Thermochemical study of the solid complex Ho(PDC)3 (o-phen)

Article abstract of DOI:10.1007/s10973-005-6910-6

A novel solid complex, formulated as Ho(PDC)₃ (o-phen), has been obtained from the reaction of hydrate holmium chloride, ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen?H ₂O) in absolute ethanol, which was characterized by elemental analysis, TG-DTG and IR spectrum. The enthalpy change of the reaction of complex formation from a solution of the reagents, Δ_r H _m ^θ (sol), and the molar heat capacity of the complex, c _m, were determined as being -19.161±0.051 kJ mol^-1 and 79.264±1.218 J mol^-1 K^-1 at 298.15 K by using an RD-496 III heat conduction microcalorimeter. The enthalpy change of complex formation from the reaction of the reagents in the solid phase, Δ_r H _m ^θ(s), was calculated as being (23.981±0.339) kJ mol^-1 on the basis of an appropriate thermochemical cycle and other auxiliary thermodynamic data. The thermodynamics of reaction of formation of the complex was investigated by the reaction in solution at the temperature range of 292.15-301.15 K. The constant-volume combustion energy of the complex, Δ_c U, was determined as being -16788.46±7.74 kJ mol^-1 by an RBC-II type rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, Δ_c H _m ^θ, and standard enthalpy of formation, Δ_f H _m ^θ, were calculated to be -16803.95±7.74 and -1115.42±8.94 kJ mol ^-1, respectively.

Full text of DOI:10.1007/s10973-005-6910-6

Journal of Thermal Analysis and Calorimetry, Vol. 83 (2006) 3, 693–700
THERMOCHEMICAL STUDY OF THE SOLID COMPLEX Ho(PDC)3
(o-PHEN)
*
G. Xie, S. P. Chen, S. L. Gao , X. X. Meng and Q. Z. Shi
Department of Chemistry, Shaanxi key Laboratory of Physico-Inorganic Chemistry, Northwest University, Xi ’an
Shaanxi 710069, P. R. China
A novel solid complex, formulated as Ho(PDC)3 (o-phen), has been obtained from the reaction of hydrate holmium chloride, ammo-
nium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen·H2O) in absolute ethanol, which was characterized by
elemental analysis, TG-DTG and IR spectrum. The enthalpy change of the reaction of complex formation from a solution of the re-
agents, ΔrHm(sol), and the molar heat capacity of the complex, cm, were determined as being –19.161 0.051 kJ mol–1 and
θ
79.264 1.218 J mol–1 K–1 at 298.15 K by using an RD-496 III heat conduction microcalorimeter. The enthalpy change of complex
formation from the reaction of the reagents in the solid phase, ΔrHm(s), was calculated as being (23.981 0.339) kJ mol–1 on the basis
θ
of an appropriate thermochemical cycle and other auxiliary thermodynamic data. The thermodynamics of reaction of formation of
the complex was investigated by the reaction in solution at the temperature range of 292.15–301.15 K. The constant-volume com-
bustion energy of the complex, ΔcU, was determined as being –16788.46 7.74 kJ mol–1 by an RBC-II type rotating-bomb calorime-
θ
ter at 298.15 K. Its standard enthalpy of combustion, ΔcHm, and standard enthalpy of formation, Δf Hm, were calculated to be
θ
–16803.95 7.74 and –1115.42 8.94 kJ mol–1, respectively.
Keywords: ammonium pyrrolidinedithiocarbamate (APDC), hydrate holmium chloride, 1,10-phenanthroline (o-phen·H2O),
thermochemistry
Introduction
been devoted to synthesize a novel complex Ho(PDC)3
(o-phen) by the reaction of hydrous holmium chloride
with ammonium pyrrolidinedithiocarbamate (APDC)
and 1,10-phenanthroline (o-phen·H2O) in absolute eth-
anol, and characterize the complex by chemical analy-
sis, elemental analysis, IR spectrum and TG-DTG
technique. The enthalpy change of the reaction in solu-
tion and the molar heat capacity of the resultant com-
plex at 298.15 K were determined by a microcalori-
meter. The enthalpy change of complex formation
from the reaction of the reagents in solid phase was de-
rived from a thermochemical cycle. The thermody-
namic of the reaction in solution at different tempera-
tures was investigated and the thermochemical param-
eters, the apparent reaction rate constant (k), the appar-
ent activation energy (E), the pre-exponential constant
(A), the reaction order (n), the activation enthalpy
There has been a significant increase interest in re-
search of the complexes containing the bond
‘lanthanide-sulfur’ over the past decades one part
since they have potential applications in the ceramics
industry and thin materials [1]. Another reason stems
from the challenge that the binary complexes exhibit
high sensitivity to moisture, so the syntheses of these
complexes should be performed under strongly anhy-
drous condition [2]. In particular, the class of these
complexes can be used as precursors to generate the
lanthanide sulfide nanocrystallites via thermo-
decomposition conveniently [3–5].
As chemical and physical processes are accompa-
nied by heat effects calorimetry represents a unique
technique to gather information about thermodynamics
and kinetics [6–8]. Reaction calorimetry has a wide ap-
plication in thermal and kinetic analyses of chemical re-
actions in the context of thermal process safety and pro-
cess development. Although there have been reports on
these complexes [9–12], both structurally and spectro-
scopically, experimental data on the thermodynamic be-
haviors of these coordination compounds are sparse.
As an extension of our previous studies on the
complexes of lanthanides with sulfur-containing lig-
ands, it is in the present work that many efforts have
θ
(ΔH≠ ), the activation entropy (ΔS≠ ), the activation
θ
θ
θ
free energy (ΔG≠ ) and the activation enthalpy (Δr H≠ ),
were obtained on the basis of reaction thermodynamic
and kinetic equations. The constant-volume combus-
tion energy, ΔcU, of the complex was measured by an
RBC-II rotating-bomb calorimeter at 298.15 K. Its
θ
standard enthalpy of combustion, Δc Hm , and the stan-
θ
dard enthalpies of formation, Δf Hm , were calculated.
*
Author for correspondence: gaoshli@nwu.edu.cn
1388–6150/$20.00
© 2006 Akadémiai Kiadó, Budapest
Akadémiai Kiadó, Budapest, Hungary
Springer, Dordrecht, The Netherlands

XIE et al.
Experimental
and under dynamic atmosphere of high purity N2 (mass
fraction 0.9999) with flow rate of 60 cm3 min–1 and a
heating rate of 10 K min–1. The ICP-OES spectroscopy
was carried out for checking the progress of the reaction
occurring in the calorimetric experiments using a Perkin
Elmer ICP Liberty 150 instrument. The phase structure
of the solid combustion product was identified by a
Rigua D/max-IIIC X-ray diffractometer using CuKα ra-
diation. An X-ray power diffractometer typed in
D/max-III with CuK radiation was used. The calorimet-
ric experiment were performed using an RD496-III type
microcalorimeter and an RBC-II type rotating-bomb
calorimeter [15, 16]. The purity of the compound was
attested by an HP-1100 type high performance liquid
chromatography analyzer, and the solvent is CH2Cl2, the
rinsing reagent is CH2Cl2 and the column is contra-
phase carbon –18.
Materials
Reagents
HoCl3·4.56H2O was prepared according to reference
[13], the hydration number of which was determined by
EDTA titration. Ammonium pyrrolidinedithio-
carbamate (abbreviated as APDC, mass fraction higher
than 0.9950) and 1,10-phenanthroline (abbreviated as
o-phen·H2O, mass fraction higher than 0.9950) were
commercially obtained from Shanghai Reagent Factory.
They were maintained in desiccators over P4O10 before
the calorimetric measurements. Absolute ethanol and
dichloromethane are of A. R. grade from Xi’an chemi-
cal reagent company. Potassium chloride (mass fraction
0.9999) was purchased from Shanghai No. 1 Reagent
Factory, Shanghai, China, and dried in a vacuum oven
at 500 K for 8 h prior to use. Thianthrene purchased
from Tokyo Kasei Kogyo Co., Ltd is of GC grade with
the purity of 99%, which was recrystallized with mass
fraction better than 99.99% characterized by HPLC, and
was stored in desiccator containing P4O10. The gamma
aluminum oxide are of spectroscopic pure from Shang-
hai No. 1 Reagent Factory, which was transformed to al-
pha aluminum oxide in muffle oven at 1473 K prior to
use and maintained in desiccator with P4O10.
RD496-III heat conduction calorimeter
All the enthalpies of solutions and that of reaction
were measured by an RD496-III micro-calorimeter as
described before [15]. The working temperature of
the calorimeter lies in the range of 77.15–473.15 K.
The baseline stability was determined at a constant
temperature and with a rising temperature at a stated
heating rate. Keeping the temperature at 313.15 K for
50 h, the baseline change was less than 0.2 μV.
While raising the temperature from 313.15 to 73.15 K
at the speed of 1 K h–1, the stability is 0.4 μV K–1.
The calorimetric constants at 292.15, 295.15,
298.15 and 301.15 K were determined by the Joule ef-
fect before experiment, which are 63.691 0.035,
The relative atomic masses used were those
recommended by IUPAC Commission in 1999 [14].
Synthesis of the complex
A mixture of HoCl3·4.56H2O, o-phen·H2O and APDC
in a molar relation salt/phen/APDC of 1/1/3, were dis-
solved independently in a minimal amount of abso-
lute ethanol. To the mixed ethanolic solution of
o-phen·H2O and APDC, the ethanolic solution of salt
was slowly drop-wise under electromagnetically stir-
ring. The reaction mixture was allowed to stand for
30 min resulting in the formation of a solid which was
filtered, washed with three small portions of absolute
ethanol and purified with CH2Cl2. The resulting crys-
tals were dried in vacuum and stored in a desiccator
over P4O10 ready to be used.
63.799 0.042,
63.901 0.030
and
64.000 0.026 μV mW–1. The reliability of the calo-
rimeter was verified by measuring the dissolution
enthalpy of KCl (calorimetrically primary standard)
in double distilled water at 298.15 K. The average
enthalpy of dissolution of KCl determined from the 6
tests was, ΔsHm,KCl =17.581 0.039 kJ mol–1, which is
θ
in agreement with the published value
17.584 0.007 kJ mol–1 [8, 17].
RBC-II rotating-bomb combustion calorimeter
The constant-volume combustion energy of the com-
pound was measured by an RBC-type II precision rotat-
ing-bomb combustion calorimeter. The structure and
principle of the calorimeter have been described in de-
tail previously elsewhere [8, 16]. It is mainly composed
of a thermostatic trough with an outer casing, a calori-
metric tube and a system for the temperature measure-
ment. The temperature of the thermostatic water in the
bath was automatically maintained at 298.15 0.001 K
by means of a precise thermistor. The temperature
gauge from the digital indicator with integrated circuit
Equipment and methods of analyses
The contents of Ho3+ and Cl–1 were determined volu-
metrically with EDTA by complexometric titration and
gravimetrically, respectively; C, H, N and S contents
were carried out by an instrument of Vario EL III
CHNOS of German. Spectra were obtained with sam-
ples in KBr matrix for the title complex and ligands. A
BEQ UZNDX–550 series FT-IR spectrophotometer in
the region of 400–4000 cm–1 was used. The TG-DTG
tests were performed in a Perkin Elmer thermobalance
694
J. Therm. Anal. Cal., 83, 2006

Ho(PDC)3 (o-PHEN) SOLID COMPLEX
XRD and IR data
The main XRD data of ligands and the complex
was used to measure the temperature of the calorimetric
tube. The bicyclic structure of the crucible support in the
oxygen bomb was constructed so that the bomb can
make a compound rotation about an axis perpendicular
to the bomb axis (i.e., end-over-end rotation) and about
the bomb axis (axial rotation) at the same time, which
assured the complete combustion of the compound.
The temperature rise was corrected on the basis
of the heat exchange between the calorimetric tube
and its surroundings. The correction value of the heat
exchange was calculated according to [18].
are shown in Table 1. Clearly, the main XRD data of
the complex are very different from that of hydrate
holmium chloride (L.C.D.D. card) and ligands,
indicating that the complex is a new phase.
The preliminary identification regarding the na-
ture of bonding of the ligands o-phen·H2O and APDC
to holmium ion has been obtained from the IR data.
Figure 1 shows the IR spectra of hydrate holmium
chloride, ligands and the complex. The IR spectra re-
veal that both ligands o-phen·H2O and APDC are co-
ordinated to the holmium ion [20, 21]. Comparing
with the spectra of hydrate holmium chloride (a) and
o-phen·H2O (b), the characteristic absorption band at-
tributed to the stretching vibration of the hydroxyl
group of water molecules, is observed at 3390 and
3388 cm–1, respectively. The band is not observed in
the complex spectrum. The IR spectrum of Ho(PDC)3
(o-phen) showed the absorption bands at 1625, 1590,
1573 and 1517 cm–1, which are attributed to the skele-
ton vibration of the benzene ring when compared with
that of free o-phen. Absorption bands at 843 and
727 cm–1 are attributed to the bend vibration of C–H
group in the complex. These vibrations are found to
be shifted to higher frequencies in the complex rela-
tive to free o-phen, suggesting that the two coordina-
tion of two nitrogen atoms of o-phen to Ho3+. In con-
trast with the absorption band found at 1417 cm–1 in
The analyses of the final gas of the combustion re-
action were referred to [8, 16]. The amount of CO2(g)
was determined through the mass increment of the tube
containing alkali asbestos after absorbing the carbon
dioxide. The total amount of acid was obtained through
titration with a standard solution of NaOH [8]. The
identity of the final solid product was checked by the
chemical analysis and XRD. The analyses of the com-
bustion products indicated that the compound was
combusted to CO2(g), H2O(l), H2SO4(aq) and Ho2O3(s)
under the excess oxygen.
The energy equivalent of the RBC-type II calo-
rimeter was determined from 6 combustion experi-
ments using about 0.8 g of NIST 39i benzoic acid
with a certified massic energy of combustion,
ΔcU= –26434 3 J g–1, under the same experimental
conditions to be of εcalor=17775.09 7.43 J K–1 [8].
In order to evaluate the precision and the accuracy
of the measurement of the standard energy of combus-
tion for the compound involved of sulfur element, the
standard energy of combustion of thianthrene was de-
termined by employing our rotating-bomb set, as being
–33507.76 14.13 J g–1 [19].
Results and discussion
Characterization of the complex
The elemental analyses results of the title complex are
as follows: mfound Ho 20.95%, C 41.14%, H 3.95%,
N 8.81%, S 24.49%; mcalculated: Ho 21.04%, C 41.37%,
H 4.11%, N 8.93%, S 24.54%, which is identified as
the formula of Ho(PDC)3(o-phen). The complex was
checked by HPLC and its purity is excellent (mass
fraction 0.9999).
Fig. 1 Comparison of IR spectra of a – HoCl3·4.56H2O,
b – o-phen·H2O, c – APDC and d – Ho(PDC)3 (o-phen)
Table 1 Main XRD data of the title complex Ho(PDC)3(o-phen), ligands o-phen·H2O and ammonium
pyrrolidinedithiocarbamate (APDC)
Compound
APDC
Main X-ray powder diffraction data
I/I0
40
100
12
26
62
10
20
13
d/nm
0.1099
0.5507
0.4736
0.4107
0.3675
0.2877
0.2641
0.2206
I/I0
46
26
54
99
72
34
25
33
o-phen·H2O
d/nm
0.8909
0.6189
0.5169
0.4454
0.3959
0.3847
0.3149
0.2817
I/I0
57
49
99
56
42
76
61
68
Ho(PDC)3(o-phen)
d/nm
9.839
8.631
7.922
6.702
5.719
4.892
4.211
3.900
J. Therm. Anal. Cal., 83, 2006
695

XIE et al.
Calculation of the standard molar enthalpy change
for the reaction in the solid-state
the ligand APDC (c), due to the stretching vibration
of the group CN (νCN) shifts to higher frequencies
(1425 cm–1), featuring a double bond character of the
CN bond. The C4H8NCSS– ion may be represented by
resonance hybrid of the structures [10, 22]:
θ
The molar enthalpy of solution Δsol Hm (1), Δsol Hm (2)
θ
θ
and Δsol Hm (3) of HoCl3·4.56H2O, APDC and
o-phen·H2O in absolute ethanol at 298.15 K are given
in Table 2, respectively. The mixed enthalpy of the
mixture of the two ethanolic solutions of the ligands
θ
mix Hm and the enthalpy change for the reaction in
Δ
θ
solution Δr Hm (sol) are listed in Table 3. The
θ
enthalpy of dissolution, Δsol Hm (4)of water in ethanol
is so small that it can be regarded as zero.
The application Hess’ law to the series of equa-
tions shown in Table 4 gives a thermochemical cycle,
from which the enthalpy change of the reaction in the
solid-state is derived as being 23.981 0.339 kJ mol–1
according to Eq. (2), where the uncertainty is given as
the standard deviation of the mean.
The second structure is favored when the two
sulfur atoms of ligand coordinate to Ho3+ to form a
four-number ring, accordingly νCN moves to a higher
frequency. Additionally, corresponding to the peak of
938 cm–1 ascribable to the characteristic absorption of
–CSS2– in the ligand of APDC, it spites into two peaks
of 1011 and 949 cm–1 in the complex. Obviously, the
resulting four-number ring increases the vibration in-
tensity of νCN [21]. The changes of νCN and νCSS indi-
cate that the two sulfur atoms of C4H8NCSS– coordi-
nate to Ho3+ in a bidentate ligand manner.
θ
θ
θ
θ
Δr Hm (s)=Δsol Hm (1)+3Δsol Hm (2)+Δsol Hm (3)
θ
+Δmix Hm +Δr Hm (l)–Δsol Hm (4)=
θ
θ
[(–47.034 0.178) +3(19.538 0.090)
+(20.970 0.071) + (10.592 0.049)
+ (–19.161 0.051) – 0] kJ mol–1=
(23.981 0.339) kJ mol–1
(2)
Some efforts have been devoted to test the
reasonability of the thermochemistry cycle. The crude
products from liquid-phase reaction were collected
and separated by centrifugal effect. The solid crude
products was purified and identified as being the
same product as that obtained in the direct synthesis.
The concentration of Ho3+ retained in the centrifugal
liquid was determined as 6·10–3 μg mL–1 by the
ICP-AES experiment, indicating that the starting
reactants have been transformed fully to the title
products, that is, the liquid-phase reaction proceeds in
100%. All of these show that the final thermodynamic
states of the title solid-phase reaction and is the same
with that of liquid-phase reaction, and the designed
thermochemistry cycle is correct.
Thermostability of Ho(PDC)3 (o-phen)
TG-DTG curve of the complex is presented in Fig. 2.
The complex is decomposed into the final compounds
in one step, which begin at 303.15 and complete
745.15 K, accompanying with the mass loss of
69.60%. In order to explore the decomposition process
of the title complex, the final compounds determined
by XRD are of the mixture of Ho2S3 and deposited car-
bon in which Ho2S3 predominates [23]. Based on the
above analyses, the decomposition process is postu-
lated as Eq. (1), where 228°C is the peak value in DTG
curve and 30.24% is the calculated value of the mass
residual. Clearly, the experimental result is in good
agreement with the calculated result.
30°C~228°C~472°C; 30.40% (30.24%)
Ho[(C5H8NS2)3(C12H8N2)]⎯⎯⎯⎯⎯⎯⎯⎯⎯→
1/2Ho2S3+2C
(1)
Calculation of the thermodynamic parameters for the
reaction in the liquid-state
The calorimetric experiment showed that this reaction is
an exothermic one. Based on thermokinetic data of the
reaction in solution at different temperatures as shown in
Table 5, and the thermodynamic equations [6], the ther-
modynamic parameters and kinetic parameters of the re-
action in solution are obtained and shown in Table 6.
Molar heat capacity of Ho(PDC)3 (o-phen)
To gain the value of molar heat capacity of the solid
compound, the empty cell (system I), the cell containing
sample with unknown specific heat c (system II), the
Fig. 2 TG -DTG curve of Ho(PDC)3 (o-phen)
696
J. Therm. Anal. Cal., 83, 2006

Ho(PDC)3 (o-PHEN) SOLID COMPLEX
Table 2 Enthalpies of solution of HoCl3·4.56H2O, ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline
(o-phen·H2O) in absolute ethanol at 298.15 K
θ
ΔsolHm(1)/
kJ mol–1
θ
ΔsolHm(2)/
kJ mol–1
θ
ΔsolHm(3)/
kJ mol–1
m/
mg
Q/
mJ
m/
mg
Q/
mJ
m/
mg
Q/
mJ
No.
1
80.61 –11333.968
80.60 –11222.976
80.59 –11390.995
80.60 –11161.595
80.61 –11389.102
80.56 –10234.888
–47.213
–46.756
26.29 3099.238
26.25 3121.801
26.27 3171.104
26.24 3082.010
26.33 3157.941
26.28 3117.297
19.368
19.539
19.832
19.297
19.705
19.488
31.71 3351.540
31.77 3393.602
31.76 3343.271
31.73 3356.008
31.68 3315.208
31.73 3379.615
20.950
21.173
2
3
–47.461
20.866
4
–46.500
20.965
5
–47.448
20.746
6
–46.827
21.123
(x σa)a
–47.034 0.178
19.538 0.090
20.970 0.071
θ
θ
ΔsolHm(1) represents the enthalpy of solution of HoCl3·4.56H2O in absolute ethanol; ΔsolHm(2) represents the enthalpy of solution of
6
θ
APDC in absolute ethanol; ΔsolHm(3) represents the enthalpy of solution of o-phen·H2O in absolute ethanol; a σa = (x – x)2 /n(n–1)
∑
i=1
1
where n is the experimental number; xi, a simple value in a set of measurements; x, the mean value of a set of measurement results.
Table 3 The mixed enthalpy of the ethanolic solution of APDC and o-phen·H2O, and the enthalpy change of the reaction in liq-
θ
uid-state ΔrHm(sol) (HoCl3·4.56H2O)·xC2H5OH(l)+[3APDC·yC2H5OH(l)+[(o-phen·H2O)·zC2H5OH(l)]=
Ho(PDC)3(o-phen)(s)+3NH4Cl(s)+5.56H2O·(x+3y+z)C2H5OH(l), at 298.15 K
No.
Q1/mJ
Δ
mixHm/kJ mol–1
Q2/mJ
ΔrHm/kJ mol–1
θ
θ
1
84.809
86.293
10.601
10.787
10.529
10.508
10.498
10.626
–153.693
–153.012
–154.456
–152.574
–152.032
–153.965
–19.212
–19.127
2
3
84.231
–19.307
4
86.064
–19.072
5
83.987
–19.004
6
85.006
–19.246
(x σa)a
85.065 0.421
10.592 0.049
–153.289 0.407
–19.161 0.051
θ
mixHm is the mixed enthalpy of the ethanolic solution of APDC and o-phen·H2O; and Δr Hm(l) is the enthalpy change of the
θ
Δ
liquid-phase reaction (HoC3·4.56H2O)·xC2H5OH(l)+3APDC·yC2H5OH(l)+[(o-phen·H2O)·zC2H5OH(l)]=
6
Ho(PDC)3(o-phen)(s)+3NH4Cl(s)+5.56H2O·(x+3y+z)C2H5OH(l); a σa = (x – x)2 /n(n–1) where n is the experimental number; xi,
∑
i=1
1
a simple value in a set of measurements; x, the mean value of a set of measurement results.
θ
Table 4 Thermochemical cycle and results for ΔHm
Reaction
ΔHm/kJ mol–1
θ
1
2
3
4
HoCl3·4.56H2O(s)+xC2H5OH(l)=(HoCl3·4.56H2O)·xC2H5OH(l)
–47.034 0.178
19.538 0.090
20.970 0.071
10.592 0.049
3APDC(s)+yC2H5OH(l)=3(APDC·yC2H5OH)(l)
o-phen·H2O(s)+zC2H5OH(l)=(o-phen·H2O)·zC2H5OH(l)
[3APDC·yC2H5OH(l)]+[(o-phen·H2O)·zC2H5OH(l)]=(3APDC)(o-phen·H2O)·(y+z)(C2H5OH)(l)
[(HoCl3·4.56H2O)·xC2H5OH(l)+3APDC·yC2H5OH(l)+[(o-phen·H2O)·zC2H5OH(l)]=
Ho(PDC)3(o-phen)(s)+3NH4Cl(s)+5.56H2O·(x+3y+z)C2H5OH(l)
5
–19.161 0.051
6
7
5.56H2O+(x+3y+z)C2H5OH(l)=5.56H2O·(x+3y+z)C2H5OH(l)
0
HoCl3·4.56H2O(s)+3APDC(s)+o-phen·H2O(s)=Ho(PDC)3(o-phen)(s)+3NH4Cl(s)+5.56H2O
23.981 0.339
cell containing first standard substance with known spe-
cific heat c1 (system III), and the cell containing second
standard substance with known specific heat c2 (sys-
tem I) are uniformly heated by the same Peltier current
for 1 h. When thermal equilibrium of systems I–IV is es-
tablished, it can be shown that, (a) the temperature is
uniform within the cell, and (b) the equilibrium temper-
ature θ is the same for a given Peltier current, whatever
the cell contents. When the Peltier current is cut off, the
quantities of heat q0, q, q1 and q2 retained by the sys-
tems I–IV are given by the following Eqs (3)–(6).
J. Therm. Anal. Cal., 83, 2006
697

XIE et al.
Table 5 Thermokinetic data of liquid-phase of formation reaction (HoCl3·4.56H2O)·xC2H5OH(l)+[3APDC·yC2H5OH(l)]
+[(o-phen·H2O)·zC2H5OH(l)]=Ho(PDC)3(o-phen)(s)+3NH4Cl(s)+5.56H2O·(x+3y+z)C2H5OH(l)
292.15 K
dHi/dt/
295.15 K
dHi/dt/
298.15 K
dHi/dt/
301.15 K
dHi/dt/
t/s
t/s
t/s
t/s
Hi/H0
Hi/H0
Hi/H0
Hi/H0
10–4 J s–1
10–4 J s–1
10–4 J s–1
10–4 J s–1
200
205
210
215
220
225
230
235
240
245
0.5821
0.5948
0.6074
0.6197
0.6318
0.6437
0.6553
0.6667
0.6779
0.6888
5.4168
5.3226
5.2127
5.1185
5.0243
4.9301
4.8201
4.7259
4.6317
4.5375
120 0.3328
125 0.3494
130 0.3657
135 0.3819
140 0.3978
145 0.4134
150 0.4288
155 0.4439
160 0.4588
165 0.4734
7.0221
6.9123
6.8183
6.7086
6.5832
6.5048
6.3951
6.2854
6.1913
6.0816
85 0.2631
90 0.2820
95 0.3007
100 0.3191
105 0.3373
110 0.3551
115 0.3726
120 0.3898
125 0.4067
130 0.4233
6.4788
6.3849
6.2753
6.1814
6.0562
5.9780
5.8841
5.7902
5.6963
5.6024
145 0.5972
150 0.6157
155 0.6338
160 0.6514
165 0.6686
170 0.6852
175 0.7014
180 0.7170
185 0.7323
190 0.7470
3.0469
2.9688
2.8750
2.7969
2.7188
2.6250
2.5469
2.4688
2.3906
2.3125
H0=0.2683 J (292.15 K), 0.2164 J (295.15 K), 0.1537 J (298.15 K) and 0.0846 J (301.15 K); t – time
Table 6 Kinetic, thermodynamic parameters of liquid-phase reaction (HoCl3·4.56H2O)·xC2H5OH(l)+[3APDC·yC2H5OH(l)]
+[(o-phen·H2O)·zC2H5OH(l)]=Ho(PDC)3 (o-phen)(s)+3NH4Cl(s)+5.56H2O·(x+3y+z)C2H5OH(l)
Temperature/
K
k·103/
s–1
E/
kJ mol–1
ΔG≠ /
kJ mol–1 kJ mol–1 J mol–1 K–1
θ
θ
ΔH≠ /
θ
ΔS≠ /
n
r
lnA
r
r
292.15
295.15
298.15
301.15
3.4156
4.1469
5.0498
6.1926
0.6023 0.9998
0.6056 0.9994
0.5936 0.9991
0.5957 0.9998
85.30
85.72
45.8525 –135.0436
86.13
48.32
5.677
0.9996
0.9995
86.51
r – linear correlation coefficient
Molar heat capacity of the complex was deter-
For system I
q0=aθ
(3)
mined by an RD496-III type microcalorimeter when
changing the samples in the sample cell. The values of
q are obtained by the testing method presented as a
curve in Fig. 3. In Fig. 3, AG is baseline; at time B, a
constant Peltier current is generated in the laboratory
cell; at CD, the steady state of the system is estab-
lished; at point D, the Peltier effect is cut off; at point
E, the state of the system returned to the experimental
initial state after cutting off the Peltier current. q is the
total heat, as shown as the shadow area. So the molar
heat capacity of the sample is derived from Eq. (7). The
results of the experiments are shown in Table 7.
For system II
For system III
For system IV
q=(a+mc)θ
q1=(a+m1c1)θ
q2=(a+m2c2)θ
(4)
(5)
(6)
where a (in J K–1) is the apparent heat capacity of the
empty cell, θ (in K) is the equilibrium temperature for
a given Peltier current, m (in g), m1 (in g) and m2 (in g)
are masses of the investigated sample, the first stan-
dard substance and second standard substance, re-
spectively; c (in J mol–1 K–1), c1(in J mol–1 K–1) and c2
(in J mol–1 K–1) are molar heat capacity of the investi-
gated sample, the first standard substance and second
standard substance, respectively; q0 (in J), q (in J),
q1 (in J) and q2 (in J) are the quantities of heat retained
by the systems I–IV when they were heated up by a
given Peltier current.
Combustion energy of Ho(PDC)3 (o-phen)
The determination method of combustion energy for
the complex was the same as for the calibration of the
calorimeter with benzoic acid. The combustion ener-
gies of the samples were calculated in accord with [18].
The results of the calculations are given in Table 8.
Combination of the Eqs (3)–(6), Eq. (7) is ob-
tained.
c= [(q–q0)/2m][m1c1/(q1–q0) +m2c2 /(q2–q0)] (7)
Standard combustion enthalpy of Ho(PDC)3 (o-phen)
The value of c of the investigated sample can be
obtained from Eq. (7) if the values of c1 and c2 of two
standard substances are known.
The standard combustion enthalpy of the complex,
θ
Δc Hm (complex, s, 298.15 K), refers to the combus-
698
J. Therm. Anal. Cal., 83, 2006

Ho(PDC)3 (o-PHEN) SOLID COMPLEX
Table 7 Experimental data used for calculating the molar heat capacity of Ho(PDC)3(o-phen), cm, at 298.15 K
Experimental data
Empty cell
Benzoic acid
α-Al2O3
Ho(PDC)3 (o-phen)
4453.908
4444.543
4432.133
4447.035
4438.165
4450.647
6088.611
6080.422
6094.207
6098.640
6075.115
6073.035
4959.916
4962.776
4977.771
4984.568
4967.144
4983.760
5008.360
4973.729
4998.337
4994.254
4985.635
4980.327
q/mJ
(x σa)a
4444.405 3.610
1.816·10–3
6085.005 4.672
1.717·10–3
4.51478
4972.656 4.824
2.169·10–3
4990.107 5.664
2.538·10–3
precision (σa/x)
m/g
2.68416
2.75901
c/J mol–1 K–1
c0 of lit./J mol–1 K–1
accuracy (c0–c)/c0
78.707 2.927
79.03 [24]
4·10–3
145.923 0.562
145.327 [25]
4·10–3
79.264 1.218
6
aσa = (x – x)2 /n(n–1) where n is the experimental number; xi, a simple value in a set of measurements; x, the mean value of a set
∑
i=1
1
of measurement results
Table 8 Experimental results for the combustion energy of the complex Ho(PDC)3 (o-phen)
Compound
No.
m/g
Qc/J
QN/J
ΔT/K
–ΔcU/J g–1
1
0.72532
0.72527
0.72130
0.71056
0.72455
0.71690
9.90
10.80
12.60
12.60
12.60
12.60
1484.57
1484.41
1476.26
1474.75
1482.91
1467.26
0.9574
0.9585
0.9514
0.9521
0.9569
0.9484
21402.14
21429.56
2
3
21381.34
Ho(PDC)3(o-phen)
4
21422.66
5
21411.18
6
21450.74
(x σa)a
21416.10 9.87
6
aσa = (x – x)2 /n(n–1) where n is the experimental number; xi, a simple value in a set of measurements; x, the mean value of a set
∑
i=1
1
of measurement results; m – mass of complexes, Qc – calibrated heat of combustion wire, QN – calibrated heat of acid, –ΔcU – com-
bustion energy of complex
θ
Δc Hm (complex, s, 298.15 K)=
ΔcU (complex, s, 298.15 K)+ΔnRT
Δn=ng(products)–ng(reactants)
(9)
(10)
where ng is the total amount in moles of gases present
as products or as reactants, R=8.314 J K–1 mol–1,
T=298.15 K. The standard combustion enthalpy of the
complex is of –16803.95 7.74 kJ mol–1.
Fig. 3 Curve of measurement of the molar heat capacity of the
complex Ho(PDC)3 (o-phen)
Standard enthalpy of formation of Ho(PDC)3 (o-phen)
The standard enthalpy of formation of the complex,
θ
Δf Hm (complex (s), 298.15 K), is calculated by Hess’s
tion enthalpy change of the following ideal combus-
tion reaction at 298.15 K and 100 kPa.
law according to the thermochemical equation above.
θ
Δf Hm [Ho(PDC)3 (o-phen)(s)]=
Ho(PDC)3 (o-phen)(s)+167/4O2(g)=
θ
[1/2Δf Hm (Ho2O3(s))+27Δf Hm (CO2(g))
θ
1/2Ho2O3(s)+27CO2(g)+16H2O(l)+6SO2(g)
+5/2N2(g)
(8)
θ
+16Δf Hm (H2O(l))+6Δf Hm (SO2(g))
θ
θ
+5/2Δf Hm (N2(g))]
The standard combustion enthalpy of the
complex calculated by Eqs (9) and (10).
θ
–Δc Hm [Ho(PDC)3 (o-phen)(s)]
(11)
699
J. Therm. Anal. Cal., 83, 2006

XIE et al.
θ
where Δf Hm (Ho2O3(cr), 298.15 K)= –1883.3
4 T. Jiang, W. Zhang and J. Shen, Rare Earths, 21 (2000) 39
(in Chinese).
8.2 kJ mol–1 [24]; Δf Hm (CO2(g))= –393.51
θ
0.13 kJ mol–1, Δf Hm
(H2O(l))= –285.830
θ
5 T. Ren, J. Xia and J. Zhang, Tribology, 18 (1998) 268
(in Chinese).
mol–1,
θ
Δf Hm (SO2(g))= –296.81
0.20 kJ mol–1 [26–29]. Its standard enthalpy of forma-
tion, Δf Hm , is calculated to be –1115.42 8.94 kJ mol–1.
0.042
kJ
6 Sh. L. Gao, M. Ji, S. P. Chen, R. Z. Hu and Q. Zh. Shi,
J. Therm. Anal. Cal., 66 (2001) 423.
θ
7 Z. H. Zhang, Z. J. Ku, H. R. Li, Y. Liu and S. S. Qu,
J. Therm. Anal. Cal., 79 (2005) 169.
8 S. Gao, S. Chen, G. Xie, G. Fan and Q. Shi,
J. Therm. Anal. Cal., 81 (2005) 387.
Conclusions
9 V. L.Varand, L. A. Glinskaya and R. F. Klevtsova,
Struct. Chem., 41 (2000) 544.
The ternary complex formulated as Ho(PDC)3
(o-phen) has been synthesized in absolute ethanol by
HoCl3·4.56H2O reacting with the mixed ligands of
APDC and o-phen. The calorimetrical investigation at
298.15 K reflects that the reaction in the liquid-state
occurs smoothly while the solid reaction does not.
The molar heat capacity of the complex, cm, was
determined as being 79.264 1.218 J mol–1 K–1 at
298.15 K by using an RD496-III heat conduction
10 C. Y. Su, M. Y. Tan and N. Tang, J. Coord. Chem.,
38 (1996) 207.
11 V. L. Varand, L. A. Glinskaya and R. F. Klevtsova,
J. Struct. Chem., 39 (1998) 244.
12 C. Y. Su, N. Tang and M. Y. Tan, Polyhedron,
15 (1996) 233.
13 H. Zh. Ma, B. Wang and Q. Zh. Shi, Synth. React. Inorg.
Met. Org. Chem., 32 (2002) 617.
14 T. Coplen, J. Phys. Chem. Ref. Data, 30 (2001) 701.
15 M. Ji, M. Y. Liu, S. L. Gao and Q. Z. Shi,
Instrum. Sci. Techn., 29 (2001) 53.
microcalorimeter. Through
a designed thermo-
chemical cycle, the standard molar enthalpy of reac-
tion for the title solid-phase reaction was derived as
being 23.981 0.339 kJ mol–1 at 298.15 K.
16 X. W. Yang, S. P. Chen and S. L. Gao, Instrum. Sci. Techn.,
30 (2002) 311.
17 V. Marthada and J. Kilday, Res. Nat. Bur. Stand.,
85 (1980) 467.
Based on thermokinetic data of liquid-phase
reaction at different temperatures, the thermodynamic
parameters and kinetic parameters of the reaction in
the liquid-state are obtained. The apparent activation
energy of the reaction is higher than the activation
energy 63 kJ mol–1 at which the reaction occurs
instantaneously at room temperature, showing that
the title reaction proceeds feasibly in ethanol solution.
TG-DTG investigations indicate that the title
complex is decomposed into Ho2S3 and deposited
carbon in one step, which provide a probe for the
preparation of rare earth chalcogenide sulfide.
18 M. M. Popov, Thermometry and Calorimetry [M]. Moscow
University Publishing House, Moscow 1954, p. 382.
19 W. H. Johnson, J. Res. Nat. Bur. Stand, 79 (1975) 561.
20 Q. N. Dong, IR Spectroscopy, Chemical and Industrial Press,
1979, p. 99 (in Chinese).
21 K. Nakamoto, in: D. J. Huang, R. Q. Wang (transl.). Infrared
and Raman Spectra of Inorganic and Coordination Com-
pounds. Beijing, Chemical and Industrial Press (4th Edn.),
1991, p. 253 (in Chinese).
22 K. Nakamoto, J. Fujita and R A. Condrate, J. Chem. Phys.,
39 (1963) 423.
23 T. Tito, O. Paul and L. P. Nigel, Chem. Mater.,
13 (2001) 3843.
The standard enthalpy of formation of the title com-
plex was determined as being –1115.42 8.94 kJ mol–1,
showing that the complex is of quite thermal stability.
24 D. A. Ditmars, S. Ishihara, S. S. Chang and G. Bernstein,
J. Res. Nat. Br. Stand., 87 (1982) 159.
25 A. Rojas-Aguilar and E. Orozoco-Guareno,
J. Chem. Thermodyn., 32 (2000) 767.
26 E. H. P. Cordfunke and R. J. M. Kongings,
Thermochim. Acta, 375 (2001) 65.
Acknowledgements
27 J. D. Cox, D. D. Wangman and V. A. Medvedev,
CODATA Key Values for Thermodynamics, Hemisphere,
New York 1989.
The Authors thank the financial support from the National Nat-
ural Science Foundation of China (Grant No. 20471047), Edu-
cation Committee of Shannxi Province (Grant Nos. 01JK229,
FF02328 and 05JK291).
28 J. D. Cox, J. Chem. Thermodyn., 10 (1978) 903.
29 D. W. Donald, H. E. William, B. P. Vivian, H. S. Pichard,
H. Iva, M. B. Sylvia, L. C. Kenneth and L. N. Ralph,
Translated by T. Liu and M. Zhao, Chinese Standards
Press, Beijing 1998 (in Chinese).
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J. Therm. Anal. Cal., 83, 2006