1,8-Dioxyanthracene-Derived Crown Ethers: Synthesis, Complexation with Paraquat and Assembly of a Tetracationic Cyclophane-Crown Ether Based [2]Catenane.

1,8-Dioxyanthracene-based bisarylene crown ethers, composed of ethylene glycol chains and aromatic moieties, have been synthesized. Complexation studies revealed that these crown ethers could form 1:1 complexes with methyl viologen dication ( N, N′-dimethyl-4,4′-bipyridinium dication; MV²⁺) in a mixed solvent of CDCl₃ and CD₃CN (1:1 v/v) with association constants in a range of (1.2 ± 0.1) × 10³ M^-1 to (1.6 ± 0.2) × 10⁴ M^-1. The structure of the complex and the strength of the π-donor/π-acceptor interactions between the 1,8-dioxyanthracene planes and the pyridinium rings of MV²⁺ are highly dependent on the length of the polyether chains of the ethers. Structural analysis showed that the tetraethylene glycol-derived bis-1,8-dioxyanthracene-based crown ether 9 forms a U-shaped host-guest complex with MV²⁺ by inserting the coplanar pyridinium rings of MV²⁺ between the two parallel oriented 1,8-dioxyanthracene units of 9, which is driven predominantly by π-donor/π-acceptor interactions. The pentaethylene glycol-derived bis-1,8-dioxyanthracene-based crown ether 10, however, adopts a crescent-shaped conformation in complex 10⊃MV²⁺ with the MV²⁺ guest being encapsulated by the polyether chains, propelled mainly by the hydrogen-bonding interactions between the hydrogen atoms of MV²⁺ and the oxygen atoms of the polyether chains of 10. Similarly, the hexaethylene glycol-derived bis-1,8-dioxyanthracene-based crown ether 11 forms a complex with MV²⁺. However, only weak π-donor/π-acceptor interactions between the aromatic groups of the mixed bisarylene crown ethers 12 and 13, and MV²⁺ were observed, and construction of tetracationic cyclophane [CBPQT⁴⁺] and crown ether 13 based [2]catenane 15 was achieved through supramolecular interactions between the [CBPQT⁴⁺] ring and naphtho unit in the crown ether. [ABSTRACT FROM AUTHOR]