Pyrene Substituent Research Articles

HPLC fluorescence assay for measuring the activity of NAPE-PLD and the action of inhibitors affecting this enzyme

N-Acyl phosphatidylethanolamine-hydrolyzing phospholipase D (NAPE-PLD) is the major enzyme for the biosynthesis of the endocannabinoid anandamide. The role of NAPE-PLD in various physiological and pathophysiological conditions is currently under investigation. For example, the enzyme might be involved in the control of neuronal activity, embryonic development and pregnancy, and prostate cancer. We synthesized a novel NAPE-PLD substrate with a fluorogenic pyrene substituent at the N-acyl residue as tool compound for studying this enzyme. As shown by HPLC with fluorescence detection, in rat brain microsomes the substrate was transformed into the expected pyrene-labeled N-acylethanolamine (NAE), but minor amounts of three by-products could also be detected. In the presence of pan-serine hydrolase and secretory phospholipase A2 inhibitors, the generation of these compounds, whose identity was verified using reference substances, was abolished. Based on these results, a method for determining the activity of NAPE-PLD was developed, validated, and applied to evaluate the action of known inhibitors of this enzyme. With human sperm, it was shown that the fluorescent substrate can also be used to study NAPE metabolism in intact cells.

Molecular structure tuning impact on optical linearity and nonlinearity of novel push-pull conjugated organic systems for photonic applications

In the present work, we have designed and synthesized push-pull conjugated (symmetric d-π-A-π-D type) organic chromophores 2-(2,6-bis((E)-2-(anthracen-9-yl) vinyl)-4H-pyran-4-ylidene)malononitrile (M2) and 2-(2,6-bis((E)-2-(pyren-1-yl) vinyl)-4H-pyran-4-ylidene) malononitrile (M3). These chromophores are the derivatives of 2-(2, 6-dimethyl-4H-pyran-4-ylidene) malononitrile (DPM) with DPM acting as an electron acceptor unit whereas anthracene and pyrene substituents are represented as the electron donor units in M2 and M3 respectively. The structural and photophysical properties of these compounds have been analyzed using IR, NMR, UV–Vis absorption and emission spectroscopies. We comparatively investigated the third-order NLO properties of these novel compounds in CHCl3 for different dye solution concentrations and various laser powers. Moreover, the effect of substitution (electron acceptor unit anthracene and pyrene) on the nonlinear optical properties have been discussed based on the structural modification. The quantum chemical calculations (DFT) were performed to obtain optimized geometry, frontier molecular orbitals, natural bond orbitals (NBO), and NLO parameters of these compounds. The time-dependent density functional theory (TD-DFT) was employed for insight into the electronic structure, photophysical, and NLO properties of these compounds. Experimental results have been supported by the obtained theoretical results.

The magic of biaryl linkers: the electronic coupling through them defines the propensity for excited-state symmetry breaking in quadrupolar acceptor-donor-acceptor fluorophores.

Charge transfer (CT) is key for molecular photonics, governing the optical properties of chromophores comprising electron-rich and electron-deficient components. In photoexcited dyes with an acceptor-donor-acceptor or donor-acceptor-donor architecture, CT breaks their quadrupolar symmetry and yields dipolar structures manifesting pronounced solvatochromism. Herein, we explore the effects of electronic coupling through biaryl linkers on the excited-state symmetry breaking of such hybrid dyes composed of an electron-rich core, i.e., 1,4-dihydropyrrolo[3,2-b]pyrrole (DHPP), and pyrene substituents that can act as electron acceptors. Experimental and theoretical studies reveal that strengthening the donor-acceptor electronic coupling decreases the CT rates and the propensity for symmetry breaking. We ascribe this unexpected result to effects of electronic coupling on the CT thermodynamics, which in its turn affects the CT kinetics. In cases of intermediate electronic coupling, the pyrene-DHPP conjugates produce fluorescence spectra, spreading over the whole visible range, that in addition to the broad CT emission, show bands from the radiative deactivation of the locally excited states of the donor and the acceptors. Because the radiative deactivation of the low-lying CT states is distinctly slow, fluorescence from upper locally excited states emerge leading to the observed anti-Kasha behaviour. As a result, these dyes exhibit white fluorescence. In addition to demonstrating the multifaceted nature of the effects of electronic coupling on CT dynamics, these chromophores can act as broad-band light sources with practical importance for imaging and photonics.

Hybrid material based on single walled carbon nanotubes and cobalt phthalocyanine bearing sixteen pyrene moieties as a sensing layer for hydrogen sulfide detection

We report on a sensor platform for the determination of hydrogen sulfide based on a new hybrid material obtained by the non-covalent functionalization of single-walled carbon nanotubes (SWCNT) with a novel cobalt phthalocyanine bearing 16 pyrene substituents (CoPc-Pyr). The structural features of the hybrid were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis spectroscopy, and thermogravimetric analysis (TGA). The sensor characteristics of SWCNT/CoPc-Pyr hybrid layers prepared by spin coating of its suspension in dichloromethane were studied against low concentrations of hydrogen sulfide (0.5–50 ppm) with the limit of detection (LOD) of 38 ppb and response and recovery time of 60 s and 80 s, respectively. This LOD value lies in the appropriate range and the prepared hybrid material is promising for the creation of the sensors for the detection of H2S, which can be used as an important biomarker of halitosis and asthma. It was shown that the SWCNT/CoPc-Pyr hybrid could be successfully used for the selective detection of H2S in the presence of carbon dioxide, hydrogen, ethanol, acetone, and dichloromethane.

Hybrid materials based on pyrene-substituted metallo phthalocyanines as sensing layers for ammonia detection: Effect of the number of pyrene substituents

In this work, the effect of the number of pyrene substituents in zinc(II) phthalocyanine molecules on the sensor properties of their hybrid materials with single-walled carbon nanotubes (SWCNT) is studied. For this purpose, hybrid materials of SWCNTs modified with five different trioxyethylenethio substituted zinc(II) phthalocyanines containing 0, 1, 2, and 4 methoxypyrene substituents in the phthalocyanine ring were prepared and characterized by Raman spectroscopy, scanning electron microscopy and inductively coupled plasma atomic emission spectrometry. The chemiresistive sensor response of the prepared hybrids toward low concentrations of ammonia (1–100 ppm) was studied to reveal the effect of the number of pyrene substituents in the phthalocyanine ring on the sensor performance of the hybrid materials. It was demonstrated that the hybrids with zinc(II) phthalocyanine bearing four methoxypyrene substituents exhibited the maximal sensor response to ammonia with the limit of detection of 0.4 ppm. The sensitivity of the hybrid materials to ammonia was shown to be much higher than to CO2, H2, H2S, CH4, ethanol, acetone, and dichloromethane vapors, however, an oxidizing gas such as NO2 was an interfering compound in the determination of ammonia. 1 ppm NO2 show the same absolute value of the response than 10 ppm NH3. The quantum-chemical calculations were performed to explain this effect as well as the dependence of the binding energy of substituted zinc(II) phthalocyanines with carbon nanotubes on the number of pyrene substituents.

Passerini Multicomponent Reactions Enabling Self-Reporting Photosensitive Tetrazole Polymers.

We introduce the synthesis of photosensitive tetrazole monomers via Passerini multicomponent reactions (MCRs). We exploit the MCR's tolerance toward various functional groups under mild, catalyst-free conditions in a one-pot reaction setup to generate tetrazole-containing monomers featuring a methacrylic moiety, which enables their subsequent reversible addition-fragmentation chain transfer (RAFT) polymerization. By employing tetrazoles with either a 4-methoxy phenyl or a pyrene substituent, further modifications of the polymers in a wavelength-orthogonal, self-reporting fashion upon irradiation with either UV or visible light become possible.

Mono- and Di-Pyrene [60]Fullerene and [70]Fullerene Derivatives as Potential Components for Photovoltaic Devices

In the present work, we report the successful synthesis and characterization of six (two new) fullerene mono- and di-pyrene derivatives based on C60 and C70 fullerenes. The synthesized compounds were characterized by spectral methods (ESI-MS, 1H-NMR, 13C-NMR, UV-Vis, FT-IR, photoluminescence and photocurrent spectroscopy). The energy of HOMO and LUMO levels and the band gaps were determined from cyclic voltammetry and compared with the theoretical values calculated according to the DFT/B3LYP/6-31G(d) and DFT/PBE/6-311G(d,p) approach for fully optimized molecular structures at the DFT/B3LYP/6-31G(d) level. Efficiency of solar cells made of PTB7: C60 and C70 fullerene pyrene derivatives were analyzed based on the determined energy levels of the HOMO and LUMO orbitals of the derivatives as well as the extensive spectral results of fullerene derivatives and their mixtures with PTB7. As a result, we found that the electronic and spectral properties, on which the efficiency of a photovoltaic cell is believed to depend, slightly changes with the number and type of pyrene substituents on the fullerene core. The efficiency of constructed solar cells largely depends on the homogeneity of the photovoltaic layer, which, in turn, is a derivative of the solubility of fullerene derivatives in the solvent used to apply these layers by spincoating.

Immobilization of dipyrenylphosphinic acid to boehmite: Fluorescent hybrid with weakened pyrene-aggregation

Ethyldipyrenylphosphate (DPyPOOEt) was designed and synthesized by utilizing ethyldichlorophosphate as the core and 1-bromopyrene as substituting groups, and afterwards dipyrenylphosphinic acid (DPyPOOH) was synthesized by the hydrolysis reaction of DPyPOOEt by using bromotrimethylsilane (TMSBr). Fluorescent hybrid was finally prepared by the dehydration condensation between DPyPOOH and hydroxyl groups on the surface of boehmite. The chemical structure of DPyPOOEt and DPyPOOH were characterized by 1H NMR and 13C NMR. Crystal structure, chemical structure and microtopography of hybrid were characterized by X-ray diffraction spectra (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM), respectively. The results demonstrate that the incorporation of two pyrene substituent groups into phosphine oxide can be successfully immobilized on the surface without any change of crystal structure of boehmite. Fluorescence spectra in solution and powder further demonstrated the occurrence of shape-changed and red-shifted emission peaks of DPyPOOEt and DPyPOOH than that of pyrene. In particular, compared to DPyPOOEt and DPyPOOH in solid, the hybrid shows blue-shifted fluorescence. Optimized molecular conformation, ground electronic structure of DPyPOOEt has been investigated in detail by quantum chemistry method. The introduction of phosphine oxide tunes the conjugated structure of pyrene-ring and spatial conformation between the pyrene-ring. In addition, intramolecular V-shanped conformation when DPyPOOH confined to boehmite surface reduce π-π aggregation between pyrene rings. Therefore, these results indicate that the hybrid is expected to highly efficient blue light-emitting material.

A bioinspired strategy for designing well-ordered nanotubular structures by templateless electropolymerization of thieno[3,4-b]thiophene-based monomers.

Here, a bioinspired strategy is used to prepare well-ordered nanotubular structures, as observed in animals and plants, such as gecko toe pads or corals. The nanotubes are obtained by templateless electropolymerization of thieno[3,4-b]thiophene-based monomers with various aromatic groups in an organic solvent (dichloromethane). The most interesting and robust structures were obtained with carbazole and pyrene substituents to the base monomer structure, since these groups participate significantly in the polymerization and also have strong π-stacking interactions. The addition of water to electropolymerization solvent significantly impacted the formation of nanotubes, as it caused the release of a significant amount of H2 and O2 bubbles, depending on the electropolymerization method. Identifying templateless approaches to vary nanotubular structures is very interesting, as these materials are sought-after for applications in water harvesting systems. This article is part of the theme issue 'Bioinspired materials and surfaces for green science and technology (part 3)'.

Tuning nanotubular structures by templateless electropolymerization with thieno[3,4-b]thiophene-based monomers with different substituents and water content

Here, templateless electropolymerization is employed to produce nanotubular structures from various thieno[3,4-b]thiophene-based monomers that differ in substituent structure and size, as well as the linker connecting the thieno[3,4-b]thiophene core and substituent. The formation of densely packed vertically aligned are obtained from monomers with a pyrene substituent and when a significant amount of water (CH2Cl2 + H2O) is included in the solvent. The geometrical parameters of the nanotubes are highly dependent on the electopolymerization method. A significant amount of air is trapped within the structure of the densely packed open nanotubes obtained with Qs = 100 mC cm−2 causing an increase in water contact angle (θw) up to 82.6° (intermediate state between the Wenzel and the Cassie-Baxter state), and θw can become even more hydrophobic by further modifying the deposition method or the electrolyte.

Theoretical analysis of the stabilization of graphene nanosheets by means of strongly polarized pyrene derivatives

Functionalized pyrenes have been used in experimental work as dispersants to avoid the re-association of graphene sheets in order to produce single (few) layer graphene sheets. In the present studies, the adsorption processes of various pyrene derivatives on a planar model graphene layer were studied theoretically to determine the influence of different polar pyrene substituents on the strength of their interaction with graphene. Based on the previous experimental work, the following substituted pyrenes were investigated: pyrene butanol, pyrene sulfonic acid, neutral, charged or with counter ion, and pyrene tetra-sulfonic acid, either negatively charged or neutral. The calculations were based on density functional theory and the effects of the solvents water and ethanol were included via a continuum approach and explicit solvent interactions. The results show that the number of polar substituents is a decisive factor for stabilization of the pyrenes on the graphene surface.

Nanotubular structures through templateless electropolymerization using thieno[3,4-b]thiophene derivatives with different substituents and water content

Here, we report a strategy to prepare controllable nanotubular structures using a templateless electropolymerization process in organic solvent (CH2Cl2) and without surfactant. We use thieno [3,4-b]thiophene derivatives with various substituents including hydrocarbon chains, fluorocarbon chains and aromatic groups of various size. The influence of the water content (CH2Cl2 + H2O) in also studied in order to release in-situ a higher amount of gas bubbles (O2 and/or H2). The best results are obtained with the pyrene substituent, which lead to highly densely packed nanotubular structures while the water content allows to highly increase their porosity, changing the resulting surface morphology from tree-like to coral-like structure. This is probably due to both high π-stacking interaction of pyrene and its polymerization capacity in the same potential range. This change also induces an increase in surface hydrophilicity because the water highly penetrates these porous structures. Moreover, both the poly (thieno [3,4-b]thiophene) polymers and the substituents participate to the film fluorescence while the nanostructures seem to amplify their intensity. Such surfaces are extremely interesting for potential applications in sensors or in water harvesting systems.

Designing bioinspired coral-like structures using a templateless electropolymerization approach with a high water content.

Here, with the aim of obtaining densely packed porous nanostructures of various shape using templateless electropolymerization in organic solvent (dichloromethane), original thieno[3,4- b]thiophene-based monomers with different substituents are studied. First of all, the adding of water in solution has a huge influence on the formation of porous structures because a much higher amount of gas (O2 and/or H2) is released. Rigid substituents such as aromatic groups have a beneficial effect on the formation of nanotubular structures contrary to flexible ones such as alkyl chains. Special results are obtained with the pyrene substituent (Thieno-Pyr). With this monomer, coral-like structures are obtained. These structures are obtained by the formation first on long nanotubular structures and their sagging due to their weight. Then, the released gas is trapped inside these structures leading to huge craters. These exceptional surfaces could be used in the future in various potential applications such as in drug delivery, cell growth, sensors, optical devices or surface adhesion. This article is part of the theme issue 'Bioinspired materials and surfaces for green science and technology (part 2)'.

Synthesis, Characterization, Hydrolytic Stability, Nickel(II) Chloride Complex and Anti-Parasitic Activity of Pyrene-Tethered Silatranes

The known silatrane chemistry with polycyclic aromatic hydrocarbons (PAHs) has not been extensively investigated. The current study features synthesis and characterization of silatranes bearing pyrene substituent at the apical silicon site starting from 1-pyrenecarboxaldehyde and N-(3-(trimethoxysilyl)propyl)ethane-1,2-diamine. The synthesized silatranes were subjected to time-dependent hydrolysis study to examine their hydrolytic stability. In addition, one of the silatrane has been used to entrap nickel chloride to obtain complex of 1:1 composition. Mass, IR spectroscopic data and theoretical study revealed about the chelate structure of the complex in which silatrane acts as a bidentate ligand. The protozoans are cause of numerous infective diseases and so the article also assesses the anti-parasitic potential of the prepared compounds. Both the silatranes showed significant activity against Giardia lamblia and Entamoeba histolytica and very low IC50 values of (6) against G. lamblia and (7) against E. histolytica indicate their potential to act as efficient drug in comparison to standard drug, metronidazole.

Design, characterization, optical and photophysical properties of novel thiophene monomers and polymers containing pyrene moieties linked via rigid and flexible spacers

Herein, we report the synthesis of three novel thiophene monomers connected to pyrene moieties via a flexible oligo(ethylene glycol) (OEG) spacer with an oxygen α-to-pyrene (T1), a flexible OEG spacer with an oxygen β-to-pyrene (T2), and a rigid acetylene spacer (T3). These monomers were prepared in an easy manner from commercially available 3-bromo-4-methylthiophene and further characterized by NMR spectroscopy and mass spectrometry. Monomer T2 exhibited the absorption band at 344 nm and a strong “monomer” emission band at 375 nm typical of a 1-pyrenemethyl derivative. Moreover, T1 and T3 showed red shifted absorption bands at 352 and 384 nm arising from the pyrene substituents, namely the electron-donating oxygen α−to-pyrene and the extended conjugation length, respectively. These compounds exhibited a broad “monomer” emission band between 360˜480 nm without excimers. Homopolymers (OHP1, OHP2, and OHP3) obtained from these monomers were partially soluble and their photophysical properties such as quantum yield and lifetime were characterized. Emission spectra of the oligomers OHP1 and OHP3 exhibited an emission band at ˜500 nm, which is due to the conjugated polythiophene backbone and does not arise from intramolecular pyrene-pyrene interactions.

1,7-Dipyrene-Containing Aza-BODIPYs: Are Pyrene Groups Effective as Ligands To Promote and Direct Complex Formation with Common Nanocarbon Materials?

A series of 1,7-dipyrene-aza-BODIPY and 1,7-dipyrene-3,5-diferrocene-aza-BODIPY derivatives 5a–e with pyrene ligands covalently attached to the β-pyrrolic positions of the boron-azadipyrromethene (aza-BODIPY) core have been prepared and characterized by NMR, UV–vis, and steady-state fluorescence spectroscopy; high-resolution mass spectrometry; and X-ray crystallography. The redox processes of these donor–acceptor aza-BODIPY systems were investigated by electrochemistry (cyclic voltammetry and differential pulse voltammetry methods) and spectroelectrochemistry. The potential of the closely spaced 1,7-dipyrene fragments to promote formation of noncovalent π-complexes with nanocarbon materials (C60, C70, (6,5)-single-walled carbon nanotube, and graphene) was explored. UV–vis, steady-state fluorescent, and time-resolved transient absorption spectroscopy data indicated that the interaction between the new pyrene-aza-BODIPYs and C60 or C70 fullerenes in solution is weak, and time-resolved transient absorption spectroscopy provided no evidence of photoinduced electron transfer. X-ray crystallography on a binary solid of aza-BODIPYs 5b and C60 was indicative of a pyrene–pyrene rather than pyrene–C60 interaction motif, whereas fullerenes were found to form close contacts with the electron-rich B,O-chelated part of aza-BODIPY 5b. In contrast, pyrene–pyrene and pyrene–C60 but not aza-BODIPY–C60 interactions were observed in the crystal structure of aza-BODIPY 5d and C60. Density functional theory (DFT) and time-dependent DFT calculations were used to support conclusions based on experimental data and are suggestive of rather weak interaction energies between 1,7-dipyrene-aza-BODIPYs and nanocarbon materials. Direct comparison with an analogous control compound lacking the pyrene ligands demonstrated that the pyrene substituents were ineffective at promoting and directing complex formation with nanocarbon materials. A common measurement of complex formation, emission loss in the presence of a nanocarbon acceptor, was demonstrated to have an alternative explanation in these systems, and the general effectiveness of using pyrene ligands to build noncovalent complexes was drawn into question.

Photochemical Properties of Supramolecular Dyad with Pyrenylethenylquinoline as a Photochrome

Spectral and photochemical properties of a bichromophoric dyad with two photochromes, 2-[(2-(pyren-1-yl)ethenyl]quinoline (PEQ) bridged by ten methylene groups have been investigated. Stationary spectroscopy does not show substantial interaction between the PEQ groups in the dyad, but the appearance of another, more long-living component in the f luorescence decay kinetics indicates possible excimer formation. The formation of the chemically active excimer is also confirmed by the intramolecular [2+2] photocycloaddition reaction to give tetrasubstituted cyclobutane with two vicinal pyrene substituents. This reaction competes with trans–cis photoisomerization of the dyad. It has been proposed that the π-stacking interaction of two PEQ groups with a long system of π-bonds plays an important role in the excimer formation followed by the photocycloaddition reaction.

Effects of shape, size, and pyrene doping on electronic properties of graphene nanoflakes.

Effects of size, shape, and pyrene doping on electronic properties of graphene nanoflakes (GNFs) were theoretically investigated using density functional theory method with PBE, B3PW91, and M06-2X functionals and cc-pVDZ basis set. Two shapes of zigzag GNFs, hexagonal (HGN) and rhomboidal (RGN), were considered. The energy band gap of GNF depends on shape and decreases with size. The HGN has larger band gap energy (1.23-3.96eV) than the RGN (0.13-2.12eV). The doping of pyrene and pyrene derivatives on both HGN and RGN was also studied. The adsorption energy of pyrene and pyrene derivatives on GNF does not depend on the shape of GNFs with energies between 21 and 27kcal mol-1. The substituent on pyrene enhances the binding to GNF but the strength does not depend on electron withdrawing or donating capability. The doping by pyrene and pyrene derivatives also shifts the HOMO and LUMO energies of GNFs. Both positive (destabilizing) and negative (stabilizing) shifts on HOMO and LUMO of GNFs were seen. The direction and magnitude of the shift do not follow the electron withdrawing and donating capability of pyrene substituents. However, only a slight shift was observed for doped RGN. A shift of 0.19eV was noticed for HOMO of HGN doped with 1-aminopyrene (pyNH2) and of 0.04eV for LUMO of HGN doped with 1-pyrenecarboxylic acid (pyCOOH). Graphical Abstract HOMO and LUMO Energies of pyrene/pyrene derivatives doped Graphene Nanoflakes.

Star-Shaped Asymmetrically Substituted Blue Emitting Carbazoles: Synthesis, Photophyscial, Electrochemical and Theoretical Investigations

A series of star-shaped blue-emitting 1,3,6,8-tetrasubstituted carbazoles containing different functional groups are synthesized and characterized. Electron-transporting N-phenylbenzimidazole is attached to C3 and C6 positions while the chromophore at C1 & C8-positions varied from fluorene to triphenylamine. The effect of the nature of the C1 and C8 chromophores on optical, electrochemical and thermal properties is unravelled. Absorption spectra revealed that the choice of meta− mode of connectivity between the chromophores on carbazole nucleus interrupted the interchromophoric electronic interactions in the ground state. However, the molar extinction coefficients of the dyes increased significantly on the addition of chromophores at C1 and C8 attributable to the increment in the chromophore density. Interestingly, triphenylamine and pyrene containing compounds displayed positive solvatochromism in emission attributable to intramolecular charge transfer and excimer excited states, respectively. Fluorescence and thermal properties are strongly influenced by the nature of chromophores present on C1 & C8. Electrochemical studies revealed low oxidation potential for arylamine containing derivatives and led to high-lying highest occupied molecular orbital in the series. However, the lowest unoccupied molecular orbital is stabilized by pyrene substituent due to its π-acceptor character.

Understanding Noncovalent Interactions of Small Molecules with Carbon Nanotubes.

We combine experimental methods, density functional theory (DFT) calculations, and molecular dynamics (MD) simulations in the quantitative analysis of noncovalent interactions between (6,5)-enriched single-walled carbon nanotubes (SWNTs), as hosts, and a set of pyrene derivatives with different electronic properties and surface areas, as guests. The experiments and calculations were carried out in two solvents with markedly different polarities, namely 1,1',2,2'-tetrachloroethane (TCE) and N,N-dimethylformamide (DMF). Our results show that dispersion forces govern the supramolecular association of small molecules with (6,5)-SWNTs, with negligible contributions from ground-state charge-transfer effects. In the nonpolar solvent (TCE), the binding constants are highly correlated with the contact area between the SWNT and the guests. In the polar solvent (DMF), the binding constants show a complex dependence on the chemical nature of the pyrene substituents, as demonstrated by MD simulations with the explicit inclusion of solvent molecules. The solvation of the small molecules is shown to play a leading role in the binding process. Remarkably, the binding constants obtained from the MD simulations for the five guest molecules correlate with those derived from experiment. Furthermore, the MD simulations also reveal the structure of the adsorbed guest from low to high SWNT surface coverage.