Energy transfer MLCT excited state

The low-energy metal to ligand charge-transfer (MLCT) excited state has been extensively studied and involves low-lying ft -acceptor orbitals of the pyridine ligands ( ). ... 

Metal-to-Ligand Charge-Transfer (MLCT) Excited-State Energies... 

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]. 

Most robust and efficient sensitizers are based on the metal-to-ligand charge transfer (MLCT) excited states of polypyridyl Ru compounds, which have been well reviewed [254, 255]. Dye-sensitized nanocrystalline electrochemical photovoltaic system has recently become a validated and credible competitor to solid-state junction devices for the conversion of solar energy into electricity [453-455]. More details of some applications can be found in the Sect. 1.7.3.5 and Vol. 6 [456]. 

A number of cyano-bridged complexes are included here even though they strictly do not fall in the general family-type defined for the section. The syntheses and photophysical properties of [(NC)(bpy)2Ru(/r-NC)Cr(CN)5] and [(NC)5Cr(Ai-CI Ru(bpy)2(M-NC)Cr(CN)5] have been described. Absorption of visible light by the Ru(bpy)2 unit results in phosphorescence from the Cr(CN)g luminophore, and the results evidence fast intramolecular exchange energy transfer from the MLCT state of the Ru(bpy)2 chromophore to the doublet state of the Cr -based unit. Time-resolved resonance Raman and transient UV-vis absorption spectroscopies have been employed to investigate the MLCT excited states of [(NC)(bpy)2Ru(//-CN)Ru (bpy)2(CN)], [(NC)(bpy)2Ru(//-CN)Ru(phen)2(CN)]+, [(NC)(phen)2Ru(//-CN)Ru (bpy)2(CN)]+, [(NC)(bpy)2... 

Figure 2. Schematic representation of some relevant ground and excited-state properties of Ru(bpy)j. MLCT and MLCT are the spin-allowed and spin-forbidden metal-to-ligand charge transfer excited states, responsible for the high intensity absorption band with = 450 nm and the luminescence band with = 615 nm, respectively. The other quantities shown are intersystem crossing efficiency energy (E°°) and lifetime (x) of the MLCT state luminescence quantum yield ( ) quantum yield for ligand detachment (O,). The reduction potentials of couples involving the ground and the MLCT excited states are also indicated.

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