Self-Assembly, Spectroscopic, and Electrochemical Properties of [n]Rotaxanes¹

Abstract

Synthetic approaches to self-assembling [n]rotaxanes incorporating π-electron deficient bipyridinium-based dumbbell-shaped components and π-electron rich hydroquinone-based macrocycles have been developed. In particular, the so-called slippage methodology relies upon the size complementarity of preformed macrocyclic and dumbbell-shaped components. The spontaneous self-assembly of these complementary components into a rotaxane in solution can be achieved under the influence of an appropriate amount of thermal energy. The absorption spectra, luminescence properties, and electrochemical behavior of the rotaxanes and their dumbbell-shaped components have been investigated and discussed on the basis of the behavior of their chromophoric and electroactive units. Charge-transfer and energy-transfer processes between specific chromophoric subunits and unusual correlations between the redox patterns of the various compounds have been evidenced and interpreted.

Strong Induced‐Fit Binding of Viologen and Pyridine Derivatives in Adjustable Porphyrin Cavities

“…[47][48][49][50][51] At NMR concentrations (≈ 10 -3 M), it takes several days before the components reach complexation equilibrium.…”

On sublinks and their connections within the graphs of the mechanically bound molecules

“…There are the following general methods known: (1) threading-followed-bystoppering, 14 (2) "clipping," 15 and (3) slippage. 16 A very elegant application of retro-synthetic methodology has been recently used in design of both magnificent and very efficient synthesis of Borromean rings, 6a that needs only one pot procedure to make the desired compounds in up to 90% (!) yield starting from only the linear precursors and using transition metal cations as templates.…”

“…At least one of synthons must be by the conditions, an acyclic structure. The only exception of this rule seems to be the slippage methodology in synthesis of rotaxanes 16 (and thus all similar syntheses 19 ). However, the analysis presented can be of a great help to choose various synthetic ways towards topologically complex structures such as [5]-MN ( Figure 4, Table 1).…”

Templated Synthesis of Interlocked Molecules

“…The so-called slippage approach has been employed successfully, in the past three decades to self-assemble a series of linear [135][136][137][138][139] and branched [n]rotaxanes [140][141][142] under thermodynamic control. In this strategy, the macrocycle and the dumbbell, which are synthesized independently prior to self-assembly, are usually heated together in an appropriate solvent until the macrocycle slips over the dumbbell's stopper by overcoming the associated free energy of activation.…”

“…This approach has led to the preparation of rotaxanes by either threading-followedby-stoppering [152,[182][183][184] or slippage [135][136][137][138][139][140][141][142][143][144][145][146][147][148] protocols. However, in 2001, the Stoddart group [185] reported a simple and highly effective dynamic procedure (Scheme 10) for the formation of a [2]rotaxane by the clipping of a diamine with a dialdehyde, as the precursor components of a [24]crown-8-like macrocycle, around a dialkylammonium center that also acts as a template.…”