Supramolecular assembly of pyrene-DNA conjugates: influence of pyrene substitution pattern and implications for artificial LHCs.

The supramolecular self-assembly of pyrene-DNA conjugates into nanostructures is presented. DNA functionalized with different types of pyrene isomers at the 3'-end self-assemble into nano-objects. The shape of the nanostructures is influenced by the type of pyrene isomer appended to the DNA. Multilamellar vesicles are observed with the 1,6- and 1,8-isomers, whereas conjugates of the 2,7-isomer exclusively assemble into spherical nanoparticles. Self-assembled nano-spheres obtained with the 2,7-dialkynyl pyrene isomer were used for the construction of an artificial light-harvesting complex (LHC) in combination with Cy3 as the energy acceptor.

Highly Efficient Transfer Hydrogenation Catalysis with Tailored Pyridylidene Amide Pincer Ruthenium Complexes.

The rational optimization of homogeneous catalysts requires ligand platforms that are easily tailored to improve catalytic performance. Here, it is demonstrated that pyridylidene amides (PYAs) provide such a platform to custom-shape transfer hydrogenation catalysts with exceptional activity. Specifically, a series of meta-PYA pincer ligands with differently substituted PYA units has been synthezised and coordinated to ruthenium(II) centres to form bench-stable tris-acetonitrile complexes [Ru(R-PYA-pincer)(MeCN)3 ](PF6 )2 (R=OMe, Me, H, Cl, CF3 ). Analytic studies including 1 H NMR spectroscopy, cyclic voltammetry, and X-ray crystallography reveal a direct influence of the substituents on the electronic properties of the ruthenium center. The complexes are active in the catalytic transfer hydrogenation of ketones, with activities directly encoded by the PYA substitution pattern. Their perfomance improves further upon exchange of an ancillary MeCN ligand with PPh3 . While complexes [Ru(R-PYA-pincer)(PPh3 )(MeCN)2 ](PF6 )2 were only isolated for R=H, Me, an in situ protocol was developed to generate these complexes in situ for R=OMe, Cl, CF3 by using a 1:2 ratio of the complexes and PPh3 . This in situ protocol together with a short catalyst pre-activation provided highly active catalytic systems. The most active pre-catalyst featured the methoxy-substituted PYA ligand and reached turnover frenquencies of 210 000 h-1 under an exceptionally low catalyst loading of 25 ppm for the benchmark substrate benzophenone, representing one of the most active transfer hydrogenation systems known to date.

Supramolecular assembly of phenanthrene-DNA conjugates into light-harvesting nanospheres.

The self-assembly of highly functionalized phenanthrene-DNA conjugates into supramolecular nanostructures is presented. DNA oligomers modified with phenanthrene residues at the 3'-end and internal positions self-assemble into spherical nanostructures. The nanospheres exhibit light-harvesting properties. Upon irradiation of phenanthrene, the excitation energy is transferred along phenanthrene units, resulting in phenanthrene-pyrene exciplex formation.