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

Accepted Manuscript Title: Thermochemical study on the Schiff base [H2 salen=N,N -bis(salicylidene) ethylendiamine] and its 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: DOI: Reference:

S0040-6031(13)00364-X 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, Thermochemical study on the Schiff base [H2 salen=N,N -bis(salicylidene) ethylendiamine] and its binuclear copper (II) complex, Thermochimica Acta (2013), http://dx.doi.org/10.1016/j.tca.2013.07.004 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Thermochemical study on the Schiff base [H2salen=N,N′-bis(salicylidene) 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

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Yao, Wei-Peng Luo, Jin-Qi Xie, Meng-Na Peng, Lan Pan, Qiang-Guo Li*

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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

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* Corresponding author. Tel.: +86 0735 2653353; Fax: +86 0735 2653353

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E-mail address: [email protected]

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Abstract

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

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characterized by X-ray crystallography. Two thermochemical cycles were designed on basis of

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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

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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: ! H [H2salen(s), f

m

298.15K]=-(146.4 ! 1.9) kJ ! mol-1; ! f H m [Cu2(salen)2(µ-O)2(s), 298.15K]= -(171.8 ! 3.9) kJ ! mol-1. !

Keywords: Cupric acetate monohydrate; Salicylaldehyde; Ethylenediamine; Dissolution-reaction calorimeter; Standard molar enthalpy of formation

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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,

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salen-type tetradentate ligands (H2salen = N,N′-bis(salicylidene)ethylendiamine) have been known since 1933, their complexes became a standard system in coordination chemistry, and their

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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

potential chemical and special biological activities [4-10].

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in organism. The copper complexes with Schiff base are of considerable interest due to their

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The synthesis of the Schiff base (H2salen) [H2salen= N, N′-bis(salicylidene)ethylendiamine] and the complex [Cu2(salen)2(µ-O)2)] have been reported in published works [3,11-14]. But up to

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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

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fundamental academic problems together with application development. In this work, we have planned to prepare the Schiff base (H2salen) and the complex [Cu2(salen)2(µ-O)2], then further

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investigated their standard molar enthalpy of formation by the solution-reaction calorimetry, so as to

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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 Hitachi U-3010 UV/Vis spectrophotometer. FT-IR spectra in KBr (4000-400 cm-1) 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]

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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

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recrystallization and dried at 60
in a vacuum oven.

2.3. Syntheses of Cu(
) complex [14]

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An aqueous solution of NaOH (0.04g, 1mmol) was added to the solution of H2salen (0.1341g,

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0.5mmol) in 95% ethanol (20mL). After thirty minutes of stirring, an ethanolic solution of Cu(CH3COO)2 ! H2O (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

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filtered and recrystalized from ethanol, a green complex was obtained, then dried at 60
in vacuo.

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2.4. The crystal growth of complex.

The prepared complex was dissolved in a mixed solvent of DMF and methanol

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(VDMF/VMeOH=5:2) until the solution saturated, followed by filtering through a funnel with cotton

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(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

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analysis and X-ray crystallographic analysis. The results showed that the formula of complex was [Cu2(C16H14O2N2)2]. 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.

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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 -

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（29769 ! 18）J ! mol-1 and （17565 ! 14 ）J ! mol-1, respectively. Comparing with the published data

was less than 0.5% and the present calorimeter was very reliable.

The equations of two reactions as follows:

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2C7H6O2(l) + C2H8N2(l) →H2salen(s)+2H2O(l);

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2.6. Thermochemical cycle of Reaction (1a) and Reaction (1b).

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-（29776 ! 31.5） J ! mol-1 for THAM and （17536 ! 9）J ! mol-1 for KCl [15], the eventual error

2H2salen(s)+2Cu(OAc)2·H2O(s)→ Cu2(salen)2(µ-O)2(s)+4HOAc(l)+2H2O(l)

(1a) (1b)

According to the Hess’s law, we have designed the thermochemical cycle for the two reactions

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(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

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spectra and refractive indexes of solution B and D. The experimental results indicated that the

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solution B and D have same UV spectrum curves (Fig. 3) and equal refractive indexes (η25℃

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=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

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(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]. The amount of the relevant substances of reaction (1a) was as follows: C7H6O2(l) (1.0mmol),

Solution A

(2a) (3a)

H2salen(s) ! S ! Solution C

(4a)

2H2O(l) ! Solution C ! Solution D

(5a)

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C2H8N2(l) ! Solution A ! Solution B

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2C7H6O2(l) ! S !

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C2H8N2(l) (0.5mmol), H2salen(s) (0.5mmol), H2O(l) (1.0mmol).

The amount of the relevant substances of reaction (1b) was as follows: H2salen(s) (0.2mmol),

(0.2mmol). 2H2salen(s) ! S ! Solution1

(2b)

Cu2(salen)2( ! - O)2(s) ! S ! Solution3 4HOAc(l) ! 2H2O(l) ! Solution4

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2Cu(OAc)2H2O (s) ! Solution1 ! Solution2 (3b)

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Cu(OAc)2 ! H2O(s) (0.2mmol), Cu2(salen)2(µ-O)2(s) (0.1mmol), HOAc(l) (0.4mmol), H2O(l)

(4b)

(5b)

(6b)

3. Results and discussion

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Solution3 ! Solution4 ! Solution5

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3.1. IR Spectra and Crystal Structure

The pivotal frequencies of characteristic absorption bands in the IR spectra (cm-1) for the Schiff base [H2salen] and the complex [Cu2(salen)2 (µ-O)2] are listed in Table 3. There are four characteristic absorption bands for H2salen: νO-H (3445cm-1, s), νC-O (1120cm-1, s), νC=N (1636cm-1, vs) δO-H(1284cm-1, s). After coordination, νO-H and δO-H disappeared and the skeleton peak of H2salen shifted to a low wavenumber, which indicated that H2salen was coordinated with Cu2+ 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

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3.3. Treatment of ! s H !m (5a) and ! s H !m (5b) In the process of measurement, the value of ! s H !m (5a) is so quite minor that it is difficult to

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measure. Furthermore, the concentration of all the other substances in the system is relatively small. Consequently, the dilution enthalpies [ ! s H !m (5a)] can be neglected during the calculation [17].

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According to Ref. [18,19], the mixing enthalpy of (4HOAc + 2H2O) can be obtained as follow:

3.4. The molar enthalpies of reaction (1a) and reaction (1b)

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θ θ θ -1 ! s H m (5b) = 4 ! [! f H m (nHOAc : nH 2 O = 1 : 0.5) - ! f H m (HOAc, l)] = 2.24 kJ ! mol

! r H m (1a) = 2 ! s H m (2a) + ! s H m (3a) - ! s H m (4a) !

!

!

!

! -(92.884 ! 0.455) kJ ! mol-1

(0.027) 2 ! (0.391) 2 ! (0.232) 2

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! [2 ! (-4.538) ! (-57.563) - 26.245] !

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According to Hess’law, the standard molar enthalpy of reaction (1a) was obtained:

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The standard molar enthalpy of reaction (1b) was obtained:

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! ! ! ! ! ! ! r H m (1b) = 2 ! s H m (2b) + 2 ! s H m (3b) - ! s H m (4b) - ! s H m (5b) - ! s H m (6b) ! [2 ! 25.024 ! 2 ! (-22.402) - 36.792 - 2.24 - (-27.309)]

(2 ! 0.243) 2 ! (2 ! 0.319) 2 ! (0.141) 2 ! (0.208) 2

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! - (6.479 ! 0.840) kJ ! mol -1

3.5. Calculating of ! f H m [C7H6O2(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: C7H6O2(l)+15/2O2(g) →7CO2(g)+3H2O(l) ; ! -1 ! c H m[C7H6O2(l), 298.15K] ! -3328.9 kJ ! mol [20]

According to the Hess’ law: ! c H m [C7H6O2(l)] = 7 ! f H m [CO2(g), 298.15K] + 3 ! f H m [H2O(l),298.15K] - ! f H m [C7H6O2(l),298.15K] !

!

!

!

According to Ref. [21] 6

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! -1 ! f H m [H2O(l), 298.15K] ! - (285.830 ! 0.040) kJ ! mol

! -1 ! f H m [CO2(g),298.15K] ! - (393.51 ! 0.13) kJ ! mol

So that (7 ! 0.13) 2 ! (3 ! 0.040) 2

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! ! (281.1 ! 0.9) kJ ! mol -1

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! ! f H m[C7H6O2(l), 298.15K] ! [7 ! (-393.51) + 3 ! (-285.15) - (-3328.9)] !

3.6. Evaluation of ! f H m [H2salen(s), 298.15K] and ! f H m [Cu2(salen)2(µ-O)2(s), 298.15K]. !

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!

According to the Hess’ law:

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! ! ! ! ! r H m (1a) = ! f H m [H2salen(s), 298.15K] + 2 ! f H m [H2O(l), 298.15K] - 2 ! f H m [C7H6O2(l), 298.15K] - ! f H !m [C2H8N2(l), 298.15K]

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! ! ! ! r H m (1b) = ! f H m [Cu2(salen)2( ! - O)2(s), 298.15K] + 4 ! f H m [HAc(l),298.15K] + 2 ! f H !m [H2O(l),298.15K] - 2 ! f H !m [H2salen(s),298.15K] - 2 ! f ! !m [Cu(OAc)2H2O (s),298.15K]

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According to Refs. [18,22]

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! -1 ! f H m [C2H8N2(l), 298.15K] ! -(63.01 ! 0.54) kJ ! mol

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! -1 ! f H m [HOAc(l), 298.15K] ! - 483.50 kJ ! mol ! -1 ! f H m [Cu(OAc)2 ! H2O (s), 298.15K] ! -1189.1 kJ ! mol

So that

! ! f H m [H2salen(s), 298.15K] ! [(-92.884) - 2 ! ( - 285.830) ! 2 ! (- 281.1) ! (-63.01)]

!

(0.455) 2 ! (2 ! 0.040) 2 ! (2 ! 0.9) 2 ! (0.54) 2

! - (146.4 ! 1.9) kJ ! mol -1

! f H m [Cu2(salen)2(μ - O)2(s),298.15K] = [(-6.479) - 4 × (-483.50) - 2 × (-285.830) + 2 × (-146.4) !

+ 2 × (-1189.1)] !

(0.840) 2 ! (2 ! 0.040) 2 ! (2 ! 1.9) 2

= - (171.8 ! 3.9) kJ ! mol -1 4. Conclusions 7

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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 (H2salen) and the complex (Cu2(salen)2(µ-O)2) were calculated !

!

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298.15K]= -(171.8 ! 3.9) kJ ! mol-1.

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to be ! f H m [H2salen(s), 298.15K]= -(146.4 ! 1.9) kJ ! mol-1 and ! f H m [Cu2(salen)2(µ-O)2(s),

It has to be pointed out that, the solubility of cupric acetate monohydrate in the solvent of

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dimethyl formamide are not so ideal. However, it can be fully dissolved in the solution 1

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(H2salen+DMF). Therefore, we adopted the thermochemical cycle shown in Fig. 2.

Acknowledgements

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The authors thank National Natural Science Foundation of China (Nos. 20973145, 21273190), Hunan provincial key laboratory of xiangnan rare-precious metals compounds and Applications

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(2012XGJSYB02), the Educational Committee Foundation of Hunan Province (No. 11A112 and No.

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10C1233), the Science and Technology Department Foundation of Hunan Province (No. 2011TP4016-1 and No. 2012TP4021-5) and the construct program of the key discipline in Hunan

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province for financial support.

References

[1] M. Calligaris, L. Randaccio, Schiff bases as acyclic polydentate ligands, Comprehensive Coordination Chemistry, Second ed., G. Wilkinson, London: Pergamon, 1987, 715. [2] A.D. Garnovskii, A.L. Nivorozhkin, V.I. Minkin, Ligand environment and the structure of schiff base adducts and tetracoordinated metal-chelates, Cood. Chem. Rev. 126 (1993) 1-69. [3] M. Mikuriya, K. Matsunami, Synthesis and structural characterization of a series of transition metal complexes with a tetradentate Schiff-base ligand derived from salicylaldehyde and 2-(2-aminoethylamino)ethanol, Mater. Sci, 23(2005) 773-792.

8

Page 8 of 18

[4] S. Chattopadhyay, M.G.B. Drew, A. Ghosh, Synthesis, characterization, and anion selectivity of copper (
) complexes with a tetradentate Schiff base ligand, Inorg. Chim. Acta, 359 (2006) 4519-4525. [5] V.B. Sharma, S.L. Jain, B. Sain, Copper (
) Schiff base catalysed aerobic oxidative coupling of

ip t

2-naphthols: an efficient and simple synthesis of binaphthols, Journal of Molecular Catalysis A: Chemical, 219 (2004) 61-64.

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[6] M. Itagaki, K. Hagiya, M. Kamitamari, et al, Highly efficient chiral copper Schiff-base catalyst for asymmetric cyclopropanation of 2,5-dimethyl-2,4-hexadiene, Tetrahedron, 60 (2004)

us

7835-7843.

[7] G. Filomeni, G. Cerchiaro, A.M.D.C. Ferreira, J.Z. Pedersen, A. De Martino, G. Rotilio, M. R.

an

Ciriolo, Pro-apoptotic activity of novel Isatin-Schiff base Copper(II) complexes depends on oxidative stress induction and organelle-selective damage, J. Biol. Chem, 282 (2007)

M

12010-12021.

[8] A.T. Chaviara, E.E. Kioseoglou, A.A. Pantazaki, A.C. Tsipis, P.A. Karipidis, D.A. Kyriakidis, C.

d

A. Bolos, DNA interaction studies and evaluation of biological activity of homo- and hetero-trihalide mononuclear Cu (II) Schiff base complexes. Quantitative structure-activity

V.C. da Silveira, J.S. Luz, C.C. Oliveira, I. Graziani, M.R. Ciriolo, A.M.D.C. Ferreira,

Ac ce p

[9]

te

relationships, J. Inorg. Biochem, 102 (2008) 1749-1764.

Double-strand DNA cleavage induced by oxindole-Schiff base copper(II) complexes with potential antitumor activity, J. Inorg. Biochem, 102 (2008) 1090-1103. [10]

P.A.N. Reddy, M. Nethaji, A.R. Chakravarty, Hydrolytic cleavage of DNA by ternary amino

acid Schiff base Copper (II) complexes having planar heterocyclic ligands, Eur. J. Inorg. Chem, 7(2004) 1440-1446. [11]

M.M. Bhadbhade, D. Srinivas, Effects on molecular association, chelate conformation, and

reactivity

toward

substitution

in

copper

Cu(5-X-salen)

complexes,

salen

2-=

N,N'-ethylenebis(salicylidenaminato), X=H, CH3O, and Cl: synthesis, x-ray structures, and EPR investigations, Inorg. Chem, 32(1993) 6122-6130. [12]

L.C. Nathan, J.E. Koehne, J.M. Gilmore, K.A. Hannibal, W.E. Dewhirst, T.D. Mai, The X-ray structures of a series of copper (II) complexes with tetradentate Schiff base ligands

9

Page 9 of 18

derived from salicylaldehyde and polymethylenediamines of varying chain length, Polyhedron, 22(2003)887-894. [13]

Y. Ding, Z.W. Liu, Z.H. Zhang, et al, Studies of crystal structure and fluorescence activity of Schiff base tri-nuclear Zn(
) complex, Acta Chim Sinica. 65 (2007) 655-659.

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[14] Y. Ding, X.X. Hu, X.L. Sun, Z.L. Zuo, Synthesis, structural characterization, and

base ligand, J. Wuhan Univ. (Nat. Sci. Ed.) 15 (2010) 165-170.

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electrochemical properties of binuclear copper(II) complexes containing tetradentate Schiff

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[15] H.G. Yu, Y. Liu, Z.C. Tan, J.X. Dong, T.J. Zou, X.M. Huang, S.S. Qu, A solution-reaction isoperibol calorimeter and standard molar enthalpies of formation of Ln(hq)2Ac (Ln = La, Pr), Thermochim. Acta 401 (2003) 217-224.

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[16] X. Li, S.X. Xiao, L.J. Ye, A.T. Li, D.J. Yang, X. Li, Q.G. Li, Thermochemical study of [Ce(Hsal)2 · (tch)] ·2H2O, J. Chem. Eng. Data. 55 (2010) 2874-2878.

M

[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)

d

343-346.

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

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[18]

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reaction of valine with copper Acetate in Chinese, Chem. Bull. 65 (2002) 488-491. [20] R.C. Weast, Handbook of chemistry and physics, CRC Press, the 58th 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.

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Legends to Tables Table 1 Dissolution enthalpies of [C7H6O2(l)], [C2H8N2(l)] and [H2salen(s)] in the Calorimetric Solvent S at 298.15 K.

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Table 2 Dissolution enthalpies of [H2salen(s)], [Cu2(OAc)2 ! H2O(s)], [Cu2(salen)2(µ-O)2(s)] and [Solution 4(aq)] in the Calorimetric Solvent S at 298.15 K.

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Table 3 IR data of ligand and complex (cm-1).

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Table 1 Dissolution enthalpies of [C7H6O2(l)], [C2H8N2(l)] and [H2salen(s)] in the Calorimetric Solvent S at 298.15 K.

C7H6O2(l) in S

1 2 3 4 5

ma/g

tb/s

0.1219 0.1227 0.1223 0.1228 0.1229

7.97 7.48 7.52 7.70 7.83

! s H m / kJ ! mol !

-1

-4.5170 -4.5167 -4.5802 -4.5498 -4.5241

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no.

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system

! c -1c ! s H m [C7H6O2(l), 298.15 K] = - (4.538 ! 0.027 ) kJ ! mol

1 2 3 4 5

in the solution A

0.0306 0.0308 0.0298 0.0305 0.0298

35.37 48.63 52.26 48.94 49.60

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C2H8N2(l)

-57.7755 -57.6083 -57.7809 -58.0525 -57.0396

H2salen(s) in S

0.1346 0.1346 0.1345 0.1343 0.1344

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1 2 3 4 5

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! -1 ! s H m [C2H8N2(l), 298.15 K] = - (57.563 ! 0.391) kJ ! mol

19.10 19.98 20.46 20.19 20.50

26.0582 26.5936 26.1912 26.0322 26.3487

m: molar mass of sample. t: heating period of electrical calibration. Uncertainty was estimated as twice the standard deviation of the mean of the c

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results.

b

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a

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! -1 ! s H m [H2salen(s), 298.15 K] = (26.245 ! 0.232) kJ ! mol

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Table 2 Dissolution enthalpies of [H2salen(s)], [Cu2(OAc)2 ! H2O(s)], [Cu2(salen)2(µ-O)2(s)] and [Solution 4(aq)] in the Calorimetric Solvent S at 298.15 K.

1 2 3 4 5

tb/s

0.0538 0.0539 0.0537 0.0535 0.0537

6.04 7.48 7.44 7.00 7.40

! s H m / kJ ! mol !

-1

ip t

ma /g

no.

24.9093 24.6629 25.1569 25.2815 25.1127

cr

system H2salen(s) in S

! c -1c ! s H m [H2salen(s), 298.15 K] = (25.024 ! 0.243 ) kJ ! mol

0.0400 0.0400 0.0401 0.0398 0.0401

3.45 7.35 7.40 7.48 7.44

us

1 2 3 4 5

an

Cu(OAc)2 ! H2O(s) in the solution 1

-22.2754 -22.7437 -22.6960 -22.3196 -21.9768

! -1 ! s H m [Cu(OAc)2 ! H2O(s), 298.15 K] = - (22.402 ! 0.319) kJ ! mol

in S

1 2 3 4 5

0.0660 0.0662 0.0659 0.0661 0.0660

4.72 5.56 5.51 5.53 5.38

M

Cu2(salen)2(µ-O)2(s)

36.6954 37.0363 36.7873 36.7446 36.6998

1 2 3 4 5

Ac ce p

te

Solution 4 in the solution 3

d

! -1 ! s H m [Cu2(salen)2(µ-O)2(s), 298.15 K] = (36.792 ! 0.141) kJ ! mol

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

! -1 ! s H m (6b)= - (27.309 ! 0.208) kJ ! mol

a

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.

b

c

Table 3 IR data of ligand and complex (cm-1).

samples H2salen Cu2(salen)2(µ-O)2

νO-H 3445

νC-O 1120 1194

νC=N 1636 1633

δO-H 1284

13

Page 13 of 18

Legends Figures

ip t

Fig. 1. Thermochemical cycle of reaction (1a)

cr

Fig. 2. Thermochemical cycle of reaction (1b).

us

Fig. 3. UV-vis spectrum of solution B and D

te

d

M

X-ray structure of complex [Cu2(salen)2(µ-O)2]

Ac ce p

Fig. 5.

an

Fig. 4. UV-vis spectrum of solution 2 and 5

14

Page 14 of 18

!

+ 2C7H6O2(l)

H2salen(s)

2H2O(l)

+

(2a) +calorimetric solvent S

(4a) +calorimetric solvent S

Solution A

Solution C

(3a)

Thermochemical cycle of reaction (1a)

+ 2H2salen(s)

!

! r H m (1b)

Ac ce p

2Cu(OAc)2! H2O (s)

te

d

M

an

Fig. 1.

Solution D

us

Solution B

cr

(5a)

ip t

C2H8N2(l)

! r H m (1a)

(2b) +calorimetric solvent S

Cu2(salen)2(μ-O)2(s) + 2H2O(l) + 4HOAc(l) (4b) +calorimetric solvent S (5b)

Solution 1

(3b)

(6b)

Solution 2

Fig. 2.

Solution 4

Solution 3

Solution 5

Thermochemical cycle of reaction (1b).

15

Page 15 of 18

Solution B Solution D 4

Absorbance

3

1

0

100

200

300

400

500

600

700

800

us

! /nm

cr

ip t

2

Ac ce p

te

d

M

an

Fig. 3. UV-vis spectrum of solution B and D

Solution 2 Solution 5

5

Absorbance

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

ip t cr us an

X-ray structure of complex [Cu2(salen)2(µ-O)2]

Ac ce p

te

d

M

Fig. 5.

17

Page 17 of 18

Highlights

 Thermochemical cycles of two synthetic reactions were designed.  The dissolution enthalpies were measured by a solution-reaction calorimeter.

Ac ce

pt

ed

M

an

us

cr

ip t

 According to the Hess’s law, we obtained the standard molar enthalpies of formation.

Page 18 of 18