Covalent dimers arrays

Fig. 6. Example of a complex supramolecular hierarchy. The primary structures (a) and (b) are formed due to covalent bonds. When the dicarboxylic acid threads through the macrocyclic cavity of rr-deflcient tetracationic cyclophane the second level, supermolecule, is obtained (c). The next level, supramolecular array (d), is created as a result of noncovalent dimerization of the [1 2 +] supermolecule s carboxyl groups. Then the highest level, macroscopic conglomerate (e), is formed due to v-tt stacking. Adapted from M. C. T. Fyfe and J. F. Stoddart,Acc. Chem. Res. 30,393 (1997).

Through coor nation motif, a tetra-pyrazinyl porphyrin-based assembly with four dimeric [meso-tetrakis(2-carboxy-4-nonylphenyl)porphyrinato]-zinc(II) as the antenna moiety was constructed by Kuroda et al. [113]. The efficiency of energy transfer from the zinc porphyrin-pyrazine complex to the free base porphyrin has been determined to be 82%. Also for this system, the observed efficiency of energy transfer is not so high compared with those reported for covalently finked multi-porphyrin systems [114]. Himter s group has designed a pentameric porphyrin array, wtiich was built up by the complementary coordination of a tetra-pyridyl porphyrin and two zinc-porphyrin dimers [115]. Steady-state and time-resolved fluorescence spectroscopic studies revealed that the energy transfer efficiency of this array is around 70%. 

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