Prof. Portnoy Moshe
Design and investigation of nanoscale dendritic composite materials for catalysis and biomedical applications
Dendrimers are branched, highly ordered macromolecules that are assembled in a modular, iterative fashion from polyfunctional building blocks. These macromolecules are not only aesthetically
appealing, but offer chemists three-dimensional structures of nanometer-range size with a variety of interesting architecture-dictated properties for a wide spectrum of applications. The modular mode of assembly and highly ordered nature of dendrimers make them especially suitable for the building of nanoscale devices. During the past few years, my group actively pursued the preparation of dendritic molecules on insoluble support as a platform for the generation of highly active and selective heterogeneous catalysts. We developed an efficient synthesis of new poly(arylbenzylether) dendrons on solid polymer support, functionalized their termini with catalytic units and explored their properties. An unprecedented positive dendritic effect on activity and chemoselectivity of a number of organometallic catalysts immobilized on such dendronized supports was revealed in a series of studies. Another group of catalysts that were immobilized on the dendronized supports are organocatalysts, small metal-free moieties capable of promoting selectively organic transformations of considerable complexity. For instance, we demonstrated a remarkable improvement in the efficiency and enantioselectivity of polymer-supported proline in the aldol and Mannich reactions upon dendritic spacer introduction. A tremendous increase in the catalyst activity upon dendronization of the support was also demonstrated for polymer-bound N-alkylimidazole catalysts in the Baylis-Hillman reaction. Our research in the field of supported dendritic catalysis is aimed at both understanding the rationale behind the dendritic effects as well as improvement and perfection of such systems for potential use. Recently, we began exploring dendrimers as platforms for diagnostic agents for molecular imaging.