A New Motif for the Self-Assembly of [2]Pseudorotaxanes; 1,2-Bis(pyridinium)ethane Axles and [24]Crown-8 Ether Wheels

Abstract

Multiple intramolecular interactions help to stabilize the novel [2]pseudorotaxanes formed from 1,2-bis(pyridinium)ethane dications (which act as axles) and 24-membered crown ethers (which act as wheels; see structure). This is the first successful sythesis of [2]pseudorotaxanes with [24]crown-8 as the macrocycle.

Direct synthetic routes to functionalised crown ethers

“…Arenediazonium salts, which are readily complexed and stabilised by 18C6 and 21C7, were one of the first reported examples of non-metallic guests. 14 Aromatic CEs, by virtue of their π-electron rich aromatic groups, act as hosts for different π-electron poor guests such as bipyridinium, 15 diazapyrenium, 16 bis-(pyridinium)ethane, 17 imidazolium, 18 and triazolium. 19 Besides electrostatic effects, both donor-acceptor π-π interactions and strong hydrogen bonds contribute to the formation and stability of these complexes.…”

Strategies To Assemble Catenanes with Multiple Interlocked Macrocycles

“…Subsequent inclusion of the diammonium units in dibenzo-24-crown-8 (DB24C8) gave the [4]- and [7]­catenanes in quantitative yield (Figure ). Because of the weak ammonium–crown ether binding ( K ≈ 200), , an excess of DB24C8 was used to favor the formation of [ n ]­catenanes.…”

How Secondary and Tertiary Amide Moieties are Molecular Stations for Dibenzo-24-crown-8 in [2]Rotaxane Molecular Shuttles?

“…Several secondary stations for the DB24C8 have been reported in the literature to date. As a non-comprehensive list of them, we can cite the following positively charged stations: bipyridinium [ 4 , 5 , 6 , 7 , 8 , 9 , 10 ], 1,2-bis-(pyridinium)ethane [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ], triazolium [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ], pyridinium [ 31 , 32 , 33 ], pyridinium amide [ 34 , 35 , 36 , 37 ], imidazolium [ 38 , 39 , 40 , 41 ] moieties, oxidized ferrocene [ 42 ], etc. Some neutral molecular stations are also important to be mentioned, such as urea [ 43 ], thiourea [ 44 ], carbamate [ 45 , 46 , 47 , 48 , 49 , 50 ], isoxazole [ 51 ], and benzylic ester [ 52 ], that usually interact either through π-π stacking with the aromatic rings of the crown ether, or through hy...…”