De Novo Construction of Catenanes with Dissymmetric Cages by Space‐Discriminative Post‐Assembly Modification

Abstract

Considerable efforts have been made to increase the topological complexity of mechanically interlocked molecules over the years. Three‐dimensional catenated structures composed of two or several (usually symmetrical) cages are one representative example. However, owing to the lack of an efficient universal synthetic strategy, interlocked structures made up of dissymmetric cages are relatively rare. Since the space volume of the inner cavity of an interlocked structure is smaller than that outside it, we developed a novel synthetic approach with the voluminous reductant NaBH(OAc)3 that discriminates this space difference, and therefore selectively reduces the outer surface of a catenated dimer composed of two symmetric cages, thus yielding the corresponding catenane with dissymmetric cages. Insight into the template effect that facilitates the catenation of cages was provided by computational and experimental techniques.

Molecular Cages Self‐Assembled by Imine Condensation in Water

“…Future studies include self‐assembly of hosts with larger‐size chiral cavities, so that the cages are able to accommodate larger guests for applications including enantiomer separation, and molecular reaction vessels for the sake of asymmetric catalysis. These results also inspire chemists to take advantage of multivalence to overcome the labile nature of imine, and use this dynamic approach in water to self‐assemble molecules with more complex three‐dimensional architectures such as knots, [9d, 13] catenanes [10c] or polycatenanes [14] . The opportunities of using imine condensation to obtain hosts to target biological substrates such as sugar in living systems, are also opened up.…”

“…More recently,i th as been observed [10] that multivalence could help to solidify the self-assembled molecular entities. That is,e ven though each of the dynamic bonds including imine is rather labile and apt to hydrolyze,the self-assembled molecules might become rather kinetically inert, when each of the building blocks is connected with each other via multiple linkages.Simultaneous cleavage of multiple bonds is obviously much more difficult than breaking asingle dynamic bond.…”

Racemic Porous Organic Cage Crystal with Selective Gas Adsorption Behaviors

“…Porous organic cages (POCs) constructed from covalently linked discrete functional organic modules have been emerged as a new member of porous reticular frameworks. [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] In comparison with other artificial counterparts including MOFs, COFs, and hydrogen-bonded organic frameworks (HOFs), [43][44][45][46][47][48][49][50] POCs possess diverse interesting cage molecules with intrinsic cavities as building blocks. Increasingly, skilled crystal engineering connects the molecular cavities to form the highly intercrossing porosities of POCs, [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] achieving the high surface area of 3758 m 2 g À 1 for storage.…”

Water-stable hydrazone-linked porous organic cages

“…Since the first elegant report in 2009 by Cooper et al, 12 many POCs with different shapes and properties have been reported over the last decade, but they are mostly linked by dynamic and reversible imine (C=N) and B-O bonds. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] Such POC types are prone to hydrolysis and skeleton collapse upon exposure to water, rendering them nonporous nature and severely limiting their applications in a water environment. Four strategies have been validated thus far for constructing waterstable POCs: (1) using irreversible C-C or C-O bonds; [32][33][34][35] (2) introducing ethynylene linkages (C≡C); [36][37][38][39] (3) transforming labile C=N bonds to chemically robust amide (C-N) bonds by post-modification or in situ reduction method; [40][41][42][43][44] and (4) introducing alkyl groups to aldehydes for protecting POCs' C=N bonds by steric and hydrophobic control.…”