Ami Doshi

Planar Chiral Organoborane Lewis Acids Derived from Naphthylferrocene

Enantiomerically pure metalated 2-(1-naphthyl)ferrocene (NpFc) derivatives NpFcM (M=SnMe(3), HgCl) were prepared and characterized by multinuclear NMR and UV/Vis spectroscopy, cyclic voltammetry, and elemental analysis. Optical rotation measurements were performed and the absolute configuration of the new planar chiral ferrocene species was confirmed by single-crystal X-ray diffraction analysis. The mercuriated species NpFcHgCl proved suitable as a reagent for the preparation of the chiral organoborane Lewis acid NpFcBCl(2), which can in turn be converted to other ferrocenylboranes by replacement of Cl with nucleophiles. The highly Lewis acidic perfluoroarylborane derivatives NpFcB(C(6)F(5))Cl and NpFcB(C(6)F(5))(2) were successfully prepared by treatment with CuC(6)F(5). The structures were studied by single-crystal X-ray diffraction and variable-temperature (19)F NMR spectroscopy, which suggested that pi stacking of a C(6)F(5) group on boron with the adjacent naphthyl group is energetically favorable. UV/Vis absorption spectroscopy and cyclic voltammetry measurements were performed to examine the electronic properties of these novel redox-active chiral Lewis acids.

Organoboron star polymersvia arm-first RAFT polymerization: synthesis, luminescent behavior, and aqueous self-assembly

The first examples of organoboron star polymers were prepared by arm-first RAFT polymerization using a novel luminescent organoboron crosslinker in combination with PS, PNIPAM, P4VP, and PNIPAM-b-PS as linear polymer precursors. Well-defined star architectures with a luminescent core were successfully obtained as confirmed by GPC-MALLS, NMR, DLS, and TEM analysis. The PNIPAM-b-PS stars are amphiphilic and undergo self-assembly in water with formation of super-aggregates that exhibit strong green fluorescence. The P4VP stars lend themselves to further functionalization at the periphery.