Dynamic Mechanically Interlocked Dendrimers:  Amplification in Dendritic Dynamic Combinatorial Libraries

In the context of constructing nonclassical mechanically interlocked dendrimers by employing a convergent templation procedure, the “clipping” thermodynamic approach has been explored to introduce sterically bulky Fréchet-type dendrons with successive generations [G0] to [G3] onto a trivalent ammonium ion core using a seven-component self-assembly via imine bond formation. Four generations of mechanically interlocked dendrimers up to a molecular weight over 8800 Da were synthesized in a one-pot reaction by simply mixing the seven components together. The dendrimers form in excellent yield (>90%). The mechanically interlocked core of the [G0]−[G2] dendrimers can be modified and transformed into kinetically stable dendrimers by reduction of the imine bonds with borane−tetrahydrofuran complex. Moreover, the dynamic nature of the thermodynamically controlled self-assembly process is employed to obtain three dynamic combinatorial libraries of dendrimers by the treatment of the dendrons [G0]−[G3] with the complementary components in one pot. The inherent modularity of the overall process should allow for the rapid and straightforward access to many other analogues of mechanically interlocked systems for which either the branched core or the dendritic periphery can be modified to suit the needs of any potential application of these molecules.