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1.
The first cycloparaphenylene (CPP)‐based ionic donor–acceptor supramolecule Li +@C 60?[10]CPP?X ? has been synthesized. X‐ray crystallography not only confirmed the molecular structure of Li +@C 60?[10]CPP?X ? but also uncovered the formation of a unique ionic crystal. The strong charge‐transfer interaction between [10]CPP and Li +@C 60, which was confirmed by electrochemical measurement and spectroscopic analyses, caused significant delocalization of the positive charge across the entire complex. 相似文献
2.
[ n]Cycloparaphenylenes ([ n]CPPs) with n=5, 8, 10 and 12 and their noncovalent ring-in-ring and [ m]fullerene-in-ring complexes with m=60, 70 and 84 have been studied by direct and matrix-assisted laser desorption ionization ((MA)LDI) and density-functional theory (DFT). LDI is introduced as a straightforward approach for the sensitive analysis of CPPs, free from unwanted decomposition and without the need of a matrix. The ring-in-ring system of [[10]CPP⊃[5]CPP] +. was studied in positive-ion MALDI. Fragmentation and DFT indicate that the positive charge is exclusively located on the inner ring, while in [[10]CPP⊃C 60] +. it is located solely on the outer nanohoop. Positive-ion MALDI is introduced as a new sensitive method for analysis of CPP⊃fullerene complexes, enabling the detection of novel complexes [[12]CPP⊃C 60, 70 and 84] +. and [[10]CPP⊃C 84] +.. Selective binding can be observed when mixing one fullerene with two CPPs or vice versa, reflecting ideal size requirements for efficient complex formation. Geometries, binding and fragmentation energies of CPP⊃fullerene complexes from DFT calculations explain the observed fragmentation behavior. 相似文献
3.
From the analysis of the polarizability of carbon nano-onions (CNOs), it was concluded that CNOs behave as near perfect nanoscopic Faraday cages. If CNOs behave as ideal Faraday cages, the reactivity of the C 240 cage should be the same in Li +@C 240 and Li +@C 60@C 240. In this work, the Diels–Alder reaction of cyclopentadiene to the free C 240 cage and the C 60@C 240 CNO together with their Li +-doped counterparts were analyzed using DFT. It was found that in all cases the preferred cycloaddition is on bond [6,6] of type B of C 240. Encapsulation of Li + results in lower enthalpy barriers due to the decrease of the energy of the LUMO orbital of the C 240 cage. When the Li + is placed inside the CNO C 60@C 240, the decrease in enthalpy barrier is similar to that of Li +@C 240. However, the location of Li + in Li +@C 240 (off-centered) and Li +@C 60@C 240 (centered) is quite different. When Li + was placed in the center of the C 240 cage in Li +@C 240, the barriers increased significantly. Taking into account this effect, the barriers in Li +@C 240 and Li +@C 60@C 240 differ by about 4 kcal mol −1. This result can be attributed to the shielding effect of C 60 in Li +@C 60@C 240. As a result, we conclude that this CNO does not act as a perfect Faraday cage. 相似文献
4.
A triquinoline cationic moiety (TQ⋅H +) has recently been designed as a novel molecular unit for supramolecular chemistry. In addition to some useful features, TQ⋅H + has strong electron-acceptor properties, which renders the molecular cation a unique element in nanochemistry. TQ⋅H + is found to form complexes with coronene (COR) and cycloparaphenylene (CPP). In this work, we report a computational study of photoinduced electron transfer in supramolecular complexes TQ⋅H +-COR, TQ⋅H +⊂[12]CPP and (TQ⋅H +-COR)⊂[12]CPP. The electron-transfer rates are estimated by using the semi-classical approach. The results are compared with the data previously obtained for a structurally similar inclusion complex Li +@C 60⊂[10]CPP. In particular, we found a red solvatochromic shift for charge-shift bands in the TQ⋅H +-complexes unlike a blueshift showed by Li +@C 60⊂[10]CPP. This distinction is explored in terms of electronic and structural features of the systems. 相似文献
5.
Inclusion complexes of benzo‐ and dithiabenzo‐crown ether functionalized monopyrrolotetrathiafulvalene (MPTTF) molecules were formed with Li +@C 60 ( 1? Li +@C 60 and 2? Li +@C 60). The strong complexation has been quantified by high binding constants that exceed 10 6 M ?1 obtained by UV/Vis titrations in benzonitrile (PhCN) at room temperature. On the basis of DFT studies at the B3LYP/6‐311G(d,p) level, the orbital interactions between the crown ether moieties and the π surface of the fullerene together with the endohedral Li + have a crucial role in robust complex formation. Interestingly, complexation of Li +@C 60 with crown ethers accelerates the intersystem crossing upon photoexcitation of the complex, thereby yielding 3(Li +@C 60)*, when no charge separation by means of 1Li +@C 60* occurs. Photoinduced charge separation by means of 3Li +@C 60* with lifetimes of 135 and 120 μs for 1? Li +@C 60 and 2? Li +@C 60, respectively, and quantum yields of 0.82 in PhCN have been observed by utilizing time‐resolved transient absorption spectroscopy and then confirmed by electron paramagnetic resonance measurements at 4 K. The difference in crown ether structures affects the binding constant and the rates of photoinduced electron‐transfer events in the corresponding complex. 相似文献
6.
Photoinduced electron transfer is studied in a series of inclusion complexes of structurally modified phenine nanotubes ( pNT ) with C 70 using the TD-DFT method. Analysis of electronic properties of the complexes shows that the electron transfer is infeasible in pNT_4d⊃C 70 built on the tetrameric array of [6]cyclo-meta-phenylene ([6]CMP) units. However, replacing one or more [6]CMP units with a coronene moiety enables electron transfer from pNT to C 70 . The generation of the charge separated states from the lowest locally excited states occurs on a sub-nanosecond time scale. Depending on the number of the [6]CMP units, the charge recombination rate varies from 1.8 ⋅ 10 7 to 3.1 ⋅ 10 2 s −1, i. e., five orders of magnitude. 相似文献
7.
Herein, we report use of [Li +@C 60]TFSI ? as a dopant for spiro‐MeOTAD in lead halide perovskite solar cells. This approach gave an air stability nearly 10‐fold that of conventional devices using Li +TFSI ?. Such high stability is attributed to the hydrophobic nature of [Li +@C 60]TFSI ? repelling moisture and absorbing intruding oxygen, thereby protecting the perovskite device from degradation. Furthermore, [Li +@C 60]TFSI ? could oxidize spiro‐MeOTAD without the need for oxygen. The encapsulated devices exhibited outstanding air stability for more than 1000 h while illuminated under ambient conditions. 相似文献
8.
The origin of the experimentally known preference for [6,6] bonds in cycloaddition reactions involving C60 has been computationally explored. To this end, we examined the reactions of 1,3-dienes with fullerene (C60) in the context of an approach to open a large orifice on the fullerene framework by using the activation model of reactivity in combination with the energy analysis method. In this study, the effect of the alkali metal of Li+, Na+, and K+ as an encapsulated element was investigated on the kinetic and thermodynamic behaviors of the Diels–Alder (DA) process. Our calculations indicated that encapsulated Na+ and K+ cations are located close to the center of the C60 molecule; however, encapsulated Li+ is displaced from the center, which leads to a higher reactivity for Li+@C60 in DA cycloaddition reaction in the gas phase. Also, benzene as a non-polar solvent affects the DA reactions greater than water as a polar solvent. Different analyses show that solvent changes the catalysis reaction performance, in which a greater efficiency was obtained for K+ in the solvent in comparison with other alkali ions because of a facilitated mechanism of electron transfer. 相似文献
9.
Efficient photoinduced electron transfer was observed across a [10]cycloparaphenylene ([10]CPP) moiety that serves as a rigid non‐covalent bridge between a zinc porphyrin and a range of fullerenes. The preparation of iodo‐[10]CPP is the key to the synthesis of a porphyrin–[10]CPP conjugate, which binds C 60, C 70, (C 60) 2, and other fullerenes ( KA>10 5 m ?1). Fluorescence and pump–probe spectroscopy revealed intramolecular energy transfer between CPP and porphyrin and also efficient charge separation between porphyrin and fullerenes, affording up to 0.5 μs lifetime charge‐separated states. The advantage of this approach towards electron donor–acceptor dyads is evident in the case of dumbbell‐shaped (C 60) 2, which gave intricate charge‐transfer behavior in 1:1 and 2:1 complexes. These results suggest that [10]CPP and its cross‐coupled derivatives could act as supramolecular mediators of charge transport in organic electronic devices. 相似文献
10.
The complex of [10]cycloparaphenylene ([10]CPP) with bis(azafullerene) (C 59N) 2 is investigated experimentally and computationally. Two [10]CPP rings are bound to the dimeric azafullerene giving [10]CPP?(C 59N) 2?[10]CPP. Photophysical and redox properties support an electronic interaction between the components especially when the second [10]CPP is bound. Unlike [10]CPP?C 60, in which there is negligible electronic communication between the two species, upon photoexcitation a partial charge transfer phenomenon is revealed between [10]CPP and (C 59N) 2 reminiscent of CPP‐encapsulated metallofullerenes. Such an alternative electron‐rich fullerene species demonstrates C 60‐like ground‐state properties and metallofullerene‐like excited‐state properties opening new avenues for construction of functional supramolecular architectures with organic materials. 相似文献
11.
The density functional theory method at the M06-2X/6-31G(d,p) level was used to calculate the optimal geometry and thermodynamic parameters of formation of the Li +CF 3SO 3? and Li +@C 60(CF 3SO 3?) ion pairs, as well as topological characteristics of the electron density distribution in the critical point (3,?1) of bonds between lithium cation endofullerene Li +@C 60, and the triflate anion in a vacuum and in chlorobenzene. 相似文献
12.
The energetics, structures, stabilities and reactivities of[C nH 2] 2+ ions have been investigated using computational methods and experimental mass spectrometric techniques. Spontaneous decompositions of [C nH 2] 2+ into [C nH] + + H + products, observed for ions with odd-n values, have been explained by invoking the formation of excited triplet states. Even-n [C nH] + ions possess triplet ground states with low-lying excited states, whereas odd-n ions have triplet states with energies several eV above ground singlet states. Radiationless transitions of vibrationally excited long-lived triplet state ions into singlet state continua are suggested as possible mechanisms for spontaneous deprotonation processes of odd- n [C nH 2] 2+ ions. Evidence for these long-lived excited states has been obtained in bimolecular single electron transfer reactions. 相似文献
13.
Mass-analysed ion kinetic energy spectra for collisional activation (CA) of [C 6H 6] +˙ formed via electron capture by [C 6H 6] 2+ ions in collision with neutral benzene molecules have been compared for the C 6H 6 isomers benzene, 1,5-hexadiyne and 2,4-hexadiyne. Comparisons of fragment abundance and total CA fragment yields were also made for [C 6H 6] +˙ ions generated by electron ionization (EI). CA conditions of ion velocity and collision gas pressure were identical in these comparisons. In general the fragment abundance patterns for the ions formed by charge exchange were very similar to those for singly charged benzene ions generated by EI. However, significant variations in CA fragment yield (the ratio of the total CA fragment ion abundance to the abundance of the incident unfragmented ions) were observed. It is not clear from the results whether these variations reflect structurally different ions or ions of different internal energies. The CA spectra of [C 6H 6] +˙ ions derived from charge exchange reactions between the benzene dication and the target gases He, Ne, Ar, Kr and Xe have also been recorded and, once again, very similar fragment abundance patterns were observed along with large variations in total CA fragment yields. Charge exchange efficiency measurements are reported for reactions between the benzene dication and the targets He, Ne, Ar, Kr, Xe and C 6H 6 (benzene) and also for the doubly charged ions derived from the linear C 6H 6 isomers. In the latter case Xe and benzene targets were used. The energetics and efficiency measurements for the former reactions suggest that for targets such as He and Ne the processes probably involve excited states of the doubly charged ions. The efficiencies measured for the latter reactions were distinctly different for the three C 6H 6 isomers and may indicate a strong dependence of charge exchange cross-section on doubly charged ion structure. 相似文献
14.
Efficiencies and rates of electron transfer from various electron donors to excited fullerenes (C 60 and C 70) have been determined by observing the transient absorption bands in the near-IR region, where the anion radicals of fullerenes
appear. From the rise of the absorption bands of C 60
−+ and C 70
−+ in the near-IR region, electron transfer takes place via the triplet states ( TC 60
* and TC 70
*) under appropriately low concentrations of electron donors. By analysis of the rise curves C 60
−+ and C 70
−+, contribution of the excited singlet states ( SC 60
* and SC 70
*) in addition to the route of the triplet states ( TC 60
* and TC 70
*) is confirmed. The quantum yield for electron transfer via the triplet states Φ ct
T was evaluated by the ratio of [C 60
−+]/[ TC 60
*] (or [C 70
−+/[ TC 70
*]). The Φ ct
T depends upon the donor-ability, donor concentration, and solvent polarity. The back electron-transfer process, which was
evaluated by observing C 60
−+, also depends upon the solvent polarity. 相似文献
15.
The Gibbs free energies of solvation (Δ G
s) and the electronic structures of endohedral metallofullerenes M +@C 60 (M += Li +, K +) were calculated within the framework of the density functional theory and the polarizable continuum model. In water environment,
the equilibrium position of K + is at the center of the fullerene cavity whereas that of Li + is shifted by 0.14 nm toward the fullerene cage. The Li + cation is stabilized by interactions with both the fullerene and solvent. The equilibrium structures of both endohedral metallofullerenes
are characterized by very close Δ G
s values. In particular, the calculated Δ G
s values for K +@C 60 are in the range from −124 to −149 kJ mol −1 depending on the basis set and on the type of the density functional. Molecular dynamics simulations (TIP3P H 2O, OPLS force field, water sphere of radius 1.9 nm) showed that the radial distribution functions of water density around
C 60 and M +@C 60 are very similar, whereas orientations of water dipoles around the endohedral metallofullerenes resemble the hydration pattern
of isolated metal ions. 相似文献
17.
Lithium‐ion‐encapsulated [6,6]‐phenyl‐C 61‐butyric acid methyl ester fullerene (Li +@PCBM) was utilized to construct supramolecules with sulfonated meso‐tetraphenylporphyrins (MTPPS 4?; M=Zn, H 2) in polar benzonitrile. The association constants were determined to be 1.8×10 5 M ?1 for ZnTPPS 4?/Li +@PCBM and 6.2×10 4 M ?1 for H 2TPPS 4?/Li +@PCBM. From the electrochemical analyses, the energies of the charge‐separated (CS) states were estimated to be 0.69 eV for ZnTPPS 4?/Li +@PCBM and 1.00 eV for H 2TPPS 4?/Li +@PCBM. Upon photoexcitation of the porphyrin moieties of MTPPS 4?/Li +@PCBM, photoinduced electron transfer occurred to produce the CS states. The lifetimes of the CS states were 560 μs for ZnTPPS 4?/Li +@PCBM and 450 μs for H 2TPPS 4?/Li +@PCBM. The spin states of the CS states were determined to be triplet by electron paramagnetic resonance spectroscopy measurements at 4 K. The reorganization energies ( λ) and electronic coupling term ( V) for back electron transfer (BET) were determined from the temperature dependence of kBET to be λ=0.36 eV and V=8.5×10 ?3 cm ?1 for ZnTPPS 4?/Li +@PCBM and λ=0.62 eV and V=7.9×10 ?3 cm ?1 for H 2TPPS 4?/Li +@PCBM based on the Marcus theory of nonadiabatic electron transfer. Such small V values are the result of a small orbital interaction between the MTPPS 4? and Li +@PCBM moieties. These small V values and spin‐forbidden charge recombination afford a long‐lived CS state. 相似文献
18.
In the last 30 years, fullerene-based materials have become popular building blocks for devices with a broad range of applications. Among fullerene derivatives, endohedral metallofullerenes (EMFs, M@C x) have been widely studied owing to their unique properties and reactivity. For real applications, fullerenes and EMFs must be exohedrally functionalized. It has been shown that encapsulated metal cations facilitate the Diels–Alder reaction in fullerenes. Herein, the Bingel–Hirsch (BH) addition of ethyl bromomalonate over a series of ion-encapsulated M@C 60 (M=Ø, Li +, Na +, K +, Mg 2+, Ca 2+, and Cl −; Ø@C 60 stands for C 60 without any endohedral metal) is quantum mechanically explored to analyze the effect of these ions on the BH addition. The results show that the incarcerated ion has a very important effect on the kinetics and thermodynamics of this reaction. Among the systems studied, K +@C 60 is the one that leads to the fastest BH reaction, whereas the slowest reaction is given by Cl −@C 60. 相似文献
19.
The kinetics of the formation and decay of photoexcited radical ion pairs of donoracceptor charge-transfer complexes between
C 60 and N,N-diethylaniline (DEA) in chlorobenzene was studied by picosecond laser-induced diffraction gratings. It was established that
the anisotropy of polarization of the diffraction signal decreases as the concentration of DEA increases. The radical ion
states of the photoexcited C 60
−...DEA + complex have zero anisotropy. This effect is likely due to the isotropic intracomplex transfer of an electron from the local
excited state to the radical ion state. The rate constant of quenching of the singlet excited C 60 by N,N-diethylaniline (1.4·10 10 L mol −1 s −1) and the lifetimes of the solventseparated C 60
−...DEA + and tight [C 60
−...DEA +] (95±7 and 31±4 ps, respectively) radical ion pairs were measured.
Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1605–1610, September, 1997. 相似文献
20.
Macrolides are a broad spectrum of antibiotics that are commonly used in human pathologies as well as in veterinary medicine. The electrochemical detection of macrolide antibiotics were studied at various methods using amperometric and coulometric detectors. Since the discovery of fullerenes (C n), one of the main classes of carbon compounds, the unusual structures and physiochemical properties of these molecules have been discovered, and many potential applications and physicochemical properties have been introduced. Up to now, various empty carbon fullerenes with different numbers “n,” such as C 60, C 70, C 76, C 82, and C 86, have been obtained. Topological indices are digital values that are assigned based on chemical composition. These values are purported to correlate chemical structures with various chemical and physical properties. They have been successfully used to construct effective and useful mathematical methods to establish clear relationships between structural data and the physical properties of these materials. In this study, the number of carbon atoms in the fullerenes was used as an index to establish a relationship between the structures of Erythromycin-A (EA), Erythromycin-A enol ether (EMEN), Olendomycin (OM), and Anhydroerythromycin-A (AEA), 1-4 and fullerenes C n (n = 60, 70, 76, 82 and 86), which create [Tetracyclines]@C n, A-1 to A-5 ([EA]@C n), B-1 to B-5 ([EMEN]@C n), C-1 to C-5 ([OM]@C n), and D-1 to D-5 ([AEA]@C n). The relationship between the number of carbon atoms and the free energies of electron transfer (ΔG et(1) to ΔG et(4)) is assessed using the Rehm-Weller equation for A-1 to A-5, B1 to B-5, C-1 to C-5, and D-1 to D-5 supramolecular [14-MR Macrolides]@C n complexes 5-24. Calculations are presented for the four reduction potentials ( Red.E 1 to Red.E 4) of fullerenes C n . The results were used to calculate the four free-energies of electron transfer (ΔG et(1) to ΔG et(4)) of supramolecular complexes A-1 to A-18 to B-1 to B-18, C-1 to C-18, and D-1 to D-18 (5-76) for fullerenes C 60 to C 300. 相似文献
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