Metal transfer lowest excited

In a metal, there are excited states for electrons that lie below the ionization energy. This can be conceived as an electron in a "conduction band" and a "hole" that interact so that the combination is neutral but not of lowest energy. Such an excited state is called an exciton. Excitons may move by diffusion of the electron-hole pair or by transfer of a molecular exciton to another molecule. Reversion of the exciton to a lower energy state may be slow enough for the lifetime to be longer that of lattice relaxation processes. 

The lowest excited states of paramagnetic metal complexes are described by configuration interactions of the porphyrin (7T,tt ) excited singlet and triplet states and the "porphyrin-to-metal" or metal-to-porphyrin charge-transfer excited states (35,36). Thus T (phosphorescence) emission of paramagnetic metal complexes decays... 

In most of the metal-organic dyads described in this review the metal center has a d6 electronic configuration. Further, the lowest excited state typically has a metal-to-ligand charge transfer (MLCT) configuration arising from promotion of a metal centered -electron into a ligand based -tt level, e.g.,... 

Luminescence from the lowest metal-to-ligand-charge-transfer (MLCT) excited state of the Cu(I)-complexed moiety. 

The excited state properties of trans-W(N2)2(dppe)2 were the focus of several recent spectroscopic [57-59] and photochemical studies [60-64]. The lowest energy excited state was assigned to a spin forbidden transition from a metal to dppe charge transfer (MLCT) excited state. All of the reported studies of the luminescence were carried out in glassy media (2-MeTHF). At temperatures between 8 and 80K, the spectra contain one apparent vibronic progression with a spacing of about 500cm [59]. 

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