Showing papers by "J. Fraser Stoddart published in 2006"
TL;DR: The investigated system is a unique example of an artificial linear nanomotor that behaves as an autonomous linear motor and operates with a quantum efficiency up to ≈12% and works in mild environmental conditions.
Abstract: Light excitation powers the reversible shuttling movement of the ring component of a rotaxane between two stations located at a 1.3-nm distance on its dumbbell-shaped component. The photoinduced shuttling movement, which occurs in solution, is based on a “four-stroke” synchronized sequence of electronic and nuclear processes. At room temperature the deactivation time of the high-energy charge-transfer state obtained by light excitation is ≈10 μs, and the time period required for the ring-displacement process is on the order of 100 μs. The rotaxane behaves as an autonomous linear motor and operates with a quantum efficiency up to ≈12%. The investigated system is a unique example of an artificial linear nanomotor because it gathers together the following features: (i) it is powered by visible light (e.g., sunlight); (ii) it exhibits autonomous behavior, like motor proteins; (iii) it does not generate waste products; (iv) its operation can rely only on intramolecular processes, allowing in principle operation at the single-molecule level; (v) it can be driven at a frequency of 1 kHz; (vi) it works in mild environmental conditions (i.e., fluid solution at ambient temperature); and (vii) it is stable for at least 103 cycles.
426 citations
TL;DR: Inspired by the concept of multivalency in living systems, two mechanically interlocked molecules have been conceived that incorporate not once or twice but thrice the features of a pH-switchable [2]rotaxane with two orthogonal recognition sites.
Abstract: Inspired by the concept of multivalency in living systems, two mechanically interlocked molecules have been conceived that incorporate not once or twice but thrice the features of a pH-switchable [...
257 citations
TL;DR: The versatility of supramolecular chemistry has been exploited in constructing nanovalves based on mesoporous silica MCM-41 and the mutual recognition between secondary dialkylammonium ions and dibenzo[24]crown-8 (DB24C8).
231 citations
TL;DR: Single-wall carbon nanotube (SWNT) field effect transistors (FETs), functionalized noncovalently with a zinc porphyrin derivative, were used to directly detect a photoinduced electron transfer (PET) within a donor/acceptor (D/A) system.
Abstract: Single-wall carbon nanotube (SWNT) field effect transistors (FETs), functionalized noncovalently with a zinc porphyrin derivative, were used to directly detect a photoinduced electron transfer (PET) within a donor/acceptor (D/A) system. We report here that the SWNTs act as the electron donor and the porphyrin molecules as the electron acceptor. The magnitude of the PET was measured to be a function of both the wavelength and intensity of applied light, with a maximum value of 0.37 electrons per porphyrin for light at 420 nm and 100 W/m2. A complete understanding of the photophysics of this D/A system is necessary, as it may form the basis for applications in artificial photosynthesis and alternative energy sources such as solar cells.
209 citations
TL;DR: The ground-state equilibrium properties of all three bistable rotaxanes were reflective of molecular structure in all environments, providing direct evidence for the control by molecular structure of the electronic properties exhibited by the MSTJs.
Abstract: We report on the kinetics and ground-state thermodynamics associated with electrochemically driven molecular mechanical switching of three bistable [2]rotaxanes in acetonitrile solution, polymer electrolyte gels, and molecular-switch tunnel junctions (MSTJs). For all rotaxanes a pi-electron-deficient cyclobis(paraquat-p-phenylene) (CBPQT4+) ring component encircles one of two recognition sites within a dumbbell component. Two rotaxanes (RATTF4+ and RTTF4+) contain tetrathiafulvalene (TTF) and 1,5-dioxynaphthalene (DNP) recognition units, but different hydrophilic stoppers. For these rotaxanes, the CBPQT4+ ring encircles predominantly (>90 %) the TTF unit at equilibrium, and this equilibrium is relatively temperature independent. In the third rotaxane (RBPTTF4+), the TTF unit is replaced by a pi-extended analogue (a bispyrrolotetrathiafulvalene (BPTTF) unit), and the CBPQT4+ ring encircles almost equally both recognition sites at equilibrium. This equilibrium exhibits strong temperature dependence. These thermodynamic differences were rationalized by reference to binding constants obtained by isothermal titration calorimetry for the complexation of model guests by the CBPQT4+ host in acetonitrile. For all bistable rotaxanes, oxidation of the TTF (BPTTF) unit is accompanied by movement of the CBPQT4+ ring to the DNP site. Reduction back to TTF0 (BPTTF0) is followed by relaxation to the equilibrium distribution of translational isomers. The relaxation kinetics are strongly environmentally dependent, yet consistent with a single electromechanical-switching mechanism in acetonitrile, polymer electrolyte gels, and MSTJs. The ground-state equilibrium properties of all three bistable [2]rotaxanes were reflective of molecular structure in all environments. These results provide direct evidence for the control by molecular structure of the electronic properties exhibited by the MSTJs.
189 citations
TL;DR: In this article, a functional integrated nanosystem for trapping and releasing molecules under deliberate control is presented, where the openings to nanosized pores in silica particles are regulated by gatekeeper supermolecules that are controlled by pH stimulation and competitive binding.
Abstract: A functional integrated nanosystem for trapping and releasing molecules under deliberate control is prepared. The openings to nanosized pores in silica particles are regulated by gatekeeper supermolecules that are controlled by pH stimulation and competitive binding. Controlled release of fluorescent probe molecules is demonstrated using (i) organic bases, (ii) fluorodialkylammonium ions, and (iii) metal ions as actuators. The rate of the release of the probe molecules depends on the size of the base, the dimension of the probe molecules, and the binding affinity of the metal/fluorodialkylammonium cations employed.
181 citations
TL;DR: The mild reaction conditions, remarkable functional group compatibility, and complete regioselectivity of the Cu-catalyzed Huisgen 1,3-dipolar cycloaddition between organic azides and terminal alkynes have led to a threading-followed-by-stoppering approach to the synthesis of donor-acceptor rotaxanes incorporating cyclobis(paraquat-p-phenylene) (CBPQT4+) as the pi-accepting
Abstract: The mild reaction conditions, remarkable functional group compatibility, and complete regioselectivity of the Cu-catalyzed Huisgen 1,3-dipolar cycloaddition (“click chemistry”) between organic azides and terminal alkynes have led to a threading-followed-by-stoppering approach to the synthesis of donor–acceptor rotaxanes incorporating cyclobis(paraquat-p-phenylene) (CBPQT4+) as the π-accepting ring component. Rotaxane formation is initiated by reacting azide-functionalized pseudorotaxanes containing π-donating 1,5-dioxynaphthalene (DNP) recognition units with appropriate alkyne-functionalized stoppers. The high yields obtained in this efficient, kinetically controlled post-assembly covalent modification, as well as the excellent convergence of the synthetic protocol, are demonstrated by the preparation of [2]-, [3]-, and [4]rotaxanes containing multiple DNP/CBPQT4+ donor–acceptor recognition motifs.
162 citations
TL;DR: By controlling the superstructures of the supramolecular polymers with the [G1]-[G3] dendrons, it is possible to induce conformational changes within the polymer backbones, indicating that DPAs behave as increasingly rigid macromolecules with each generation in solution.
Abstract: Acid-base switchable supramolecular dendronized polyacetylenes (DPAs) with increasing steric bulk on going from generation one [G1] to three [G3], were constructed using multiple self-assembly processes between Frechet-type [G1]-[G3]-dendritic dialkylammonium salts and a dibenzo[24]crown-8-containing polymer. The formation of the supramolecular systems is acid-base switchable to either an ON (rodlike dendronized polymers) or an OFF (flexible polymers) state. Thus, by controlling the superstructures of the supramolecular polymers with the [G1]-[G3] dendrons, it is possible to induce conformational changes within the polymer backbones. The supramolecular dendronized polymers, as well as their threading-dethreading properties, were characterized by (1)H NMR and UV absorption spectroscopies, gel permeation chromatography (GPC) and light scattering (LS). Independent measures of molecular weight (GPC, LS) indicate that DPAs behave as increasingly rigid macromolecules with each generation in solution. Molecular dynamics simulations of each DPA suggest that the lengths of the polymer backbones increase accordingly. Atomic force microscopy of the [G3]-dendronized polystyrene (DPS), as well as the DPAs, reveal surface morphologies indicative of aggregated superstructures.
116 citations
TL;DR: The fusion of experimental force spectroscopy and theoretical computational modeling has revealed that the repulsive electrostatic interaction, which is responsible for the molecular actuation, is as high as 65 kcal(-1), a result that is supported by ab initio calculations.
Abstract: By applying atomic force microscope (AFM)-based force spectroscopy together with computational modeling in the form of molecular force-field simulations, we have determined quantitatively the actuation energetics of a synthetic motor-molecule. This multidisciplinary approach was performed on specifically designed, bistable, redox-controllable [2]rotaxanes to probe the steric and electrostatic interactions that dictate their mechanical switching at the single-molecule level. The fusion of experimental force spectroscopy and theoretical computational modeling has revealed that the repulsive electrostatic interaction, which is responsible for the molecular actuation, is as high as 65 kcal·mol−1, a result that is supported by ab initio calculations.
85 citations
TL;DR: The study suggests that the evaporation process primarily affects portions of the molecule exposed to the metal atom source, leaving key functionality necessary for switching intact in tightly packed monolayers.
Abstract: Langmuir−Blodgett monolayers of a bistable [2]rotaxane were prepared at packing densities of 118, 73, and 54 A^2/molecule. The monolayers were both characterized via infrared spectroscopy before and after evaporation of a 2 nm film of titanium and incorporated into molecular switch tunnel junction devices. The study suggests that the evaporation process primarily affects portions of the molecule exposed to the metal atom source. Thus, in tightly packed monolayers (73 and 54 A^2/molecule), only the portions of the [2]rotaxane that are present at the molecule/air interface are clearly affected, leaving key functionality necessary for switching intact. Monolayers transferred at a lower pressure (118 A^2/molecule) exhibit nonspecific damage and poor switching behavior following Ti deposition. These results indicate that tightly packed monolayers and sacrificial functionality displayed at the molecule/air interface are important design principles for molecular electronic devices.
84 citations
TL;DR: Mixing the dipyrido-crown-8 derivatives carrying one or two formyl group(s) on the 4 position of their pyridine ring with a 3-fold symmetrical trisammonium ion template in a 3:1 ratio in CD3NO2 results in the formation of thermodynamically stablepseudorotaxanes.
TL;DR: Charged donor-acceptorcatenanes, in which the pi-accepting cyclobis(paraquat-p-phenylene) acts as a tetracationic template for the threading-followed-by-clipping of acyclic oligoethers, are the products of copper-mediated Eglinton coupling and Huisgen 1,3-dipolar cycloaddition.
TL;DR: This work describes research into building integrated molecular electronics circuitry for a diverse set of functions, and with a focus on the fundamental scientific issues that surround this project, aimed at understanding the function of bistable rotaxane molecular electronic switches.
Abstract: We describe our research into building integrated molecular electronics circuitry for a diverse set of functions, and with a focus on the fundamental scientific issues that surround this project. In particular, we discuss experiments aimed at understanding the function of bistable [2]rotaxane molecular electronic switches by correlating the switching kinetics and ground state thermodynamic properties of those switches in various environments, ranging from the solution phase to a Langmuir monolayer of the switching molecules sandwiched between two electrodes. We discuss various devices, low bit-density memory circuits, and ultra-high density memory circuits that utilize the electrochemical switching characteristics of these molecules in conjunction with novel patterning methods. We also discuss interconnect schemes that are capable of bridging the micrometre to submicrometre length scales of conventional patterning approaches to the near-molecular length scales of the ultra-dense memory circuits. Finally, we discuss some of the challenges associated with fabricated ultra-dense molecular electronic integrated circuits.
TL;DR: In this article, a series of bistable [2] rotaxane and pseudorotaxane-based devices have been evaluated across different length scales, and the switching characteristics of these devices enable them to function as prototypes of molecular machines.
Abstract: The structure–function relationships of a series of bistable [2]rotaxane and [2]pseudorotaxane-based devices have been evaluated across different length scales. The switching characteristics of bistable [2]rotaxanes and self-assembled [2]pseudorotaxanes, which can be controlled chemically, electrochemically, or photochemically, enable them to function as prototypes of molecular machines. The switching processes are operative, not only in solution, but also in a wide variety of condensed phases. The universality of the switching mechanism demonstrates that these functional organic materials can be incorporated onto solid metallic and inorganic supports for device applications, despite the fact that interactions at the organic substrate interface can influence molecular structure and function. Through iterative design–analysis feedback loops that focus upon fine-tuning device performance, based on molecular structures and molecule-substrate interactions, the fabrication of functioning micro-actuators, nanovalves and light-harvesting devices has been achieved.
TL;DR: The design, bottom-up construction, characterization, and operation of a supramolecular system capable of mimicking the function played by a macroscopic electrical extension cable is reported, which can be switched off by dual-mode chemically controlled disassembling of the molecular components.
Abstract: We report the design, bottom-up construction, characterization, and operation of a supramolecular system capable of mimicking the function played by a macroscopic electrical extension cable. The system is made up of a light-powered electron source, an electron drain, and a cable as the molecular components programmed to self-assemble by means of two distinct plug/socket junctions. Such connections are reversible and can be operated independently by orthogonal chemical inputs. In the source–connector–drain supermolecule, photoinduced electron transfer from source to drain occurs, and it can be switched off by dual-mode chemically controlled disassembling of the molecular components.
TL;DR: A highly constrained rotaxane, constructed in such a way that the tetracationic cyclobis(paraquat-p-phenylene) ring is restricted to reside on a monopyrrolotetrathiafulvalene unit, has been synthesised and characterised.
TL;DR: Poly(norbornene)-based block copolymers containing side chains of palladated pincer complexes/dibenzo[24]crown-8 or palladator complexes/ dibenzylammonium salts were synthesized and it was found that theSelf-assembly of the recognition units along each polymer block does not preclude the self-assembly processes along the other block.
Abstract: Poly(norbornene)-based block copolymers containing side chains of palladated pincer complexes/dibenzo[24]crown-8 or palladated pincer complexes/dibenzylammonium salts were synthesized. Noncovalent functionalization was accomplished with their corresponding recognition units through simple 1:1 addition with association constants (Ka) greater than 10(5) m(-1). The self-assembly processes were monitored by using both 1H NMR spectroscopy and isothermal titration calorimetry. In all cases, we found that the self-assembly of the recognition units along each polymer block does not preclude the self-assembly processes along the other block.
TL;DR: In this paper, the binding constants for all of these 1:1 rotaxanes were determined both by isothermal titration calorimetry in MeCN solution and by the 1H NMR spectroscopic single-point method in CD3CN solution.
TL;DR: In this article, the authors investigated the organi-zation of a non-amphiphilic tricationic switchable rotaxane and its dumbbell-shaped component into Langmuir films and LBL multilayers by using a cospreading strategy.
Abstract: In this context we investigated, for the first time, the organi-zation of a non-amphiphilic tricationic switchable rotaxaneand its dumbbell-shaped component into Langmuir films andLangmuir–Blodgett (LB) multilayers by using a cospreadingstrategy. The Langmuir films have been characterized by sur-face pressure–area (
09 May 2006
TL;DR: In this paper, simplified models of the transfer processes that could be present in bistable molecular switch tunnel junction (MSTJ) devices during one complete cycle of the device from its low- to high- and back to low-conductance state were considered.
Abstract: The processes by which charge transfer can occur play a foundational role in molecular electronics. Here we consider simplified models of the transfer processes that could be present in bistable molecular switch tunnel junction (MSTJ) devices during one complete cycle of the device from its low- to high- and back to low-conductance state. The bistable molecular switches, which are composed of a monolayer of either switchable catenanes or rotaxanes, exist in either a ground-state co-conformation or a metastable one in which the conduction properties of the two co-conformations, when measured at small biases (+0.1 V), are significantly different irrespective of whether transport is dominated by tunneling or hopping. The voltage-driven generation (±2 V) of molecule-based redox states, which are sufficiently long-lived to allow the relative mechanical movements necessary to switch between the two co-conformations, rely upon unequal charge transfer rates on to and/or off of the molecules. Surface-enhanced Raman spectroscopy has been used to image the ground state of the bistable rotaxane in MSTJ-like devices. Consideration of these models provide new ways of looking at molecular electronic devices that rely, not only on nanoscale charge-transport, but also upon the bustling world of molecular motion in mechanically interlocked bistable molecules.
TL;DR: In this article, random poly(norbornene)-based terpolymers containing sulfur−carbon−sulfur (SCS) palladated pincer complexes, dibenzo[24]crown-8 (DB24C8) rings, and diaminopyridine moieties were synthesized by ring-opening metathesis polymerization.
Abstract: Random poly(norbornene)-based terpolymers containing sulfur−carbon−sulfur (SCS) palladated pincer complexes, dibenzo[24]crown-8 (DB24C8) rings, and diaminopyridine moieties were synthesized by ring-opening metathesis polymerization. Examination of the kinetics of the polymerization led to the conclusion that the polymerization of a statistical mixture of the three monomers results in the formation of random terpolymers. The terpolymers have molecular weights between 30 000 and 50 000 Da, with polydispersity indices ranging form 1.3 to 1.5, as determined by gel-permeation chromatography. Side-chain functionalization of these terpolymers was achieved by self-assembling (i) pyridines to the palladated pincer complexes, (ii) dibenzylammonium ions to the DB24C8 rings, and (iii) thymines to the diaminopyridine receptors. 1H NMR spectroscopy was used to monitor the self-assembly processes and revealed that all self-assembly steps were fast and near quantitative. Isothermal titration calorimetry was employed to d...
TL;DR: A trifurcated template, containing three secondary dialkylammonium ion recognition sites for encirclement by a dibenzo [24]crown-8-containing acyclic diene, is used to promote ADMET catalyzed by ruthenium-alkylidene complexes, affording a cyclic trimer in 55% yield.
Abstract: A trifurcated template, containing three secondary dialkylammonium ion recognition sites for encirclement by a dibenzo [24]crown-8-containing acyclic diene, is used to promote acyclic diene metatheses (ADMET) catalyzed by ruthenium−alkylidene complexes, affording a cyclic trimer in 55% yield. Following this one-step, threefold ADMET reaction, the resulting cyclic trimer was isolated by preparative HPLC and characterized by NMR spectroscopy and mass spectrometry.
TL;DR: The measured oxidation and reduction potentials provide insights into the orbital energies and electronic structure of a (monopyrrolo)tetrathiafulvalene unit when encircled by a tetracationic cyclobis(paraquat-p-phenylene) ring.
TL;DR: In this paper, the design of a new class of chiral [2] catenanes is reported, consisting of one or two 3,3′-bitolyl spacers in the π-electron-deficient component, and bis-p-phenylene-34-crown-10 (BPP 34 C 10) as the ρ-rich component.
Abstract: The design of a new class of chiral [2]catenanes is reported. The self-assembly of [2]catenanes comprising one or two 3,3′-bitolyl spacers in the π-electron-deficient component, and bis-p-phenylene-34-crown-10 (BPP 34 C 10) as the π-electron-rich component, is described. The X-ray crystal structures, together with solution-state dynamic 1H NMR spectroscopic studies, show that the degree of order characterizing the molecular structures is substantially different from that of the “parent” [2]-catenane, comprising cyclobis(paraquat-p-phenylene) and BPP34C 10. When appropriately substituted in their ortho positions, bitolyl compounds can support axial chirality: the self-assembly of axially chiral [2]catenanes, comprising one or two 3,3′-disubstituted-2,2′-dihydroxy-1,1′-binaphthyl spacers, has been achieved in good yields, showing that the introduction of the bulky, axially chiral spacer and the consequent distortion of the cavity of the π-electron-deficient component still permits good molecular recognition between the components leading to efficient catenane production. X-ray crystallography suggests that this recognition is driven by hydrogen bonding and π-π stacking interactions between the complementary subunits. The hydroxyl groups on the chiral spacer were further functionalized as benzoyl esters in a [2]catenane as well as in the tetracationic cyclophanes; that is, chemistry can be done on these catenanes. The chiral tetracationic cyclophanes exhibit good enantiomeric differentiation toward the D- and L-enantiomers of aromatic amino acids in water and their N-acetylated derivatives in organic solvents.
TL;DR: In this paper, a cyclophane-type crown ether endowed with two exTTF units forms supramolecular ensembles with different dibenzylammonium salts with a binding constant of K a ∼50 M −1 determined by 1 H NMR and fluorescence experiments.
TL;DR: In this paper, a Mark II version of this kind of two-station rotaxane comprised of six molecular modules, namely, a bisparaphenylene[34]crown-10 electron donor macrocycle M and its dumbbell-shaped component which contains a Ru(ii)-polypyridine photoactive unit P2+ as one of its stoppers, a p-terphenyl-type ring system as a rigid spacer S, (d) 4,4′-bipyridinium (A12+) and (e) 3,
Abstract: To find out how best to optimize shuttling of the macrocycle in a particular class of photochemically driven molecular abacus, which has the molecular structure of BR-I6+ in its Mark I prototype (Ashton et al., Chem. Eur. J. 2000, 6, 3558), we have synthesized and characterized a Mark II version of this kind of two-station rotaxane comprised of six molecular modules, namely (a) a bisparaphenylene[34]crown-10 electron donor macrocycle M and its dumbbell-shaped component which contains (b) a Ru(ii)-polypyridine photoactive unit P2+ as one of its stoppers, (c) a p-terphenyl-type ring system as a rigid spacer S, (d) 4,4′-bipyridinium (A12+) and (e) 3,3′-dimethyl-4,4′-bipyridinium (A22+) electron acceptor units that can play the role of stations for the macrocycle M, and (f) a tetraarylmethane group T as the second stopper. This Mark II version is identical with BR-I6+ in the Mark I series that works as a sunlight-powered nanomotor (Balzani et al., Proc. Natl. Acad. Sci. USA 2006, 103, 1178), except for the swapping of the two stations A12+ and A22+ along the dumbbell-shaped component, i.e. the Mark I and II bistable rotaxanes are constitutionally isomeric. We have found the closer the juxtaposition of the electron transfer photosensitizer P2+ to the better (A12+) of the two electron acceptors, namely the situation in BR-II6+ compared with that in BR-I6+ results in an increase in the rate — and hence the efficiency — of the photoinduced electron-transfer step. The rate of the back electron transfer, however, also increases. As a consequence, BR-II6+ performs better than BR-I6+ in the fuel-assisted system, but much worse when it is powered by visible light (e.g. sunlight) alone. By contrast, when shuttling is electrochemically driven, the only difference between the two bistable rotaxanes in the Mark I and Mark II series is that the macrocycle M moves in opposite directions.
TL;DR: A mixture of the same components in a 1:3 ratio affords a crystalline [2]pseudorotaxane after vapor diffusion of methyl-tert-butyl ether into a solution of these components in MeCN/CH( 2)Cl(2) (3:1).
01 Jan 2006
TL;DR: This chapter discussed a set of nanoscale computing modules, such as quantum and spin-based cellular logic arrays, and molecular- based cellular automata, all made from the switches presented here, an integral part of the hierarchical 3-D multiscale architecture presented.
Abstract: In this chapter, we have presented an overview of various nanoscale and molecular computing architectures. We have given a brief tutorial on various existing nanoscale and molecular devices. These include molecular switches, resonant tunnel diodes, tunnel diodes, single electron transistors, carbon nanotube field-effect transistors, quantum dots, and spin systems. We have next discussed a set of nanoscale computing modules, such as quantum and spin-based cellular logic arrays, and molecular-based cellular automata, all made from the switches presented here. These modules are an integral part of the hierarchical 3-D multiscale architecture presented. We have also showed a set of quantum and molecular self-assembled structures including molecular crossbars. The fabrication of these architectures currently faces a number of challenges, as discussed in this chapter. Nanoscale and molecular computing is a promising alternative to today’s CMOS technology but is in an infancy stage, with many interesting design issues yet to be studied and resolved.
TL;DR: In this article, the authors studied charge transport through individual Borromean ring complexes, both with and without anchor groups, in gated double-barrier tunneling junctions (DBTJs) formed using the electrical breakjunction technique on gold nanowires.
Abstract: We have studied charge transport through individual Borromean ring complexes, both with and without anchor groups, in gated double-barrier tunneling junctions (DBTJs) formed using the electrical breakjunction technique on gold nanowires. While common single-molecule device characteristics can be observed with either form of the Borromean rings, the complexes with anchor groups show a strong rectification of conduction in a relatively high percentage of samples. We present our data along with a simple model underlining the mechanism by which the arrangement and composition of the weakly bonding anchor groups attached to the electroactive element may promote a device configuration resulting in rectification.
TL;DR: It was found that polyviologens are responsive to the Bradford assay, which is traditionally highly selective for proteins, and this phenomenon demonstrates the utility of biochemical assays to address problems unique to supramolecular chemistry.
Abstract: Self-assembled multivalent pseudopolyrotaxanes, composed of lactoside-bearing cyclodextrin (CD) rings threaded on linear polyviologen polymers, have been introduced recently as flexible and dynamic neoglycoconjugates In the course of this research, it was found that polyviologens are responsive to the Bradford assay, which is traditionally highly selective for proteins The response of the pseudopolyrotaxanes to the Bradford assay was dependant on, and thus indicative of, the degree of threading of the CD rings onto the polyelectrolyte The assay was then used to report on the threading and dethreading of native and lactoside-bearing α-CD rings onto and off of polyviologen chains, a phenomenon which demonstrates the utility of biochemical assays to address problems unique to supramolecular chemistry