Enthalpies of combustion of two bis(N,N-diethylthioureas)

Article abstract of DOI:10.1016/j.jct.2006.07.007

The standard (p^{{ring operator}} = 0.1 MPa) molar energies of combustion in oxygen, at T = 298.15 K, of two crystalline bis(N,N-diethylthioureas) R(CONHCSNEt₂)₂: pyridine-2,6-dicarbonyl-bis(N,N-diethylthiourea), R = pyridyl_, abbreviated as (bis-py-DETU), and adipoyl-dicarbonyl-bis(N,N-diethylthiourea), R = (CH₂)₄, abbreviated as (bis-ad-DETU), were measured by rotating bomb calorimetry so, the standard molar enthalpies of formation of both compounds, in their crystalline phase, were derived. {A table is presented}Furthermore, the energetics of the title compounds were studied by means of density functional theory calculations at the B3LYP/ 6-311G(dp) level of theory.

Full text of DOI:10.1016/j.jct.2006.07.007

J. Chem. Thermodynamics 39 (2007) 279–283
www.elsevier.com/locate/jct
Enthalpies of combustion of two bis(N,N-diethylthioureas)
a,
a
a
Manuel A.V. Ribeiro da Silva *, Luis M.N.B.F. Santos , Bernd Schroder ,
¨
b
b
Lothar Beyer , Frank Dietze
a
ˆ
Centro de Investigac¸a˜o em Quı´mica, Departamento de Quı´mica, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 687,
P-4169-007 Porto, Portugal
Institut fu¨r Anorganische Chemie, Universita¨t Leipzig, Johannisallee 29, D-04103 Leipzig, Germany
b
Received 27 June 2006; received in revised form 5 July 2006; accepted 6 July 2006
Available online 3 August 2006
Abstract
The standard (pꢀ = 0.1 MPa) molar energies of combustion in oxygen, at T = 298.15 K, of two crystalline bis(N,N-diethylthioureas)
R(CONHCSNEt2)2: pyridine-2,6-dicarbonyl-bis(N,N-diethylthiourea), R = pyridyl, abbreviated as (bis-py-DETU), and adipoyl-dicar-
bonyl-bis(N,N-diethylthiourea), R = (CH2)4, abbreviated as (bis-ad-DETU), were measured by rotating bomb calorimetry so, the stan-
dard molar enthalpies of formation of both compounds, in their crystalline phase, were derived.
Compound
ꢁDcUꢀmðcrÞ
ꢁDf HꢀmðcrÞ
kJ ꢂ molꢁ1
kJ ꢂ molꢁ1
Pyridine-2,6-dicarbonyl-bis(N,N-diethylthiourea) [bis-py-DETU]
Adipoyl-dicarbonyl-bis(N,N-diethylthiourea) [bis-ad-DETU]
11027.1 5.2
11124.6 5.7
425.2 5.6
644.4 6.1
Furthermore, the energetics of the title compounds were studied by means of density functional theory calculations at the B3LYP/ 6-
311G(dp) level of theory.
ꢀ 2006 Elsevier Ltd. All rights reserved.
Keywords: Energy of combustion; Enthalpy of formation; Pyridine-2,6-dicarbonyl-bis(N,N-diethylthiourea); Adipoyl-dicarbonyl-bis(N,N-diethylthiou-
rea)
1. Introduction
N-acylthioureas, quadridentate bis-N-acylthioureas become
available.
Over the past two decades, various substituted N-acy-
lthioureas have been the subject of investigations, including
the thermodynamics of the complexation reactions towards
metal ions in solution, thus affording conclusions on their
extraction properties [1,2]. More recently, the thermochem-
istry of this group of compounds became the subject of
interest [3].
These ligand systems are potentially bis-bidentate, with
the capability of complex formation towards polyvalent
metal ions, resulting in stable inner chelates with S,O-coor-
dination. They already have been scrutinized concerning
their complexation behavior, revealing the formation of
oligomeric or polymeric, cyclic or chain chelates [4,5].
This work is part of an extensive study on the thermo-
chemistry of 1,3-ligand systems with (S,O,N) ligator atoms,
to contribute to the understanding of the binding process in
complexation reactions towards various transition
metal ions.The enthalpies of combustion of bis-py-DETU,
In this work, the scope was extended to bis(N,N-diet-
hylthioureas). By symmetric linking of two bidentate
*
Corresponding author. Tel.:+351 22 6082 821; fax: +351 22 6082 822.
pyridine-2,6-dicarbonyl-bis(N,N-diethylthiourea)
and
E-mail address: risilva@fc.up.pt (M.A.V. Ribeiro da Silva).
0021-9614/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jct.2006.07.007

280
M.A.V. Ribeiro da Silva et al. / J. Chem. Thermodynamics 39 (2007) 279–283
bis-ad-DETU, adipoyl-dicarbonyl-bis(N,N-diethylthiou-
rea), as shown in figure 1, were measured, at T = 298.15 K,
by rotating bomb calorimetry and the standard molar
enthalpies of formation in crystalline state were derived.
lett Packard HP 2804A) interfaced to a microcomputer
programmed to compute the adiabatic temperature change.
Ignition temperatures were chosen so that the final temper-
atures were very close to 298.15 K. The frictional work of
bomb rotation was automatically included in the correc-
tion for heat exchange and work of stirring by using the
procedure described by Good et al. [9] Data acquisition
and control of the calorimeter was performed using the
program LABTERMO [10].
The energy equivalent of the calorimeter was deter-
mined from the combustion of benzoic acid (Bureau of
Analysed Samples; Thermochemical Standard BAS-
CRM 190-r), having a massic energy of combustion under
bomb conditions of ꢁ(26431.8 3.7) J Æ Kꢁ1, as described
previously [11]. The electrical energy for the ignition was
determined from the change in potential across a capaci-
tor when 40 V were discharged through a platinum igni-
tion wire. For the cotton thread fuse (empirical formula
2. Experimental
The bis(N,N-diethylthioureas) were prepared as
described earlier [6]: 0.2 mol of the corresponding dichlo-
ride was added drop wise to a boiling mixture of 0.4 mol
potassium thiocyanate and 250 cm3 of dried acetone. The
reaction mixture was boiled under reflux for 20 min. The
precipitated potassium chloride was filtered off from
the formed solution of diisothiocyanate. After adding of
0.41 mol of diethyl amine to the filtrate under simulta-
neously heating, the mixture was kept aside overnight.
After a few hours the corresponding bis(N,N-diethylthiou-
rea) was yielded in pale, yellow crystals.
The purities of the samples were checked by elemental
analysis; the mass fraction w of C, H, N and S were as fol-
lows: for bis-py-DETU, C17H25N5O2S2, found 102
w(C) = 51.39, 102 w(H) = 6.35, 102 w(N) = 17.43, 102
w(S) = 16.13, calculated 102 w(C)= 51.62, 102 w(H) =
6.37, 102 w(N) = 17.71, 102 w(S) = 16.21; for bis-ad-
DETU, C16H30N4O2S2, found 102 w(C) = 51.21, 102
w(H) = 8.04, 102 w(N)= 15.01, 102 w(S) = 17.06, calculated
102 w(C) = 51.31, 102 w(H) = 8.07, 102 w(N) = 14.96, 102
w(S) = 17.12.
CH1.686O0.843) the massic energy of combustion is
assigned to Dcuꢀ = ꢁ16240 J Æ gꢁ1 [9], a value which was
confirmed in our laboratory. Corrections for nitric acid
formation were based on ꢁ59.7 kJ Æ molꢁ1 for the molar
energy of formation of 0.1 mol Æ dmꢁ3 HNO3(aq) from
O2, N2, and H2O (l) [12]. From eight calibration experi-
ments the energy equivalent of the calorimeter, e(calor)/
(J Æ Kꢁ1) was found to be {20677.1
3.5 (0.017%)} for
an average mass of water added to the calorimeter of
4059.0 g; the quoted uncertainty is the standard deviation
of the mean.
The relative atomic masses used were those recom-
mended by the IUPAC Commission in 2001 [7], yielding
Samples in pellet form were ignited in oxygen at a pres-
sure of 3.04 MPa with a volume of 10.00 cm3 of water
added to the bomb. The amount of nitric acid produced
was determined by ion chromatography. The densities of
the two crystalline bis(N,N-diethylthioureas) were assumed
to be 1.3 g Æ cmꢁ3. For each compound, (ou/op)T at T =
298.15 K was assumed to be ꢁ0.2 J Æ gꢁ1 Æ MPaꢁ1, a typical
value for organic compounds [13]. The standard state
corrections were calculated by the procedures given by
Hubbard et al. [14] and by Good and Scott [15].
the
molar
masses
of
395.550 g Æ molꢁ1
and
374.571 g Æ molꢁ1, respectively, for bis-py-DETU and for
bis-ad-DETU.
2.1. Combustion calorimetry
The enthalpies of combustion were measured with the
rotating-bomb calorimeter formerly used at the National
Physical Laboratory, Teddington, UK [8], with a plati-
num-lined bomb of internal volume 0.337 dm3. Water
was added to the calorimeter from a weighted acrylic ves-
sel, and for each experiment a correction to the energy
equivalent was made for the deviation from 4059.0 g of
the mass of water added. Calorimetric temperatures were
measured to 1 Æ 10ꢁ4 K with a quartz thermometer (Hew-
3. Computational thermochemistry details
For all involved species, full geometry optimizations
with Becke’s three-parameter exchange functional [16] in
combination with the Lee, Yang and Parr correlation func-
S
O
H
H
H
N
N Et2
Et2
N
N
N
NEt2
N
H
Et2
N
N
O
S
S
O
O
S
bis-ad-DETU
bis-py-DETU
FIGURE 1. General formula of the two bis(N,N-diethylthioureas). bis-py-DETU: Pyridine-2,6-dicarbonyl-bis(N,N-diethylthiourea); bis-ad-DETU:
Adipoyl-dicarbonyl-bis(N,N-diethylthiourea).

M.A.V. Ribeiro da Silva et al. / J. Chem. Thermodynamics 39 (2007) 279–283
281
tion as hybrid functional (B3LYP) [17] at a 6-311G(d,p)-
level of theory were performed first, using the implementa-
tion of DFT in the Gaussian03 suite of programs [18]. The
zero-point energies (eZPE) are scaled to 0.9804 [19]. Har-
monic vibrational frequencies were calculated at the same
level of theory, applying a scaling factor 0.9613 for the cor-
rection of anharmonicity [19].
For each compound, the products of combustion in the
experiments consist of a gaseous phase and an aqueous
mixture of sulphuric acid for which the thermodynamic
properties are known. The values of Dcuꢀ refer to the reac-
tions represented by equations (2) and (3), for bis-py-
DETU and bis-ad-DETU, respectively:
bis-py-DETU:
C17H25O2N5S2 ðcrÞ þ 25:25 O2 ðgÞ þ 219:5 H2O ðlÞ !
4. Results
17 CO2 ðgÞ þ 2:5 N2 ðgÞ þ 2½H2SO4 ꢂ 115H2Oꢃ ðlÞ
ð2Þ
Table 1 lists typical combustion results for each com-
pound in which Dm(H2O) is the deviation of the mass
added to the calorimeter from 4059.0 g, the mass assigned
to e(calor), and DUR is the correction to the standard state.
The remaining quantities are as previously described [14].
Details of all the Combustion Calorimetry experiments
are given in the Supporting Information, in Tables S1
and S2.
bis-ad-DETU:
C16H30O2N4S2 ðcrÞ þ 25:5 O2 ðgÞ þ 217 H2O ðlÞ !
16 CO2 ðgÞ þ 2 N2 ðgÞ þ 2½H2SO4 ꢂ 115H2Oꢃ ðlÞ:
ð3Þ
Table 2 lists, for each compound, the individual values of
Dcuꢀ, together with the mean and the standard deviation
of the mean.
Table 3 lists the derived standard molar values for the
energies and enthalpies of combustion, DcUꢀm, DcHmꢀ ,
respectively, as well as the standard molar enthalpies of for-
mation, Df Hꢀm, of the crystalline solids, at T = 298.15 K. In
accordance with the normal thermochemical practice, the
uncertainties assigned to the standard molar enthalpies of
combustion and formation are twice the overall standard
The internal energy for the isothermal bomb process,
DU(IBP), was calculated according to the following
equation:
DUðIBPÞ ¼ ꢁ feðcalorÞ þ cpðH2O;lÞDmðH2OÞgDTad
þ
ðTi ꢁ 298:15Þei þ ð298:15 ꢁ T i ꢁ DTadÞef þ
DUðignÞ;
ð1Þ
where DTad is the calorimeter temperature change cor-
rected for the heat exchange and the work of stirring.
TABLE 2
Individual values of the standard (pꢀ = 0.1 MPa) massic energy of
combustion, Dcuꢀ,of Pyridine-2,6-dicarbonyl-bis(N,N-diethylthiourea)
(bis-py-DETU) and of Adipoyl-dicarbonyl-bis(N,N-diethylthiourea) (bis-
ad-DETU), at T = 298.15 K
TABLE 1
Typical combustion experimental results of pyridine-2,6-dicarbonyl-
bis(N,N-diethylthiourea) (bis-py-DETU) and adipoyl-dicarbonyl-
bis(N,N-diethylthiourea) (bis-ad-DETU), at T = 298.15 K
bis-py-DETU
bis-ad-DETU
bis-py-DETU
bis-ad-DETU
ꢁDcuꢀ/(J Æ gꢁ1
)
m(cpd.)/g
m0(fuse)/g
Ti/K
0.72465
0.00383
297.1680
298.1845
0.98134
53.3
0.75689
0.00555
297.2154
298.3362
1.09258
53.4
27877.7
27876.9
27870.3
27881.8
27882.9
29707.0
29695.7
29712.8
29699.1
29706.3
29694.7
29681.5
Tf/K
DTad/K
ei(cont.)/(J.Kꢁ1
)
ef(cont.)/(J.Kꢁ1
Dm(H2O)/g
ꢁDU(IBP)a/J
DU(HNO3)/J
DU(ignition)/J
DUR/J
)
53.0
53.4
ꢁ2.1
ꢁ1.0
20333.8
46.9
22644.0
47.6
ꢁÆDcuꢀæ/(J Æ gꢁ1 a
)
27877.9 2.2
29699.6 3.9
1.2
23.1
62.2
1.2
21.4
90.1
The mean values are represented by ÆDcuꢀæ.
m0 Æ Dcuꢀ (fuse)/J
a
Mean value; given uncertainty as the standard deviation of the mean.
ꢁDcuꢀ(cpd.)/J Æ gꢁ1
27877.7
29707.0
m(cpd.) is the mass of compound burnt in each experiment; m0(fuse) is the
mass of the fuse (cotton) used in each experiment; Ti is the initial tem-
perature rise; Tf is the final temperature rise; DTad is the corrected tem-
perature rise; ei(cont.) is the energy equivalent of the contents in the initial
state; ef(cont.) is the energy equivalent of the contents in the final state;
Dm(H2O) is the deviation of mass of water added to the calorimeter from
4059.0 g; DU(IBP) is the energy change for the isothermal combustion
reaction under actual bomb conditions; DU(HNO3) is the energy correc-
tion for the nitric acid formation; DU(ignition) is the electric energy for the
ignition; DUR is the standard state correction; Dcuꢀ (fuse) is the massic
energy of combustion of the fuse (cotton); Dcuꢀ is the standard massic
energy of combustion.
TABLE 3
Derived standard (pꢀ = 0.1 MPa) molar energies of combustion, DcHmꢀ
,
standard molar enthalpies of combustion, DcHꢀm, standard molar enthal-
pies of formation, (cr), for Pyridine-2,6-dicarbonyl-bis(N,N-diethylthiou-
rea) (bis-py-DETU) and Adipoyl-dicarbonyl-bis(N,N-diethylthiourea)
(bis-ad-DETU), at T = 298.15 K
Compound
ꢁDcHꢀmðcrÞ=
ꢁDcHꢀmðcrÞ=
ꢁDf HꢀmðcrÞ=
ðkJ ꢂ molꢁ1
Þ
ðkJ ꢂ molꢁ1
Þ
ðkJ ꢂ molꢁ1
Þ
Bis-py-DETU
Bis-ad-DETU
11027.1 5.2
11041.3 5.2
425.2 5.6
11124.6 5.7
11143.2 5.7
644.4 6.1
a
DU(IBP) includes DU(ignition).

282
M.A.V. Ribeiro da Silva et al. / J. Chem. Thermodynamics 39 (2007) 279–283
deviation of the mean and include the uncertainties in cali-
bration and in the auxiliary quantities used. To derive
Df HꢀmðcrÞ from DcHꢀmðcrÞ, the standard molar enthalpies
of formation of H2O(l), CO2(g) and H2SO4 in
115 H2O(l), at T = 298.15 K, respectively, ꢁ(285.830
0.042) kJ Æ molꢁ1 [20], ꢁ(393.51 0.13) kJ Æ molꢁ1 [20],
and ꢁ(887.81 0.4) kJ Æ molꢁ1 [12] were used.
2; 6-DiacetylpyridineðgÞ þ n-butaneðgÞ !
1; 4-DiacetylbutaneðgÞ þ pyridineðgÞ;
ð6Þ
with
DrHꢀm ð6Þ ¼ Df Hꢀ ð1; 4-diacetylbutane;gÞꢁ
Df Hꢀmm ð2; 6-diacetylpyridine;gÞþ
Df Hꢀm ðpyridine;gÞ ꢁ Df Hꢀm ðn-butane;gÞ: ð7Þ
5. Discussion
Unfortunately, experimental values for the standard
molar enthalpies of formation in the gas phase, Df HꢀmðgÞ,
for both compounds, are not known. Applying bond-
energy schemes with the previously established [23]
parameters C–(H)3(C) = ꢁ42.7 kJ Æ molꢁ1, C–(H)2(C)2 =
ꢁ21 kJ Æ molꢁ1, C(H)2(CO)(C) = ꢁ22 kJ Æ molꢁ1, CO(C)2
There are no previously determined values for the stan-
dard molar enthalpies of formation of these compounds as,
at present, only a limited number of thermochemical stud-
ies on compounds containing similar structures are
available.
=ꢁ131 kJ Æ molꢁ1
,
CB(CO) = 15 kJ Æ molꢁ1
,
CB(H) =
In both cases, it was not possible to measure the stan-
dard molar enthalpies of sublimation due to thermal
decomposition reactions of the compounds occurring at
comparatively low temperatures. Therefore, we cannot
derive the respective standard molar enthalpies of forma-
tion in the gas phase, Df Hmꢀ ðgÞ. However, the comparison
with substances with the same structural motifs allows for
estimations of the standard molar enthalpies of sublima-
tion in question: assuming that the standard molar
enthalpies of sublimation of bis-py-DETU [pyridine-2,6-
dicarbonyl-bis(N,N-diethylthiourea)] and bis-ad-DETU
[adipoyl-dicarbonyl-bis(N,N-diethylthiꢁo1urea)] are nearly
equal fDðDgcrHmꢀ Þ ¼ ð0 ꢄ 10Þ kJ ꢂ mol g, the reaction
enthalpy of the following empirical group exchange reac-
tion can be derived:
14 kJ Æ molꢁ1
,
CO(C)(CB) = ꢁ129 kJ Æ molꢁ1
and
Npyr–(CB) = 69.9 kJ Æ molꢁ1, the following enthalpies of
formation were estimated: for: 4-diacetylbutane,
Df Hꢀm(C8H14O2,g) = 2 Æ C–(H)3(C) +
2 Æ C–(H)2(C)2 +
2 Æ C(H)2(CO)(C) + 2 Æ CO(C)2 = ꢁ433.4 kJ Æ molꢁ1, and
for
2,6-diacetylpyridine,
Df Hꢀ ðC9H9NO2; gÞ ¼
2 ꢂ C–ðHÞ ðCÞ þ 2 ꢂ CBðCOÞ þ 3CB–ðHÞþm 2 ꢂ COðCÞðCBÞ
3
þNpyr–ðCBÞ ¼ ꢁ201:5 kJ ꢂ molꢁ1. Using these values, the
enthalpy of the exchange reaction (6) is calculated as
DrHꢀmð6Þ ¼ þ34:3 kJ ꢂ molꢁ1
.
The ab initio B3LYP calculation at 6-311G(d,p) level of
the same reaction gives DrHꢀ ð6Þ ¼ þ39:9 kJ ꢂ molꢁ1
,
m
which is in good agreement with the group scheme esti-
mate. Turning back now to reaction (4) and calculating
the enthalpy of the empirical group exchange reaction via
DFT/B3LYP at the same level of theory, we obtain
bis-py-DETU ðgÞ þ n-butane ðgÞ !
bis-ad-DETU ðgÞ þ pyridine ðgÞ;
ð4Þ
DrHꢀ ð4Þ ¼ þ54:2 kJ ꢂ molꢁ1 which is also in agreement
m
with the experimental value DrHꢀm ð4Þ ¼ þð47 ꢄ 12Þ
kJ ꢂ molꢁ1. Table 4 shows the total energies of the reactants
of both the empirical group exchange reactions, with the
assigned energy corrections.
with
DrHꢀm ð4Þ ¼ Df Hꢀm ðbis-ad-DETU;crÞ ꢁ
Df Hꢀm ðbis-py-DETU;crÞ þ Df Hꢀm ðpyridine;gÞ ꢁ
The results of the DFT/B3LYP calculations indicate
that, for the applied level of theory, the enthalpy of the
empirical group exchange reaction can be calculated rather
precise. Furthermore, this allows for the standard molar
enthalpies of formation in gas phase, Df HꢀmðgÞ, to be esti-
mated with a sufficient accuracy – provided that, at least,
the standard molar enthalpy of formation in gas phase of
one of the reactants of the chosen empirical group
exchange reaction is known.
Df Hꢀm ðn-butane;gÞ þ DðDcgrHꢀmÞ:
ð5Þ
Using Df Hꢀ ðpyridine;gÞ ¼ ð140:6 ꢄ 1:5Þ kJ ꢂ molꢁ1 [21]
m
and Df Hꢀ ðn-butane; gÞ ¼ ꢁð125:6 ꢄ 0:67Þ kJ ꢂ molꢁ1 [22],
m
we can derive DrHꢀ ð4Þ ¼ ð47 ꢄ 12Þ kJ ꢂ molꢁ1
.
m
This can be compared with another empirical group
exchange reaction, where the functional groups of the
title compounds have merely been replaced by acetyl
groups:
TABLE 4
Total energies in kJ Æ molꢁ1 of the reactants of the empirical group exchange reactions (4) and (6)
Energy
bis-py-DETU
bis-ad-DETU
Pyridine
n-Butane
2,6-Diacetylpyridine
1,4-Diacetylbutane
e0
ꢁ4946029.47
ꢁ4944951.70
ꢁ4944873.41
ꢁ4710097.29
ꢁ4708905.29
ꢁ4708824.58
ꢁ652034.62
ꢁ651806.93
ꢁ651792.86
ꢁ416154.74
ꢁ415816.31
ꢁ415798.30
ꢁ1453809.22
ꢁ1453391.69
ꢁ1453358.26
ꢁ1217887.704
ꢁ1217358.482
ꢁ1217323.799
e0 + eZPE (scaled to 0.9804)
e0 + eZPE (scaled to 0.9804) +
Hcorr (scaled to 0.9613)
Full geometry optimizations with the B3LYP functional at a 6-311G(d,p)-level of theory were performed first, followed by frequency calculations at the
same level of theory. bis-py-DETU: pyridine-2,6-dicarbonyl-bis(N,N-diethylthiourea). bis-ad-DETU: Adipoyl-dicarbonyl-bis(N,N-diethylthiourea).
Assigned energy corrections to the total energy (kJ Æ molꢁ1): e0 – total electronic energy, eZPE – zero-point energy, Hcorr – thermal enthalpy.

M.A.V. Ribeiro da Silva et al. / J. Chem. Thermodynamics 39 (2007) 279–283
283
[11] J. Coops, R.S. Jessup, K.G. van Nes, in: F.D. Rossini (Ed.),
Experimental Thermochemistry, vol. 1, Interscience, New York, 1956
(Chapter 3).
[12] The NBS Tables of Chemical Thermodynamic Properties, J. Phys.
Chem. Ref. Data 11 (1982) Suppl. 2.
Acknowledgments
Thanks are due to Fundac¸ao para a Cieˆncia e Tecno-
˜
logia, (FCT) Lisboa, Portugal, for financial support
granted through Centro de Investigac¸ao em Qu´ımica,
˜
[13] E.N. Washburn, J. Res. Natl. Bur. Stand (U.S.) 10 (1933) 525–
558.
[14] W.N. Hubbard, D.W. Scott, G. Waddington, in: F.D. Rossini (Ed.),
Experimental Thermochemistry, vol. 1, Interscience, New York, 1956
(Chapter 5).
[15] W.D. Good, D.W. Scott, in: H.A. Skinner (Ed.), Experimental
Thermochemistry, vol. 2, Interscience, New York, 1962 (Chapter 2).
[16] A.D. Becke, Phys. Rev. A 38 (1988) 3098–3100.
University of Porto; Bernd Schro¨der gratefully thanks
FCT and the European Social Fund (ESF) under the
3rd Community Support Framework (CSF) for the
award of
a post-doctoral scholarship (SRFH/BPD/
3531/2000).
[17] A.D. Becke, J. Chem. Phys. 98 (1993) 5648–5652.
[18] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb,
J.R. Cheeseman, J.A. Montgomery Jr., T. Vreven, K.N. Kudin, J.C.
Burant, J.M. Millam, S.S. Iyengar, J. Tomasi, V. Barone, B.
Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A. Petersson, H.
Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene,
X. Li, J.E. Knox, H.P. Hratchian, J.B. Cross, C. Adamo, J.
Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin,
R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma,
G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S.
Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D.
Rabuck, K. Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G.
Baboul, S. Clifford, J. Cioslowski, B.B. Stefanov, G. Liu, A.
Liashenko, P. Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T.
Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M. Challa-
combe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, C.
Gonzalez, J.A. Pople, Gaussian 03, Revision A.1, Gaussian, Inc.,
Pittsburgh, PA, 2003.
Appendix A. Supplementary data
Tables S1 and S2 listing the details of all the Combustion
Calorimetry experiments, at T = 298.15 K, for pyridine-
2,6-dicarbonyl-bis(N,N-diethylthiourea) and adipoyl-
dicarbonyl-bis(N,N-diethylthiourea). Supplementary data
associated with this article can be found, in the online ver-
sion, at doi:10.1016/j.jct.2006.07.007.
References
[1] L. Beyer, E. Hoyer, J. Liebscher, H. Hartmann, Z. Chem. 21 (1981)
81–91.
[2] P. Muhl, K. Gloe, F. Dietze, E. Hoyer, L. Beyer, Z. Chem. 26 (1986)
¨
81–94.
[3] M.A.V. Ribeiro da Silva, M.D.M.C. Ribeiro da Silva, L.C.M.
da Silva, F. Dietze, E. Hoyer, L. Beyer, B. Schro¨der, A.M.
Damas, J.F. Liebman, J. Chem. Soc., Perkin Trans. 2 (2001)
2174–2178.
[4] R. Ko¨hler, R. Kirmse, R. Richter, J. Sieler, E. Hoyer, L. Beyer, Z.
Anorg. Allg. Chem. 537 (1986) 133–144.
[5] K.-H. Ko¨nig, M. Kuge, L. Kaul, H.-J. Pletsch, Chem. Ber. 120
(1987) 1251–1253.
[6] U. Schro¨der, L. Beyer, J. Sieler, Inorg. Chem. Commun. 3 (2000)
630–633.
[7] R.D. Loss, Pure Appl. Chem. 75 (2003) 1107–1122.
[8] J.D. Cox, H.A. Gundry, A. Head, J. Trans. Faraday Soc. 60 (1964)
653–665.
[9] W.D. Good, D.W. Scott, G. Waddington, J. Phys. Chem. 60 (1956)
1080–1089.
[19] M.W. Wong, Chem. Phys. Lett. 256 (1966) 391–399.
[20] J.D. Cox, D.D. Wagman, V.A. Medvedev (Eds.), CODATA
Key Values for Thermodynamics, Hemisphere, New York,
1989.
[21] R.J.L. Andon, J.D. Cox, E.F.G. Herington, J.F. Martin, Trans.
Faraday Soc. 53 (1957) 1074.
[22] D.A. Pittam, G. Pilcher, J. Chem. Soc., Faraday Trans. 1 68 (1972)
2224–2229.
[23] H.Y. Afeefy, J.F. Liebman, S.E. Stein, in: P.J. Linstrom, W.G.
Mallard (Eds.), Neutral Thermochemical Data, in NIST Chemistry
WebBook, NIST Standard Reference Database Number 69, National
Institute of Standards and Technology, Gaithersburg, MD, 2005.
Available from: http://webbook.nist.gov.
JCT 06-169
[10] L.M.N.B.F. Santos, Ph.D. Thesis, University of Porto, 1995.