Trinuclear and polynuclear complexes

The trinuclear complex shown in Fig. 22 [70,74] has the two bridging cyanides N-bonded to the central unit, a feature determined by the synthetic 

A more favorable situation for experimental study has been obtained with the trinuclear complex of Fig 24, which is a derivative of the previous one, with carboxylic groups in the 4,4 positions of the bipyridines of the central unit [93]. Thanks to the acceptor properties of the carboxylic groups, the MLCT states of the central unit are now definitely lower in energy than before, and the absorption spectrum shows distinct MLCT bands for the terminal (420 nm, in H2O) and central (525 nm, in H2O) chromophores, allowing selective excitation. In this case, the single emission observed, and the coincidence of its excitation spectrum with the absorption spectrum give clear evidence of the occurrence of energy transfer from the two terminal chromophores to the common central acceptor [93]. 

Aside from their greater molecular complexity, the trinuclear complexes described until now do not perform anything substantially different from the binuclear systems of section 5.1, i.e., energy transfer between adjacent 

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Likewise, trinuclear and polynuclear complexes of type E have not been... 

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