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Mechanically interlocked molecules are a class of compounds used for controlling directional movement when barriers can be raised and lowered using external stimuli. Applied voltages can turn on redox states to alter electrostatic barriers but their use for directing motion requires knowledge of their impact on the kinetics. Herein, we make the first measurements on the movement of cyclobis(paraquat‐p‐phenylene) (CBPQT4+) across the radical‐cation state of monopyrrolotetrathiafulvalene (MPTTF) in a [2]rotaxane using variable scan‐rate electrochemistry. The [2]rotaxane is designed in a way that directs CBPQT4+ to a high‐energy co‐conformation upon oxidation of MPTTF to either the radical cation (MPTTF⋅+) or the dication (MPTTF2+). 1H NMR spectroscopic investigations carried out in acetonitrile at 298 K showed direct interconversion to the thermodynamically more stable ground‐state co‐conformation with CBPQT4+ moving across the oxidized MPTTF2+ electrostatic barrier. The electrochemical studies revealed that interconversion takes place by movement of CBPQT4+ across both the MPTTF•+ (19.3 kcal mol−1) and MPTTF2+ (18.7 kcal mol−1) barriers. The outcome of our studies shows that MPTTF has three accessible redox states that can be used to kinetically control the movement of the ring component in mechanically interlocked molecules. [ABSTRACT FROM AUTHOR]

Keywords: tetrathiafulvalene; pyrrole; orthogonal building block; Sonogashira- coupling; alkylation EN tetrathiafulvalene pyrrole orthogonal building block Sonogashira- coupling alkylation 2019 2026 8 06/16/23 20230704 NES 230704 Tetrathiafulvalene (TTF, B 1 b ) and its derivatives (Figure 1) have been extensively investigated for half a century. The residue was purified by column chromatography (50 mL SiO SB 2 sb , deact. with 1% Et SB 3 sb N, 3 cm , eluent: CH SB 2 sb Cl SB 2 sb /EtOAc (9:1->4:1)). The crude product was purified by column chromatography (125 mL SiO SB 2 sb , deact. with 1% Et SB 3 sb N, 5 cm , eluent: CH SB 2 sb Cl SB 2 sb /PE (2:1)). The residue was purified by column chromatography (25 mL SiO SB 2 sb , deact. with 1% Et SB 3 sb N, 3 cm , eluent: PE/CH SB 2 sb Cl SB 2 sb (2:1 -> 1:1)). [Extracted from the article]

The newly designed [2]catenane that incorporates hydroquinone (HQ) and a sterically bulky tetrathiafulvalena (TTF) into a bismacrocyle is found to probe two classes of alongside charge-transfer (CT) interactions. The profiles of the CT bands are found to change with the ratio of the cis- to trans-TTF isomers, giving different overlap of the employed compounds.

The synthesis of several [pi]-electron-donating monopyrrolotetrathiafulvalene (MPTTF) derivatives which are conceptually divided into three classes containing none, one, or two triethylene glycol (TEG) substituents, is reported. The results have revealed that the strength of the binding between MPTTF derivatives and [CBPQT.sup.4+] is directly correlated to the [pi]-electron donating properties of the MPTTF derivatives.

The syntheses of a series of tetrathiafulvalene-substituted calix[4]pyrrole receptors, which were prepared and tested as potential electrochemical sensors, are described. Predicative X-ray crystallographic structures in the case of two of the compounds confirm that, in the absence of an added anionic guest, the systems adopt a 1,3-alternate conformation.

Surface sensitive X-ray techniques are used to elucidate the structures of amphiphilic [2]rotaxane and dumbbell monolayers at the air/water interface. Largely due to the hydrophilic nature of their tetracationic ring component, the [2]rotaxanes are found to adopt highly highdrated tilted and/or folded conformations on the water surface.

Solid-state molecular tunnel junction switching devices were fabricated by sandwiching LB monolayers of a bistable [2] catenane, a bistable [2] pseudorotaxane and a single station rotaxane between an n-type polysilicon bottom electrode and a titanium aluminum top electrode. All the devices showed a hysteretic current-voltage response that switched the device between high and low conductivity states although control devices exhibited no response. d

An active molecular plasmonics system is shown where a supramolecular chromophore generated in a host-guest binding event has coupled with the localized surface plasmon resonance (LSPR) arising from gold nanodisc gratings. The creation of a responsive plasmonic device upon the addition of the guest molecule and the subsequent coupling of the charge-transfer (CT) chromophore to the plasmon has provided good opportunities for applications in molecular sensing and active molecular plasmonics.

A snake-like trinitrodicyanomethylene-fluorene-[C.sub.60] (TNDCF-[C.sub.60]) derivative is described that can bind to a tetrathiafulvalene (TTF)-modified calix[4]pyrrole derivative through two limiting recognition modes. The differential binding process is shown in easy-to-visualize color changes and is followed by both static and time-resolved absorption spectroscopy.

Two-station [2]rotaxanes in the shape of a degenerate naphthalene (NP) shuttle and a nondegenerate monopyrrolotetrathiafulvene (MPTTF)/NP redox-controllable switch are synthesized and characterized in solution. The incorporation of a rigid spacer into the two-station [2]rotaxane results in a very favorable and temperature-independent isomeric distribution of the isolated compound.

Two switchable, palindromically constituted bistable [3]rotaxanes is designed and synthesized with a pair of mechanically mobile rings encircling a single dumbbell. These designs are found to be reminiscent of a molecular muscle for the purposes of amplifying and harnessing molecular mechanical motions.

The structure and properties self-assembled monolayers (SAMs) of a bistable [2]rotaxane on Au (111) surfaces as a function of the surface coverage using atomistic molecular dynamics (MD) simulations are reported. It is found that the SAM retains hexagonal packing, except for the case at twice the optimum packing density.

Rigid tetrathiafulvalence (TTF) cyclophanes have contributed to a fundamental understanding of CT interactions involving TTF and different acceptors, such as paraquat, diquat, and PMDI. TTF cyclophanes are also employed for the template-assisted formation of interlocked cyclo-bis (paraquat-p-phenylene) with the formation of catenanes.

An efficient method to control the electronic structure of (D(super +delta))(A(super -delta)) Langmuir-Blodgett (LB) films made from charge-transfer (CT) complexes between an amphiphilic monopyrrolo-tetrathiafulvalene (MP-TTF) derivative and different tetracyano-p-quindimethane (TCNQ) derivatives are presented. It is found that the LB films composed of mixed-stack CT complexes with tunable electronic structures are attractive candidates for the formation of nonlinear optical and dielectric materials.