Dendrimers and dendrons by George R. Newkome, Charles N. Moorefield, and Fritz Vögtle

No abstract

Dendritic Molecules by G. R. Newkome, C. N. Moorefield, and F. Vogtle

No abstract

Moleculaire architectuur

Voordracht uitgesproken tijdens de uitreiking van de NWO/Spinoza-premie op 7 februari 2002 in de Nieuwe Kerk te Den Haag

Counterintuitive consequences of competitive pathways in supramolecular polymerizations

\u3cp\u3eCompetition between supramolecular polymers for the same monomers can lead to strong responses in these systems. Using numerical simulations, we show that the sharpness and asymmetry of the transition from one thermodynamically stable polymer to another upon changing temperature is determined by the most unstable rather than the most stable supramolecular polymer. The width and asymmetry of the transitions are shown to depend on the relative and absolute nucleation penalties of the competing supramolecular polymerizations.\u3c/p\u3

The construction of supramolecular systems

Self-assembly by intermolecular non-covalent interactions directed by self-recognition created the field of supramolecular chemistry (1). However, the word “self” appears to limit this field to mixing components in one assembly step where most of the complexity is inherent in the covalently synthesized reactants, rather than the result of a series of assembly steps that build more complex structures in reproducible procedures. The paradigm shift in supramolecular chemistry that we propose is the building of multicomponent systems following a multistep pathway—the emergence of molecular complexity (see the figure). The latter is not only directed by the information stored in the covalent framework of the components, but also controlled by the kinetics and thermodynamics of the reaction pathways selected in processing this information (2)

Navigatielessen voor een betere toekomst

No abstract

Supramolecular polymers – we've come full circle

\u3cp\u3eSince the first polymers were discovered, scientists have debated their structures. Before Hermann Staudinger published the brilliant concept of macromolecules, polymer properties were generally believed to be based on the colloidal aggregation of small particles or molecules. From 1920 onwards, polymers and macromolecules are synonymous with each other; i. e. materials made by many covalent bonds connecting monomers in 2 or 3 dimensions. Although supramolecular interactions between macromolecular chains are evidently important, e. g. in nylons, it was unheard of to proposing polymeric materials based on the interaction of small molecules. Breakthroughs in supramolecular chemistry, however, showed that polymer materials can be made by small molecules using strong directional secondary interactions; the field of supramolecular polymers emerged. In a way, we have come full circle. In this essay we give a personal story about the birth of supramolecular polymers, with special emphasis on their structures, way of formation, and the dynamic nature of their bonding. The adaptivity of supramolecular polymers has become a major asset for novel applications, e. g. in the direction for the sustainable use of polymers, but also in biomedicine and electronics as well as self-healing materials. The lessons learned in the past years include aspects that forecast a bright future for the use of supramolecular interactions in polymer materials in general and for supramolecular polymers in particular. In order to give full tribute to Staudinger in the year celebrating 100 years of macromolecules, we will show that many of the concepts of macromolecular polymers apply to supramolecular polymers, with only one important difference with fascinating consequences: the dynamic nature of the bonds that form polymer chains.\u3c/p\u3

1,2-Dioxetanes as chemiluminescent intermediates in the triplet oxygen oxygenation of olefins

The reactions of the enol ethers I (R = OMe, R1 = H), II (R = H, n = 2, 8; R = CMe3, n = 2), and adamantylideneadamantane (I; RR1C = adamantylidene) with 3O2 and 1O2 were studied. Reaction with 1O2 gave 1,2-dioxetanes. Reaction with 3O2 was chemiluminescent, and the main products were the ketones obtained by C:C bond cleavage. The 1,2-dioxetanes were intermediates in this latter reaction. [on SciFinder (R)

Quadruple hydrogen-bonded supramolecular polymers : complementarity versus self-complementarity

Abstract onl