Thermochemical study on the Schiff base [H2salen = N,N′-bis(salicylidene) ethylendiamine] and its binuclear copper (II) complex

Article abstract of DOI:10.1016/j.tca.2013.07.004

The Schiff-base ligand [H2salen = N,N′-bis(salicylidene) ethylendiamine] and the binuclear copper (II) complex [Cu₂(salen) ₂(μ - O)₂] were synthesized and the structure of the complex was characterized by X-ray crystallogr

Full text of DOI:10.1016/j.tca.2013.07.004

Accepted Manuscript
Title: Thermochemical study on the Schiff base
ꢀ
[
H salen=N,N -bis(salicylidene) ethylendiamine] and its
2
binuclear copper (II) complex
Author: Chuan-hua Li Li-Ming Tao Sheng-Xiong Xiao
Ai-Tao Li Jian-Hong Jiang Xu Li Fei-Hong Yao Wei-Peng
Luo Jin-Qi Xie Meng-Na Peng Lan Pan Qiang-Guo Li
PII:
S0040-6031(13)00364-X
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.tca.2013.07.004
TCA 76554
To appear in:
Thermochimica Acta
Received date:
Revised date:
Accepted date:
3-5-2013
30-6-2013
2-7-2013
Please cite this article as: C.-h. Li, L.-M. Tao, S.-X. Xiao, A.-T. Li, J.-H. Jiang, X. Li, F.-
H. Yao, W.-P. Luo, J.-Q. Xie, M.-N. Peng, L. Pan, Q.-G. Li, Thermochemicalstudyonthe
ꢀ
Schiff base [H salen=N,N -bis(salicylidene) ethylendiamine] and its binuclear copper
2
(II) complex, Thermochimica Acta (2013), http://dx.doi.org/10.1016/j.tca.2013.07.004
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Thermochemical study on the Schiff base [H salen=N,N′-bis(salicylidene)
2
ethylendiamine] and its binuclear copper (
) complex
Chuan-hua Li, Li-Ming Tao, Sheng-Xiong Xiao, Ai-Tao Li, Jian-Hong Jiang, Xu Li, Fei-Hong
Yao, Wei-Peng Luo, Jin-Qi Xie, Meng-Na Peng, Lan Pan, Qiang-Guo Li*
Hunan Provincial Key Laboratory of Rare-Precious Metals Compounds and Applications, Department of Chemistry
and Life Science, Xiangnan University, Chenzhou 423000, Hunan Province, PR China
*
Corresponding author. Tel.: +86 0735 2653353; Fax: +86 0735 2653353
E-mail address: liqiangguo@163.com
Abstract
The Schiff-base ligand [H
2
salen=N,N′-bis(salicylidene) ethylendiamine] and the binuclear
(µ-O) ] were synthesized and the structure of the complex was
copper (
) complex [Cu (salen)
2
2
2
characterized by X-ray crystallography. Two thermochemical cycles were designed on basis of
Hess’s law. According to the two cycles, the dissolution enthalpies of relevant substance in the
calorimetric solvent of DMF were determined by a solution-reaction isoperibol calorimeter. The
measurement experiment was performed at a constant ambient temperature of 298.15 K. After that,
the rationality of these two thermochemical cycles was demonstrated by UV spectra and refractive
indexes. Base on the measurement results and relevant literature data, the standard molar enthalpies
!
of formation of the Schiff base and the complex were reckoned to be: !
f
H
m
[H
2
salen(s),
-1
!
-1
298.15K]=-(146.4 ! 1.9) kJ
!
mol ; !
f
H
m
[Cu
2
(salen)
2
(µ-O)
2
(s), 298.15K]= -(171.8 ! 3.9) kJ
!
mol .
Keywords: Cupric acetate monohydrate; Salicylaldehyde; Ethylenediamine; Dissolution-reaction
calorimeter; Standard molar enthalpy of formation
1
Page 1 of 18

1. Introduction
The chemistry of Schiff base and its application have received renewed attention because of
their preparative accessibility, diversity and structural variability. Transition-metal complexes
coordinated with tetradentate Schiff-base ligands have been studied extensively [1,2]. In particular,
2
salen-type tetradentate ligands (H salen = N,N′-bis(salicylidene)ethylendiamine) have been known
since 1933, their complexes became a standard system in coordination chemistry, and their
application as inorganic-organic composite materials was investigated[3]. It's also worth mentioning
that the copper is one of the essential elements of biological system, which plays an important role
in organism. The copper complexes with Schiff base are of considerable interest due to their
potential chemical and special biological activities [4-10].
2 2
The synthesis of the Schiff base (H salen) [H salen= N, N′-bis(salicylidene)ethylendiamine]
and the complex [Cu (salen) (µ-O) )] have been reported in published works [3,11-14]. But up to
2
2
2
now, their thermodynamic properties hasn't been in the press. As is known, the thermochemical
parameters are an indispensable part of chemical thermodynamics, which closely relates to
fundamental academic problems together with application development. In this work, we have
2 2 2 2
planned to prepare the Schiff base (H salen) and the complex [Cu (salen) (µ-O) ], then further
investigated their standard molar enthalpy of formation by the solution-reaction calorimetry, so as to
provide some valuable reference data for the further study about the Schiff-base complexes.
2
. Experimental
2.1. Materials and Physical Measurement
All chemicals used herein were analytic grade. Absorption spectra were measured with a
-1
Hitachi U-3010 UV/Vis spectrophotometer. FT-IR spectra in KBr (4000-400 cm ) were recorded at
an Avatar 360 spectrometer. Thermochemical analysis was performed using the solution-reaction
isoperibol calorimeter (SRC-100, constructed by the thermochemical laboratory of Wuhan
University, china). X-ray diffraction measurements were done with a Bruker ApexII Kappa CCD
diffractometer using graphite-monochromated Cu-Kα radiation (λ = 0.71073 Å).
2.2. Syntheses of the Schiff -base ligand [13]
2
Page 2 of 18

The N,N′-bis(salicylidene)ethylendiamine was prepared by mixing salicylaldehyde and
ethylenediamine in ethanol in 2:1 molar ratio, being refluxed for 2h. The yellow solid formed was
filterated after concentration by rotary evaporation to a small volume. The product was purified by
recrystallization and dried at 60
in a vacuum oven.
2.3. Syntheses of Cu(
) complex [14]
2
An aqueous solution of NaOH (0.04g, 1mmol) was added to the solution of H salen (0.1341g,
0.5mmol) in 95% ethanol (20mL). After thirty minutes of stirring, an ethanolic solution of
3 2
Cu(CH COO)2 ! H
O (0.0998g, 0.5mmol ) was slowly added dropwise to the mixed solution at 50

for 1h. The reaction mixture was continuously stirred by a magnetic stirrer for about 2h. After
filtered and recrystalized from ethanol, a green complex was obtained, then dried at 60
in vacuo.
2.4. The crystal growth of complex.
The prepared complex was dissolved in a mixed solvent of DMF and methanol
(VDMF/VMeOH=5:2) until the solution saturated, followed by filtering through a funnel with cotton
(medical grade). One week later, the black-green block crystals were formed in the clear filtrate
under the conditions of room temperature. The crystals were characterized by spectroscopic
analysis and X-ray crystallographic analysis. The results showed that the formula of complex was
2 14 2 2 2
[Cu (C16H O N ) ]. On the basis of the formula, purity of the complex was measured by titrate
analysis and the result showed its purity was more than 99.0%.
2.5. Solution-Reaction Isoperibol Calorimeter and Calibration.
The operating principle of solution-reaction isoperibol calorimeter (SRC-100) and its
calibration have been described in prevous literiature [15]. During the course of this experiment, the
system temperature was controlled at 298.15K by using DWT-702 precise temperature control
instrument, the resistance of heater was 1212.3! , and the current was 21.813 mA. The volume of
calorimetric solvent in dewar vessel was 100 mL and the dewar vessel was submerged in water
thermostat. The precision values of temperature control and temperature measurement were
!
0.001 and ! 0.0001 K, respectively.
3
Page 3 of 18

This calorimeter is calibrated by measuring the dissolution enthalpies of THAM (NBS 742a,
USA) in 0.0001 mol/mL HCl and KCl (calorimetric primary standard) in water at 298.15K. After
five parallel measurements, the average values of dissolution enthalpies for THAM and KCl were -
-
1
-1
（
29769! 18）J
（29776! 31.5） J
was less than 0.5% and the present calorimeter was very reliable.
!
mol and （17565! 14 ）J
!
mol , respectively. Comparing with the published data
-1
-1
-
!
mol for THAM and （17536! 9）J
!
mol for KCl [15], the eventual error
2.6. Thermochemical cycle of Reaction (1a) and Reaction (1b).
The equations of two reactions as follows:
2
2
C
7
H
6
O
2
(l) + C
2
H
8
N
2
(l) →H
2
salen(s)+2H
2
O(l);
2 2
(µ-O) (s)+4HOAc(l)+2H O(l)
(1a)
(1b)
H
2
salen(s)+2Cu(OAc)
2
·H O(s)→ Cu
2
2
(salen)
2
According to the Hess’s law, we have designed the thermochemical cycle for the two reactions
as shown in Fig. 1 and Fig. 2). The thermochemical analysis was carried out by an isoperibol
(
calorimeter (SRC-100). After the heat-measurement experiments, we further determined the UV
spectra and refractive indexes of solution B and D. The experimental results indicated that the
solution B and D have same UV spectrum curves (Fig. 3) and equal refractive indexes (η25℃
=
1.4279). The same case also occurs in solution 2 and 5, their UV spectrum curve as shown in the
Fig. 4 and they also have equal refractive indexes (η25℃=1.4288). These facts showed that solution
B and D has the same thermodynamics state, so were solution 2 and 5. Accordingly, the two cycles
of reaction (1a) and (1b) are reasonable.
The selected calorimetric solvent must completely and rapidly dissolve the investigated
substances in the sample cell. After several tests, the relevant substances in the two reactions are
very soluble in dimethyl formamide (DMF). Consequently, it was chosen as calorimetric solvent.
2.7. Determination of Dissolution Enthalpies.
The solid samples were dried and grinded fully in an agate motar in advance, the calorimetric
solvent S (100.00mL) was added into the reaction vessel and a certain amount of the samples were
placed exactly into the sample vessel. After the calorimeter was adjusted to the constant temperature
4
Page 4 of 18

(
298.15 ! 0.001K), the samples were added into the reaction container, then their dissolution
enthalpies were measured. After five parallel measurements, the obtained results were listed in
Table 1 and Table 2. More detailed operating process was described in the Ref. [16].
7 6 2
The amount of the relevant substances of reaction (1a) was as follows: C H O (l) (1.0mmol),
C
2
H
8
N
2
(l) (0.5mmol), H
(l) ! S ! Solution A
(l) ! Solution A ! Solution B
salen(s) ! S ! Solution C
O(l) ! Solution C ! Solution D
2
salen(s) (0.5mmol), H
2
O(l) (1.0mmol).
(2a)
2
C
7
H
6
O
2
C
2H
8N
2
(3a)
(4a)
(5a)
H
2
2
H
2
The amount of the relevant substances of reaction (1b) was as follows: H
2
salen(s) (0.2mmol),
Cu(OAc)
0.2mmol).
salen(s) ! S! Solution1
Cu(OAc)
Cu (salen)
HOAc(l) ! 2H
Solution3 ! Solution4 ! Solution5
2
!
H
2
O(s) (0.2mmol), Cu
2
(salen)
2
(µ-O)
2
(s) (0.1mmol), HOAc(l) (0.4mmol), H O(l)
2
(
2
H
2
(2b)
2
2
H2O (s) ! Solution1! Solution2 (3b)
2
2
(! - O)
2(s) ! S ! Solution3
(4b)
(5b)
(6b)
4
2
O(l) ! Solution4
3. Results and discussion
3.1. IR Spectra and Crystal Structure
-1
The pivotal frequencies of characteristic absorption bands in the IR spectra (cm ) for the Schiff
base [H salen] and the complex [Cu (salen) (µ-O) ] are listed in Table 3.
2
2
2
2
-1
-1
There are four characteristic absorption bands for H
2
salen: νO-H (3445cm , s), νC-O (1120cm , s),
-1
-1
ν
C=N (1636cm , vs) δO-H(1284cm , s). After coordination, νO-H and δO-H disappeared and the
skeleton peak of H
2
2
salen shifted to a low wavenumber, which indicated that H salen was
2+
coordinated with Cu after removing the hydrogen of the hydroxyl group. Also, the molecular
structure of the complex is further confirmed by X-ray single crystal diffraction (Fig. 5).
3.2. Result of calorimetric experiment
The results of calorimetric measurements are given in Table 1 and Table 2.
5
Page 5 of 18

!
m
!
m
3.3. Treatment of
(5a) and
(5b)
H
!
s
H
!
s
!
In the process of measurement, the value of ! H (5a) is so quite minor that it is difficult to
s
m
measure. Furthermore, the concentration of all the other substances in the system is relatively small.
!
m
Consequently, the dilution enthalpies [
(5a)] can be neglected during the calculation [17].
!
s
H
According to Ref. [18,19], the mixing enthalpy of (4HOAc + 2H
2
O) can be obtained as follow:
θ
m
θ
m
θ
m
-1
! s H (5b) = 4! [! H (n
: n =1:0.5) - ! H (HOAc, l)]= 2.24 kJ mol
!
f
HOAc
H O
f
2
3.4. The molar enthalpies of reaction (1a) and reaction (1b)
According to Hess’law, the standard molar enthalpy of reaction (1a) was obtained:
!
m
!
m
!
m
!
m
!
r
H
(1a) = 2!
s
H
(2a) + !
s
H
(3a) - !
s
H
(4a)
2
2
2
!
!
[2! (-4.538) ! (-57.563) - 26.245] ! (0.027) ! (0.391) ! (0.232)
-
1
-(92.884 ! 0.455) kJ !mol
The standard molar enthalpy of reaction (1b) was obtained:
!
!
!
!
!
!
!
r
H
m
(1b) = 2!
s
H
m
(2b) + 2!
s
H
m
(3b) - !
s
H
m
(4b) - !
s
H
m
(5b) - !
s
H
(6b)
m
!
!
!
[2! 25.024 ! 2! (-22.402) - 36.792 - 2.24 - (-27.309)]
2
2
2
2
(2! 0.243) ! (2! 0.319) ! (0.141) ! (0.208)
-1
- (6.479 ! 0.840) kJ
!
mol
!
3.5. Calculating of !
f
H
m
[C
7
H
6
O
2
(l), 298.15K]
The standard molar enthalpy of formation of salicylaldehyde can be calculated by its heat of
combustion. Its process of the calculation is as follows:
C
7
H
6
O
2
2 2 2
(l)+15/2O (g) →7CO (g)+3H O(l) ;
!
m
-1
! c H [C
7H
6O
2
(l), 298.15K] ! -3328.9 kJ mol [20]
!
According to the Hess’ law:
!
!
!
!
m[
C7
H6
O2(l)]= 7
m[CO
2(g), 298.15K] + 3
m[H
2O(l),298.15K]-
m[C
7H
6
O (l),298.15K]
2
!
c
H
!
f
H
!
f
H
f
! H
According to Ref. [21]
6
Page 6 of 18

!
m
-1
!
!
f
f
H
H
[H2
O(l), 298.15K] ! - (285.830 ! 0.040) kJ
!
mol
!
m
-1
[CO (g),298.15K] ! - (393.51! 0.13) kJ mol
2
!
So that
!
m
2
2
!
f
H
[C7
H6
O (l), 298.15K] ! [7! (-393.51) + 3! (-285.15) - (-3328.9)]! (7! 0.13) ! (3! 0.040)
2
-1
!
! (281.1! 0.9) kJ mol
!
!
!
3.6. Evaluation of !
f
H
m
[H
2
salen(s), 298.15K] and !
f
H
m
[Cu
2
(salen)
2
2
(µ-O) (s), 298.15K].
According to the Hess’ law:
!
m
!
!
!
(
1a) =
m[H
2
salen(s), 298.15K] + 2
m[H
2O(l), 298.15K]- 2
m[C
7
H
6
O (l), 298.15K]
2
!
!
r
r
H
H
!
!
f
f
H
H
!
f
H
!
f
H
!
-
m[C
2
H
8
N (l), 298.15K]
2
!
m
!
!
(
1b) =
m[Cu
2
(salen)
2
(! - O)
2
(s), 298.15K]+ 4
m[HAc(l),298.15K]
!
f
H
!
f
H
!
m
!
m
+
2! H [H
2O(l),298.15K]- 2! H [H
2
salen(s),298.15K]
f
f
!
m
-
2! ! [Cu(OAc)
2
H2O (s),298.15K]
f
According to Refs. [18,22]
!
-1
m[
C2H
8N
2
(l), 298.15K] ! -(63.01! 0.54) kJ mol
!
!
!
!
f
f
f
H
H
H
!
m
-1
[HOAc(l),298.15K] ! - 483.50 kJ mol
!
!
m
-1
[Cu(OAc)2 !
H2
O (s), 298.15K] ! -1189.1kJ mol
!
So that
!
m[
H salen(s), 298.15K]! [(-92.884) - 2! ( - 285.830) ! 2! (- 281.1) ! (-63.01)]
2
!
f
H
2
2
2
2
!
(0.455) ! (2! 0.040) ! (2! 0.9) ! (0.54)
-1
!
- (146.4 ! 1.9) kJ mol
!
!
m[Cu
2
(salen)
2
(μ - O) (s),298.15K] =[(-6.479) - 4×(-483.50) - 2×(-285.830) + 2×(-146.4)
2
!
f
H
2
2
2
+
2×(-1189.1)]! (0.840) ! (2! 0.040) ! (2! 1.9)
-1
=
- (171.8 ! 3.9) kJ mol
!
4. Conclusions
7
Page 7 of 18

The complex was synthesized by using copper (II) and the Schiff-base ligand, being
characterized by the X-ray diffraction experiment. At a constant temperature of 298.15 K, the
dissolution enthalpies were measured when relevant substances were dissolved. The standard molar
enthalpy of formation of Schiff base (H
2
salen) and the complex (Cu
2
(salen)
2
(µ-O)
2
) were calculated
!
-1
!
to be !
f
H
m
[H
2
salen(s), 298.15K]= -(146.4 ! 1.9) kJ
!
mol and !
f
H
m
[Cu
2
(salen) (µ-O) (s),
2
2
-1
2
98.15K]= -(171.8 ! 3.9) kJ mol .
!
It has to be pointed out that, the solubility of cupric acetate monohydrate in the solvent of
dimethyl formamide are not so ideal. However, it can be fully dissolved in the solution 1
salen+DMF). Therefore, we adopted the thermochemical cycle shown in Fig. 2.
(H
2
Acknowledgements
The authors thank National Natural Science Foundation of China (Nos. 20973145, 21273190),
Hunan provincial key laboratory of xiangnan rare-precious metals compounds and Applications
(2012XGJSYB02), the Educational Committee Foundation of Hunan Province (No. 11A112 and No.
1
2
0C1233), the Science and Technology Department Foundation of Hunan Province (No.
011TP4016-1 and No. 2012TP4021-5) and the construct program of the key discipline in Hunan
province for financial support.
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Ce(Hsal) · (tch)] ·2H O, J. Chem. Eng. Data. 55 (2010) 2874-2878.
[
2
2
[
17] Q.G. Li, L.J. Ye, B. Den, L.P. Zhao, Thermochemistry of the ternary solid complex of
Samarium chloride six-hydrate with alanine and glycine in Chinese, Chemical World 44 (2003)
343-346.
[
18] D.D. Wagman, W.H. Evans, V.B. Parker et al., J. Phys. Chem. Ref. Data, 11(1982) 2-158.
19] C.P. Zhou, Y. Liu, Z.P. Rao, S.S. Qu, Study on Thermochemistry of solid state coordination
reaction of valine with copper Acetate in Chinese, Chem. Bull. 65 (2002) 488-491.
[
th
[
20] R.C. Weast, Handbook of chemistry and physics, CRC Press, the 58 ed., 1977, D-276.
[
21] J.D. Cox, D.D. Wagman, V.A. Medvedev, CODATA key values for thermodynamics,
hemisphere publishing corp, New York, 1984, Chapter 1.
[22] W.D. Good, R.T. Moore, Enthalpies of formation of ethylenediamine, 1,2,-propanediamine,
1,2,-butanediamine, 2-methyl-1,2-propanediamine, and isobutylamine. C-N and N-F
thermochemical bond energies, J. Chem. Eng. Data, 15 (1970) 150-154.
10
Page 10 of 18

Legends to Tables
7 6 2 2 8 2 2
Table 1 Dissolution enthalpies of [C H O (l)], [C H N (l)] and [H salen(s)] in the Calorimetric
Solvent S at 298.15 K.
Table 2 Dissolution enthalpies of [H
2 2 2 2 2 2
salen(s)], [Cu (OAc)2 ! H O(s)], [Cu (salen) (µ-O) (s)] and
[Solution 4(aq)] in the Calorimetric Solvent S at 298.15 K.
-1
Table 3 IR data of ligand and complex (cm ).
11
Page 11 of 18

Table 1
Dissolution enthalpies of [C
7
H
6
O
2
(l)], [C
2
H
8
N
2
2
(l)] and [H salen(s)] in the Calorimetric Solvent S at
298.15 K.
a
b
!
m
-1
system
no.
m /g
t /s
! H / kJ
!
mol
s
C
7
H
6
O
2
(l) in S
1
2
3
4
5
0.1219
0.1227
0.1223
0.1228
0.1229
7.97
7.48
7.52
7.70
7.83
-4.5170
-4.5167
-4.5802
-4.5498
-4.5241
!
m
c
-1c
[
[
[
C
C
7
H
H
6
O
2
(l), 298.15 K] = - (4.538 ! 0.027 ) kJ mol
!
!
!
!
s
H
C
2
H
8
N
2
(l)
1
2
3
4
5
0.0306
0.0308
0.0298
0.0305
0.0298
35.37
48.63
52.26
48.94
49.60
-57.7755
-57.6083
-57.7809
-58.0525
-57.0396
in the solution A
!
m
-1
N
2
(l), 298.15 K] = - (57.563 ! 0.391) kJ
!
mol
s
H
2
8
H
2
salen(s) in S
1
2
3
4
5
0.1346
0.1346
0.1345
0.1343
0.1344
19.10
19.98
20.46
20.19
20.50
26.0582
26.5936
26.1912
26.0322
26.3487
!
m
-1
salen(s), 298.15 K] = (26.245 ! 0.232) kJ mol
!
s
H
H
2
a
b
c
m: molar mass of sample. t: heating period of electrical calibration. Uncertainty was estimated as twice the standard deviation of the mean of the
results.
12
Page 12 of 18

Table 2
Dissolution enthalpies of [H
2
salen(s)], [Cu
2
(OAc)2 !
H
2
O(s)], [Cu
2
(salen)
2
(µ-O)
2
(s)] and [Solution
4(aq)] in the Calorimetric Solvent S at 298.15 K.
a
b
!
m
-1
system
salen(s) in S
no.
m /g
t /s
! H / kJ
!
mol
s
H
2
1
2
3
4
5
0.0538
0.0539
0.0537
0.0535
0.0537
6.04
7.48
7.44
7.00
7.40
24.9093
24.6629
25.1569
25.2815
25.1127
!
m
c
-1c
[
[
H salen(s), 298.15 K] = (25.024 ! 0.243 ) kJ
!
mol
!
!
!
s
H
H
H
2
Cu(OAc)2 !
H
2
O(s)
1
2
3
4
5
0.0400
0.0400
0.0401
0.0398
0.0401
3.45
7.35
7.40
7.48
7.44
-22.2754
-22.7437
-22.6960
-22.3196
-21.9768
in the solution 1
!
m
-1
Cu(OAc)2
!
H O(s), 298.15 K] = - (22.402 ! 0.319) kJ
!
mol
s
2
Cu
2
(salen)
2
(µ-O)
2
(s)
1
2
3
4
5
0.0660
4.72
5.56
5.51
5.53
5.38
36.6954
37.0363
36.7873
36.7446
36.6998
0.0662
0.0659
0.0661
0.0660
in S
!
-1
[
m
Cu
2
(salen)
2
(µ-O)
2
(s), 298.15 K] = (36.792 ! 0.141) kJ mol
!
s
Solution 4
1
2
3
4
5
0.0278
0.0269
0.0265
0.0274
0.0273
5.51
5.54
5.72
5.60
5.85
-27.4954
-27.4136
-27.3908
-27.2800
-26.9640
in the solution 3
!
m
-1
(
6b)= - (27.309 ! 0.208) kJ mol
!
!
s
H
a
b
c
m: molar mass of sample. t: heating period of electrical calibration. Uncertainty was estimated as twice the standard deviation of the mean of the
results.
Table 3
-1
IR data of ligand and complex (cm ).
samples
salen
2 2
Cu (salen) (µ-O)
ν
O-H
ν
C-O
ν
C=N
δ
O-H
H
2
3445
1120
1194
1636
1633
1284
2
13
Page 13 of 18

Legends Figures
Fig. 1. Thermochemical cycle of reaction (1a)
Fig. 2. Thermochemical cycle of reaction (1b).
Fig. 3. UV-vis spectrum of solution B and D
Fig. 4. UV-vis spectrum of solution 2 and 5
2 2 2
Fig. 5. X-ray structure of complex [Cu (salen) (µ-O) ]
14
Page 14 of 18

!
!
r
H
m
(1a)
C H N (l) + 2C H O (l)
H salen(s)
+
2H O(l)
2
2
8
2
7
6
2
2
+
calorimetric
solvent S
(4a) +calorimetric
solvent S
(2a)
Solution A
Solution C
(3a)
(5a)
Solution B
Solution D
Fig. 1. Thermochemical cycle of reaction (1a)
!
m
!
r
H
(1b)
2Cu(OAc)2
!
H O (s) + 2H salen(s)
Cu (salen) (μ-O) (s) + 2H O(l) + 4HOAc(l)
2 2 2 2
2
2
(
2b) +calorimetric
solvent S
(4b) +calorimetric
solvent S
(5b)
Solution 1
Solution 3
Solution 4
(
3b)
(6b)
Solution 2
Solution 5
Fig. 2. Thermochemical cycle of reaction (1b).
15
Page 15 of 18

Solution B
Solution D
4
3
2
1
0
100
200
300
400
500
600
700
800
!
/nm
Fig. 3. UV-vis spectrum of solution B and D
Solution 2
Solution 5
5
4
3
2
1
0
100
200
300
400
500
600
700
800
!
/nm
Fig. 4. UV-vis spectrum of solution 2 and 5
16
Page 16 of 18

2 2 2
Fig. 5. X-ray structure of complex [Cu (salen) (µ-O) ]
17
Page 17 of 18

Highlights

Thermochemical cycles of two synthetic reactions were designed.


The dissolution enthalpies were measured by a solution-reaction calorimeter.
According to the Hess’s law, we obtained the standard molar enthalpies of
formation.
Page 18 of 18