The enthalpy of formation of fullerene fluoride C60F 18 and the C-F bond energy

Article abstract of DOI:10.1134/S0036024407100020

The enthalpy of combustion of crystalline fullerene fluoride C ₆₀F₁₈ was determined in an isoperibolic calorimeter with a rotating platinized bomb, and the enthalpy of formation of the compound was calculated. The enthalpy of sublimation of C₆₀F₁₈ measured earlier was used to calculate the enthalpy of formation of fullerene fluoride in the gas phase and the mean enthalpy of dissociation of C-F bonds in this compound.

Full text of DOI:10.1134/S0036024407100020

ISSN 0036-0244, Russian Journal of Physical Chemistry A, 2007, Vol. 81, No. 10, pp. 1560–1564. © Pleiades Publishing, Ltd., 2007.
Original Russian Text © T.S. Papina, V.A. Luk’yanova, A.A. Goryunkov, I.N. Ioffe, I.V. Gol’dt, A.G. Buyanovskaya, N.M. Kabaeva, L.N. Sidorov, 2007, published in Zhurnal
Fizicheskoi Khimii, 2007, Vol. 81, No. 10, pp. 1753–1757.
CHEMICAL THERMODYNAMICS
AND THERMOCHEMISTRY
The Enthalpy of Formation of Fullerene Fluoride C F
60 18
and the C–F Bond Energy
a
a
a
a
a
T. S. Papina , V. A. Luk’yanova , A. A. Goryunkov , I. N. Ioffe , I. V. Gol’dt ,
b
b
a
A. G. Buyanovskaya , N. M. Kabaeva , and L. N. Sidorov
a
Faculty of Chemistry, Moscow State University, Leninskie gory, Moscow, 119992 Russia
Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
b
ul. Vavilova 28, Moscow, GSP-1, 117813 Russia
e-mail: papina@phys.chem.msu.ru
Received April 20, 2006
Abstract—The enthalpy of combustion of crystalline fullerene fluoride C F was determined in an isoperi-
6
0 18
bolic calorimeter with a rotating platinized bomb, and the enthalpy of formation of the compound was calcu-
lated. The enthalpy of sublimation of C F measured earlier was used to calculate the enthalpy of formation
6
0 18
of fullerene fluoride in the gas phase and the mean enthalpy of dissociation of C–F bonds in this compound.
DOI: 10.1134/S0036024407100020
INTRODUCTION
tion times of fluorinated fullerene ë derivatives [5].
60
The contents of ë , ë F , and C F were determined
60
60 18
60 36
Fluorinated fullerenes possess high oxidative and
fluorinating ability and therefore offer promise for the
synthesis of new materials with unusual properties [1].
In recent years, methods for synthesizing ë F ,
quantitatively using preliminarily determined calibra-
tion plots for the dependence of the analytic signal (area
under the chromatographic peak) on the concentrations
of these components. Calibration was performed using
solutions with known concentrations (1–100 µg/ml)
of C60 (Term USA, 99.98 wt %), C60F18 (more than
6
0 48
ë F , and ë F fluorinated fullerenes in amounts
6
0
36
60 18
sufficient for the determination of their thermochemical
properties have been developed. The enthalpies of for-
mation of fullerene fluorides ë F and ë60F36 were
9
6 wt %), and C F (more than 95 wt %). The content
60 36
6
0 48
of the C F CF impurity was estimated with the use of
6
0
17
3
determined in [2] and [3], respectively. The present
work continues these studies.
the calibration plot constructed for C F because of
6
0 18
similar structures and, therefore, extinction coeffi-
cients of these fluorinated fullerenes. For the other
compounds, calibration coefficients were found by
linear interpolation between the calibration coeffi-
cients of fullerene ë60 (30 π-bonds) and fluoride
ë F (21 π-bonds) depending on the number of dou-
EXPERIMENTAL
The synthesis and characteristics of samples. Two
fluorinated fullerene ë F samples (A and B) used in
6
0 18
6
0 18
this work for calorimetric measurements were synthe-
sized according to [4]. A finely ground mixture of
fullerene C60 and potassium hexafluoroplatinate(IV)
taken in a 1 : 8.5 molar ratio was heated at 465 ± 5°C
for 6 h in a dynamic vacuum (2 Pa). Fluorinated
fullerene C F formed in the reaction
ble bonds these compounds contained.
Chromatographic analysis performed this way
allowed the main impurities in samples A and B to be
determined. These were C F , C F CF , and unre-
60 36
60 17
3
acted fullerene ë . Small amounts of C (CF ) , lower
60
60
3 2
60 18
fluorofullerenes C F (n = 2, 4, 6, and 8), and oxyfluo-
6
0 n
ë + 4.5K PtF = ë F + 4.5Pt + 9äF.
6
0
2
6
60 18
ride C F O were also detected. The chromatographic
6
0 4
Fullerene fluoride C F with a small amount of impu- data on both samples are given in Table 1. These results
60 18
rities sublimed from the reaction zone and condensed were used to calculate the empirical formulas of the
on cold reactor walls. Fullerene fluoride samples A and samples, ë60
F
é
0.010 ± 0.005 (sample A) and
ë F é0.012 ± 0.003 (sample B).
60 16.5 ± 0.4
17.8 ± 0.8
B obtained this way were characterized by electron ion-
ization mass spectrometry and high-performance liquid
chromatography.
We also determined the elemental composition of
samplesA and B. Fluorine was determined according to
Qualitative and quantitative analyses of C F were Schenniger with detection by spectrophotometry. The
6
0 18
performed by high-performance liquid chromatogra- samples were burned on a platinum wire in a flask with
phy (a Cosmosil Buckyprep, Nacalai Tesque, Inc., 4.6 × oxygen. To improve burning and quantitatively trans-
2
50 mm column; eluent toluene, 2 ml/min, 290 nm). form fluorine into fluoride ions, the samples were
The components were identified from the known reten- burned together with a filter paper strip impregnated
1
560

THE ENTHALPY OF FORMATION OF FULLERENE FLUORIDE C F
0 18
1561
6
with potassium nitrate. The combustion products were Table 1. Composition of C F samples (wt %) according
6
0 18
to the high-performance liquid chromatography data (errors
absorbed with water. The absorption solution was ana-
lyzed by differential spectrophotometry on the basis of
the discoloration of the thorium complex with arsenazo
I under the action of fluoride ions [6]. Carbon was
determined on a Carlo Erba, model 1106, automated
CHN analyzer using special oxidation tube packing,
which could be used to analyze organofluorine com-
pounds [7].According to the data obtained, the contents
of F and C were 32.1 and 67.6 wt % in sample A and
are represented by root-mean-square deviations)
Component
Sample A
Sample B
C60
3.13 ± 0.17
9.40 ± 1.71
0.24 ± 0.14
0.65 ± 0.09
1.47 ± 0.41
0.75 ± 0.38
0.51 ± 0.16
0.58 ± 0.06
4.91 ± 0.26
78.37 ± 2.16
8.40 ± 0.16
12.47 ± 0.66
0.23 ± 0.01
1.12 ± 0.04
1.79 ± 0.34
0.96 ± 0.22
0.75 ± 0.03
1.72 ± 0.10
4.23 ± 0.24
68.33 ± 1.25
C F
0 36
6
C (CF )
3 2
6
0
C F
60
2
4
2
9.9 and 69.8 wt % in sample B, respectively. Measure-
ment errors were less than 0.3 wt % for fluorine and
.5 wt % for carbon. According to these data, the
n(F)/n(C ) ratio was 18.0 ± 0.3 for sample A and
C F
6
0
C F O
6
0
4
6
8
0
C F
6
0
6
0
C F
1
6.2 ± 0.3 for sample B. The results obtained were in
60
agreement with the high performance liquid chroma-
tography data to within measurement errors (Table 1).
C F CF
6
0
17
18
3
C F
6
0
The density of fullerene fluoride ë F , ρ =
6
0 18
Note: According to the chemical analysis data, n(F)/n(C ) = 18.0 ±
3
60
1
.97 g/cm , was estimated from the X-ray structure
0
.3 and 16.2 ± 0.3 for samples A and B, respectively.
data on a ë F single crystal [14], and its molecular
6
0 18
weight, M(ë F ) = 1062.6132, was calculated using
6
0 18
the relative atomic weights from [8].
theoretical and actual amounts of ëé in combustion
2
Apparatus and procedure. The energy of combus-
tion of ë F samples was determined using an isother-
products. Corrections for the energy of ëF hydrolysis
4
6
0 18
(
qCF4 ) formed as a side product of C F combustion
60 18
mic-shell calorimeter with a platinized bomb rotating
about two mutually perpendicular axes [9]. The inside
were calculated.
3
bomb volume was 120 cm . Temperature rise (~0.7 K)
The amount of hydrofluoric acid HF formed in the
bomb was found from the total content of acids (HF +
was measured by a copper resistance thermometer incor-
–5
porated into a bridge scheme of sensitivity 5 × 10 K.
HNO ) determined by the titration of the bomb solution
3
The energy equivalent of the calorimeter was deter- with a 0.08524 N solution of NaOH. The amount of
mined against standard benzoic acid (K-1 brand, Men- HNO was taken to be equal to the average value
3
deleev Research Institute of Metrology) whose com-
bustion energy was certified to be –26434.0 ± 2.2 J/g.
The energy equivalent of the calorimeter with an empty
bomb, W' = (95703 ± 22.0) J/Ω, was determined in a
series of 10 measurements.
obtained in calibration experiments. The difference
between the theoretical and actual amounts of HF was
also used to calculate the correction qCF4 . In all experi-
ments with the combustion of fullerene fluoride, traces
of carbon black in the crucible were observed. One
more correction was introduced for its burning to ëé2.
Fullerene fluoride ë F (~0.04 g) was pressed into
6
0 18
pieces and placed into a Terylene film ampule together
with a benzoic acid pellet (~0.44 g). To more com-
Experimental data. The energy of combustion of
pletely burn the substance studied in oxygen, a thin- fluorinated fullerene ë60F18 was determined from the
walled platinum crucible was used. Water (10 ml) was results of seven calorimetric experiments with two sam-
introduced into the bomb to dissolve HF and NO2 ples A and B. The data obtained are listed in Table 2.
vapors formed in the combustion of fullerene fluoride
and nitrogen present in oxygen as an impurity. The ini-
tial oxygen pressure and temperature in the bomb were
The specific energy of combustion was calculated
by the equation
4
.0 MPa and 298.18 ± 0.03 K, respectively. The ampule
with the substance was ignited by a platinum wire
0.1 mm in diameter) heated by current passage from a
∆ u° = (Qtot – qaux + q – qign + qCF4 – qst – qHNO3 )/m,
c C
Q was calculated as the product of the energy equiva-
tot
(
capacitor. The correction for the energy of ignition was lent of the calorimeter (taking into account the heat
calculated in each experiment, it was of 1.7–2.1 J.
capacities of combustion products) and the temperature
rise in the experiment. The standard specific heats of
combustion of auxiliary substances were –22927.9 ±
After calorimetric measurements, ëé was deter-
2
mined in gaseous combustion products according to
Rossini [10] to within ±0.0004 g; CO was determined
using indicator tubes (TU (specifications) 12.43.20-76).
Carbon monoxide was detected in none of the experi-
6
.3 J/g for Terylene film [11] and –26413.7 ± 2.2 J/g for
benzoic acid (calculated from the certified value given
above); these data were used to calculate q . The spe-
aux
–
6
cific energy of combustion of carbon black (–32763 ±
ments (analysis sensitivity 6 × 10 g CO). The amount
1
1 J/g) for calculating q was calculated from the stan-
C
of ëF formed as a side product in the combustion of
4
dard enthalpy of formation of ëé [12]. The q cor-
CF4
ë F was determined from the difference between the
2
6
0 18
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 81 No. 10 2007

1
562
PAPINA et al.
Table 2. Data of C F combustion experiments (298.15 K)
60 18
qCF4 , J
–∆ u°, J/g
c
m, g
Q , J
qaux, J
qC, J
qign, J
qst, J
tot
CO2
HF
CO2
HF
Sample A
1.7
0
0
0
.044680
.048947
.056027
12728.5
12929.4
12865.1
11622.7
11719.0
11483.4
0.7
0.3
0.6
0.0
1.3
0.0
1.0
1.5
2.1
36.0
36.4
36.2
23882
23946
23964
23904
23950
24001
1.7
1.7
Sample B
1.8
0
0
0
0
.039052
.041200
.042510
.044649
13227.6
13035.7
13113.0
12540.3
12231.2
11983.4
12030.7
11409.0
2.8
1.1
1.5
0.5
2.6
0.5
1.8
2.1
0.7
0.3
0.4
0.7
37.9
37.2
37.4
35.6
24590
24587
24566
24516
24542
24582
24533
24485
1.9
2.1
1.9
Note: m, g, is the sample weight; Qtot, J, is the total amount of heat released; qaux, J, is the correction for the energy of combustion of
auxiliary substances (Terylene film and benzoic acid); q , J, is the correction for the energy of combustion of carbon black; qign, J,
C
is the correction for the energy of ignition; qCF4 , J, is the correction for the energy of hydrolysis of CF (the amount of CF was
4
4
calculated by two methods, see text); q , J, is the correction for reduction to the standard state; and ∆ u°, J/g, is the specific energy
st
c
of combustion of the sample.
rection was calculated from the molar energy, ∆ U° = these values, we must introduce corrections for the
r
m
energies of combustion of impurities. However, the
energies of combustion were determined experimen-
tally only for C [18] and C F [3]. The energies of
combustion of the other impurities were obtained from
the enthalpies of the gas phase reactions
–
173.1 ± 1.3 kJ/mol, of the hypothetical reaction of
hydrolysis of ëF [13]. The correction for the reduction
to the standard state, q , was calculated as recom-
mended by Good and Scott [14] for organofluorine
compounds, using the enthalpy of vaporization of H é
and the enthalpy of solution of é in water from hand-
4
6
0
60 36
st
2
C F + C = 2C F , ∆H = –87.4 kJ,
(1)
60 36
60
60 18
1
2
book [15], the solubility constant and the energy of
C (CF ) = 1/3C F + 42/60C ,
6
0
3
2
60 18
60
solution of ëé in HF [16], and the enthalpy of dilution
2
(2)
of HF [17]. The correction for the energy of formation
∆H
2
= 114.1 kJ,
of a solution of nitric acid qHNO3 was taken to be equal
C F = 1/9C F + 8/9C , ∆H = –31.7 kJ, (3)
60
2
60 18
60
3
to the average value, 1.8 J, found in calibration experi-
ments. Lastly, qign is the correction for the energy of
ignition (see above).
C F = 2/9C F + 7/9C , ∆H = –40.7 kJ, (4)
6
0
4
60 18
60
4
C F = 1/3C F + 2/3C , ∆H = –42.2 kJ, (5)
60
6
60 18
60
5
C F = 4/9C F + 5/9C , ∆H = –48.6 kJ, (6)
The standard specific energy of combustion of sam-
60
8
60 18
60
6
ple A was found to be –23931 ± 107 or –23952 ±
C F CF + 17/180C = 10/9C F ,
6
0
17
3
60
60 18
1
20 J/g depending on the method used for calculating
(
(
7)
8)
qCF4 (from the shortage of ëé or HF). We used the
∆H = 71.3 kJ,
2
7
weighted mean value, ∆ u°(Ä) = –23940 ± 80 J/g. Sim-
c
C F O + CO = 2/9C F + 7/9C + CO ,
6
0
4
60 18
60
2
ilar calculations performed for sample B gave the
standard specific energy of combustion –24565 ± 54
or –24536 ± 63 J/g and the weighted mean value
∆cu°(B) = –24553 ± 41 J/g (Table 2). Errors were cal-
culated as the product of the standard deviation and the
Student test value corresponding to a 95% significance
level.
∆H = –185.6 kJ
8
calculated by the density functional theory method
using the PRIRODA program [19] with the
exchange-correlation PBE functional [20] and the
(
∆
11s6p2d)/[6s3p2d] triple-zeta basis set. First, the
H –∆H values were used to calculate the enthalpies
1
8
of formation in the gaseous state of all compounds on
the left-hand sides of Eqs. (2)–(8), which were impuri-
ties in the samples studied. To pass to the crystalline
DISCUSSION
The substantial difference exceeding 600 J/g state, their enthalpies of sublimation were estimated by
between the energies of combustion of samples A and comparing the known enthalpies of sublimation of C ,
6
0
B is caused by the difference in their composition. To ë F , and C F (167 ± 9, 197 ± 10, and 135 ±
6
0
18
60 36
obtain the energy of combustion of pure ë F from 8 kJ/mol, respectively [21]). All the characteristics of
6
0 18
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 81 No. 10 2007

THE ENTHALPY OF FORMATION OF FULLERENE FLUORIDE C F
0 18
1563
6
Table 3. Thermochemical properties of substance-impurities
∆fH° (g)
∆ H°
∆ H° (cr)
–∆ H° (cr)
–∆ U° (cr)
c m
m
s
m
f
m
c
m
–∆ u°(cr),
c
Formula
M
J/g
kJ/mol
C60
C F
720.642
1404.5845
758.6388
796.6356
812.6350
834.6324
872.6292
858.6538
1112.6208
2522
–5227
2118
1692
1554
1258
829
167
135
167
167
167
180
180
167
197
2355 ± 15
–5362 ± 201
1951
25965
24692
25920
25851
25713
25762
25691
26490
25526
25965
24714
25921
25853
25717
25766
25696
26494
25538
36030 ± 16
17595 ± 142
34168
6
0
36
2
C F
6
0
C F
1525
32453
6
0
4
C F O
1387
31646
6
0
4
6
8
C F
1078
30871
6
0
C F
649
29447
6
0
C (CF )
3 2
1186
–1861
1019
30855
6
0
C F CF
3
–2058
22953
6
0
17
Note: The values for C60 and C F were determined experimentally in [18] and [3], respectively; the thermodynamic properties of the
60
36
other substances were estimated from the enthalpies of reactions (1)–(8); M is the molecular weight.
substance-impurities obtained this way are listed in
Table 3.
The values necessary for these calculations,
∆fH° (F, g) = 79.38 ± 0.30, ∆ H° (C , cr) = 2355 ± 15,
m
f
m
60
The introduction of corrections for impurities
and ∆ H° (C ) = 167 ± 9 kJ/mol, were taken from [12],
s
m
60
changed the energies of combustion to –23855 ± 84 and
[
18], and [21], respectively. The enthalpy of reaction
–
23833 ± 50 J/g for samples A and B, respectively. The
(
10) was found to be 5266 ± 52 kJ/mol or 292.5 ±
uncertainties specified included errors in the energy
equivalent value and the energies of combustion of aux-
iliary substances and C and C F impurities. Both
2
.9 kJ/mol per one C–F bond. The latter value, which is
the mean enthalpy of dissociation of the C–F bond, can
6
0
60 36
be compared with similar values obtained for C F
6
0 36
values characterize the pure ë F compound, and the
6
0 18
and C F , 294.9 ± 5.6 [3] and 287.5 ± 3.5 kJ/mol [2],
6
0 48
difference between them is much smaller than the
uncertainties they involve. The recommended energy of
combustion ∆ u°(ë F ) was calculated as the
respectively. It follows that the enthalpies of C–F bond
dissociation in two less fluorinated fullerenes are equal
to within uncertainties. Deeper fluorination (to C F )
c
60 18
6
0 48
weighted mean of these two values, –23839 ± 43 J/g.
The molar energy of combustion is therefore
decreases this value slightly.
∆cU° (ë F , cr) = –25332 ± 46 kJ/mol. This value
corresponds to the reaction
m
60 18
REFERENCES
1
. L. N. Sidorov, M. A. Yurovskaya, A. Ya. Borshchevskii,
C F (cr) + 55.5O (g) + 9H O(l) + aq
6
0
18
2
2
and I. V. Trushkov, Fullerenes (Ekzamen, Moscow,
(9)
2
004) [in Russian].
=
60CO (g) + 18HF(sln HF, 20H O).
2 2
2
3
. T. S. Papina, V. P. Kolesov, V. A. Lukyanova, et al.,
J. Chem. Thermodyn. 31, 1321 (1999).
. T. S. Papina, V. P. Kolesov, V. A. Lukyanova, et al.,
J. Phys. Chem. B 104, 5403 (2000).
It was used to calculate the enthalpy of combustion and
formation of C F in the crystalline and gaseous
60 18
states. These calculations were performed using the
–
enthalpies of formation of CO (g), H O(l), and F (aq)
4. I. V. Goldt, O. V. Boltalina, L. N. Sidorov, et al., Solid
2
2
State Sci. 4, 1395 (2002).
recommended in [12] (–393.51 ± 0.13, −285.830 ±
0
.040, and –335.35 ± 0.65 kJ/mol, respectively). The
5. A. Yu. Lukonin, V. Yu. Markov, and O. V. Boltalina,
values obtained were (kJ/mol):
Vestn. Mosk. Univ., Ser. 2: Khim. 42, 3 (2001).
6
7
8
9
. N. E. Gel’man, E. A. Terent’eva, T. M. Shanina, et al.,
Methods of Quantitative Organic Elemental Microanal-
ysis (Khimiya, Moscow, 1987) [in Russian].
. N. D. Maslennikova, L. M. Kiparenko, A. G. Bu-
yanovskaya, and E. A. Terent’eva, Zh. Anal. Khim. 48
(3), 547 (1993).
. “Atomic Weights of the Elements 1995: IUPAC Comis-
sion on Atomic Weights and Isotopic Abundances,” Pure
Appl. Chem. 68, 2339 (1996).
∆cH°(cr) = – 25321 ± 46,
m
∆fH°(cr) = – 1511 ± 48,
m
∆sH°(627 K) = 197 ± 10, ∆ H°(g) = – 1314 ± 49.
m
f
m
The ∆ H° (C F , g) enthalpy was used to calculate
f
m
60 18
the enthalpy of the reaction
C F (g) = ë (g) + 18F(g).
. V. P. Kolesov, G. M. Slavutskaya, S. P. Alekhin, and
S. M. Skuratov, Zh. Fiz. Khim. 46 (8), 2138 (1972).
(10)
6
0
18
60
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 81 No. 10 2007

1
564
PAPINA et al.
1
0. F. D. Rossini, in Experimental Thermochemistry, Ed. by 15. Thermal Constants of Substances: A Handbook, Ed. by
F. D. Rossini (Interscience, New York, 1956), Vol. 1,
p. 59.
V. P. Glushko (Nauka, Moscow, 1965), Vol. 1 [in Rus-
sian].
1
1
1
6. J. D. Cox and A. J. Head, Trans. Faraday Soc. 58, 1839
1
1
1. T. S. Papina, S. M. Pimenova, V. A. Luk’yanova, and
(1962).
V. P. Kolesov, Zh. Fiz. Khim. 69 (12), 2148 (1995).
7. G. K. Johnson, P. N. Smith, and W. N. Hubbard, J. Chem.
2. CODATA Recommended Key Values for Thermodynam-
ics, Ed. by J. D. Cox, D. D. Wagman, and V. A. Med-
vedev (Hemisphere, New York, 1989).
Thermodyn. 5, 793 (1973).
8. V. P. Kolesov, S. M. Pimenova, V. K. Pavlovich, et al.,
J. Chem. Thermodyn. 28, 1121 (1996).
1
1
3. J. D. Cox, H. A. Gundry, and A. J. Head, Trans. Faraday
1
2
9. D. N. Laikov, Chem. Phys. Lett. 281, 151 (1997).
Soc. 61, 1594 (1965).
0. J. P. Perdew, K. Burke, and M. Ernzerhof, Phys. Rev.
Lett. 771, 3865 (1996).
4. W. D. Good and D. W. Scott, in Experimental Thermo-
chemistry, Ed. by H. A. Skinner (Wiley, New York, 21. G. Gigli, G. Balducci, V. Yu. Markov, et al., J. Chem.
1
962), Vol. 2, p. 24.
Thermodyn. 34, 57 (2002).
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 81 No. 10 2007