Photon Antennae Assembled by Hydrogen Bonding

In attempting to mimic the essential features of green plant and bacterial photosynthetic organisms many elaborate molecular systems have been built [23-25]. Most attention has focussed on the reaction center complex [26,27], where rapid electron transfer reactions result in efficient spatial separation of charge, although sporadic attempts have been made to 

In order to extend these studies, it is necessary to employ D-S-A systems having well-defined geometric arrangements. Much of the earlier work involving flexible spacer groups [49-53] gave little useful mechanistic information because the molecular architecture was unknown and probably involved many different conformations of the same D-S-A unit. 

Recently, there have been several reports of self-assembling molecular systems in which association of individual subunits arises from molecular recognition features [60-62], Molecular recognition is the most recent term for well-established chemical phenomena [63]. The field covers inclusion 

Photophysical properties of the above porphyrin-nucleic acid base conjugates were measured both as individual species in dilute chloroform solution and as mixtures at high concentration (ca. 2 mM) in chloroform. As individual species, the photophysical properties were very similar, if not 

Aoyama et al. [76] have described a more direct approach in which 5,15-cis-bis(2-hydroxy-l-naphthyl)octaethylporphyrin is used to bind p-quinones in chloroform solution (13). This strategy positions the quinone in a face-to-face orientation immediately on top of the porphyrin plane. The quinone quenches porphyrin fluorescence, presumably due to photoinduced electron transfer, but time-resolved fluorescence or transient absorption studies have not been reported, to date. The close proximity of the reactants, however, is expected to favor rapid electron transfer. 

---