C60 Complexes Research Articles

Host-Guest Mechanism via Induced Fit Fullerene Complexation in Porphin Receptor to Probe Salivary Alpha-Amylase in Dental Caries for Clinical Applications.

Salivary α-amylase is the most abundant protein of human saliva that potentially binds to streptococcus and other bacteria via specific surface-exposed α-amylase-binding proteins and plays a significant role in caries development. The detection of α-amylase in saliva can be used as a bioindicator of caries development. Herein, a facile strategy has been applied, tailoring the photochemical properties of 5,10,15,20-tetrakis(4-hydroxyphenyl)-21H,23H-porphine (TPPOH) and the fullerene C60 complex. The fluorescence emission of TPPOH is quenched by starch-coated fullerene C60 via charge-transfer effects, as determined by UV absorption and fluorescence spectroscopic studies. The starch-coated C60 has been thoroughly characterized via Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), optical microscopy, thermal gravimetric analysis (TGA), static water contact angle measurements, and zeta potential measurements. The analytical response of the assay showed a linear fluorescent response in α-amylase concentrations ranging from 0.001-0.1 Units/mL, with an LOD of 0.001 Units/mL. The applicability of the method was tested using artificial saliva with quantitative recoveries in the range 95-100%. The practicability of the procedure was verified by inspecting saliva samples of real clinical samples covering all age groups. We believe that the proposed method can serve as an alternative analytical method for caries detection and risk assessment that would also minimize the cost of professional preventive measures and treatments.

Supramolecular complexation of C60 with branched polyethylene.

Fullerene C60 is a ubiquitous material for application in organic electronics and nanotechnology, due to its desirable optoelectronic properties including good molecular orbital alignment with electron-rich donor materials, as well as high and isotropic charge carrier mobility. However, C60 possesses two limitations that hinder its integration into large-scale devices: (1) poor solubility in common organic solvents leading to expensive device processing, and (2) poor optical absorbance in the visible portion of the spectrum. Covalent functionalization has long been the standard for introducing structural tunability into molecular design, but non-covalent interactions have emerged as an alternative strategy to tailor C60-based materials, offering a versatile and tuneable alternative to novel functional materials and applications. In this work, we report a straightforward non-covalent functionalization of C60 with a branched polyethylene (BPE), which occurs spontaneously in dilute chloroform solution under ambient conditions. A detailed characterization strategy, based on UV-vis spectroscopy and size-exclusion chromatography was performed to verify and investigate the structure of the C60+BPE complex. Among others, our work reveals that the supramolecular complex has an order of magnitude higher molecular weight than its C60 and BPE constituents and points towards oxidation as the driving force behind complexation. The C60+BPE complex also possesses significantly broadened optical absorbance compared to unfunctionalized C60, extending further into the visible portion of the spectrum. This non-covalent approach presents an inexpensive route to address the shortcomings of C60 for electronic applications, situating the C60+BPE complex as a promising candidate for further investigation in organic electronic devices.

Investigation of Magnetic Electrodes in Conducting Polymeric Materials: Electrochemical Properties of a Fullerene[C60 ]-Pd Polymer and Iron Oxide Magnetic Nanocomposite.

A composite of iron oxide magnetic nanoparticles and coordination fullerene polymer (C60 Pd3 )n is formed by chemical deposition of spherical polymer nanoparticles on iron oxide magnetic nanoparticles in benzene containing C60 and Pd(0) complex. The composition of the composite can be controlled by the amount of magnetite and concentration of polymerization precursors as well as the time of polymerization. The magnetic composite material Fe3 O4 -γFe2 O3 /(C60 Pd3 )n is used as a model system to investigate its deposition on a magnetic electrode and its electrochemical properties. The iron oxide magnetic nanoparticles ensure both the magnetic activity of the composite and its nanostructured morphology. Both of these factors are responsible for the enhancement of the electrochemical activity of the polymer phase forming the composite in comparison to the pure polymer material deposited on the same magnetic electrode. In the magnetic field of the electrode, the composite undergoes permanent and strong bonding with the surface of the electrode. The nanostructured morphology of the Fe3 O4 -γFe2 O3 /(C60 Pd3 )n composite also provides very good capacitive properties.

Subphthalocyanine metallo-organic cage as catalytic molecular photoreactor for the functionalization of fullerenes

ABSTRACT Subphthalocyanines (SubPcs) are aromatic chromophores with a bowlshaped structure and outstanding optoelectronic properties. The cavity formed by a C3-symmetry trispyridyl-SubPc, Pd(II)-metalloorganic capsule has proved an optimal, shape-complementary space for the complexation of C60. Taking advantage of the intense green light absorption of the SubPc components of the capsule, and their ability to transfer energy/electrons from the excited state, our group has recently described the unprecedented use of SubPc cages as molecular photoreactors to perform photoredox-triggered addition of diphenylamine radicals over encapsulated C60. Unfortunately, the reaction could only be performed using stoichiometric amounts of the cage due to inhibition of the SubPc cavity by the addition compound. Here, we describe the preparation of a more flexible SubPc cage built with a related C1-symmetry trispyridyl-SubPc (C1-SubPc-cage), which could facilitate the exchange between the complexed addition compound and pristine fullerene, thus allowing to use it in catalytic amounts. After assessing the ability of C1-SubPc-cage to host C60, the addition of α-aminoalkyl radicals in the presence of the cage under green light irradiation was tested. Curiously, optimisation of the reaction conditions (using catalytic amounts of C1-SubPc-cage in diluted solutions) rendered a different reaction outcome, that is, a cyclopropanated fullerene, in remarkably high yields.

Synthese von C60/[10]CPP‐Catenanen durch Regioselektive Nanokapsel‐Templierte Bingel Bis‐Addition

AbstractDie Addition von zwei unsymmetrischen Malonsäureestern an das Buckminster‐Fulleren C60 kann zu 22 spektroskopisch unterscheidbaren isomeren Produkten führen und stellt daher eine beachtliche synthetische Herausforderung dar. In dieser Arbeit erreichen wir eine Selektivität von 87 % für die Bildung eines einzigen (in,out‐trans‐3)‐Isomers, indem wir drei Methoden kombinieren: (i) wir verwenden ein Ausgangsmaterial, in dem die beiden Malonsäureester kovalent verbunden sind (Tether); (ii) wir bilden den starken supramolekularen Komplex von C60 mit dem formstabilen [10]CPP‐Makrozyklus (Nanohoop‐Template) und (iii) wir schlossen diesen Komplex weiter in eine selbstorganisierte Nanokapsel ein (Schattenmaske). Die Variation der Alkylkette zeigte die Limitationen der Methode auf und die Ringdynamik in den ungewöhnlichen [2]Catenanen wurde in silico mit atomistischer Auflösung untersucht. Diese Arbeit erweitert das Spektrum der mechanisch ineinandergreifenden Architekturen mit Cycloparaphenylen (CPP) erheblich.

Synthesis of C60 /[10]CPP-Catenanes by Regioselective, Nanocapsule-Templated Bingel Bis-Addition.

The addition of two unsymmetric malonate esters to the Buckminster fullerene C60 can lead to 22 spectroscopically distinguishable isomeric products and therefore represents a formidable synthesis challenge. In this work, we achieve 87 % selectivity for the formation of a single (in,out-trans-3) isomer by combining three approaches: (i) we use a starting material, in which the two malonates are covalently connected (tether approach); (ii) we form the strong supramolecular complex of C60 with the shape-persistent [10]CPP macrocycle (template approach) and (iii) we embed this complex further within a self-assembled nanocapsule (shadow mask approach). Variation of the spacer chain shed light on the limitations of the approach and the ring dynamics in the unusual [2]catenanes were studied in silico with atomistic resolution. This work significantly widens the scope of mechanically interlocked architectures comprising cycloparaphenylenes (CPP).

(Invited) Photoinduced Electron Transfer in Dyads Involving Complexes of C60 and Nanohoops. Effect of π-Extension and Aromaticity of the Nanohoop

Conversion of the sunlight into chemical energy is considered to be one of the most important and fundamental chemical reactions in nature. A broad variety of artificial photosynthetic systems based on dyads, triads and up to pentads involving electron donor and acceptor moieties have been designed and synthesized in order to investigate artificial photoinduced energy and electron transfer processes. One type of dyads with potential applications in solar cells is the one combining C60 complexed with nanohoops.[1] In this work, we discuss a series of computational studies that involves the photoinduced charge separation in complexes of C60 and Li+@C60 with a series of different nanohoops, such as the [10]cycloparaphenylene ([10]CPP) ring,[2] π-extended CPPs such as the hexa-peri-benzocoronene (HBC) or the tribenzo[fj,ij,rst]pentaphene (TBP),[3] and [n]cyclodibenzopentalenes ([n]CDBPs) as antiaromatic curved nanorings.[4] The analysis of complexes of C60 with nanohoops having different degrees of π-conjugation and aromaticity allow us to discuss the effect in the charge transfer separation and recombination on the level of π-extension and aromaticity present in the nanohoops.

Fullerenes on a Nanodiamond Platform Demonstrate Antibacterial Activity with Low Cytotoxicity.

Carbon nanoparticles with antimicrobial properties, such as fullerenes, can be distinguished among the promising means of combating pathogens characterized by resistance to commercial antibiotics. However, they have a number of limitations for their use in medicine. In particular, the insolubility of carbon nanoparticles in water leads to a low biocompatibility and especially strong aggregation when transferred to liquid media. To overcome the negative factors and enhance the action of fullerenes in an extended range of applications, for example, in antimicrobial photodynamic therapy, we created new water-soluble complexes containing, in addition to C60 fullerene, purified detonation nanodiamonds (AC960) and/or polyvinylpyrrolidone (PVP). The in vitro antibacterial activity and toxicity to human cells of the three-component complex C60+AC960+PVP were analyzed in comparison with binary C60+PVP and C60+AC960. All complexes showed a low toxicity to cultured human skin fibroblasts and ECV lines, as well as significant antimicrobial activity, which depend on the type of microorganisms exposed, the chemical composition of the complex, its dosage and exposure time. Complex C60+PVP+AC960 at a concentration of 175 µg/mL showed the most stable and pronounced inhibitory microbicidal/microbiostatic effect.

Influence of Substitution on the Supramolecular Chemistry of Cycloparaphenylene‐Fullerene Complexes

AbstractWe present a comprehensive host‐guest study of four substituted and unsubstituted [10]cycloparaphenylenes with the fullerenes C60 and C70. Within this study, the influence on the complexation behavior was investigated experimentally and computationally. Due to the increased steric demand the substitution on the nanohoop results in an energetic penalty, which could be partially compensated by additional substituent‐fullerene interactions. These attractive interactions are intensified in the C70 complexes and with an increased degree of substitution. For the computational investigation conformer ensembles were taken into account, providing reliable structures with Boltzmann weighted energies. An analysis of the noncovalent interactions elucidated the origin of the enhanced substituent‐C70 interaction. The ellipsoid fullerene C70 can be considered as a π‐extended version of C60, which is able to increase the attractive van der Waals interactions within these supramolecular complexes.

Buckyball-metal Complexes as Potential Carriers of Astronomical Unidentified Infrared Emission Bands

Efforts over 40 yr still leave the source of astronomical infrared emission bands largely unidentified. Here, we report the first laboratory infrared (6–25 μm) spectra of gas-phase fullerene-metal complexes, [C60-Metal]+ (Metal = Fe, V) and show with density functional theory calculations that complexes of C60 with cosmically abundant metals, including Li, Na, K, Mg, Ca, Al, V, and Fe, all have similar spectral patterns. Comparison with observational infrared spectra from several fullerene-rich planetary nebulae demonstrates a strong positive linear cross-correlation. The infrared features of [C60-Metal]+ coincide with four bands attributed earlier to neutral C60 bands and in addition also with several bands unexplained to date. Abundance and collision theory estimates indicate that [C60-Metal]+ could plausibly form and survive in astrophysical environments. Hence, [C60-Metal]+ are proposed as promising carriers, in supplement to C60, of observational bands, potentially representing the largest molecular species in space other than C60, C60 +, and C70.

N]Cycloparaphenylene-Pillar[5]arene Bismacrocycles: Their Circularly Polarized Luminescence and Multiple Guest Recognition Properties.

Both pillar[n]arenes (P[n]As) and [n]cycloparaphenylenes ([n]CPPs) play an important role in supramolecular chemistry. Herein, we report the precise synthesis of two multifunctional bismacrocycles [n]CPP-P[5]A by integrating P[5]A into the [n]CPP backbone. The photoluminescence quantum yield (ΦF ) of the bismacrocycles was found to show a dramatic increase relative to the corresponding [n]CPPs. The chiral enantiomers (pR)/(pS)-[8]CPP-P[5]A were successfully isolated by chiral HPLC, and showed promising properties of circularly polarized luminescence (glum ≈0.02). In addition, [n]CPP-P[5]A bismacrocycles are capable of binding pyridinium salts and fullerene derivatives with high affinity and specificity within the two distinct cavities. Transient absorption studies showed that photo-induced electron transfer occurs in [10]CPP-P[5]A⊃C60 complex. Our results suggest that [n]CPP-P[5]A are potentially useful in CPL-active materials, multiple guest recognition and supramolecular polymer preparation.

N]Cycloparaphenylene‐Pillar[5]arene Bismacrocycles: Their Circularly Polarized Luminescence and Multiple Guest Recognition Properties

AbstractBoth pillar[n]arenes (P[n]As) and [n]cycloparaphenylenes ([n]CPPs) play an important role in supramolecular chemistry. Herein, we report the precise synthesis of two multifunctional bismacrocycles [n]CPP‐P[5]A by integrating P[5]A into the [n]CPP backbone. The photoluminescence quantum yield (ΦF) of the bismacrocycles was found to show a dramatic increase relative to the corresponding [n]CPPs. The chiral enantiomers (pR)/(pS)‐[8]CPP‐P[5]A were successfully isolated by chiral HPLC, and showed promising properties of circularly polarized luminescence (glum≈0.02). In addition, [n]CPP‐P[5]A bismacrocycles are capable of binding pyridinium salts and fullerene derivatives with high affinity and specificity within the two distinct cavities. Transient absorption studies showed that photo‐induced electron transfer occurs in [10]CPP‐P[5]A⊃C60 complex. Our results suggest that [n]CPP‐P[5]A are potentially useful in CPL‐active materials, multiple guest recognition and supramolecular polymer preparation.

Intersystem crossing rate of C60-tryptophan

One of the most important processes for photosensitisers is the intersystem crossing to the triplet state. We considered theoretically this process for the complex of fullerene C60 with the amino acid tryptophan (Trp) in comparison with pure fullerene C60 and C60 modified with trimalonic acid by use of density functional theory. Our comparative findings suggest that C60-Trp possesses high intersystem crossing rate to saturate T1 state. We suppose that C60-Trp could bind to DNA aptamer by CO-NH bonds creating novel conjugates with carriers for specific purposes on the cell surface without affecting the photosystem, which may allow it to efficiently generate reactive oxygen species.

Spin and orbital magnetism of exohedral fullerene doped with single transition metal atom (Sc-Ni): A relativistic density functional theory study

Relativistic density functional theory calculations have been implemented to study the structural configurations, electronic and magnetic properties of exohedral 3d transition metal atoms doping on C60 fullerene (TM-C60) by a full potential local orbital method. The calculated binding energies revealed that the TM-C60 molecules are energetically stable in all adsorption sites. We also found that the TM-doped exohedral C60 complexes are more reactive than pure C60 fullerene. The spin and orbital magnetic moments were also determined. We have indicated that in all of the five adsorption sites, exohedral TM-C60 molecules (except for Ni-C60) are magnetized. Our magnetic calculations show that the total spin magnetic moments of TM-C60 molecules mainly come from the TM atoms. We found that the spin magnetic moments of adsorbed TM atoms in exohedral doping C60 fullerene from Sc to Mn (HH adsorption site) and for Sc to Cr (HP and P adsorption sites) are greater than their free states. Our calculations suggest that exohedral doping 3d TM-C60 complexes can almost maintain spin magnetic moments. We have indicated that the magnetic properties of exohedral TM-C60 molecules change in the presence of spin–orbit coupling. Significant orbital contributions to magnetic moments are recognized in these configurations while the spin moments are unaffected. We found that Co in exohedral doping of C60 fullerene shows a robust orbital moment in all the five adsorption sites.

C–H⋯S Hydrogen Bond Assisted Supramolecular Encapsulation of Fullerenes with Nanobelts

C–H⋯S Hydrogen Bond Assisted Supramolecular Encapsulation of Fullerenes with Nanobelts

On the Origins of Stereo- and Regio-Selectivities in the Formation of Fullerene-Fluorene Dyads.

Recently, a novel [2+2] cycloaddition between the classical Ih-C60 and a fluorenylideneallene complex has been achieved experimentally. In the fullerene-fluorene dyad product, stereo- and regio-selectivities were found in the experiment, but the reasons are still unknown. Our theoretical studies suggest that, based on a diradical pathway, the structural selectivity of the product strongly depends on the structural/electronic features of the fluorenylideneallene and C60 complexes. When the R1 group in fluorenylideneallene denotes the H atom, the E-type product is more stable than the Z-type one, whereas other bulkier R1 groups lead to the reverse due to their steric hindrance. The π orbital conjugation between the fluorenyl group and the Cβ═Cγ bond in fluorenylideneallene is the main reason for the high selectivity of β,γ-cycloaddition. Analyses of both frontier orbitals and spin density for the intermediate structure suggest a diradical pathway of the reaction between fluorenylideneallene and C60 and uncover a decisive role of the LUMO of C60 toward regio-selectivity, which conduces to a high selectivity of the (6,6)-addition product.

Initiating Electron Transfer in Doubly Curved Nanographene Upon Supramolecular Complexation of C60.

The formation of supramolecular complexes between C60 and a molecular nanographene endowed with both positive and negative curvatures is described. The presence of a corannulene moiety and the saddle shape of the molecular nanographene allows the formation of complexes with 1:1, 1:2, and 2:1 stoichiometries. The association constants for the three possible supramolecular complexes were determined by 1H NMR titration. Furthermore, the stability of the three complexes was calculated by theoretical methods that also predict the photoinduced electron transfer from the curved nanographene to the electron acceptor C60. Time‐resolved transient absorption measurements on the ns‐time scale showed that the addition of C60 to NG‐1 solutions and photo‐exciting them at 460 nm leads to the solvent‐dependent formation of new species, in particular the formation of the one‐electron reduced form of C60 in benzonitrile was observed.

Water Splitting by C60 -Supported Vanadium Single Atoms.

Water splitting is an important source of hydrogen, a promising future carrier for clean and renewable energy. A detailed understanding of the mechanisms of water splitting, catalyzed by supported metal atoms or nanoparticles, is essential to improve the design of efficient catalysts. Here, we report an infrared spectroscopic study of such a water splitting process, assisted by a C60 supported vanadium atom, C60 V+ +H2 O→C60 VO+ +H2 . We probe both the entrance channel complex C60 V+ (H2 O) and the end product C60 VO+ , and observe the formation of H2 as a result from resonant infrared absorption. Density functional theory calculations exploring the detailed reaction pathway reveal that a quintet-to-triplet spin crossing facilitates the water splitting reaction by C60 -supported V+ , whereas this reaction is kinetically hindered on the isolated V+ ion by a high energy barrier. The C60 support has an important role in lowering the reaction barrier with more than 70 kJ mol-1 due to a large orbital overlap of one water hydrogen atom with one carbon atom of the C60 support. This fundamental insight in the water splitting reaction by a C60 -supported single vanadium atom showcases the importance of supports in single atom catalysts by modifying the reaction potential energy surface.

Catalytically active hybrid complex of fullerene C60 and vitamine B12

The reaction of hydroxycobinamide, a catalytically active derivative of vitamin B12, with an amino acid derivative of fullerene C60 affords a hybrid complex. The catalytic activity of the complex is demonstrated by the autoxidation reaction.

Fluorescent Bis-Calix[4]arene-Carbazole Conjugates: Synthesis and Inclusion Complexation Studies with Fullerenes C60 and C70.

Supramolecular chemistry has become a central theme in chemical and biological sciences over the last decades. Supramolecular structures are being increasingly used in biomedical applications, particularly in devices requiring specific stimuli-responsiveness. Fullerenes, and supramolecular assemblies thereof, have gained great visibility in biomedical sciences and engineering. Sensitive and selective methods are required for the study of their inclusion in complexes in various application fields. With this in mind, two new fluorescent bis-calix[4]arene-carbazole conjugates (4 and 5) have been designed. Herein, their synthesis and ability to behave as specific hosts for fullerenes C60 and C70 is described. The optical properties of the novel compounds and their complexes with C60 and C70 were thoroughly studied by UV-Vis and steady-state and time-resolved fluorescence spectroscopies. The association constants (Ka) for the complexation of C60 and C70 by 4 and 5 were determined by fluorescence techniques. A higher stability was found for the C70@4 supramolecule (Ka = 5.6 × 104 M−1; ΔG = −6.48 kcal/mol). Evidence for the formation of true inclusion complexes between the host 4 and C60/C70 was obtained from NMR spectroscopy performed at low temperatures. The experimental findings were fully corroborated by density functional theory (DFT) models performed on the host–guest assemblies (C60@4 and C70@4).