Energy transfer from transition metal ions

A technological interesting possibility is the energy transfer from transition-metal ions to f elements. Transition-metal ions offer broad absorption bands which can be easily excited by flashlamps. A subsequent energy transfer to an f element can then result in a sharp emission... 

Figure 9.29 Photo-induced spin crossover in transition metal ions (a) incident photons can successively promote electrons from the ground t2g state to the high-energy eg state and (b) spin crossover involving election transfer and excitation in KFeCo(CN)6-...

SN P spontaneously releases N O both thermally and photochemically [61-65], but is quite stable in the dark and in aqueous in vitro physiological media [66]. This implies that absorption of heat and light energy induces electron transfer from the Fe2+ center to the N 0+ ligand, resulting in weakening of the Fe-N O bond and subsequent release of NO [65]. SNP also decomposes in an aqueous environment in the presence of biological reductants [65, 66] and some transition metal ions to produce nitric oxide. 

Calixarene containing a dioxotetraaza unit, PET-18, is responsive to transition metal ions like Zn2+ and Ni2+. Interaction of Zn2+ with the amino groups induces a fluorescence enhancement according to the PET principle. In contrast, some fluorescence quenching is observed in the case of Ni2+. PET from the fluorophore to the metal ion is a reasonable explanation but energy transfer by electron exchange (Dexter mechanism) cannot be excluded. 

There are three possible mechanisms whereby an excited atom or ion can undergo an electronic transition near a metal surface (1) de-excitation involving the emission of radiation, (2) de-excitation involving a two electron Auger process, and (3) a resonance process whereby an electron is transferred from the metal to an equivalent energy level in the ion or a similar transition where the electron goes from the ion to the metal. However, Schekhter has shown that the probability... 

Balzani et al. prepared dendrimers with metal complexes serving both as core [36] and as branching unit The metallodendrimer in Fig. 2.10 is constructed solely from polypyridine ligands and transition metal ions. Such dendritic transition metal complexes can be synthesised both convergently and divergently and different transition metal ions (ruthenium/osmium) can be incorporated. This provides a means of influencing the luminescence properties of the den-drimer. Thus the energy transfer process proceeds from the inside outwards in... 

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