Structural Analysis of Cylindrical and Spherical Supramolecular Dendrimers Quantifies the Concept of Monodendron Shape Control by Generation Number

Abstract

In 1989, it was predicted that a change in dendritic shape to a nearly spherical one should occur upon increasing the generation number (Naylor, A. M.; Goddard, W. A., III; Kiefer, G. E.; Tomalia, D. A. J. Am. Chem. Soc. 1989, 111, 2339). The absence of long-range order required for X-ray analysis allowed only indirect evidence to be provided for this concept. This publication reports the synthesis of three generations of self-assembling monodendrons based on the AB3 building block methyl 3,4,5-trihydroxybenzoate. The first 3,4,5-tris[p-(n-dodecan-1-yloxy)benzyloxy]benzoic acid and the second-generation methyl 3,4,5-tris{3‘,4‘,5‘-tris[p-(n-dodecan-1-yloxy)benzyloxy]benzyloxy}benzoate monodendrons self-assemble into cylindrical supramolecular dendrimers that self-organize in a two-dimensional p6mm lattice. The third-generation monodendron 3,4,5-tris(3‘,4‘,5‘-tris{3‘‘,4‘‘,5‘‘-tris[p-(n-dodecan-1-yloxy)benzyloxy]benzyloxy}benzyloxy)benzoate self-assembles in a spherical dendrimer that self-organizes in a three-dimensional cubic Pm3̄n lattice. Structural analysis of these lattices by X-ray diffraction provided the first direct demonstration of the supramolecular dendrimer shape change from cylindrical to spherical and indirect determination of the average shape change of the monodendron from a quarter of a disk to a half of a disk and to a sixth of a sphere as a function of generation number. These results have demonstrated the concept of monodendron and supramolecular dendrimer shape control by generation number.

Dendrimers and supramolecular chemistry

“…In their seminal work Percec et al (32,33) have used van der Waals interactions and H-bonding to self-assemble functionalized polyether dendrons into cylindrical columnar or spherical assemblies that mimic the shape and architecture of certain types of viruses. Aida and coworkers (34) have used an analogous strategy involving weak metal-metal interactions to effect the hierarchical selforganization of small dendrimers into luminescent superhelical fibers (Fig.…”

Functional liquid-crystalline polymers and supramolecular liquid crystals

“…112 The LC phases can be systematically modulated by changing the volume of dendritic moieties. 113,114 Attachment of rigid-rod mesogenic moieties on the terminal position of the dendrimers can produce LC dendritic molecules. 41,42,[115][116][117] Shibaev and Frey elaborated LC carbosilane dendrimers decorated with terminal mesogenic groups.…”

Self-interrupted synthesis of sterically hindered aliphatic polyamide dendrimers

“…Their nanoarchitecture emerges by increasing their generation number from ellipsoidal or disk-like 2D to 3D globular constructs (16,(19)(20)(21)(22)(23)(24)(25). Their core and branch multiplicities, as well as branch cell segment length (l), determine the generation number at which dendrimers become globular (19)(20)(21).…”

“…Their nanoarchitecture emerges by increasing their generation number from ellipsoidal or disk-like 2D to 3D globular constructs (16,(19)(20)(21)(22)(23)(24)(25). Their core and branch multiplicities, as well as branch cell segment length (l), determine the generation number at which dendrimers become globular (19)(20)(21). Dendrimers synthesized by divergent iterative methods are expected to contain their functional groups, which increase in number with core and branch multiplicities as well as with their generation number, at the periphery of their 2D or 3D architectures (16,19,21).…”

“…Dendrimers synthesized by divergent iterative methods are expected to contain their functional groups, which increase in number with core and branch multiplicities as well as with their generation number, at the periphery of their 2D or 3D architectures (16,19,21). Dendrons and dendrimers produced by convergent strategies contain one functional group at their apex, whereas the rest of them are at their periphery (16,17,20,(23)(24)(25). Ultimately at a certain generation, dendrons also become globular dendrimers with their functional group from the apex becoming encapsulated at the core of the globular object (22)(23)(24)(25).…”