Excess electron is trapped in a large single molecular cage C60F60.
ABSTRACT A new kind of solvated electron systems, sphere-shaped e(-)@C60F60 (I(h)) and capsule-shaped e(-)@C60F60 (D6h), in contrast to the endohedral complex M@C60, is represented at the B3LYP/6-31G(d) + dBF (diffusive basis functions) density functional theory. It is proven, by examining the singly occupied molecular orbital (SOMO) and the spin density map of e(-)@C60F60, that the excess electron is indeed encapsulated inside the C60F60 cage. The shape of the electron cloud in SOMO matches with the shape of C60F60 cage. These cage-like single molecular solvated electrons have considerably large vertical electron detachment energies VDE of 4.95 (I(h)) and 4.67 eV (D6h) at B3LYP/6-31+G(3df) + dBF level compared to the VDE of 3.2 eV for an electron in bulk water (Coe et al., Int Rev Phys Chem 2001, 20, 33) and that of 3.66 eV for e(-)@C20F20 (Irikura, J Phys Chem A 2008, 112, 983), which shows their higher stability. The VDE of the sphere-shaped e(-)@C60F60 (I(h)) is greater than that of the capsule-shaped e(-)@C60F60 (D6h), indicating that the excess electron prefers to reside in the cage with the higher symmetry to form the more stable solvated electron. It is also noticed that the cage size [7.994 (I(h)), 5.714 and 9.978 A (D6h) in diameter] is much larger than that (2.826 A) of (H2O)20- dodecahedral cluster (Khan, Chem Phys Lett 2005, 401, 85).
- SourceAvailable from: Yin-Feng Wang[Show abstract] [Hide abstract]
ABSTRACT: For unusual e(2)@C(60)F(60)(I(h), D(6h), and D(5d)) cage structures with two excess electrons, it is reported that not only the lone pair in singlet state but also two single excess electrons in triplet state can be encapsulated inside the C(60)F(60) cages to form single molecular solvated dielectrons. The interesting relationship between the shape of the cage and the spin state of the system has revealed that ground states are singlet state for spherical shaped e(2)@C(60)F(60)(I(h)) and triplet states for short capsular shaped e(2)@C(60)F(60)(D(6h)) and long capsular shaped e(2)@C(60)F(60)(D(5d)), which shows a spin evolution from the singlet to triplet state with the deformation of the cage from spherical to capsular shape. For these excess electron systems, the three ground state structures have large vertical electron detachment energies (VDEs (I) of 1.720-2.283 eV and VDEs (II) of 3.959-5.288 eV), which shows their stabilities and suggests that the large C(60)F(60) cage is the efficient container of excess electrons.Journal of Computational Chemistry 04/2011; 32(9):2012-21. · 3.84 Impact Factor
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ABSTRACT: A new type of molecular quantum-dot cellular automata (MQCA) candidates is suggested using the double-cage fluorinated fullerene molecules, e(-)@C(20)F(18)(XH)(2)C(20)F(18) (X = N, B), which have bistable charge configurations that could be used to encode binary information. The electron switch between the two cages leads to the QCA function.Physical Chemistry Chemical Physics 08/2011; 13(36):16134-7. · 4.20 Impact Factor
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ABSTRACT: A series of spiral donor-π-acceptor frameworks (i.e. 2-2, 3-3, 4-4, and 5-5) based on 4-nitrophenyldiphenylamine with π-conjugated linear acenes (naphthalenes, anthracenes, tetracenes, and pentacenes) serving as the electron donor and nitro (NO2 ) groups serving as the electron acceptor were designed to investigate the relationships between the nonlinear optical (NLO) responses and the spirality in the frameworks. A parameter denoted as D was defined to describe the extent of the spiral framework. The D value reached its maximum if the number of NO2 groups was equal to the number of fused benzene rings contained in the linear acene. A longer 4-nitrophenyldiphenylamine chain led to a larger D value and, further, to a larger first hyperpolarizability. Different from traditional NLO materials with charge transfer occurring in the one-dimensional direction, charge transfer in 2-2, 3-3, 4-4, and 5-5 occur in three-dimensional directions due to the attractive spiral frameworks, and this is of great importance in the design of NLO materials. The origin of such an enhancement in the NLO properties of these spiral frameworks was explained with the aid of molecular orbital analysis.ChemPhysChem 02/2014; · 3.35 Impact Factor
Excess Electron is Trapped in a Large Single
Molecular Cage C60F60
YIN-FENG WANG,1ZHI-RU LI,1DI WU,1CHIA-CHUNG SUN,1FENG-LONG GU2
1State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical
Chemistry Jilin University, Changchun 130023, China
2Faculty of Engineering Sciences, Department of Molecular and Material Sciences,
Kyushu University, Fukuoka 816-8580, Japan
Received 6 February 2009; Accepted 24 March 2009
Published online 6 May 2009 in Wiley InterScience (www.interscience.wiley.com).
Abstract: A new kind of solvated electron systems, sphere-shaped e2@C60F60(Ih) and capsule-shaped e2@C60F60
(D6h), in contrast to the endohedral complex M@C60, is represented at the B3LYP/6-31G(d) 1 dBF (diffusive basis
functions) density functional theory. It is proven, by examining the singly occupied molecular orbital (SOMO) and the
spin density map of e2@C60F60, that the excess electron is indeed encapsulated inside the C60F60cage. The shape of
the electron cloud in SOMO matches with the shape of C60F60cage. These cage-like single molecular solvated elec-
trons have considerably large vertical electron detachment energies VDE of 4.95 (Ih) and 4.67 eV (D6h) at B3LYP/6-
311G(3df) 1 dBF level compared to the VDE of 3.2 eV for an electron in bulk water (Coe et al., Int Rev Phys Chem
2001, 20, 33) and that of 3.66 eV for e2@C20F20(Irikura, J Phys Chem A 2008, 112, 983), which shows their higher
stability. The VDE of the sphere-shaped e2@C60F60(Ih) is greater than that of the capsule-shaped e2@C60F60(D6h),
indicating that the excess electron prefers to reside in the cage with the higher symmetry to form the more stable sol-
vated electron. It is also noticed that the cage size [7.994 (Ih), 5.714 and 9.978 A˚(D6h) in diameter] is much larger
than that (2.826 A˚) of (H2O)20
2dodecahedral cluster (Khan, Chem Phys Lett 2005, 401, 85).
q 2009 Wiley Periodicals, Inc.J Comput Chem 31: 195–203, 2010
Key words: excess electron; cage-like single molecular solvated electron; encapsulated electron; vertical electron
detachment energy; fluorinated fullerene
An excess electron can be trapped in a small cavity (cage),
formed by some surrounding polar solvent molecules in liquids
and molecular clusters, to form solvated electrons,1–11and if it is
trapped at anion vacancy in solid salt, an electride is formed.12–14
The investigation of the solvated electron plays a prominent role
in physics, chemistry, and biochemistry.15Stabilization of numer-
ous bound electrons could provide new approaches to preparing
conductive materials with unusual optical16(a)or magnetic prop-
erties.13Therefore, the structure and stabilization for the excess
electron is an important study field.6–11,13,14
For the solvated electron systems, the debate3(a),4(a)continues
regarding how the excess electron is bounded in (H2O)n
an interior or surface electronic state. Recently, Jordan et al.4(a)
has identified a third binding motif, namely, network permeating
state. Neumark and his coworkers’ results3(b)imply that the
excess electron in water cluster anions, with higher vertical
binding energies, is internally solvated. In addition, the ammoni-
ated electron is regarded as a solvent stabilized multimer radical
anion.10For small cluster anions, different kinds of solvated
electron systems, in which the excess electron is trapped in a
small cavity formed by surrounding polar solvent molecules,
have been included in a review article.5The single molecular
calixcyclohexanol with a trapped electron was reported.11
For the other kind of excess electron systems in solids, i.e.,
electrides,12–14there are many electrons (as especial anions)
trapped in a many-cage system. For example, in a single crystal-
line electride of [Ca24Al28O64]41(e2)4,13,14each cage has 12
neighboring cages, the concentration fraction of anionic electron
is 1/3 per cage and the electron mostly has other electrons in a
Notice that, in the cage-like solvated-electron systems, the
dipoles of the polar molecules are directed toward the internal
excess electron in such an orientation that would be quite ener-
getically unfavorable if the excess electron were not present.5
Contract/grant sponsor: National Natural Science Foundation of China;
contract/grant numbers: 20773046, 20573043
Correspondence to: Z.-R. Li; e-mail: email@example.com; G.-L. Gu; e-mail: gu@
q 2009 Wiley Periodicals, Inc.
This kind of cage with such orientation is formed by weak
hydrogen bonds of several polar solvent molecules4(b),10(c)and
the interaction between excess electron and the surrounding
polar molecules. It is wondering, however, whether or not an
excess electron can be encapsulated inside the cage of a covalent
molecule to form a single molecular solvated electron system?
This is an interesting and challenging question.
The related researches on the endohedral complexes are
reported.17,18Cioslowski et al.17(a,b),18(a)has carried out pioneer-
ing theoretical research regarding species trapped inside the C60
cage to generate endohedral complexes and suggested a new
form of endohedral chemistry.18(a)The C60cage can encapsulate
single atom (such as Ne, K, Li, and O),17(b–d)small molecule
(such as N2, H2, HF, LiF, LiCl, NaF, and C4H4),18(b–d)cation
(such as Na1, Mg21, and Al31),17(b)and anion (such as F2)17(b)
to generate endohedral complexes. It is noticed that the anion
can be encapsulated inside the C60cage.17(b)Thus, can an excess
electron, the especial anion,13be encapsulated inside the C60
cage? Unfortunately, the C60cage does not have sufficient inte-
rior attractive potential to encapsulate an excess electron to form
solvated electron with interior state but instead it forms a usual
for a single molecular cage with sufficient potential to encapsu-
late an excess electron. In 2005, Schleyer and Schaefer III
groups reported that ‘‘extra’’ electron is delocalized in the
multiatom SOMOs of anionic c-CnF2n
and their coworker reported21(a)that an electron can be trapped
in single molecular C20F20 cage to form solvated electron
e2@C20F20. Recently, Irikura21(b)designed some small fluori-
nated cages as electron boxes to form small cage-like single
molecular solvated electron systems.
In 1991, Halloway et al.22firstly suggested the existence of
C60F60. Scuseria et al.23confirmed this prediction by theoretical
calculations (the same and next year) and pointed out that the
synthesis difficulty of C60F60 comes from the thermodynamic
forces against it.24Recently, Wu and coworkers25have theoreti-
cally studied the structure and stability of a set of large neutral
C60F60 cages. Two structures of those cages with Ih and D6h
symmetry are the ones that we just seek for. Each cage has 60
exo polar C? ?F bonds and the dipoles of the C? ?F bonds are
directed to the center of the cage. Therefore, the C60F60cage
should have sufficient attractive potential to trap an excess elec-
tron to form large single molecular solvated electrons.
In this article, our investigation aims at obtaining the struc-
tures and stabilities of the single molecular solvated electrons
e2@C60F60, showing an excess electron encapsulated inside sin-
gle molecular cage, exhibiting the characteristics of single
molecular cages encapsulating the excess electron, revealing the
large vertical electron detachment energies (VDEs) of them, and
enhancing the knowledge on excess electron and endohedral
2anion with surface state.19Therefore, it is desired to look
2(n 5 3–5).20(a)Wu, Jiao,
For the geometry optimization, Becke-3-three-parameter density
functional theory (DFT) and Lee-Yang-Parr correlation func-
tional (B3LYP)26(a–d)level with the 6-31G(d) basis set has been
successfully used for the neutral C60F60 cages25and C20F20–
cage21by Wu and coworkers.
Jordan and Luken,27(a)and Griffing et al.27(b)suggested that
the diffusive basis functions should be used in the calculations
of systems with excess electron. Simons and coworkers28(b)have
used the diffusive basis functions (dBF) to describe the diffuse
characteristic of the excess electron.
In the present work, for the description of diffuse characteris-
tic of the excess electron located at the center of the C60F60
cage, the extra diffuse basis functions (dBF) are supplemented
in 6-31G(d) basis set. According to reference 28, for each orbital
symmetry, we started to build up the exponents of the extra dif-
fuse basis functions from the lowest exponent of the same sym-
metry included in the 6-31G(d) basis set for carbon (0.1687144
for s and p). The dBF diffuse basis set consisted of the follow-
ing four s and p diffuse orbitals (uncontracted Gaussian
s(0.01687144), s(0.001687144), s(0.0001687144), p(0.1687144),
p(0.01687144), p(0.001687144), and p(0.0001687144). Notice
that, the additional diffuse basis functions (dBF) are located at
the center of the C60F60cage (i.e., in the symmetry center noted
by red dot in Fig. 1).
The equilibrium geometries and the natural bond orbital
(NBO) analysis29of the two structures of e2@C60F60 were
obtained at B3LYP/6-31G(d) 1 dBF level.
Many literatures about the controversy whether or not the den-
sity functional theory (DFT) can yield reasonably good adiabatic
electron affinities (EAs)6,30or VDEs.8,20,21,31The DFT exhibits
significant overbinding for water cluster anions. Notably, this
overbinding can easily be obscured by the use of an insufficient
diffuse basis set.8(d)For the VDEs of large water clusters anions,
the B3LYP result calculated by Khan8(a–c)is basically close to
the experimental value8(a)[overestimate the VDE by 0.13 eV for
BLYP functionals are the excellent choices for EA predictions of
anions. On the basis of our analysis for the percentages of the cal-
culated value closest to the experimental value, we confirm this
conclusion. The DFT is suitable for the fluorinated cage
anions.20,21For the single molecular cage-like solvated electron
system, Wu, Jiao, and their coworker21(a)studied the electron
affinity of C20F20at B3LYP/6-3111G(d). Irikura21(b)reported the
EAs of some fluorinated compounds at B3LYP/6-311G(d) level.
In our previous work,32the BHandHLYP26(e)method is good for
the calculation of the electric properties.
For the two open shell molecular anions e2@C60F60,
B3LYP, BLYP, and BHandHLYP methods were used to calcu-
late the VDEs. The values of hS2i are 0.75. The 6-31G(d) 1
dBF, 6-311G(d) 1 dBF, 6-311G(2d) 1 dBF, and 6-311G(3df)
1 dBF basis sets were used.
According to reference 30, the vertical electron detachment
energy (VDE) was determined as:
2]. Schaefer’s article30points out that the B3LYP and
VDE ¼ E½C60F60? ? E½e?@C60F60?
All the calculations were performed with the GAUSSIAN 03
program package.33(a)The molecular orbitals were plotted with
GaussView program,33(b)the molecular structures and the spin
density maps were generated with the MOLDEN program.33(c)
196Wang et al. • Vol. 31, No. 1 • Journal of Computational Chemistry
Journal of Computational ChemistryDOI 10.1002/jcc
Figure 1. Optimized geometries at B3LYP/6-31G(d) 1 dBF level.
Figure 2. SOMO and LUMO for the two e2@C60F60at the isovalue of 0.023 au. Orbital energies (in
eV) in parentheses.
197Excess Electron in Single Molecular Cage C60F60
Journal of Computational ChemistryDOI 10.1002/jcc
Results and Discussions
The optimized geometric structures of the e2@C60F60 with Ih
and D6hsymmetry are shown in Figure 1. The e2@C60F60with
Ihsymmetry has a sphere-shaped structure, whereas the one with
D6hsymmetry has a capsule-shaped structure.
The C60F60cage has 60 exo polar C? ?F bonds. The dipoles
of those 60 C? ?F bonds are directed toward the center of the
cage to form an interior attractive potential. This interior attrac-
tive potential provides possibility to encapsulate the excess elec-
tron inside the cage.
The size of the C60F60cage in e2@C60F60has very small
changes under the effect of the excess electron. Comparing
e2@C60F60 to the corresponding neutral C60F60 cage,25as
shown in Table 1, two very small changes are found: (1) The
lengths of C? ?C bond in e2@C60F60 are slightly shorter
(?0.006 A˚) than the corresponding lengths in neutral C60F60; (2)
The lengths of C? ?F bond in e2@C60F60 are slightly longer
(?0.007 A˚) than the corresponding lengths in neutral C60F60.
Because the electronegativity of C atom is smaller than that of F
atom, the charge of C atom is positive and that of F atom is
negative. The small shortening of C? ?C bond enhances the posi-
tive electric field in the center of the cage, and the slight elonga-
tion of C? ?F bond enhances its dipole moment. This indicates
the small geometric change of each cage slightly increases the
attractive potential of the cage.
It’s noticed that the C60F60 cage without the encapsulated
electron is also stable,25but the other kind of cages formed by
polar molecules (for molecular cluster anions) are not so stable
if the excess electron were not present.5This can be well under-
stood that the C60F60cage in e2@C60F60is combined by cova-
lent bonding, while the cage in many reported solvated electron
systems is formed by hydrogen bonding among many polar mol-
ecules4(b),10(c)and the interaction between excess electron and
the surrounding polar molecules.
In addition, the two structures of e2@C60F60 have large
sizes. The comparison of the diameter for different solvated-
electron structures are tabulated in Table 2. From Table 2, the
diameter of the sphere-shaped e2@C60F60(Ih) is 7.994 A˚, and
the diameters of the capsule-shaped e2@C60F60 (D6h) in the
middle and between the ends are 5.714 and 9.978 A˚, respec-
tively. Obviously, these diameters are larger than that of 4.326
A˚21(b)for e2@C20F20and much larger than that of 2.826 A˚8(a)
2dodecahedral cluster with Ihsymmetry.
Table 2. The Comparison Between e2@C60F60and the Relative Cage-Like Solvated Electrons Systems.
Point groupDiameter (A˚) VDE/(eV)Reference Expt.Reference
Table 1. The Comparison of the Structural Parameters (in A˚) Between
C? ?C bond
C? ?F bond
198Wang et al. • Vol. 31, No. 1 • Journal of Computational Chemistry
Journal of Computational ChemistryDOI 10.1002/jcc
Location of the Excess Electron Inside the C60F60Cage
The solvated electrons with interior state have special structures
that an excess electron is surrounded by several polar molecules
to form an electron-encapsulating cage (cavity).5The excess
electron occupies thehighest
(HOMO). The excess electron cloud is mostly located within the
cage formed by the surrounding polar molecules. For example,
the singly occupied molecular orbital (SOMO) for (H2O)4
ter8(e)and the dodecahedral (H2O)20
s-like electron cloud is located within the cage formed by the
surrounding water molecules, suggesting the presence of excess
electron in the molecular cluster cage. It is wondering whether
or not the excess electron is encapsulated inside the C60F60cage
or somewhere else?
To identify the location of the excess electron, the SOMO
and LUMO of each e2@C60F60 are studied and presented in
For e2@C60F60, as given in Figure 2, the green sphere (or
ellipsoid) in SOMO shows the s-like electron cloud with the
character of the ground-state excess electron is located within
the C60F60cage. It implies the presence of excess electron inside
the single molecular cage. Likewise, the p-like electron cloud
with the character of the excited-state excess electron repre-
2cluster8(a)shows that the
sented by a red and green sphere in LUMO is located in the
C60F60 cage also suggesting the presence of excess electron
inside the molecular cage.
An excess electron density is companied with its spin den-
sity. To further understand the location of the excess electron
inside the cage, the spin density map of the e2@C60F60is given
in Figure 3. The blue contour is the excess electron spin density
distribution, which indicates that most of the spin density in
e2@C60F60is located within the cage. Those spin density results
are well in accordance with that of excess electron density,
which also indicates that the location of the excess electron is
inside the C60F60cage.
The NBO and Mulliken charges of the two e2@C60F60struc-
tures calculated at B3LYP/6-31G(d) 1 dBF level are listed in
Table 3. From Table 3, large negative charges in the centers of
the C60F60cages representing the excess electronic charges are
exhibited, which gives a support for the location of the excess
electron inside the C60F60cage.
It can be concluded that the excess electron is located inside
the C60F60 cage to form cage-like single molecular solvated
From SOMOs in Figure 2, it is exhibited that the shape of
the electron cloud matches with the shape of C60F60cage. In the
sphere-shaped cage, the shape of the electron cloud is spherical,
while the shape of the electron cloud is ellipsoidal in the cap-
Comparing the energies of the SOMO at B3LYP/6-31G(d) 1
dBF level, 22.966 eV of e2@C60F60(Ih) with the higher sym-
metry is obviously lower than 22.467 eV of e2@C60F60(D6h)
with the lower symmetry, which shows that the excess electron
prefers to reside in the cage with the higher symmetry to form
the more stable cage-like single molecular solvated electron.
Large Vertical Electron Detachment Energy
The calculated vertical electron detachment energies (VDE) of
the two structures of e2@C60F60are listed in Table 4.
From Table 4, using the same basis set, the results show that
the values of VDE at BHandHLYP and B3LYP level are close
to each other and larger than that at BLYP level. Using 6-
311G(3df) 1 dBF basis set, the VDE of 5.09 eV at BHandH-
LYP level is close to 4.95 eV at B3LYP level for the sphere-
shaped e2@C60F60 (Ih), in which the difference between
BHandHLYP and B3LYP level is about 3%. For the capsule-
Table 3. The Charges for the Two e2@C60F60at
B3LYP/6-31G(d) 1 BF level.
Table 4. The Vertical Electron Detachment Energies (in eV) of the Two e2@C60F60.
6-31G(d) 1 dBFb
6-311G(d) 1 dBFb
6-311G(2d) 1 dBFb
6-311G(3df) 1 dBFb
4.45 4.95 (5.24)4.67 (4.43)
The HF results in parentheses.
aThe number of basis functions.
bThe diffuse basis function, refer text.
199Excess Electron in Single Molecular Cage C60F60
Journal of Computational ChemistryDOI 10.1002/jcc
shaped e2@C60F60(D6h), the VDE of 4.67 eV at BHandHLYP
level is very close to 4.66 eV at B3LYP level using 6-
311G(3df) 1 dBF basis set. The VDE values at BHandHLYP
and B3LYP level are about 0.2–0.4 eV larger than that at BLYP
Comparing the difference of VDE values between HF and
B3LYP method, the value at HF level is about 6% larger and
about 5% smaller than that at B3LYP level for Ihand D6hstruc-
ture, respectively. These show that the electron correlation effect
relates to the molecular shape.
Considering the basis set effects, the number of basis func-
tions increases by 1440 from 6-311G(2d) 1 dBF (2776) to
6-311G(3df) 1 dBF (4216), the VDE value only changes by
1% for each of the e2@C60F60, which shows that the
6-311G(3df) 1 dBF is suitable for the calculation of VDE.
We have used the B3LYP method with the 6-311G(3df) 1
dBF basis set, which is feasible with the available computer
resources, to determine the VDEs of the two e2@C60F60struc-
tures. The resulting VDEs for e2@C60F60(Ih) and e2@C60F60
(D6h) are 4.95 and 4.67 eV, respectively.
The VDEs of e2@C60F60are considerably large. For the pur-
pose of comparison, the VDEs of the two e2@C60F60structures
and that of the other cage-like solvated electrons are listed in
Table 2. From Table 2, Coe has suggested7a value of 3.2 eV,
which is appropriate to an electron in bulk water. In addition,
Kammrath et al.9(a)conducted a systematic study of the photo-
electron spectra of large water cluster anions but did not observe
the isomers with VDEs higher than 3.2 eV. For the single mo-
lecular cage-like solvated electron system, Wu, Jiao, and their
coworker21(a)recently reported an electron affinity of 3.66 eV at
B3LYP/6-3111G(d) and Irikura21(b)reported the value of about
3.4 eV at B3LYP/6-311G(d) level for C20F20. Obviously, the
VDE values for the large e2@C60F60 (4.95 and 4.67 eV) are
the largest, which indicates the high stability of the e2@C60F60.
From Table 4, the VDE value of 4.95 eV for e2@C60F60(Ih)
with the higher symmetry is obviously larger than that of 4.67
eV for e2@C60F60(D6h) with the lower symmetry, which shows
that the excess electron prefers to reside in the cage with the
higher symmetry to form the more stable cage-like single molec-
ular solvated electron with the larger VDE.
The VDE can provide an estimation of the average diffuse
electron radius hri. Simons5has suggested the formula:
hri ¼ 3? h=½2ð2meVDEÞ1=2?
As given in Table 5, the hri values are 1.397 and 1.528 A˚
for the e2@C60F60(Ih) and e2@C60F60(D6h), respectively.
The electronic spatial extent hR2i characterizes the electron
density volume around the molecule.34As a rough estimation,
the shape of electronic distribution is as a spherical shape. Thus,
the electron cloud radius re5 (3hR2i/4p)1/3. The electronic spa-
tial extent of an excess electron DhR2i is written as:
DhR2i ¼ hR2iðe?@C60F60Þ ? hR2iðC60F60Þ
As given in Table 5, the electron cloud radius refor the two
e2@C60F60cages are 1.544 (Ih) and 1.576 A˚(D6h), which are
close to the corresponding average diffuse electron radii hri.
From Table 5, not only the average diffuse electron radius
hri but also the electron cloud radius reof the excess electron in
each e2@C60F60structure is smaller than 1.6 A˚, whereas the
radii of the C60F60cages Rcare about 3–5 A˚. Obviously, the ra-
dius of the excess electron is much shorter than the radius of the
C60F60cage Rc. Those results give another support for the loca-
tion of the excess electron inside the C60F60cage to form stable
cage-like single molecular solvated electron with interior state,
although the debate continues regarding how the excess electron
is bound in water cluster anions, as an interior, bulk-like, or
surface electronic state.3(a),4(a)
Characteristics of the Cage Encapsulating the Electron
The cage-like e2@C60F60are analogues to, but different from
the conventional the endohedral complexes M@C60.17,18For
e2@C60F60, the center of the cage is occupied by an excess
electron, while M@C60, its center is an atom or ion. For the sat-
urated C60F60cage, the 60 exo polar C? ?F bonds directing to-
ward the center of the cage form an interior attractive potential,
whereas the C60is an unsaturated cage with the rich p-electrons
and it does not have polar bonds to form the attractive potential.
What kind of single molecular cages can encapsulate the
excess electron? (1) The cage has polar bonds and the dipoles of
those polar bonds are directed to the center of the cage to gener-
ate sufficiently interior attractive potential. (2) The cage is a sat-
urated molecule and can provide an internal s-type LUMO for
the occupancy of one additional electron (refer Fig. 4). When
such cage encapsulates an excess electron and forms the cage-
like single molecular solvated electron system, the s-type
LUMO of the cage hosts the electron and become s-type SOMO
of the solvated electron system (refer Fig. 2).
Although the synthesized C60F48cage35has sufficiently inte-
rior attractive potential, this unsaturated cage with cage-surface
p-type LUMO can not provide an internal s-type LUMO for
hosting one additional electron. Owing to the cage-surface p-
type LUMO of C60without sufficient interior attractive potential,
C60cage does not encapsulate an excess electron to form cage-
like single molecular solvated electron system but instead it
forms usual C60
with an interior repulsive potential, it does not encapsulate an
2anion with surface state.19For the C60H60cage
Table 5. The Average Diffuse Electron Radius hri, the Electron Cloud
Radius re, and the Radius of the Cage Rc.
hri 5 3h ?/[2(2meVDE)1/2] see Reference 5.
aDhR2i 5 hR2i (e2@C60F60)2hR2i (C60F60).
200Wang et al. • Vol. 31, No. 1 • Journal of Computational Chemistry
Journal of Computational ChemistryDOI 10.1002/jcc
Figure 3. The spin density maps of the two e2@C60F60at the isovalue of 0.0002 au.
Figure 4. LUMO and LUMO 1 1 for the two C60F60at B3LYP/6-31G(d) 1 dBF level (isovalue of
0.023 au). Orbital energies (in eV) in parentheses.
This article gives contributions in two important aspects. (1) In
solvated electron, the large cage-like single molecular solvated
electron with interior state is given although the debate contin-
ues regarding how the excess electron is bound in water cluster
anions, as an interior or surface electronic state.3(a),4(a)(2) In
endohedral complex, new endohedral complexes, the electron
endohedral fluorinated fullerene complex e2@C60F60 is repre-
Those cage-like single molecular solvated electron system
exhibit six characteristics. (1) The excess electron is encapsu-
lated inside the single molecular cage to form new cage-like sin-
gle molecular solvated electron system. (2) Those single molecu-
lar solvated electrons have considerably large vertical electron
detachment energies [VDE: 4.95 (Ih) and 4.67 eV (D6h)], which
shows large stabilities of e2@C60F60. The large stability also
relates to (3) those used C60F60 cages are covalent molecules
with large stabilities and sufficient interior attractive potentials.
(4) Because of the covalent C60F60cage with certain rigidity, its
change is very small under the effect of the excess electron,
while the polar molecular cluster cage in the cluster anion is
unstable if the excess electron were not present.5(5) The excess
electron prefers to reside in the cage with the higher symmetry
to form the more stable cage-like single molecular solvated elec-
tron because the VDE of the sphere-shaped e2@C60F60(Ih) is
greater than that of the capsule-shaped e2@C60F60 (D6h). (6)
Those used single molecular cages have large sizes [7.994 (Ih),
5.714 and 9.978 A˚(D6h) in diameter], which are larger than that
of 4.326 A˚21(b)for e2@C20F20 and much larger than that of
2.826 A˚8(a)for (H2O)20
These cage-like single molecular solvated electron systems
may provide great convenience to the preparation, analytical
measure and application of the stable solvated electrons. This
work provides new knowledge on the excess electron.
2dodecahedral cluster with Ihsymmetry.
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