On the pairwise hydrophobic interaction of fullerene (original) (raw)
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Journal of Chemical Sciences, 2017
The thermodynamics of association of fullerene [C 60 ] and water-soluble fullerene derivatives, i.e., fullerols [C 60 (OH) n , where, n = 2, 4, 8, 12] in aqueous solutions have been studied using molecular dynamics simulations. The potentials of mean force (PMFs) bring out the tendency of aggregation of these nanostructures in water. The extent of hydroxylation seems to have a minor effect on the depth of the contact minima (the first minimum in the PMFs). The positions of the subsequent minima and maxima in the PMFs change with the size of the solute molecules. Higher stability of the contact state of highly hydroxylated fullerols is due to the van der Waals interactions whereas intermolecular solute-solvent hydrogen bonding nearly flattens the PMFs beyond the 2nd minima for higher fullerols. The solvent contributions to the PMFs for all the solute particles studied here are positive. Entropic and enthalpic contributions to the association of solute molecules are calculated in the isothermal-isobaric (NPT) ensemble. We find that the contact pair formation is governed by entropy with the enthalpic contributions being highly unfavorable, whereas the solvent assisted and solvent separated configurations show entropy-enthalpy compensation.
Carbon, 2009
The Gibbs free energy of solvation (DG solv) for C 60 , and six other idealized, non-functionalized, fullerene particles of differing size and shape has been determined in octanol and water solvents from molecular dynamics simulations using thermodynamic integration. In particular, we have studied Buckminster fullerene (C 60) and open and capped carbon nanotubes of different aspect ratios and solvent accessible surface areas. Knowledge of the DG solv of a molecule in octanol and water can be used to understand the partitioning of the molecule between organic and aqueous phases and is one of several parameters used to model the fate of chemicals in the natural environment. The simulations were performed at ambient conditions, i.e., a temperature of 25°C and a pressure of 1 bar. The fullerene molecules are all found to have a very high DG solv in water, and a very low DG solv in octanol, suggesting a strong preference for the organic phase. From a comparison of the results for capped and uncapped carbon nanotubes we found that the uncapped tubes exhibit significantly higher DG solv than capped tubes. Furthermore, for capped carbon nanotubes, hydrophobic/organophilic shifts are observed with increasing excluded volume and solvent accessible surface area.
The Journal of Chemical Physics, 2015
Fullerene C60 sub-colloidal particle with diameter ∼1 nm represents a boundary case between small and large hydrophobic solutes on the length scale of hydrophobic hydration. In the present paper, a molecular dynamics simulation is performed to investigate this complex phenomenon for bare C60 fullerene and its amphiphilic/charged derivatives, so called shape amphiphiles. Since most of the unique properties of water originate from the pattern of hydrogen bond network and its dynamics, spatial, and orientational aspects of water in solvation shells around the solute surface having hydrophilic and hydrophobic regions are analyzed. Dynamical properties such as translational-rotational mobility, reorientational correlation and occupation time correlation functions of water molecules, and diffusion coefficients are also calculated. Slower dynamics of solvent molecules—water retardation—in the vicinity of the solutes is observed. Both the topological properties of hydrogen bond pattern and ...
Journal of Molecular Structure, 2007
Density functional theory calculations have been carried out to analyze the effect of hydrogen halides and H 2 O molecule interactions with the three lowest energy isomers the ring, bowl and cage of C 20 fullerene. The single-point energy calculations have also been performed at MP2/6-31+G*//B3LYP/6-31G* level of theory. The complexes (C 20 Á Á ÁH-X and H 2 O, where X = F, Cl, and Br) are bounded by two interactions namely: (i) very weak X-HÁ Á Áp H-bond interactions and (ii) long range van der Waals interactions of H-XÁ Á ÁC type. These interactions produced negligible distortion in the structures and a good correlation between electron density and stabilization energy of the complexes is found. The counterpoise correction to the interaction energies and the study of topology of the electron density for all the complexes have been performed. The charge transfer and the maneuver of resonance interaction in the interacting orbitals have been investigated by natural bond orbital (NBO) approach.
Fullerene-Naphthalene Interaction on the Water Surface and in the Binary Film
Fullerenes Nanotubes and Carbon Nanostructures, 2007
This work continues the studies on the non‐covalent fullerene–donor interaction that were recently conducted by non‐spectroscopic methods in solution. The Langmuir–Blodgett (LB) technique is engaged as a main experimental tool to exclude interfering solvent effects. Methods to prepare a stable low‐dimensional fullerene–water system and to monitor intermolecular interactions therein are proposed. As a molecular partner of fullerene, β‐benzylnaphthalene (BN) modeling a functional π‐donor is used. No pair C60–BN interactions were found in both C60–BN–H2O and C60–BN systems. Thus, a lack of molecular affinity of fullerene for typical π‐donors is stated not only in solution but in solvent‐free systems as well. For this reason, none of classic non‐covalent interactions can be exploited to control the state of fullerene in solid composites.
The Journal of Chemical Physics, 2008
On the basis of a gaussian quasi-chemical model of hydration, a model of non van der Waals character, we explore the role of attractive methane-water interactions in the hydration of methane and in the potential of mean force between two methane molecules in water. We find that the hydration of methane is dominated by packing and a mean-field energetic contribution. Contributions beyond the mean-field term are unimportant in the hydration phenomena for a hydrophobic solute such as methane. Attractive solute-water interactions make a net repulsive contribution to these pair potentials of mean force. With no conditioning, the observed distributions of binding energies are super-gaussian and can be effectively modeled by a Gumbel (extreme value) distribution. This further supports the view that the characteristic form of the unconditioned distribution in the high-ε tail is due to energetic interactions with a small number of molecules. Generalized extreme value distributions also effectively model the results with minimal conditioning, but in those cases the distributions are sufficiently narrow that details of their shape aren't significant.
Chemistry - A European Journal, 2012
FULL PAPER orientation of the H 2 O molecule inside the fullerene C 60 cage. The observation [27] is in agreement with the report of Shameema et al. [30] who showed, with RHF/6-31G geometry, that the up-shift in the OÀH stretching frequency is a result of an increase in the excitation energy (DE) of the OÀH bond, where DE = E s(OÀH) ÀE s*(OÀH) = 1124 kcal mol À1 at RMP2/6-31G//RHF/6-31G. The above results [27, 30] are further in agreement with a recent MD and ab initio MD (AIMD) oriental relaxation study, which advocates the presence of weak interactions between the entrapped H 2 O molecule and the interior of the C 60 cage. [25] According to Bucher, the H 2 O molecule is capable of interacting with the outside environment as well, [25] although the nuclear spin relaxation study indicates that the endo-H 2 O is sufficiently electrically isolated from the surrounding solvent that its motion is not detectably affected by interaction of the electric dipole moment with a polar medium. [26] The above reports [27, 30] demonstrate a significant decrease in the molecular dipole moment (m) of H 2 O upon encapsulation, and yet the MX06-2X/6-311GA C H T U N G T R E N N U N G (2d,p) calculations of Kurotobi and Murata [18] surprisingly predicted a marginal increase in the value of m (2.02 D for isolated H 2 O and 2.03 D for H 2 O@C 60). This has led them to conclude that the single H 2 O molecule inside the C 60 cage will completely be localized at the center of the C 60 cage. This study revisits to explore the nature of interaction between an encapsulated H 2 O and the interior of the C 60 cage. Towards this aim, we have used density functional theory (DFT) electronic structure calculations to investigate both the qualitative and quantitative aspects of the nature of: 1) the intermolecular potential energy surface, 2) the dipole moment function within the adiabatic approximation, and 3) the charge redistribution both in H 2 O and C 60 upon encapsulation. Particular emphasis has been placed on exploring possible factors that lead to a significant decrease in the value of m upon H 2 O confinement, and the shifts in the vibrational frequency of the OÀH stretching modes as predicted by others. [27, 30] In particular, we address whether encapsulation leads to any significant charge transfer between H 2 O and C 60 , a well-known effect in endohedral fullerene chemistry, in which the C 60 cage effectively accommodates excess charges from an encaged species [12] (rather than having a high hydrophobic interior as previously suggested) [18, 21] regardless of whether the dopant is metallic or non-metallic, charged or neutral. [31-35] We investigate the nature of the electrostatic potential in the radial direction, as this is known to control the bonding in these systems. [32, 33, 36] Particular use is made of several IUPAC recommendations [37, 38] for characterizing noncovalent interactions. Applications of the quantum theory of atoms-in-molecules (QTAIM), [6] a theory that defines atoms and their interactions (bonds) in a molecule in terms of the electron charge density, [5, 6, 38-46] as well as of natural population and bond orbital analyses [2] are used to conclude the bonding interactions in the H 2 O@C 60 system. Computational Methods Computational details are given in the Supporting Information. Briefly, DFT calculations were conducted by using GAUSSIAN 03/09. [47, 48] For reasons of chemical accuracy, [49] and unless and otherwise stated, the present calculation makes use of the one-parameter exchange-correlation functional of Perdew-Burke-Ernzerhof [50] (PBE1PBE, in short PBE0) level together with a triple-x valence quality, 6-311
Electronic interactions in fullerene molecules
1993
We study the Coulomb interactions in fullerene molecules within a continuum formalism. The model gives rise to a renormalizable field theory, which has many similarities to standard quantum electrodynamics. The effective electric charge at low energies is reduced by screening processes. The associated renormalization of the one electron Green's function leads to the vanishing of the quasiparticle pole. It implies the dissappearance of coherent one particle excitations, in close analogy to the one dimensional Luttinger liquid. The relevance of these results for C 60 and related molecules is discussed. 75.10.Jm, 75.10.Lp, 75.30.Ds.
Chemical Physics, 2011
We study the structure and orientation of water molecules at model hydrophobic surfaces by means of molecular dynamics. We focus here on the role of geometry in water hydration by comparing the situation for a planar graphene sheet with convex surfaces with different curvature: the exterior surfaces of carbon nanotubes and fullerenes of different radii. In all cases, we find the first water hydration layer to be more structured than the bulk. Additionally, the first water layers are found to be well oriented with respect to the surface normal in a way consistent with a local Ice Ih-like structuring, but differently form the water-air interface (along the opposite direction with respect to ice Ih basal plane). We also show that as the curvature of the surface gets more pronounced, the water molecules get less structured and oriented. This monotonic loss of local structure for proximal water represents a smooth tendency whenever we deal with an extended surface. However, when the surface becomes partially or completely non-extended (within the sub-nanometric regime), the surface water layer becomes to quickly lose structuring and orientation.