a The data in brackets are calculated values.

1.2 Apparatus and experimental procedures
The constant volume combustion energy of a compound can be determined by the precision rotating bomb(RBC-type 1)^[8].  The room temperature was regulated to 25±1°C, the temperature of outer casing water bath of the rotating bomb was controlled to 25.0000±0.0005°C,the water temperature in the caloritube was adjusted lower than that of the outer casing and certain amount of pure water was added to the caloritube. The sample was put into the crucible fixed onto the support in the rotating bomb but not fallen into the solution, the combustion wire was fixed in the bomb, the initial bomb solution was injected into the rotating bomb, 2533.125 kPa oxygen was filled after sealing the bomb and a constant rate of temperature change of the calorimeter was kept. The temperature was read every 30 seconds after the experiment began and recorded 10 times. At the eleventh time, the complex was ignited and the temperature read once every minute till the temperature changes at a constant rate. Then, the temperature was read once every 30 seconds and recorded 10 times. The final products of the combustion reaction are analyzed after the experiment.
    The energy equivalent of the RBC-type 1 calorimeter was calculated according to the following equation
    (1)
where W is the energy equivalent of the RBC-type 1 calorimeter (in J·K^-1),Q the combustion enthalpy of benzoic acid (in J·g^-1), a the mass of the determined benzoic acid (in g),G the combustion enthalpy of Ni-Cr wire for ignition (0.9 J·cm^-1),b the length of actual Ni-Cr wire consumed (in cm), 5.983 the formation enthalpy and solution enthalpy of nitric acid corresponding to 1 cm³ of 0.1000 mol·dm^-3 solution of NaOH (in J·cm^-3)and c the volume (in cm³) of consumed 0.1000 mol·dm^-3 solution of NaOH and DT  the correct value of the temperature rise.
    The correct value of the heat exchange was calculated by the following equation^[11]

     (2)
where D(DT) denotes the correct value of the heat exchange, n is the number of readings for the reaction period.V₀ and V_n are  the rate of temperature change at the initial and final stages (V is positive when temperature decreases) respectively. and are  the average temperatures of the calorimeter at the initial and final stages (average temperature for the first and last reading) respectively. T₀ is the final reading of the initial stage while T_n the first reading of the final stage. is the sum of all the readings except the last one of the main period.( V_n V₀ ) / () are constants.
    The calorimeter RBC-type 1 was calibrated by benzoic acid with   purity of 99.999%. The isothermal heat of combustion of benzoic acid is -26476.0±5.8 J·g^-1 at 25°C.The calibrated experimental results with an uncertainty 0.16% are summarized in Table 2.
Table 2 Calibrated experimental results for the energy equivalent of the calorimeter using benzoic acid

W=17.9359±0.0288kJ·K^-1

1.3 Analysis of   the final products in oxygen-bomb
1.3.1 Analysis of the final gaseous products
The gases formed in the combustion reaction are collected in a gas-collecting bag. The amount of gas is measured by a gasometer fixed between the bag and the gas determination instrument.
   The analytical principle and technique of carbon dioxide: The gaseous CO₂ formed in the combustion reaction was absorbed through a weighed absorption pipe with alkali asbestos. The amount of CO₂ could be determined through the weight increment of the pipe after it  sucked up. The amount of CO₂ dissolved in the final acidic solution is ignored. 
  Each measurement has four absorption pipes connected with each other. The first one was filled with P₄O₁₀ and CaCl₂ (anhydrous) to suck up the water vapor in the gas. The second  was filled with active MnO₂ in order to absorb the nitrogen oxides. The third  was filled with alkali asbestos to absorb the CO₂ for the measurement. The fourth  was also filled with P₄O₁₀ and CaCl₂ to absorb the water formed in the combustion reaction.
    The analytical principle and technique of sulfur dioxide: A steady complex dichloride sulphurous acid salt is formed when sulfur dioxide is absorbed by tetrachloromercurate(TCM). This complex reacts with formalin and pararosaniline, producing a purplish red complex. The amount of sulfur dioxide could be determined through TCM-Pararosaniline colorimetric analysis.
    The analytical principle and technique of nitrogen oxides (NO_x): Azo dye was formed when the NO₂ was sucked up by the absorption solution in the first pipe.  NO does not react with the absorption solution but becomes NO₂ when it went through an oxide pipe.  NO₂ was absorbed by the solution in the second flask. The amount of NO₂ and NO could be determined by the absorbancy at wavelength between 540 and 545nm (Saltzman colorimetric analysis method).
1.3.2 Analysis of the final solution
The fittings and the inside wall of the bomb were washed by quadratic distilled water. Then the bomb solution (including the washing solution) was transferred to a cone bottle completely and heated to boiling point to remove CO₂. It was titrated to the final point of phenolphthalein using  standard solution of NaOH to get the total amount of acids. After neutralization, this was cooled to the room temperature and transferred into a volumetric flask. If a compound contains chlorine, sulfur and nitrogen, the final bomb solution would contain HCl ₍ aq ₎, H₂SO_{4 (} aq ₎ and HNO_{3 (} aq ₎. In analysis, the total amount of acids was measured first. The amount of H₂SO₄ can be obtained using the weight method of BaSO₄. The amount of HNO₃ can be determined by Devarda's alloy method. The amount of HCl in the solution was corrected with the difference value of the total amount of acids and the amount of HNO₃ and H₂SO₄ in the solution. Then, the corrected heat of acid was obtained based on the results.
1.3.3 Analysis of final solid products
Since the crucible in the rotating bomb was fixed onto the support, the final solid products were obtained inside it after the experiment. The final product was only ZnO proved by IR spectra and chemical analyses.
    The analytical results of the final products indicate that the combustion reactions were complete. Carbon deposits and carbon monoxide are not formed during the combustion reactions, and the amount of NO_x in the final gas phase was insignificant.
2.RESULTS
2.1 Combustion Energy of Solid Sample of the Complexes
The method for determining the combustion energy for the sample is the same as the calibration of the calorimeter with benzoic acid. The samples weight are adjusted to vacuum. The combustion energies of the samples were calculated according to the formula
   (3)
where D_c,coorE(in J·g^-1) denotes the constant volume combustion energy of the sample and a is the mass (in g) of the adjusted sample. The other symbols are the same as indicated in Eq.(1). The results of the calculations are given in Table 3.
Table 3 The experimental results for the combustion energies of the samples

2.2 Standard Combustion Enthalpies of the Complexes
The standard combustion enthalpies of the complexes, D_c,coorH^q, refer to the combustion enthalpy change of the following ideal combustion reactions at 298.15K and 101.325kPa
Zn(Try)₂(s)+O₂(g)ZnO(s)+22CO₂(g)+2N₂(g)+12H₂O(l)                                            (4)
Zn(Leu)₂(s)+17O₂(g)ZnO(s)+12CO₂(g)+N₂(g)+13H₂O(l)                                               (5)
Zn(Val)₂·H₂O(s)+14O₂(g)ZnO(s)+ 10CO₂(g)+ N₂(g)+ 11H₂O(l)                                    (6)
Zn(Leu)SO₄·H₂O(s)+O₂(g)ZnO(s)+6CO₂(g)+SO₂(g)+N₂(g)+7H₂O(l)                (7)
Zn(Val)SO₄·H₂O(s)+O₂(g)ZnO(s)+5CO₂(g)+SO₂(g)+ N₂(g)+H₂O(l)                (8)
Zn(Thr)SO₄·H₂O(s)+O₂(g)ZnO(s)+4CO₂(g)+SO₂(g)+N₂(g)+H₂O(l)                 (9)
The standard combustion enthalpies of the complexes were calculated from the combustion energy by the equations
D_c,coorH^q=D_c,coorE+DnRT                                                            (10)
Dn=n_gas(products)-n_gas(reactants)                                                   (11)
where n_gas is the total amount(in moles) of gas present as products or reactants, R=8.314 J·mol^-1·K^-1, T=298.15K.The results of the calculations are shown in Talbe 4.
2.3 Standard Enthalpies of Formation of the Complexes
The standard enthalpies of formation of the complexes, D_f,coorH^q, were calculated by Hess's law according to the thermochemical equations
a. The standard enthalpy of formation of Zn(Try)₂
D _f,coor(s)H^q=(D_f,ZnO(s)H^q+22 (g)H^q+12_(l)H^q)-D_c,coor(s)H^q              (12)

b. The standard enthalpy of formation of Zn(Leu)₂
D _f,coor(s)H^q=(D_f,ZnO(s)H^q+12_(g)H^q+13_(l)H^q)-D_c,coor(s)H^q               (13)

c. The standard enthalpy of formation of Zn(Val)₂·H₂O
D_f,coor(s)H^q=(D_f,ZnO(s)H^q+10_(g)H^q+11_(g)H^q-D_c,coor(s)H^q                 (14)

d. The standard enthalpy of formation of Zn(leu)SO₄·H₂O
D_f,coor(s)H^q=(D_f,ZnO(s)H^q+6_(g)H^q)+_(g)H^q+7_(l)H^q-D_c,coor(s)H^q      (15)