Predicting the structure of supramolecular dendrimers via the analysis of libraries of AB3 and constitutional isomeric AB2 biphenylpropyl ether self-assembling dendrons.

The synthesis of 4'-hydroxy-4-biphenylpropionic, 3',4'-dihydroxy-4-biphenylpropionic, 3',5'-dihydroxy-4-biphenylpropionic, and 3',4',5'-trihydroxy-4-biphenylpropionic methyl esters via three efficient and modular strategies including one based on Ni-catalyzed borylation and sequential cross-coupling is reported. These building blocks were employed in a convergent iterative approach to the synthesis of one library of 3,4,5-trisubstituted and two libraries of constitutional isomeric 3,4- and 3,5-disubstituted biphenylpropyl ether dendrons. Structural and retrostructural analysis of supramolecular dendrimers revealed that biphenylpropyl ether dendrons self-assemble and self-organize into the same periodic lattices and quasi-periodic arrays observed in previously reported libraries, but with larger dimensions, different mechanisms of self-assembly, and improved solubility, thermal, acidic, and oxidative stability. The different mechanisms of self-assembly led to the discovery of two new supramolecular structures. The first represents a new banana-like lamellar crystal with a four layer repeat. The second is a giant vesicular sphere self-assembled from 770 dendrons that exhibits an ultrahigh molar mass of 1.73 x 10(6) g/mol. Thus, the enhanced size of the self-assembled structures constructed from biphenylpropyl ether dendrons permitted for the first time discrimination of various molecular mechanisms of spherical self-assembly and elaborated a continuum between small filled spheres and very large hollow spheres that is dictated by the primary structure of the dendron. The comparative analysis of libraries of biphenylpropyl ether dendrons with the previously reported libraries of benzyl-, phenylpropyl-, and biphenyl-4-methyl ether dendrons demonstrated biomimetic self-assembly wherein the primary structure of the dendron and to a lesser extent the structure of its repeat unit determines the supramolecular tertiary structure. A "nanoperiodic table" of self-assembling dendrons and supramolecular dendrimers that allows the prediction of the general features of tertiary structures from primary structures was elaborated.

Expanding the structural diversity of self-assembling dendrons and supramolecular dendrimers via complex building blocks.

The design and synthesis of the first examples of AB4 and AB5 dendritic building blocks with complex architecture are reported. Structural and retrostructural analysis of supramolecular dendrimers self-assembled from hybrid dendrons based on different combinations of AB4 and AB5 building blocks with AB2 and AB3 benzyl ether dendrons demonstrated that none of these new hybrid dendrons exhibit the previously encountered conformations of libraries of benzyl ether dendrons. These hybrid dendrons enabled the discovery of some highly unusual tapered and conical dendrons generated by the intramolecular back-folding of their repeat units and of their apex. The new back-folded tapered dendrons have double thickness and self-assemble into pine-tree-like columns exhibiting a long-range 7/2 helical order. The back-folded conical dendrons self-assemble into spherical dendrimers. Non-back-folded truncated conical dendrons were also discovered. They self-assemble into spherical dendrimers with a less densely packed center. The discovery of dendrons displaying a novel crown-like conformation is also reported. Crown-like dendrons self-assemble into long-range 5/1 helical pyramidal columns. The long-range 7/2 and 5/1 helical structures were established by applying, for the first time, the helical diffraction theory to the analysis of X-ray patterns obtained from oriented fibers of supramolecular dendrimers.