engleski

Oligonucleotides with Pendant Porphyrins: towards Self-Assembled Multi-Porphyrinic Nano-Materials

The light-harvesting antennae in the photosynthetic system consist of a large number of pigments, which are responsible for absorption of photons. The extraordinary efficiency of the excited state migration among the pigments is ascribed to their parallel orientation and favoured spacing within the light-harvesting complexes. This arrangement, controlled by weak interactions between pigments and polypeptides, assumes three ring-shaped light-harvesting antennae. Aiming to organize porphytins in accordance with the natural system, we have chosen oligonucleotidic backbone for the elaboration of multi-porphyrinic nanosystems. In this, respect, the synthesis of oligonucleotides functionalized with porphyrins was realized. The preparation of theses systems was based on oligomerization of at O-3' and O-5' positions of the 2'-deoxyuridine derivative functionalized with a porphyrin. Architecture of our system has been designed on the basis of rigid and flexible linkers. The porphyrins were appended to C-5 position of the uracil by a rigid linker and the uridines were mutually linked by a flexible linker, with a goal to work out parallel orientation of porphyrins via anticipated conformation of the oligonucleotidic chain. In this context, we have synthetized the mino-, di-, tetra-, and octa-deoxynucleosidies with pendant porphyrins. An appropriate arrangement of free-base and zinc(II) porphyrins within the oligonucleotidic moleculčar wire allowed us to highlight an energy transfer. The contribution of the zinc(II)-porphyrin to the emission of the free-base porphyrins was evidenced. The range of oligonucleotides have been metallated with zinc(II) targeting to examine effectiveness of the oligomerization degree of these molecular architectures on their ability to complex a bidentate base such as DABCO. We have observed that the coordination of DABCO is favoured as one goes toward higher degree of oligomerization due to imposes conformational pre-organization within the oligonucleotidic backbone. At last, we were intersted in self-assembly by means of hydrogen bonding, which could be established between the uracil nucleobase and a complementary synton such as triazine functionalized with porphyrins. The quantitative studies of dtability of those supramolecular architectures have evidenced an infkuence of secondary intermolecular pi-pi interactions between the porphyrins within the supramolecular complex.

Porphyrins; Uridines; Oligonucleotides; Hydrogen Bond; Self-assembly; Supramolecular complexes; Energy transfer; Fluorescence

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