstitution is initiated from a ligand field excited state, not an MLCT excited state. A metal-ligand chai ge transfer increases the oxidation state of the metal, which would strengthen, not weaken, the bond between the metal and a cr-base-like pyridine. 

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