Intramolecular Repulsion Research Articles

The Dual Role of Bridging Phenylene in an Extended Bipyridine System for High-Voltage and Stable Two-Electron Storage in Redox Flow Batteries.

Aqueous organic redox flow batteries (AORFBs) are regarded as a promising solution for grid-scale and sustainable energy storage, but some long-standing problems such as low energy density and cycling stability should be resolved. Herein, a highly soluble bipyridine modified with a bridging phenylene group and two quaternary ammonium terminals, namely, [(NPr)2PV]·4Cl, was synthesized and used as an ultralow-potential and two-electron storage anolyte for AORFBs. The phenylene group, which is linked but not coplanar with the two pyridinium redox centers, can thus prevent their communication and result in an exceptionally low redox potential (-0.77 V vs standard hydrogen electrode, 2e-). Moreover, the introduction of a phenylene group can warrant a certain degree of large π-conjugation effects and mitigate the intramolecular Coulombic repulsion between the two positively charged pyridinium centers, thus helping to enhance the electrochemical stability. When paired with 4-trimethylammonium-TEMPO as the catholyte, [(NPr)2PV]·4Cl enabled an exceptionally high cell voltage up to 1.71 V. The AORFB delivers outstanding battery performances, specifically, ∼89% energy efficiency, ∼100% Coulombic efficiency, and ∼99.94% capacity retention per cycle during a long-term cycling process. The two overlapped single-electron reductions of [(NPr)2PV]·4Cl from the initial cationic form to the monoradical form and then to the quinoid form during the charging process were clearly verified by a series of spectroscopic techniques, including no-deuterium nuclear magnetic resonance and electron paramagnetic resonance. This work presents a significant improvement for the construction of high-voltage AORFBs by virtue of the designability, diversity, and tunability of multiredox organic molecules.

Overcoming intra-molecular repulsions in PEDTT by sulphate counter-ion

ABSTRACT We set out to demonstrate the development of a highly conductive polymer based on poly-(3,4-ethylenedithia thiophene) (PEDTT), PEDOTs structural analogue historically notorious for structural disorder and limited conductivities. The caveat therein was previously described to lie in intra-molecular repulsions. We demonstrate how a tremendous >2600-fold improvement in conductivity and metallic features, such as magnetoconductivity can be achieved. This is achieved through a careful choice of the counter-ion (sulphate) and the use of oxidative chemical vapour deposition (oCVD). It is shown that high structural order on the molecular level was established and the formation of crystallites tens of nanometres in size was achieved. We infer that the sulphate ions therein intercalate between the polymer chains, thus forming densely packed crystals of planar molecules with extended π-systems. Consequently, room-temperature conductivities of above 1000 S cm−1 are achieved, challenging those of conventional PEDOT:PSS. The material is in the critical regime of the metal–insulator transition.

Measuring Electronic Structure of Multiply Charged Anions to Understand Their Chemistry: A Case Study on Gaseous Polyhedral closo-Borate Dianions.

Research on multiply charged anions (MCAs) in the gas phase has been intensively performed during the past decades, mainly to understand fundamental molecular physics phenomena, for example, intramolecular Coulomb repulsion and existence of the repulsive Coulomb barrier. However, the relevance of these investigations with respect to understanding MCAs' chemistry appears often vague. Here, we discuss how insights into the electronic structure obtained from negative ion photoelectron spectroscopy (NIPES) combined with theoretical calculations and collision-induced dissociation can provide a fundamental understanding of the intrinsic chemical reactivity of MCAs and their fragments. This is exemplified in our studies on polyhedral closo-borate dianions [BnXn]2- (n = 6, 10, 11, 12; X = H, F-I, CN) and their fragment ions. For example, the rational design of closo-borate dianions with specific electronic properties is described, which leads to generating highly reactive fragments. Depending on the dianionic precursor, these fragments are tuned to either bind noble gases effectively or activate small molecules like CO and N2. The intrinsic electronic properties of closo-borate dianions are further compared to their electrochemistry in solutions, revealing solvent effects on the redox potentials. Neutral host molecules such as cyclodextrins are found to bind strongly to [BnXn]2-, and gas phase NIPES provides insights into the intrinsic host-guest interactions. Finally, outlooks including the direct NIPES of molecular fragment ions that cannot be generated in the condensed phase and their utilization in preparative mass spectrometry are discussed.

The effects of intramolecular and intermolecular electrostatic repulsions on the stability and aggregation of NISTmAb revealed by HDX-MS, DSC, and nanoDSF.

The stability and aggregation of NIST monoclonal antibody (NISTmAb) were investigated by hydrogen/deuterium exchange mass spectrometry (HDX-MS), differential scanning calorimetry (DSC), and nano-differential scanning fluorimetry (nanoDSF). NISTmAb was prepared in eight formulations at four different pHs (pH5, 6, 7, and 8) in the presence and absence of 150 mM NaCl and analyzed by the three methods. The HDX-MS results showed that NISTmAb is more conformationally stable at a pH near its isoelectric point (pI) in the presence of NaCl than a pH far from its pI in the absence of NaCl. The stabilization effects were global and not localized. The midpoint temperature of protein thermal unfolding transition results also showed the CH 2 domain of the protein is more conformationally stable at a pH near its pI. On the other hand, the onset of aggregation temperature results showed that NISTmAb is less prone to aggregate at a pH far from its pI, particularly in the absence of NaCl. These seemingly contradicting results, higher conformational stability yet higher aggregation propensity near the pI than far away from the pI, can be explained by intramolecular and intermolecular electrostatic repulsion using Lumry-Eyring model, which separates folding/unfolding equilibrium and aggregation event. The further a pH from the pI, the higher the net charge of the protein. The higher net charge leads to greater intramolecular and intermolecular electrostatic repulsions. The greater intramolecular electrostatic repulsion destabilizes the protein and the greater intermolecular electrostatic repulsion prevents aggregation of the protein molecules at pH far from the pI.

Molecular Dynamics Simulations of Human FOXO3 Reveal Intrinsically Disordered Regions Spread Spatially by Intramolecular Electrostatic Repulsion.

The human transcription factor FOXO3 (a member of the ‘forkhead’ family of transcription factors) controls a variety of cellular functions that make it a highly relevant target for intervention in anti-cancer and anti-aging therapies. FOXO3 is a mostly intrinsically disordered protein (IDP). Absence of knowledge of its structural properties outside the DNA-binding domain constitutes a considerable obstacle to a better understanding of structure/function relationships. Here, I present extensive molecular dynamics (MD) simulation data based on implicit solvation models of the entire FOXO3/DNA complex, and accelerated MD simulations under explicit solvent conditions of a central region of particular structural interest (FOXO3120–530). A new graphical tool for studying and visualizing the structural diversity of IDPs, the Local Compaction Plot (LCP), is introduced. The simulations confirm the highly disordered nature of FOXO3 and distinguish various degrees of folding propensity. Unexpectedly, two ‘linker’ regions immediately adjacent to the DNA-binding domain are present in a highly extended conformation. This extended conformation is not due to their amino acid composition, but rather is caused by electrostatic repulsion of the domains connected by the linkers. FOXO3 is thus an IDP present in an unusually extended conformation to facilitate interaction with molecular interaction partners.

Hydrogels Generated from Cyclic Poly(2-Oxazoline)s Display Unique Swelling and Mechanical Properties.

Cyclic macromolecules do not feature chain ends and are characterized by a higher effective intramolecular repulsion between polymer segments, leading to a higher excluded-volume effect and greater hydration with respect to their linear counterparts. As a result of these unique properties, hydrogels composed of cross-linked cyclic polymers feature enhanced mechanical strength while simultaneously incorporating more solvent with respect to networks formed from their linear analogues with identical molar mass and chemical composition. The translation of topology effects by cyclic polymers into the properties of polymer networks provides hydrogels that ideally do not include defects, such as dangling chain ends, and display unprecedented physicochemical characteristics.

Repulsive Backbone-Backbone Interactions Modulate Access to Specific and Unspecific Binding Sites on Surface-Bound Mucins.

Mucin glycoproteins are the matrix-forming key components of mucus, the innate protective barrier protecting us from pathogenic attack. However, this barrier is constantly challenged by mucin-degrading enzymes, which tend to target anionic glycan chains such as sulfate groups and sialic acid residues. Here, we demonstrate that the efficiency of both unspecific and specific binding of small molecules to mucins is reduced when sulfate groups are enzymatically removed from mucins; this is unexpected because neither of the specific mucin-binding partners tested here targets these sulfate motifs on the mucin glycoprotein. Based on simulation results obtained from a numerical model of the mucin macromolecule, we propose that anionic motifs along the mucin chain establish intramolecular repulsion forces which maintain an elongated mucin conformation. In the absence of these repulsive forces, the mucin seems to adopt a more compacted structure, in which the accessibility of several binding sites is restricted. Our results contribute to a better understanding on how different glycans contribute to the broad spectrum of functions mucin glycoproteins have.

Stabilization of the [cyclo‐N5]− anion by Lewis acid‐base interactions

AbstractIt is an attractive problem to stabilize cyclopentazolate anion [cyclo‐N5]− due to its promising application in the field of high‐energy density materials. The instability of [cyclo‐N5]− is caused by the repulsion of the neighbored lone pairs of electrons localized on N atoms. In this study, two anions of [N5(BH3)5]− and [N5(AgCN)5]− have been designed to reduce the intramolecular repulsion. [N5(H2O)5]− is designed to evaluate the effect of intramolecular hydrogen bond on the stabilization. For all the structures, we apply density functional theory and the Car‐Parrinello molecular dynamics method to study the bonding properties and thermal stabilities. Based on the results, we confirm that the individual [cyclo‐N5]− anion can be effectively stabilized through coordination with acidic ligands rather than the hydrogen bond, which will provide a new method to synthesize full‐nitrogen compounds.

2-Halo- and/or 4-ethoxycarbonyl-substituted asymmetric 1,3-diaryltriazenes and 1,3-diarylamidines as well as N-methylated congeners

1,3-Diaryltriazenes Ar–NN–N(R)-R’ [R = H; Ar/R’ = C6H4-4-COOEt/Ph (1), C6H3-2-Br-4-COOEt/Ph (2), CH2Ph/C6H4-4-COOEt (3)] and the N-methylated congeners [R = Me; Ar/R’ = C6H4-4-COOEt/Ph (9), C6H2-2,5-Br2-4-NH2/Ph (10), C6H4-4-Br/C6H4-4-COOEt (11), C6H2-2-Br-4-COOEt/Ph (12), C6H2-2-Br-4-COOEt-6-Me/C6H4-2-Me (13), C6H3-2-Br-4-F/Ph (14), C6H3-2-Br-6-F/Ph (15), C6H3-2-Br-4-Cl/Ph (16), C6H3-2,4-Br2/Ph (17)] as well as 1,3-diarylformamidines of the type Ar–NCH–N(R)-R’ [R = H; Ar/R’ = C6H3-4-COOEt/Ph (4), C6H3-2-Br-4-COOEt/Ph (5), C6H3-2-Br-4-F/Ph (6)] and 1,3-diaryl-3-methylamidines [R = Me; Ar/R’ = C6H3-4-COOEt/Ph (18), C6H3-2-Br-4-COOEt/Ph (19), C6H3-2-Br-4-Cl/Ph (20), C6H3-2,4-Br2/Ph (21)] crystallize preferably with (syn-E) configuration. For comparison reasons sterically crowded Ph-N(R)-C (R′) = N–C6H3-2-Br-4-COOEt [R = H, R’ = Ph (7), tBu (8); R = Me, R’ = Ph (22), tBu (23)] are included. Large substituents destabilize this isomeric form due to intramolecular steric repulsion. 1,3-Diarylformamidines dimerize via two nearly parallel N–H⋯N hydrogen bridges. This kind of aggregation is very beneficial because the NC–N bond angles are slightly larger than 120°. Narrower NN–N bond angles are found for the 1,3-diaryltriazenes and therefore, aggregation occurs via intermolecular N–H⋯O hydrogen bridges to O-Lewis bases. The 1,3-diaryl-3-methylformamidines and -triazenes show very similar bonding parameters. Thus, the bond lengths of the NC/NN double bonds are approx. 4–9 pm shorter than the N–C/N–N single bonds, supporting charge delocalization within the diazaallyl- and triazaallyl systems regardless of N-methylation.

Effect of side chain on conformational properties of comb-like polycarboxylate in salt solutions

To investigate the effect of side-chain structure of comb-like polycarboxylates (PCE) on conformational properties in salt solutions, PCE with polyethyleneoxide (PEO) of different lengths were synthesized using methallyl polyethylene glycol (MPEG, Mw = 1200, 2400, 4000). Adding counter-ions (i.e., Na+, Ca2+) to dilute PCE solutions was found to induce a more complicated conformational changes, since the screening of the electrostatic intramolecular repulsion and the different complexation behaviors of Ca2+ with carboxylic groups. Laser light scattering (LLS) and conductivity measurements were used to investigate the conformations of PCE at various pH values. PCE of a long side chain polymer and the sparse grafting studied herein possesses a more coiled polymer backbone due to the intramolecular steric hindrance, which resulted in a more exposed extent of carboxylic groups on the backbone at the same pH values. Obviously, the solution conformation of PCE strongly impacts the accessible carboxylic groups contribution to complexation of the carboxylic oxygen atoms of PCE with Ca2+. In this way it may provide a new insight to design the polymer dispersants.

Histidine-Mediated Intramolecular Electrostatic Repulsion for Controlling pH-Dependent Protein-Protein Interaction.

Protein-protein interactions that can be controlled by environmental triggers have immense potential in various biological and industrial applications. In the current study, we aimed to engineer a pH-dependent protein-protein interaction that employs intramolecular electrostatic repulsion through a structure-guided histidine substitution approach. We implemented this strategy on Streptococcal protein G, an affinity ligand for immunoglobulin G, and showed that even a single point mutation effectively improved the pH sensitivity of the binding interactions without adversely affecting its structural stability or its innate binding function. Depending on the pH of the environment, the protein-protein interaction was disrupted by the electrostatic repulsion between the substituted histidine and its neighboring positively charged residues. Structurally, the substituted histidine residue was located adjacent to a lysine residue that could form hydrogen bonds with immunoglobulin G. Thermodynamically, the introduced electrostatic repulsion was reflected in the significant loss of the exothermic heat of the binding under acidic conditions, whereas accompanying enthalpy-entropy compensation partly suppressed the improvement of the pH sensitivity. Thus, the engineered pH-sensitive protein G could enable antibody purification under mildly acidic conditions. This intramolecular design can be combined with conventional protein-protein interface design. Moreover, the method proposed here provides us with additional design criteria for optimization of pH-dependent molecular interactions.

Synthesis and characterization of TPP/chitosan nanoparticles: Colloidal mechanism of reaction and antifungal effect on C. albicans biofilm formation.

In the present study chitosan (Chit) nanoparticles were synthetized by the ionic gelation process, using tripolyphosphate (TPP) as crosslinking agent. The TPP/Chit nanoparticle formation was evaluated by titrations, measuring electrical conductivity (k), zeta potential (ZP), hydrodynamic diameter (Dh), viscosity (η) and heat by isothermal calorimetry (ITC). The antifungal effects were evaluated by C. albicans time-kill assays, inhibition of C. albicans initial adhesion and biofilm formation in comparison with nystatin and chitosan. Conductometric titration exhibited a typical precipitation profile, with an inflection at molar ratio of [TPP]/[Chitmon] ≈ 0.3, suggesting a 1:3.3 stoichiometry. The highest Dh, ZP and η values were shown at the beginning of titrations, due to the intramolecular repulsion between Chit-Chit. With addition of TPP, the values showed gradual reduction, with an intermediary transition at [TPP]/[Chitmon] ≈ 0.16, which was attributed to the partial breakdown of interchain crosslinking and formation of discrete charged aggregates. After this point, reaction should occur by neutralization of these assemblies, causing new reduction in values of Dh, ZP and η until [TPP]/[Chitmon] ≈ 0.3, when they reached their lowest values. ITC experiment also showed the occurrence of two bindings (K1 = 3.6 × 103 and K2 = 7.7 × 104), which were entropy driven. Biological results showed lower C. albicans viability for TPP/Chit over 24 h compared with chitosan and nystatin at MIC and 2 MIC. Moreover, TPP/Chit showed 25-50% inhibition of C. albicans adhesion and biofilm formation. The results showed that TPP/Chit nanoparticles reduced the initial adhesion and biofilm formation of C. albicans and demonstrated potential for use in a formulation for the treatment of oral candidiasis.

Acid-Catalyzed Versus Thermally Induced C1-C1' Bond Cleavage in 1,1'-Bi-2-naphthol: An Experimental and Theoretical Study.

Experiments show that 1,1'-bi-2-naphthol (BINOL) undergoes facile C1-C1' bond cleavage under action of triflic acid at temperatures above 0 °C to give mainly 2-naphthol along with oligomeric material. CASSCF and MRMP//CASSCF computations have demonstrated unambiguously that this unusual mode of scission of the biaryl bond can occur in the C1,C1'-diprotonated form of BINOL via a mechanism involving homolytic cleavage prompted by the intramolecular electrostatic repulsion. These findings also provide insights into the mechanism of a comparatively easy thermal cleavage of BINOL, implying the intermediacy of its neutral diketo form.

Effect of counter-ions on the solution conformation and adsorption behaviors of comb-like polycarboxylates on calcium carbonate

Three kinds of polycarboxylate ether (PCE) polymers with the same length of side chains but different backbone length were synthesized by aqueous free radical polymerization. Adding counter-ions (i.e., Na+, Ca2+) to dilute PCE solutions was found to induce a more complicated conformational change, since the screening of the electrostatic intramolecular repulsion and the different complexation behaviors of Ca2+ with carboxylic groups. Further characterization on the adsorption indicated that the differences of the adsorption ability resulted from the difference in the solution conformation of PCE molecule. PCE of a medium backbone length studied herein possesses a more extended polymer backbone due to the intermolecular steric hindrance, which result in more carboxylic groups could be accessible for adsorption. Obviously, the solution conformation of PCE strongly impacts the accessible carboxylic group contribution to adsorption. In this way it may provide a new insight to design the polymer structures of PCE with superior adsorption ability.

Side chain electrostatic interactions and pH-dependent expansion of the intrinsically disordered, highly acidic carboxyl-terminus of γ-tubulin.

Intramolecular electrostatic attraction and repulsion strongly influence the conformational sampling of intrinsically disordered proteins and domains (IDPs). In order to better understand this complex relationship, we have used nuclear magnetic resonance to measure side chain pKa values and pH-dependent translational diffusion coefficients for the unstructured and highly acidic carboxyl-terminus of γ-tubulin (γ-CT), providing insight into how the net charge of an IDP relates to overall expansion or collapse of the conformational ensemble. Many of the pKa values in the γ-CT are shifted upward by 0.3-0.4 units and exhibit negatively cooperative ionization pH profiles, likely due to the large net negative charge that accumulates on the molecule as the pH is raised. pKa shifts of this magnitude correspond to electrostatic interaction energies between the affected residues and the rest of the charged molecule that are each on the order of 1 kcal mol-1 . Diffusion of the γ-CT slowed with increasing net charge, indicative of an expanding hydrodynamic radius (rH ). The degree of expansion agreed quantitatively with what has been seen from comparisons of IDPs with different charge content, yielding the general trend that every 0.1 increase in relative charge (|Q|/res) produces a roughly 5% increase in rH . While γ-CT pH titration data followed this trend nearly perfectly, there were substantially larger deviations for the database of different IDP sequences. This suggests that other aspects of an IDP's primary amino acid sequence beyond net charge influence the sensitivity of rH to electrostatic interactions.

Ionic Strength-Dependent Interactions and Dimensions of Adsorbed Zwitterionic Copolymers.

We report direct measurements of ionic strength-dependent interactions between different molecular weights of zwitterionic triblock copolymers adsorbed to hydrophobic colloids and surfaces. The zwitterionic copolymers investigated include phosphorylcholine [poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC)] and sulfopropylbetaine [poly(3-( N-2-methacryloyloxyethyl- N, N-dimethyl)ammonatopropanesulfonate) (PMAPS)] end blocks separated by poly(propylene oxide) center blocks. The range of repulsion between adsorbed PMAPS copolymer layers increases with increasing NaCl from 0.01 to 3 M, and layer thicknesses range from ∼50 to 100% of the PMAPS block contour length. In contrast, repulsion between PMPC layers does not change for 0.01-3 M NaCl, and layers remain near full extension at their contour length. NaCl-dependent interactions and inferred layer dimensions correlate with hydrodynamic layer thickness and polymer second virial coefficients. These results suggest that the interaction range and layer thickness of adsorbed zwitterionic copolymers arise from a balance of intramolecular dipolar attraction and repulsion possibly mediated by water solvation. The balance between these competing effects and resulting ionic strength dependence is determined by specific zwitterionic moieties.

Effects of End-Caps on the Atropisomerization, Polymerization, and the Thermal Properties of ortho-Imide Functional Benzoxazines.

A new type of atropisomerism has recently been discovered in 1,3-benzoxazines, where the intramolecular repulsion between negatively charged oxygen atoms on the imide and the oxazine ring hinders the rotation about the C–N bond. The imide group offers a high degree of flexibility for functionalization, allowing a variety of functional groups to be attached, and producing different types of end-caps. In this work, the effects of end-caps on the atropisomerism, thermally activated polymerization of ortho-imide functional benzoxazines, and the associated properties of polybenzoxazines have been systematically investigated. Several end-caps, with different electronic characteristics and rigidities, were designed. 1H and 13C nuclear magnetic resonance (NMR) spectroscopy and density functional theory (DFT) calculations were employed to obtain structural information, and differential scanning calorimetry (DSC) and in situ Fourier transform infrared (FT-IR) spectroscopy were also performed to study the thermally activated polymerization process of benzoxazine monomers. We demonstrated that the atropisomerization can be switched on/off by the manipulation of the steric structure of the end-caps, and polymerization behaviors can be well-controlled by the electronic properties of the end-caps. Moreover, a trade-off effect were found between the thermal properties and the rigidity of the end-caps in polybenzoxazines.

Enhancing the electrochemical properties of the p-type conductive polymer on the surface of the new synthesized 2-(pyridin-3-ylmethylene) hydrazine-1-carbothioamide-modified electrode: computational and electrochemical study

Herein, 2-(pyridin-3-ylmethylene)hydrazine-1-carbothioamide(3PHCT)was first fabricated through a chemical method, and subsequently, polyorthoaminophenol (POAP)/3PHCT films were prepared using electropolymerization of POAP, carried out in the presence of the as-prepared 3PHCT to serve as the active electrode for electrochemical application. Geometry optimization and calculations of structural and electronic/vibrational properties of the 3PHCT system are studied (based on the quantum atom-in-molecule theory, QTAIM). In addition, the local intra-molecular electron density, and its Laplacian, and, thus, intra-molecular virial forces, of this molecule system are calculated. These results show that the oxygen and sulfur atoms play domain role in intra-molecular charge and energy transfer in this molecular system. In addition, based on the QTAIM, it is predicted that a single electrochemical molecular system can be grouped into p-type-like and n-type-like sections, and would be good candidate to reduce intra-molecular repulsion of the bipolaron during electrochemical polymerization of POAP. Galvanostatic charge–discharge experiments, cyclic voltammetry and electrochemical impedance spectroscopy, were conducted to characterize the prepared composite films and investigate the performance of the system, respectively. In this study, novel POAP/3PHCT are presented for electrochemical redox capacitors possessing the merits of high active surface area, stability in an aqueous electrolyte and ease of synthesis.

Structural analysis of helicene molecules adsorbed on symmetric surfaces.

Helicenes are chiral polyaromatic hydrocarbon molecules which self-assemble into ordered monolayers on solid substrates, and are of current interest in the study of supramolecular systems and the development of smart materials. In this work we investigate the geometry of helicene monomers and stacked dimers on (111) facets of coinage metals. The geometry of the adsorbed molecules is shaped by the coupling of intermolecular dispersive forces, intramolecular steric repulsion between end rings and surface-molecule interactions. Thus, binding and stereospecificity outcomes vary broadly depending on the identity of molecule/surface pair. Overall, homochiral interactions are found to be more effective than heterochiral stacking, due to a better fit between the helical structures in like dimers. On a surface, this effect is enhanced by the flattening of surface-proximal molecular rings. However, our results show that the "sandwich" effect of the second molecular layer increases molecular footprints in the first layer, with potentially large implications in monolayer organization and surface commensuration.

Fluoride‐Controlled Molecular Brake Systems

AbstractThe approaches towards molecular brakes reported to date are not diversified enough. Fluoride is a unique species because it is an anion but can also act as a base. Herein a new strategy utilizing fluoride anions is reported to regulate the rotation of a kind of phenol‐succinimide‐based molecular rotors, in which braking of the rotors was achieved by using fluorides to deprotonate the molecules to introduce an intramolecular electrostatic repulsion. Subsequent addition of lithium cations defunctionalized the fluoride anions, thus enabling the rotors to rotate fast again. By using cyclic fluoride‐then‐lithium mediation, transformation between the “brake‐on” and the “brake‐off” state of the rotors could be achieved in a highly reversible manner. The stimuli group is superior to regular acid/base in speed regulation of the rotors due to its higher efficiency and predictability of the usage.