Supramolecular Assemblies by Charge-Transfer Interactions between Donor and Acceptor Chromophores

Photo-responsive liposomes composed of spiropyran-containing triazole-phosphatidylcholine: investigation of merocyanine-stacking effects on liposome-fiber assembly-transition

A spiropyran-containing triazole-phosphatidylcholine (SPTPC) was synthesized through a copper-catalyzed azide alkyne cyclo-addition (CuAAC) reaction. In water, SPTPCs self-assembled and a spontaneous spiropyran-to-merocyanine (SP-to-MC) isomerization occurred, resulting in coexistence of liposomes and fibers, and switching from the spiropyran (SP) to the merocyanine (MC) isomeric structure induced a reversible transition between these molecular assemblies. Study of the self-assembly of SPTPCs and photo-induced liposome-fiber assembly-transition revealed that the presence of MC enabled additional inter-membrane interaction during self-assembly and that the MC-stacking effect was the driving force for the assembly-transition. Exposure to UV light induced switching from SP to MC, where the planar structure of MC and the confinement of MC led to enhanced MC-stacking. The effect of MC-stacking was both advantageous and disadvantageous: MC-stacking perturbed the hydrophobic phase in the bilayer membrane and facilitated the liposome-to-fiber transition, otherwise the MC-stacking retarded switching of MC to SP, and caused an incomplete recovery of MC to SP during fiber-to-liposome recovery, thus a fatigue of SP was induced by MC-stacking during the liposome-to-fiber transition cycle. To decrease the intermolecular interactions and suppress MC-stacking, photo-inert triazole-phosphatidylcholine (TPC) was incorporated to prepare two-component TPC/SPTPC-liposomes, which exhibited better recovery kinetics. The photo-adaptive behavior of TPC/SPTPC-liposomes confirmed the disturbance of bilayer membranes by inter-membrane MC-stacking and the formation of MCTPC-enriched phases in the bilayer membrane.

Mechanistic Insights into the Self-Assembly of an Acid-Sensitive Photoresponsive Supramolecular Polymer

The supramolecular polymerization of an acid‐sensitive pyridyl‐based ligand (L₁) bearing a photoresponsive azobenzene moiety was elucidated by mechanistic studies. Addition of trifluoroacetic acid (TFA) led to the transformation of the antiparallel H‐bonded fibers of L₁ in methylcyclohexane into superhelical braid‐like fibers stabilized by H‐bonding of parallel‐stacked monomer units. Interestingly, L₁ dimers held together by unconventional pyridine–TFA N⋅⋅⋅H⋅⋅⋅O bridges represent the main structural elements of the assembly. UV‐light irradiation caused a strain‐driven disassembly and subsequent aggregate reconstruction, which ultimately led to short fibers. The results allowed to understand the mechanism of mutual influence of acid and light stimuli on supramolecular polymerization processes, thus opening up new possibilities to design advanced stimuli‐triggered supramolecular systems.

Hollow and Solid Spheres Assembled from Functionalized Macrocycles Containing Adamantane

An adamantane-based macrocycle possessing eight hydroxyl groups (1) was synthesized, in which the macrocyclic framework comprises two disubstituted adamantane molecules bearing phenyl derivatives connected to two biphenylene spacers by oxygen atoms. Furthermore, functionalized macrocycles containing methyl (2) and methoxycarbonylmethyl (3) groups were prepared. From the X-ray crystallographic analysis, the backbone of the macrocycles in all crystals had a nearly hexagonal shape with a cavity and these macrocycles could be arranged into different tubular structures dependent on the substituents. In acetone, macrocycle (1) formed stable hollow spherical aggregates with multilayer membranes. In contrast, macrocycle (3) exhibited no production of self-assembled materials in chloroform. The addition of hexane into the solution caused the generation of solid spheres and their fused network aggregates, which were finally transformed into crystals owing to the solvent effects.

Future of Supramolecular Copolymers Unveiled by Reflecting on Covalent Copolymerization

Supramolecular copolymers are an emerging class of materials, and in the last years their potential has been demonstrated on a broad scale. Implementing noncovalent polymers with multiple components can bring together useful features such as dynamicity and new functionalities. However, mastering and tuning the microstructure of these systems is still an open challenge. In this Perspective, we aim to trace the general principles of supramolecular copolymerization by analyzing them through the lens of the well-established field of covalent copolymerization. Our goal is to delineate guidelines to classify and analyze supramolecular copolymers in order to create a fruitful platform to design and investigate new multicomponent systems.

Unorthodox Combination of Cation-π and Charge-Transfer Interactions within a Donor-Acceptor Pair

Cation-π and charge-transfer (CT) interactions are ubiquitous in nature and involved in several biological processes. Although the origin of both the interactions in isolated pairs has extensively been studied, CT interactions are more prominent in supramolecular chemistry. Involvement of cation-π interactions in the preparation of advanced functional soft materials is uncommon. Moreover, a combination of these two interactions within a pair of electron donor (D) and acceptor (A) is uncharted. Here, we present a rational design to incorporate a combination of these two interactions within a D-A pair. A pyrene-peptide conjugate exhibits a combination of cation-π and CT interactions with a cationic naphthalenediimide (NDI) molecule in water. Nuclear Overhauser effect spectroscopy NMR along with other techniques and density functional theory calculations reveal the involvement of these interactions. The π-planes of pyrene and NDI adopt an angle of 56° to satisfy both the interactions, whereas β-sheet formation by the peptide sequence facilitates self-assembly. Notably, the binary system forms a self-supporting hydrogel at a higher concentration. The hydrogel shows efficient self-healing and injectable property. The hydrogel retains its thixotropic nature even at an elevated temperature. Broadly, we demonstrate a pathway that should prove pertinent to various areas, ranging from understanding biological assembly to peptide-based functional soft materials.

Charge transfer liquid: a stable donor–acceptor interaction in the solvent-free liquid state

A new charge transfer solvent-free liquid having high stability even with donor–acceptor ratio of 1000 : 1 is demonstrated.

Mechanical properties of supramolecular polymeric materials cross-linked by donor–acceptor interactions

We prepare a tough elastomer with aromatic donor and acceptor molecules introduced on the same polymer side chain.

Light-Written Reversible 3D Fluorescence and Topography Dual-Pattern with Memory and Self-Healing Abilities

To achieve the dynamical dual-pattern with multiplex information of complex topography and 3D fluorescence is challenging yet promising for wide applications ranging from visual bioassays, memory, smart devices to smart display. Here, we develop a convenient, reliable, and versatile method to realize the well-ordered dual-pattern with reversible topography and 3D fluorescence via a light direct-writing approach based on the wrinkle mechanism. By introducing the charge transfer (CT) interaction between π-electron-rich anthracene (AN) and π-electron-poor naphthalene diimide (NDI) into the polymer system, both modulus and fluorescence of the polymer films can be spatially regulated through the photodimerization of AN, which is controlled in-plane by photomasks, and becomes gradient in the vertical direction due to the filter effect of light. Therefore, the exposed sample displays a well-ordered complex pattern with the same topography as the applied photomask and 3D gradient change of fluorescence from red to green laterally across the layers simultaneously. The spatial cross-linking and CT interaction of the gradient layer can be controlled independently, which not only provides the reliability and reversibility of the topographical and fluorescence dual-pattern but also endows the possibility for tailoring the pattern with memory and self-healing. These characters of the dual-pattern with reversible topography and 3D fluorescence declare the clear applications in smart multiplex displays, memory, anticounterfeiting, visual detections, and so on.

Living in the salt-cocrystal continuum: indecisive organic complexes with thermochromic behaviour

The thermochromic behaviour of the haloaniline – 3,5-dinotrobenzoic acid cocrystals over the temperature range from 30–108 °C.

Supramolecular complexation between chain-folding poly(ester-imide)s and polycyclic aromatics: a fractal-based pattern of NMR ring-current shielding

Supramolecular complexation of pyrene with a chain-folding, NDI-based co-poly(ester-imide) generates a ¹H NMR pattern showing fractal-type character.

Unipolar to ambipolar semiconductivity switching in charge transfer cocrystals of 2,7-di-tert-butylpyrene

Charge transfer cocrystals of 2,7-di-tert-butylpyrene donor and tetracyanoquinodimethane, tetracyanobenzene and 1,3-dinitrobenzene acceptor exhibited switchable semi-conductivity.

Aromatic donor–acceptor interaction promoted catalyst assemblies for hydrolytic kinetic resolution of epichlorohydrin

The catalyst activity of bis-acceptor functionalized Co(iii)–salen in hydrolytic kinetic resolution can be fine-tuned by introducing a proper donor compound.

Robust Nanoporous Supramolecular Network Through Charge-Transfer Interaction

A robust nanoporous supramolecular network stabilized by charge-transfer interactions has been successfully constructed based on bipyridinium and bicarboxylic acid with electron-donating hydroxyl pendant groups, which exhibit high durability toward extensive acid/base condition (pH: 2-12), organic solvents, and the plucking of metal ions. Furthermore, the separation capacity toward rhodamine B and other dyes with the same charge and smaller molecular sizes has been realized in it.

Raising the Bar in Aromatic Donor-Acceptor Interactions with Cyclic Trinuclear Gold(I) Complexes as Strong π-Donors

Aromatic donor-acceptor interactions are of high importance in supramolecular chemistry, materials science and biology. Compared to other noncovalent interactions, such as hydrogen bonding, the binding is often weak. Here we show that strong donor-acceptor interactions between planar aromatics with binding free energies down to -10.1 kcal mol^-1 and association constants of up to 2.34 × 10⁷ L mol^-1 for 1:1 complexes can be realized using cyclic trinuclear complexes of gold(I) with pyridinate, imidazolate, or carbeniate ligands. Data were obtained through NMR and UV/vis absorption spectroscopic studies and supported by quantum chemical calculations for a variety of acceptors. By using a specifically designed bridged naphthalene diimide-based acceptor with only one binding site, we furthermore show that a 1:2 (donor:acceptor) binding model is best suited to quantify the donor and acceptor/complex equilibrium. Scanning electron microscopy on selected donor-acceptor pairs shows crystalline supramolecular assemblies. We anticipate this study to be relevant for the future design of supramolecular systems and chemical sensors and the determination of binding energies between planar donors and acceptors.

Controlled Formation of a Main Chain Supramolecular Polymer Based on Metal-Ligand Interactions and a Thiol-Ene Click Reaction

Supramolecular polymers with multiple functionalities and hierarchical structures have received considerable attention and become a hot research topic over the past years. Herein, a main-chain supramolecular polymer has been successfully fabricated by using metal-ligand interactions and a thiol-ene click reaction. ¹ H NMR, UV/Vis, DOSY, and viscosity measurements were carried out to investigate the molecular recognition and the process of supramolecular polymerization. From the study, the orthogonality between thiol-ene click reactions and the terpyridine-metal ions complexation behavior was testified, and supramolecular polymeric assemblies could be constructed by a one pot method. In the meantime, due to the incorporation of metal-ligand interactions, the supramolecular polymer shows stimuli-responsive properties toward chemical stimuli. Hence, this work could provide a methodology for developing supramolecular polymers as smart materials.

Fluorophobic Effect Promoting Lamellar Self-Assembly of Donor Acceptor Dyes

To combine liquid crystalline and linear optical properties in the same molecule, the fluorophobic effect was probed for the first time in donor acceptor dyes. Thus, a series of mono-, bi-, and tricyclic donor acceptor dyes with 1H,1H-perfluorinated alkyl chains of different lengths as donor units and nitrile, malononitrile or barbiturate as acceptor units was synthesized in 5 steps and 1.4-6.6 % overall yield. UV/Vis and fluorescence spectroscopy, cyclic voltammetry and DFT calculations revealed that absorption and emission maxima, Stokes shifts and LUMO energies were mainly governed by the chromophore size and acceptor strengths. The perfluorinated chain was electronically almost decoupled from the remaining chromophore and induced only slight changes of the absorption maxima as compared to the alkyl substituted counterparts. However, in contrast to the non-mesomorphic alkyl donor-substituted derivatives, the perfluorinated donors resulted in self-assembly into partially interdigitated SmA bilayers according to differential scanning calorimetry (DSC), polarizing optical microscopy (POM), X-ray diffraction (WAXS, SAXS) studies and electron density profile calculations.

Organic 2D Optoelectronic Crystals: Charge Transport, Emerging Functions, and Their Design Perspective

2D organic semiconductor crystals are emerging as a fascinating platform with regard to their applications in organic field-effect transistors (OFETs), attributed to their enhanced charge transport efficiency and their new optoelectronic functions, based on their unique morphological features. Advances in material processing techniques have not only enabled easy fabrication of few-monolayered 2D nanostructures but also facilitated exploration of the interesting properties induced by characteristic 2D morphologies. However, to date, only a limited number of representative organic semiconductors have been utilized in organic 2D optoelectronics. Therefore, in order to further spur this research, an intuitive crystal engineering principle for realizing organic 2D crystals is required. In this regard, here, not only the important implications of applying 2D structures to OFET devices are discussed but also a crystal engineering protocol is provided that first predicts molecular arrangements depending on the molecular factors, which is followed by realizing 2D supramolecular synthon networks for different molecular packing motifs. It is expected that 2D organic semiconductor crystals developed by this approach will pave a promising way toward next-generation organic 2D optoelectronics.

Cooperative supramolecular polymers with anthracene‒endoperoxide photo-switching for fluorescent anti-counterfeiting

Innovative technologies are highly pursued for the detection and avoidance of counterfeiting in modern information society. Herein, we report the construction of photo-responsive supramolecular polymers toward fluorescent anti-counterfeit applications, by taking advantage of multicycle anthracene‒endoperoxide switching properties. Due to σ-metalation effect, photo-oxygenation of anthracene to endoperoxide is proceeded under the mild visible light irradiation conditions, while the backward conversion occurs spontaneously at room temperature. Supramolecular polymers are formed with cooperative nucleation‒elongation mechanism, which facilitate fluorescence resonance energy transfer process via two-component co-assembly strategy. Fluorescence resonance energy transfer efficiency is delicately regulated by either light-triggered anthracene‒endoperoxide conversion or vapor-induced monomer–polymer transition, leading to high-contrast fluorescent changes among three different states. On this basis, dual-mode anti-counterfeiting patterns have been successfully fabricated via inkjet printing techniques. Hence, cooperative supramolecular polymerization of photo-fluorochromic molecules represents an efficient approach toward high-performance anti-counterfeit materials with enhanced security reliability, fast response, and ease of operation.

There is a continual pursuit for different ways to detect counterfeiting in today’s society. Here the authors show photo-responsive supramolecular polymers can be used in fluorescent anti-counterfeit applications, by taking advantage of multicycle anthracene‒endoperoxide switching properties.

Tetrathiafulvalene - a redox-switchable building block to control motion in mechanically interlocked molecules

With the rise of artificial molecular machines, control of motion on the nanoscale has become a major contemporary research challenge. Tetrathiafulvalenes (TTFs) are one of the most versatile and widely used molecular redox switches to generate and control molecular motion. TTF can easily be implemented as functional unit into molecular and supramolecular structures and can be reversibly oxidized to a stable radical cation or dication. For over 20 years, TTFs have been key building blocks for the construction of redox-switchable mechanically interlocked molecules (MIMs) and their electrochemical operation has been thoroughly investigated. In this review, we provide an introduction into the field of TTF-based MIMs and their applications. A brief historical overview and a selection of important examples from the past until now are given. Furthermore, we will highlight our latest research on TTF-based rotaxanes.

Supramolecular alternate donor-acceptor copolymers mediated by PtPt metal-metal interactions and their photocatalytic applications

Precise arrangement of the aromatic donor-acceptor units is of paramount importance to dictate the performance of multi-component π-functional materials. Herein a novel strategy has been developed toward alternate donor-acceptor copolymers, by incorporating Pt(ii)Pt(ii) metal-metal interactions for the hetero-complexation process. The proximity of Pt atoms endows the resulting supramolecular copolymers with metal-metal-to-ligand charge-transfer transitions in the visible/NIR region. The signals have been further applied for low-energy visible-light photo-catalysis that is unattainable for the individual species. More interestingly, "on-demand" photo-catalytic efficiency can be achieved by manipulating the reversibility of the supramolecular copolymerization process. Hence, the current work demonstrates the efficiency of fabricating multi-component π-functional materials via the elaborate manipulation of non-covalent driving forces.

Donor-acceptor-type supramolecular polymers on the basis of preorganized molecular tweezers/guest complexation

The bottom-up self-assembly of donor-acceptor (D-A) units has received tremendous attention in recent years. Charge-transfer interactions, which are inherently embedded in D-A pairs, have suffered from some disadvantages such as erratic arrangements and weak binding affinity, thus hampering the precise arrangement of D-A units into long-range-ordered supramolecular polymers. To address this issue, a feasible protocol is to incorporate D-A units into molecular tweezers/guest recognition motifs, which concurrently feature high complexation directionality, strong binding affinity and stimuli-responsiveness. In this tutorial review, we have summarized the recent advances on the tweezering directed formation of D-A-type supramolecular polymers, with particular emphasis on the design principles of monomers and macroscopic behaviors of supramolecular polymers, together with future challenges in this research field.

Strategy for Constructing Shape-Memory Dynamic Networks through Charge-Transfer Interactions

Recently, charge transfer (CT) interactions have received attention for the fabrication of supramolecular architectures due to their inherent compatibilities, directional nature and solvent tolerance. In this study, we report a shape-memory dynamic network constructed by the CT interaction between π-electron-rich naphthalene embedded in poly(ethylene glycol) (PEG-Np) and π-electron-poor six-arm methyl-viologen-ended poly(ethylene glycol) (⁶PEG-MV), which was verified by ultraviolet-visible spectroscopy (UV-vis), fluorescence spectra and swelling tests. Interestingly, the mechanical properties of this CT complex were dramatically enhanced compared with the control without CT interaction. Moreover, the excellent shape-memory effect (SME) was realized due to the good crystallization of the PEG segment and stable netpoints based on the CT interaction. In addition, as we expected, this supramolecular polymer network is self-healable and reprocessable.

Cobalt complexes with redox-active anthraquinone-type ligands

Three anthraquinone-type multidentate ligands, HL1-3 (HL = 2-R-1H-anthra[1,2-d]imidazole-6,11-dione; HL1: R = (2-pyridyl), HL2; R = (4,6-dimethyl-2-pyridyl), HL3; R = (6-methoxy-2-pyridyl)), were prepared, and their complexation behaviour was investigated. Three bis-chelate cobalt complexes with the formula [CoII(L1-3)2]·n(solv.) (1, 2, and 3 for HL1, HL2, and HL3, respectively), in which the ligands adopted tridentate binding modes, were synthesized and structurally characterized by single-crystal X-ray analyses. Electrochemical studies of 1-3 in CH2Cl2 reveal three reversible redox waves, assigned to ligand and cobalt-centred processes. Additional complexes were obtained in which HL1 adopted a bidentate binding mode, stabilising the mono-chelate [CoII(HL1)(NO3)2(DMF)2] (4) species and tris-chelate [CoIII(L1)3] (5) complex in which the cobalt ion was in its 3+ state. The electrochemical properties of complex 5 were investigated in DMF, and the Co(ii)/Co(iii) redox couple was found to be negatively shifted compared to that of complex 1, while the ligand-based processes became irreversible. Tridentate chelation is found to stabilise the anthraquinone ligands and unlocks their redox multi-stability.

Reversible Surface Dual-Pattern with Simultaneously Dynamic Wrinkled Topography and Fluorescence

The reversible surface patterns with fluorescence and topography can possibly enable information recording and reading and provide an important alternative to realize the higher information security. We demonstrated a reversible dual-pattern with simultaneously responsive fluorescence and topography using an anthracene (AN) and naphthalene diimide (NDI) containing copolymer (PAN-NDI-BA) as the skin layer, in which the reversible photodimerization of AN can simultaneously control the cross-linking and CT interaction between AN and NDI. Upon irradiation with UV light and thermal treatment, the resulting pattern assumes a reversible change between smooth and wrinkled states, and its fluorescence changes reversibly from red to white to blue-green. The smart surfaces with dynamic hierarchical wrinkles and fluorescence were achieved by selective irradiation with photomasks and can be employed for potential applications in smart displays and anticounterfeiting.

Melatonin-directed micellization: a case for tryptophan metabolites and their classical bioisosteres as templates for the self-assembly of bipyridinium-based supramolecular amphiphiles in water

The bulk solution properties of amphiphilic formulations are derivative of their self-assembly into higher ordered supramolecular assemblies known as micelles and of their ordering at the air-water interface. Exerting control over the surface-active properties of amphiphiles and their propensity to aggregate in pure water is most often fine-tuned by covalent modification of their molecular structure. Nevertheless structural constraints which limit the performance of amphiphiles do emerge when trying to develop more sophisticated systems which undergo for example, shape-defined controlled assembly and/or respond to external stimuli. In this regard, the template-modulated assembly of the so-called "supramolecular amphiphiles" continues to make progress ordering molecules that otherwise have very little to no driving force to aggregate in a prescribed manner in aqueous solutions. Herein we describe the template-modulated micellization and ordering at the air-water interface of bipyridinium-based supramolecular amphiphiles triggered by host-guest interactions with high specificity for the neurotransmitter melatonin over its biosynthetic synthon l-tryptophan and the thermodynamic parameters governing the template-modulated micellization process. When bound to the bipyridinium units of micellized surfactant molecules, melatonin effectively serves as "molecular glue" capable of lowering the CMC by 52% as compared to untemplated solutions. Analysis of this system suggests that a hallmark of donor-acceptor template-modulated micellization in water is a strong positively correlated temperature dependence of the CMC and the absence of a U-shaped CMC-temperature curve. Our findings make a case for the incorporation of l-tryptophan-based metabolites and their classical synthetic pharmaceutical bioisosteres as potential targets/components of donor-acceptor CT-based supramolecular amphiphile systems/materials operating in water.

Tuning the Mesomorphism and Redox Response of Anionic-Ligand-Based Mixed-Valent Nickel(II) Complexes by Alkyl-Substituted Quaternary Ammonium Cations

The combination of the redox-active mesogenic anion [Ni^II (Bdt)(BdtSQ)]^- (Bdt=1,2-benzenedithiolato; BdtSQ=1,2-dithia-semi-benzoquinonato) with alkyl-substituted ammonium cations afforded a series of redox-active ionic complexes of the type [NR₄ ][Ni^II (Bdt)(BdtSQ)] [R=nC₁₆ H₃₃ (NC16₄ Ni) and C8,10 (NC8,10₄ Ni); C8,10=6-octylhexadecyl] or [NMe₂ R₂ ][Ni^II (Bdt)(BdtSQ)] [R=nC₁₆ H₃₃ (NMe₂ C16₂ Ni) and C8,10 (NMe₂ C8,10₂ Ni)]. X-ray crystallographic analyses of NMe₂ C16₂ Ni and NC16₄ Ni revealed the formation of cation-dependent integrated ionic layers separated by interdigittated alkyl chains. Complexes NMe₂ C16₂ Ni and NC16₄ Ni commonly form crystalline phases at room temperature, whereas complexes NMe₂ C8,10₂ Ni and NC8,10₄ Ni, which contain branched alkyl chains, form a metastable mesophase and an amorphous phase at the same temperature, respectively. Furthermore, complexes NMe₂ C16₂ Ni, NMe₂ C8,10₂ Ni, and NC16₄ Ni commonly form a smectic A phase (SmA) at 375, 317, and 342 K, respectively. For the four complexes, well-defined cyclic voltammetry responses, derived from ligand-based oxidation and reduction, were observed in solution and the condensed phases, that is, upon casting these complexes on an indium-doped tin oxide working electrode. The present study demonstrates the tunability of the mesomorphism of ionic molecular assemblies composed of alkyl-substituted quaternary ammonium cations, while maintaining the well-defined redox responses of the anions even in the condensed phases.

Donor-acceptor interactions between cyclic trinuclear pyridinate gold(i)-complexes and electron-poor guests: nature and energetics of guest-binding and templating on graphite

Aromatic stacking interactions of π-basic Au(i) complexes with π-acids were analyzed experimentally, theoretically and at the solid/liquid interface using STM.

Donor–acceptor-type interactions between π-electron systems are of high relevance in the design of chemical sensors. Due to their electron-rich nature, cyclic trinuclear complexes (CTCs) of gold(i) are ideal receptor sites for electron-deficient aromatic analytes. Scanning tunneling microscopy provided insight into the structures of two-dimensional crystals of pyridinate gold CTCs that form on a graphite template at the solid/liquid interface. One polymorph thereof – in turn – templated the on-top co-adsorption of π-acidic pyrazolate CTCs as electron-poor guests up to a certain threshold. From NMR titration experiments, we quantified free energies of –6.1 to –7.5 kcal mol^–1 for the binding between pyridinate gold(i) CTCs and π-acidic pyrazolate CTCs. Quantum chemical calculations revealed that these interactions are largely dominated by London dispersion. These results give a more detailed insight into a rational design of sensitive CNT- or graphene-based sensors for π-acidic analytes, such as electron-deficient aromatics.