Supramolecular Fullerene Research Articles

Cover Feature: Supramolecular Ensembles Formed via Calix[5]arene‐Fullerene Host‐Guest Interactions (Chem. Asian J. 16/2022)

Calix[5]arenes have drawn attention due to their encapsulation capability for fullerenes. The high binding affinity between calix[5]arene and fullerene has enabled the development of various kinds of supramolecular fullerene polymers (such as linear fullerene polymers, helical fullerene polymers, and two-dimensionally extended fullerene networks) and the structural regulation of covalent polymers. Herein, supramolecular ensembles formed via calix[5]arene-fullerene complexation are reviewed in detail. More information can be found in the Review by Takehiro Hirao and Takeharu Haino.

Supramolecular Ensembles Formed via Calix[5]arene-Fullerene Host-Guest Interactions.

This Review introduces the research directions for the synthesis of supramolecular fullerene polymers. First, the discovery of host-guest complexes of pristine fullerenes is briefly outlined. We focus on progress in supramolecular fullerene polymers directed by the use of calix[5]arene-fullerene interactions, which comprise linear, networked, helical arrays of fullerenes in supramolecular ensembles. The unique self-sorting behavior of right-handed and left-handed helical supramolecular fullerene arrays is discussed. Thereafter, an extensive investigation of the calix[5]arene-fullerene interaction for control over the chain structures of covalent polymers is introduced.

Zero-to-Two Nanoarchitectonics: Fabrication of Two-Dimensional Materials from Zero-Dimensional Fullerene

Nanoarchitectonics of two-dimensional materials from zero-dimensional fullerenes is mainly introduced in this short review. Fullerenes are simple objects with mono-elemental (carbon) composition and zero-dimensional structure. However, fullerenes and their derivatives can create various types of two-dimensional materials. The exemplified approaches demonstrated fabrications of various two-dimensional materials including size-tunable hexagonal fullerene nanosheet, two-dimensional fullerene nano-mesh, van der Waals two-dimensional fullerene solid, fullerene/ferrocene hybrid hexagonal nanosheet, fullerene/cobalt porphyrin hybrid nanosheet, two-dimensional fullerene array in the supramolecular template, two-dimensional van der Waals supramolecular framework, supramolecular fullerene liquid crystal, frustrated layered self-assembly from two-dimensional nanosheet, and hierarchical zero-to-one-to-two dimensional fullerene assembly for cell culture.

Sequential Tether-Directed Synthesis of New [3 : 2 : 1] Hexakis-Adducts of C60 with a Mixed Octahedral Addition Pattern.

A new concept for the regioselective synthesis of [3 : 2 : 1] hexakis‐adducts of fullerene C60 was developed. Based on sequential tether‐directed remote functionalizations, chiral [3 : 2] pentakis‐adducts with an incomplete octahedral addition pattern were synthesized via stepwise cyclopropanation of C60 with suitable macrocyclic tri‐ and bifunctional cyclomalonate tethers. The four resulting stereoisomers were isolated using chiral HPLC. The corresponding pairs of enantiomers show mirror image behavior in their CD‐spectra. The pentakis‐adducts served as suitable building blocks for the spatially controlled synthesis of mixed hexakis‐adducts. Implementation of functional group‐bearing monomalonates afforded octahedral [3 : 2 : 1] hexakis‐adducts suitable for the construction of larger molecular and supramolecular fullerene architectures in excellent yield.

Self-sorting behavior in supramolecular fullerene polymerization directed by host-guest complexation between calix[5]arene and C60.

We describe self-sorting supramolecular polymerization that uses chiral calix[5]arene hosts and a dumbbell-shaped fullerene guest. In a solution containing the racemic host and the guest, the (S)-host and the (R)-host preferably formed their homomeric complexes to form helical supramolecular fullerene polymers in a self-sorting manner. The self-sorting behavior has been studied using diffusion-ordered 1H NMR (DOSY) and circular dichroism (CD) studies. The present findings show that it is possible to accomplish controlled supramolecular polymerization.

Formation of Semiconducting Supramolecular Fullerene Aggregates in a Dipeptide Organogel

AbstractThe formation of nanostructured fullerene aggregate inside supramolecular gels is a topic of great interest because of the potential applications of these nanostructures in photoelectronics. Gel phase facilitates the aggregation of fullerene by restricting the movement of solvent molecules, thereby increasing the local fullerene concentration. Herein, the supramolecular nanostructure formation of fullerene (C60) in a minimalistic dipeptide (diphenylalanine, FF) organogel is reported. The resulting composite FF/Fullerene gels exhibit improved mechanical properties and semiconductivity. While fullerene nanostructures do not disturb the FF aggregation pattern, they adhere to the FF fibers via non‐covalent interaction. Morphological analysis reveals the presence of spherical clusters and nanorods of fullerene attached to the dipeptide fibers. The composite gel with highest fullerene concentration exhibits linear current–voltage response with a current magnitude of ≈0.3 nA. Moreover, poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is incorporated in the FF/Fullerene system yielding tri‐hybrid donor–acceptor gels which exhibit photoresponsive conductivity. Therefore, the FF/Fullerene and the tri‐hybrid gel have interesting properties, and holds significant promise toward photoelectronic device applications.

Supramolecular Fullerene Sponges as Catalytic Masks for Regioselective Functionalization of C60

Summary Isomer-pure poly-functionalized fullerenes are required to boost the development of fullerene chemistry in all fields. On a general basis, multi-adduct mixtures with uncontrolled regioselectivity are obtained, and the use of chromatographic purification is prohibitively costly and time consuming, especially in the production of solar cells. Single-isomer poly-functionalized fullerenes are only accessible via stoichiometric, multistep paths entailing protecting-unprotecting sequences. Herein, a nanocapsule is used as a supramolecular tetragonal prismatic mask to exert full control on the reactivity and the equatorial regioselectivity of Bingel-Hirsch cyclopropanation reactions of a confined C60 guest. Thus, equatorial bis-, tris-, and tetrakis-C60 homo-adducts are exclusively obtained in a stepwise manner. Furthermore, isomer-pure equatorial hetero-tetrakis-adducts or hetero-Th-hexakis-adducts are synthesized at will in one-pot synthesis for the first time. This work provides a synthetically valuable path to produce a plethora of new pure-isomer poly-functionalized C60-based compounds as candidates for testing in solar cell devices and biomedical applications. Video Abstract Download : Download video (34MB)

Controlling the enthalpy-entropy competition in supramolecular fullerene liquid crystals by tuning the flexible chain length.

We present here that in two-dimensional (2D) fullerene supramolecular liquid crystals (SLCs), the phase diagram and lamella thickness of SLCs and 2D crystals can be tuned by the flexible alkyl tail and spacer length, due to their different effects on enthalpy and entropy changes during SLC formation.

Optical charge transfer transitions in supramolecular fullerene and porphyrin compounds

By the DFT method with the planar wave basis set and in the PAW approximation the geometric and electronic structures of four supramolecular compounds of porphyrin and fullerene molecules in the crystalline state are performed: H2TPP·C60·3 toluene, H2TpivPP·C60, H2T3,5-dimethylPP·C70·4 toluene, and NiT4-methylPP·2C70·2 toluene. The geometry is optimized using the PBE functional and the Grimme DFT-D2 dispersion interaction correction. The electronic structure and absorbance spectra are calculated using the HSE functional. It is shown that the H2TPP·C60·3 toluene structure having a sufficiently wide absorbance wavelength range, which results in a photoinduced electron transition from the higher occupied states formed by porphyrin molecules to the lower unoccupied states formed by fullerene molecules, is most promising for the design of photogalvanic elements.

Back Cover: Supramolecular Fullerene Polymers and Networks Directed by Molecular Recognition between Calix[5]arene and C60 (Chem. Eur. J. 49/2014)

Back Cover: Supramolecular Fullerene Polymers and Networks Directed by Molecular Recognition between Calix[5]arene and C₆₀ (Chem. Eur. J. 49/2014)

Supramolecular fullerene polymers and networks directed by molecular recognition between calix[5]arene and C60.

A biscalix[5]arene-C60 supramolecular structure was utilized for the development of supramolecular fullerene polymers. Di- and tritopic hosts were developed to generate the linear and network supramolecular polymers through the complexation of a dumbbell-shaped fullerene. The molecular association between the hosts and the fullerene were carefully studied by using (1) H NMR, UV/Vis absorption, and fluorescence spectroscopy. The formation of the supramolecular fullerene polymers and networks was confirmed by diffusion-ordered (1) H NMR spectroscopy (DOSY) and solution viscometry. Upon concentrating the mixtures of di- or tritopic hosts and dumbbell-shaped fullerene in the range of 1.0-10 mmol L(-1) , the diffusion coefficients of the complexes decreased, and the solution viscosities increased, suggesting that large polymeric assemblies were formed in solution. Scanning electron microscopy (SEM) was used to image the supramolecular fullerene polymers and networks. Atomic force microscopy (AFM) provided insight into the morphology of the supramolecular polymers. A mixture of the homoditopic host and the fullerene resulted in fibers with a height of (1.4±0.1) nm and a width of (5.0±0.8) nm. Interdigitation of the alkyl side chains provided secondary interchain interactions that facilitated supramolecular organization. The homotritopic host generated the supramolecular networks with the dumbbell-shaped fullerene. Honeycomb sheet-like structures with many voids were found. The growth of the supramolecular polymers is evidently governed by the shape, dimension, and directionality of the monomers.

Synthesis and Properties of [60]Fullerene Derivatives Functionalized through Copper Catalyzed Huisgen Cycloaadition Reactions.

Fullerenes are fascinating carbon molecules that attract an increasing attention due to their interesting properties and possibilities of application. For these applications fullerenes need to be connected to the macroscopic world via their exterior. Hence, the modification of fullerenes to acquire the desired exterior functionality is of major importance to utilize them effectively as bulk materials in practical applications. In last years, the copper-catalyzed Huisgen’s 1,3-dipolar cycloaddition of azides and terminal alkynes (CuAAC) has been revealed as an efficient tool for the preparation of a variety of fullerene derivatives with interesting applications. In this review we will brush up the variety of fullerene building blocks developed to be used in CuAAC reactions and we will critically examine the variety of reaction conditions that have been used to perform the CuAAC in connection with the nature of the moieties attached to the fullerene core. Moreover, the properties and applications of [60]fullerene derivatives obtained via the CuAAC “click” methodology will be reviewed including their use as mimics of the photosynthetic antenna-reaction center, their biological activity, their use as thermoresponsive water-soluble polymers and their role in the preparation of supramolecular fullerene motifs. Keywords: Alkynes, azides, click chemistry, cycloaddition, fullerene, synthetic methods.

Supramolecular Fullerene Polymers Formed by Host-Guest Complexation Between Calix[5]Arene and C60

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Synthesis of Diverse N,O-Bridged Calix[1]arene[4]pyridine-C60 Dyads and Triads and Formation of Intramolecular Self-Inclusion Complexes

Starting from both the bridging nitrogen atom-functionalized and the upper rim-functionalized N,O-bridged calix[1]arene[4]pyridine reactants, different types of heteracalixaromatics-C(60) dyads and triads of varied spacers were expediently synthesized using mainly the click reaction as the key step. By means of various spectroscopic methods, the heteracalixaromatics-C(60) dyads and triads obtained have been shown to form intramolecular self-inclusion complexes rather than oligomers or polymers in solution because of a flexible spacer in between the heteracalixaromatic ring and C(60) moiety. The current study, coupled with previous investigations, would provide the guideline for the construction of supramolecular fullerene motifs based on molecular design of the dyads and triads.

Self-Assembly of Supramolecular Fullerene Ribbons via Hydrogen-Bonding Interactions and Their Impact on Fullerene Electronic Interactions and Charge Carrier Mobility

The anisotropy of the electronic interactions between fullerenes in crystalline solids was examined using a confocal fluorescence microscope by probing the polarization of the fluorescence emission arising from fullerene excimer-like emitting states. Crystals of C(60) obtained by vacuum-sublimation or from chloroform solution exhibited no or little polarization (p = 0 or 0.11, respectively), as expected from the high symmetry of the C(60) fcc lattice or the low degree of anisotropy induced by included solvent molecules. The use of hydrogen-bonding to supramolecularly control interfullerene electronic interactions was explored using a fullerene derivative (1) combining a solubilizing 3,4-di-tert-butylbenzene group and a barbituric acid hydrogen-bonding (H-B) moiety. The crystal structure of 1 establishes the existence of fullerene H-B tapes along which interfullerene electronic interactions are expected to be large. In agreement with this, we observe very strong polarization of the fullerene excimer-like emission (p = 0.78), indicative of a high degree of anisotropy in the fullerene interactions. The charge-carrier mobility of 1 as determined from OFET devices was found to be lower than that of C(60) (1.2 x 10(-4) vs 1.2 x 10(-2) cm(2)/s V), which is rationalized on the basis of the reduced dimensionality of 1 as a wire-like semiconductor and variations in the morphology of the device active layer revealed by AFM measurements.

Recent progress in morphology control of supramolecular fullerene assemblies and its applications

Self-organisation is an elegant tool for the creation of assemblies controlled in all dimensions with tunable properties in natural as well as artificial supramolecular systems. Especially, the supramolecular organisation of fullerene (C(60)) using π-stacking interaction to form various functional assemblies is of particular importance as it can provide excellent optoelectronic properties. Interestingly, the insufficient solubility of C(60) has been overcome through the noncovalent interaction with other hosts and covalent functionalisation with organic moieties. This has resulted in supramolecular assemblies at the nano/micro/macro scales under different preparation conditions. The developments in the area of fullerene self-assembly during the last few decades have significantly contributed to the sensible design and fabrication of organic electronic devices. A summary of the very recent reports regarding the organisation of pristine C(60), its coassembly with other hosts, unique polymorphs of fullerene derivatives, functional liquid crystalline assemblies, donor/acceptor heterojunctions and its applications will be presented in this tutorial review. Future research directions in which the supramolecular fullerene assembly may achieve more precision and improve the efficiency of the photovoltaic devices are also discussed.

Supramolecular donor–acceptor hybrids of porphyrins/phthalocyanines with fullerenes/carbon nanotubes: electron transfer, sensing, switching, and catalytic applications

Since the three-dimensional electron-accepting fullerene has been found to be an excellent building block for self-assembled supramolecular systems, we have investigated photoinduced electron transfer processes in supramolecular fullerene systems with porphyrins and phthalocyanines as electron donors to mimic natural photosynthesis. We have successfully formed self-assembled supramolecular dyads and triads via metal-ligand coordination, crown-ether inclusion, ion pairing, hydrogen-bonding, or pi-pi stacking interactions. Although the single mode of binding gives usually flexible supramolecular structures, the newly developed strategy of multiple modes of binding results in conjugates of defined distance and orientation between the donor and acceptor entities, which influences the overall electron transfer reactions. In these conjugates, we observe the anticipated acceleration of the charge separation process and deceleration of the charge recombination process. Applications of these supramolecular systems for reversible photoswitching of inter- and intramolecular electron transfer events open up new opportunities in the area of photosensors. Extension of the self-assembly approaches to single wall carbon nanotubes (SWNT) results in SWNT-porphyrin/phthalocyanine nanohybrids capable of undergoing photoinduced electron transfer. These photochemical processes lead to photocatalytic reactions accumulating redox active substances of electron acceptor/mediator entities with the help of a sacrificial electron donor. Studies on these self-assembled supramolecular dyads, triads, tetrads, etc., are only in the beginning stages and future studies anticipate involvement of more complex systems targeted for better performances in light-driven devices.

Modification of electronic structure in supramolecular fullerene–porphyrin systems studied by fluorescence, photoacoustic and photothermal spectroscopy

Three fullerene–porphyrin hybrids (fullerene–porphyrin, fullerene–porphyrin dyad, two fullerenes–porphyrin dyad) in dimethylsulfoxide and chloroform were investigated. Strong interaction in the porphyrins covalently linked to the fullerene C 60 was studied with the electronic absorption and fluorescence examinations as well as with the steady-state photoacoustic and time-resolved optoacoustic spectroscopy (LIOAS). Analysis of LIOAS waveforms was done with Marti et al . approach and Rudzki-Small et al . deconvolution procedure. The basic spectral parameters of the fullerene–porphyrin systems were evaluated: locations of absorption/fluorescence bands, fluorescence quantum yields, thermal deactivation parameters, yields of triplet state population, thermal relaxation of triplet states of porphyrin moieties and their alteration upon the presence of covalent linkage to fullerene. Formation of an excimer with participation of the porphyrin second excited singlet state was shown. The changes in triplet state behaviour were discussed in terms of changes in fullerene–porphyrin hybrids electronic structure due to the strong interaction of porphyrin and fullerene subunits. It was also shown that LIOAS experiment can be used not only in establishing the basis spectral features of molecular triplet states, but it is an excellent tool for investigation of the changes in the electronic molecular structure in porphyrin species in the presence of fullerene covalent linkage.

Hierarchical Supramolecular Fullerene Architectures with Controlled Dimensionality.

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Supramolecular fullerene architectures by quadruple hydrogen bonding

The synthesis and full characterization of a quadruple bonded fullerene dimer using self-complementary 2-ureido-4[1H]pyrimidinone units with high dimerization constants is described. The chemical integrity of the monomeric moiety in either compound is fully preserved, also with respect to its redox and UV-Vis behavior. Two novel supramolecular dyads consisting of an oligo(p-phenylene vinylene) (OPV) donor and fullerene (C-60) acceptor are created via quadruple hydrogen bonding upon mixing the fullerene dimer and an OPV dimer. In these supramolecular dyads, singlet-energy transfer from the excited OPV unit to the fullerene causes a strong quenching of the OPV fluorescence. The high association constant of the 2-ureido-4[1H]-pyrimidinone quadruple hydrogen-bonding unit results in high quenching factors (Q(max) greater than or equal to 90). The lower limit obtained for the rate constant for energy transfer (k(EN) greater than or equal to 6 x 10(10) s(-1)) is rationalized in terms of the Forster mechanism.