[2]Pseudorotaxanes, [2]rotaxanes and metal–organic rotaxane frameworks containing tetra-substituted dibenzo[24]crown-8 wheels

Abstract

[2]Pseudorotaxanes, [2]rotaxanes and metal–organic rotaxane framework materials that utilise DB24C8 as the wheel component are well known and structural variations based on changing the axle component are common. Studies in which the DB24C8 wheel is structurally modified are much more limited. Herein, is described the synthesis of symmetrical DB24C8 analogues containing four CH₂OR (R = CH₂CH₂CH₃, CH₂(C₆H₅), C₆H₅ and C₆H₄(4-COOEt)) substituents on the 4 and 5 positions of the aromatic rings. The effect of these molecular appendages on the stability and structures of the interpenetrated and interlocked molecules derived from these new wheels is described. The major effects are an increase in association constants for the formation of [2]pseudorotaxanes relative to DB24C8, the crystal packing of [2]rotaxanes and a change on the internal structure of a 2D MORF (R = C₆H₅) compared to DB24C8.