Networks from Dinuclear Units

The same authors also studied the related complexes [Au2(L-L)(i-mnt)] (L-L = dmpm, dppe i-mnt= S2C2(CN)22 ) [29], the first (dmpm complex) being a helical extended polymer and the second (dppe) a monomer. In the former, the intramolecular distances are 2.925(3)-2.893(3) A, and the intermolecular distances 3.171 

In contrast, in the related ylide complexes of stoichiometry [Au2(L-L) (CH2)2S(0) NMe2 ] (L-L = dpmp, dppm, dppe) [32], the same group describes oligomerization processes in solution, even when these molecules are not polymers in the solid state. 

In this case, the oligomerization process is detected by absorption measurements because the spectra of the dppm and dpmp complexes are concentration dependent. 

At this point, it seems that in these binudear units, which act as building blocks of supramolecular systems, the existence of different gold-gold interactions does not affect the extited states from which the emissions are produced. In other words, the emissions do not depend on the type of interactions in the complexes but only on their number or length. This is surprising since one would expect different excited states to arise from the interactions that appear as a consequence of intramolecular and intermolecular interaction, above all when the distances are quite different. This problem was first considered by Fackler and coworkers in complexes of the type 

Based on lifetime measurements, the authors also propose that the high energy emission is fluorescent and the low energy one is phosphorescent, the latter being strongly influenced by the close proximity of the gold centers of different molecules because it disappears completely when there are no intermolecular interactions. 

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Thus, in the next examples, we comment on supramolecular entities, including linear chains, two-dimensional sheets, and even three-dimensional networks. From them, perhaps the most common structural arrangement is that in which the metals form extended linear systems, usually built from mononuclear units, dinuclear, using polydentate donor ligands and polymetallic units. It is worth mentioning that in this part and also in the following we consider only structures built by gold-heterometal interactions, not bonds thus formal clusters will not be considered. 

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