In Search of Wasserman's Catenane.

We repeat the earliest claimed [2]catenane synthesis, reported by Wasserman over 60 years ago, in order to ascertain whether or not a nontemplate, statistical synthesis by acyloin macrocyclization does indeed form mechanically interlocked rings. The lack of direct experimental evidence for Wasserman's catenane has led to it being described as a "prophetic compound", a technical term used in patents for claimed molecules that have not yet been synthesized. Contemporary synthetic methods were used to reconstruct Wasserman's deuterium-labeled macrocycle and other building blocks on the 10-100 g reaction scale necessary to generate, in principle, ∼1 mg of catenane.

Coaxial assembly of helical aromatic foldamers by metal coordination.

Deprotonation of acid-terminated helical aromatic foldamers with a mineral base in chlorinated solvents led to their dimerization through the coordination of a metal cation (Li, Na, K, Ag, or Hg) with the terminal carboxylate functions. This new ligation method was applied to oligomerize diacid-functionalized foldamers.

Template-directed self-assembly of dynamic covalent capsules with polar interiors.

Chiral polyimine molecular capsules with polar interiors have been prepared through template covalent dynamic self-assembly. An aryl-extended tetraaldehyde calix[4]pyrrole scaffold was condensed with suitable diamines as linkers using templates for efficient self-assembly. The capsular complexes were characterized in solution, gas phase and the solid-state.

A chiral "Siamese-Twin" calix[4]pyrrole tetramer.

We describe our results in the attempted template syntheses of oligomacrocycle calix[4]pyrrole dimer , using Hay coupling reaction conditions, tetraalkynyl calix[4]pyrrole as starting material and two bipyridyl -oxides of different length as templates. We found that the short bis--oxide was not an efficient template for the macrocyclization reaction producing an insoluble crude reaction mixture containing exclusively oligomerization and polycondensation products. On the other hand, when we used the long bis--oxide as template we obtained a soluble crude reaction mixture in which we did not detect the expected calix[4]pyrrole dimer .

Stabilization of reactive species by supramolecular encapsulation.

Molecular containers have attracted the interest of supramolecular chemists since the early beginnings of the field. Cavitands' inner cavities were quickly exploited by Cram and Warmuth to construct covalent containers able to stabilize and assist the characterization of short-lived reactive species such as cyclobutadiene or o-benzyne. Since then, more complex molecular architectures have been prepared able to store and isolate a myriad of fleeting species (i.

Solid lipid nanoparticles from amphiphilic calixpyrroles.

Hypothesis: Macrocyclic amphiphiles form interesting self-assembling structures, including solid lipid nanoparticles, which have potential applications in drug encapsulation. Aryl-extended calixpyrroles, which act as anion binding hosts, are expected to form solid lipid nanoparticles, even though the alkyl chains have unusual perpendicular geometry with respect to the hydrophilic head group. The preparation conditions and the alkyl chain length should affect the size and stability of the particles.

Ordered co-encapsulation of chloride with polar neutral guests in a tetraurea calix[4]pyrrole dimeric capsule.

In this work, we describe the stoichiometrically controlled self-assembly process of tetraurea calix[4]pyrrole with a polar neutral guest, trimethylamine -oxide or beta-alanine betaine, and methyltrioctylammonium chloride (MTOACl) salt into two supramolecular architectures which differ in morphology and stoichiometry. Whereas an equimolar solution of tetraurea calixpyrrole , polar guest and MTOACl produces a four-particle inclusion assembly, a mixture of the same components in a 2 : 1 : 1 molar ratio induces the formation of a dimeric capsular assembly displaying multiple guests which are orderly co-encapsulated. The influence of other polar guests and ammonium salts on the self-assembly process is also described.

Tetra-phosphonate calix[4]pyrrole cavitands as multitopic receptors for the recognition of ion pairs.

The synthesis, structural characterization, and binding properties of two unprecedented multitopic receptors for ion-pair recognition are described. We isolated two of the six possible diastereomeric deep cavitand receptors resulting from the installation of four phosphonate groups at the upper rim of a calix[4]pyrrole-resorcin[4]arene hybrid scaffold. The isolated tetra-phosphonate receptors display either three (iooo) or four (oooo) of their P═O groups oriented away from the deep and functionalized aromatic cavity.

Synthesis, structure, and binding properties of lipophilic cavitands based on a calix[4]pyrrole-resorcinarene hybrid scaffold.

We report the synthesis, structural characterization, and binding properties of a series of unprecedented cavitands based on a meso-dodecyl-calix[4]pyrrole-resorcin[4]arene hybrid scaffold. The reported structural and conformational features of the prepared cavitands are derived from results obtained in solution, solid state, and molecular modeling studies. In the solid state, these cavitands are exclusively observed in the kite C4 structure and as a racemic mixture of two cyclochiral conformers, which are interconverting fast on the (1)H NMR time scale, according to solution studies.

Kinetic stabilization of N,N-dimethyl-2-propyn-1-amine N-oxide by encapsulation.

Thermally and in nonprotic media N,N-dimethyl-2-propyn-1-amine N-oxide undergoes two consecutive sigmatropic rearrangements affording propenal. Two molecular containers capable of the quantitative inclusion/encapsulation of the N-oxide are described. The N-oxide becomes kinetically stabilized when included in the containers.