Dalton Transactions

View Article Online View Journal

Accepted Manuscript

This article can be cited before page numbers have been issued, to do this please use: S. M. Shugurov, S. I. Lopatin, A. I. Panin and K. A. Emelyanova, Dalton Trans., 2015, DOI: 10.1039/C5DT00660K.

This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.

www.rsc.org/dalton

Page 1 of 18

Dalton Transactions View Article Online

DOI: 10.1039/C5DT00660K

Formation and thermodynamics of the gaseous germanium and tin vanadates. A mass spectrometric and quantum chemical study

Published on 21 April 2015. Downloaded by Freie Universitaet Berlin on 06/05/2015 18:29:38.

The stability of gaseous germanium and tin vanadates was confirmed by high temperature mass spectrometry and their structures were determined by quantum chemical calculations. A number of gas phase reactions involving these gaseous salts were studied. On the basis of the equilibrium constants, the standard formation enthalpies of gaseous GeV2O6 (−1520±42 kJ/mol) and SnV2O6 (−1520±43 kJ/mol) at temperature 298 K were determined.

1. Introduction Vanadium compounds find a wide application in many branches of industry, in particular, in chemical industry as catalysts, in organic synthesis, polymer material making, glazing, ceramics, textile, paintwork and rubber-processing industry, in photographic chemistry and cinematographic work, in medicine, agriculture, etc. Vanadates of rare-earth metals display luminescent properties. Vanadates of some metals are produced by high-temperature synthesis. In course of synthesis a mixture of V2O5 with metal salts or oxides which are cations in the vanadates is heated to high temperature. Study of formation of various vanadates including gas phase ones and their physical-chemical properties is very important for real-world problems including intensification of technological processes of vanadium and its compounds production, clarification of chemical nature of vanadium catalysts, investigation of vanadium corrosion process of high-temperature-resistant engineering material.1 Volatile compounds may be formed in course of high-temperature synthesis of vanadates. On heating the initial components transformation of these oxides into vapor occurs. These species may serve as precursors in various CVD methods for obtaining thin films of semiconductors2,3. It is known that doping of vanadium oxide films with W, Nb and Mo lowers the transition temperature and that doping with Ge and Sn raises the transition temperature of the vanadium oxides thin films4. For characterization of such processes both qualitative and quantitative information on the composition of gaseous phase must be known as well as the thermodynamic properties of gaseous species. Besides the practical interest in such compounds there is also a theoretical one. The gaseous tin and germanium oxyacid salts are not well studied yet and their *Institute of Chemistry, St. Petersburg State University, 198504 St. Petersburg, Russia. E-mail: [email protected]. Electronic supplementary information (ESI) available.

Dalton Transactions Accepted Manuscript

S.M. Shugurov,* A.I. Panin, S.I. Lopatin and K.A. Emelyanova

Dalton Transactions

Page 2 of 18 View Article Online

DOI: 10.1039/C5DT00660K

2

5-9

thermodynamic characteristics are not determined. By now only eight germanium

and seven

tin10-12 gaseous oxyacid salts are known. The existence of gaseous vanadates of alkali13-17 and alkali-earth18 metals as well as

Published on 21 April 2015. Downloaded by Freie Universitaet Berlin on 06/05/2015 18:29:38.

Balducci et al13-14 and Semenov et al15 found that vanadates of alkali metals evaporate mainly as monomers. Vanadates of potassium, rubidium, and cesium undergo congruent evaporation without dissociation13-15,17 whereas vanadates of lithium and sodium are evaporated with partial dissociation.16,17 In the vapor over lithium vanadate besides the monomer molecule LiVO3 the presence of Li2VO3 was established.16 K2VO3 molecule was found in flames containing potassium and vanadium.21 When studying vaporization of vanadates of calcium, strontium, and barium besides the A, AO, VO, and VO2 species the AVO3 and AVO2 compound molecules (A = Ca, Sr, Ba) were detected in the vapor. Measurement of reactions (1) and (2) equilibrium constants made it possible to determine standard enthalpies of formation of gaseous AVO3 and AVO2 AO (g) + VO (g) = AVO2 (g)

(1)

AO (g) + VO2 (g) = AVO3 (g)

(2)

In vapor over the PbO–V2O5 system PbV2O6 molecule was found.19 Presence of the PbO, V4O10, and PbV2O6 species in the vapor over the investigated system allowed to measure the equilibrium constant of reaction (3) and to determine standard enthalpies of formation of gaseous lead vanadate. PbO + 0.5 V4O10 = PbV2O6

(3)

In vapor over the mixture of Eu2O3 and V2O5 oxides europium vanadates were detected.9 EuO (g) + VO (g) = EuVO2 (g)

(4)

EuO (g) + VO2 (g) = EuVO3 (g)

(5)

Vanadium oxide V4O10 possesses pronounced acid properties and in reactions of synthesis of gaseous vanadates it shows itself only as anion-forming oxide13-15,19 whereas VO and VO2 display amphoteric properties and can manifest themselves both as anion- and cation-forming oxides.22,23 Shugurov et al

22

studied reactions (6)-(8) of synthesis of gaseous vanadium

phosphates. Equilibrium constants of these reactions were determined and standard formation enthalpies of VPO2 (g) and VPO3 (g) were obtained. VO (g) + PO2 (g) = VPO3 (g)

(6)

VO2 (g) + PO (g) = VPO3 (g)

(7)

Dalton Transactions Accepted Manuscript

lead19 and europium20 vanadates is experimentally proved.

Page 3 of 18

Dalton Transactions View Article Online

DOI: 10.1039/C5DT00660K

3

VO (g) + PO (g) = VPO2 (g)

(8)

During the vaporization of V2O3 from molybdenum and tungsten effusion cells VMoO4, VWO3 and VWO4 molecules were found in the vapor.23 Determination of equilibrium constants and enthalpies of reactions (9)-(11) made it possible to calculate the values of standard enthalpies of

VO (g) + XO3 (g) = VXO4 (g)

(9)

VO2 (g) + XO2 (g) = VXO4 (g)

(10)

VO (g) + WO2 (g) = VWO3 (g)

(11)

Here X = Mo, W. In the present work we discuss the formation and stability of gaseous germanium and tin vanadates GeV2O6 and SnV2O6. The structures and thermodynamic properties of these gaseous oxyacid salts are also reported and discussed.

2. Results and discussion

2.1 Mass spectrometric study In the condensed phase GeO2 and SnO2 are the most stable oxides. According to ref24 vaporization of germanium and tin dioxides in the temperature range 1250-1540 K proceeds generally with formation of GeO (SnO) and O2 in the vapor. The vapor composition over pure V2O5 evaporated from platinum Knudsen cell was studied by high temperature mass spectrometry method.25 According to the data of that work the vapor over V2O5 consists of V4O10 (main component) and small amount of V6O14, V6O12, V4O8, and V2O4. The authors believe that V2O5 evaporates mainly in the form of V4O10. It was shown that the vapor composition continually changes during vaporization making useless any quantitative measurements. When studying the vaporization processes in oxide systems containing V2O5 a serious problem is the choice of cell material. Vanadium(V) oxide is a strong oxidant and therefore the use of molybdenum or tungsten effusion cells is unacceptable. Molybdenum and tungsten being reducing agents can reduce V2O5 to VO2 or V2O319 transition of which to vapor requires essentially higher temperatures.23 In this case molecules VO and VO2 are found in the vapor. The use of platinum as a cell material is also unacceptable. Being heated without reducing agent, V2O5 may partially decompose to gaseous O2 and solid VO2.25,26 The latter evaporates at temperatures higher than the melting point of platinum (2042 К). In the present investigation zirconium dioxide effusion cell was employed. ZrO2 is thermally stable up to temperatures about 2700 К and does not possess reducing properties. This

Dalton Transactions Accepted Manuscript

Published on 21 April 2015. Downloaded by Freie Universitaet Berlin on 06/05/2015 18:29:38.

formation of gaseous vanadium molybdates and tungstates

Dalton Transactions

Page 4 of 18 View Article Online

DOI: 10.1039/C5DT00660K

4

cell is not suitable for investigation of evaporation of pure oxides. All of them interact with cell material to form solid solutions. In our case, however, we study only gas phase reactions whose equilibrium constants do not depend on the cell material. In mass-spectra of the vapor over GeO2-V2O5 and SnO2-V2O5 oxide mixtures in the

Published on 21 April 2015. Downloaded by Freie Universitaet Berlin on 06/05/2015 18:29:38.

V4O10+ and MV2O6+ (M = Ge, Sn) were recorded. Typical mass spectrum at the beginning of the experiment is presented in Figure 1a. The spectrum was normalized. As one can see the most abounded ion is SnO+. The same mass spectrum normalized in the mass range 200-400 is presented in Figure 1b. All isotopic compositions of ions correspond to the theoretically calculated ones. a)

b)

Figure 1. Mass-spectra of the vapor over the mixture SnO2-V2O5 at T = 1725 K a) mass range 100-400 b) mass range 200-410. The ratio of ion current values depended on the vaporization time and temperature. During the vaporization the relative intensity of the V4O10+ ion current constantly decreased due to the following reasons: 1) Greater volatility of V2O5 in comparison with SnO2; 2) Partial thermal dissociation of V2O5 to VO2 (solid) as described before; 3) Formation of solid solutions with the cell material. The intensities of SnO+, Sn2O2+ and Sn+ currents also decreased but to a lesser extent than the V4O10+ current. This fact also may be explained by the formation of a solid solution with the

Dalton Transactions Accepted Manuscript

temperature range from 1500 to 1800 K peaks corresponding to cations M+, MO+, Sn2O2+,

Page 5 of 18

Dalton Transactions View Article Online

DOI: 10.1039/C5DT00660K

5

cell material. After decrease of ion current intensities to the background level temperature was raised to 2000 K. Peaks corresponding to VO2+ and V2O4+ ions were detected confirming the results of Berkowitz et al25and Chizikov et al.26 In order to determine the vapor composition, appearance energies of the ions were measured

ion currents reaches zero value. Because of problems associated with registration of small ion currents the reference substances (such as gold) are used. This method is described in details elsewhere.28-29 The plot of ionization efficiency curves is shown in Fig 2. The curves have no inflexion points which would indicate the complex scheme of genesis of ions under consideration. The appearance energies obtained were (eV): (16.0±0.5) Ge+, (15.1±0.5) Sn+, (10.2±0.3) GeO+, (10.6±0.3) SnO+, (10±1) Sn2O2+, (10.5±0.3) V4O10+, (11.5±0.5) GeV2O6+, (11.4±0.5) SnV2O6+.

100

+

I , relative units

Published on 21 April 2015. Downloaded by Freie Universitaet Berlin on 06/05/2015 18:29:38.

eV.27 In the vanishing current method the ionization voltage is decreased until the intensity of

2 3 6 5 7

1

80 60 40

8

9

19

20

4

20 0 9

10

11

12

13

14

15

16

17

18

U ioniz., V

Fig. 2. The ionization efficiency curves of detected ions: (1) – Au+, (2) – SnO+, (3) – GeO+, (4) Sn2O2+, (5) – V4O10+, (6) – GeV2O6+, (7) – SnV2O6+, (8) – Sn+, (9) – Ge+. Comparing these values with the literature data concerning the ionization energies of germanium (11.5±0.5), tin (10.5±0.5), and vanadium (11.8) oxides27 we came to conclusion, that the vapor over GeO2−V2O5 and SnO2-V2O5 systems consists of germanium or tin oxides and V4O10. The calculated ionization energies for germanium and tin vanadates are IE(GeV2O6) = 11.5 eV and IE(SnV2O6) = 11.5 eV (Koopman’s theorem). +

Under the conditions of our

experiment M ions were the fragmented species of MO molecules.5,7,10,12

Dalton Transactions Accepted Manuscript

using the vanishing current method with Au as a standard, ionization energy of which is 9.2

Dalton Transactions

Page 6 of 18 View Article Online

DOI: 10.1039/C5DT00660K

6

Partial vapor pressures of the gaseous species were calculated by the ion current comparison method, eq 12, using Au as the internal pressure standard.30 p2 I1 T1 σ 2 γ 2 I 2 T2 σ 1 γ 1

(12)

Published on 21 April 2015. Downloaded by Freie Universitaet Berlin on 06/05/2015 18:29:38.

In this equation Ii is the total ion current, Ti is temperature, σi is the ionization cross section, γi is the secondary electron multiplier gain factor that is known to be proportional to the square root of the molecular mass of the corresponding molecule, pi is partial pressure of the ith species, while indices “1” and “2” label the sample and the standard, correspondingly. Molecular cross sections were obtained by the additivity rule for gaseous germanium, tin vanadium oxides and MV2O6 molecules, atomic cross sections were taken from31. Cross sections of V4O10 and MV2O6 molecules were multiplied by 0.7, according to the suggestion of Guido et al.32 for five and more atomic molecules. Enthalpies of reactions under study were calculated using eq 13,

∆ r H 00 = T∆ r ΦT0 − RT ln K p (T )

(13)

where ∆ r H 00 , ∆ r H T0 and ∆ r Φ T0 are the changes of the enthalpy and Gibbs reduced energy of the reaction under consideration at temperatures 0 and T K, correspondingly, R is the gas constant, Kp is the equilibrium constant of the reaction. Gibbs reduced energy of any reaction is defined by

eq 14. Φ T0 ≡ −

(GT0 − H 00 ) ( H 0 − H 00 − TS T0 ) ≡− T T T

(14)

The values of ∆ r H 00 were subsequently recalculated to the temperature 298 K. To determine standard enthalpies of gaseous germanium and tin vanadates formation the equilibrium constants of reactions (15) and (16) were evaluated. MO (g) + 0.5 V4O10 (g) = MV2O6 (g)

(15)

Sn2O2 (g) + V4O10 (g) = 2 SnV2O6 (g)

(16)

Thermodynamic functions of gaseous germanium, tin and vanadium oxides were taken from the reference book,33 and thermodynamic functions of MV2O6 were calculated by methods of statistical thermodynamics in the “rigid rotor – harmonic oscillator” approximation. Partial

Dalton Transactions Accepted Manuscript

p1 =

Page 7 of 18

Dalton Transactions View Article Online

DOI: 10.1039/C5DT00660K

7

pressures, equilibrium constants and reaction enthalpies obtained are listed in Tables S1 and S2 (ESI√). Bond lengths and angles along with vibrational frequencies for these salts were obtained as a result of theoretical study of these molecules.

Published on 21 April 2015. Downloaded by Freie Universitaet Berlin on 06/05/2015 18:29:38.

dependence of equilibrium constant on temperature over a wide temperature range and to determine enthalpies of these reactions according to eq 17. ∆ r Η T0 (T )=− R

∂ ln K p (T ) ∂ (1 / T )

(17)

Here ∆ r H T0 is the change of the enthalpy of the reaction under consideration at temperature T K, R is the gas constant, Kp is the equilibrium constant of the reaction. The average temperature over the measurement range is equal to 1636 K and enthalpies of reactions (15) and (16) at this temperature are −123±12 and 49±17 kJ/mol, respectively.

2.2. Theoretical Results To get structure parameters and vibrational frequencies of gaseous MO, V4O10, MV2O6 (M=Ge, Sn) and to determine theoretical enthalpy values for reactions (15) and (16) quantum chemical investigation of these molecules was undertaken. We started calculations of compounds with the gross formula MV2O6 (M=Ge, Sn) with the analysis of geometries, energies and frequencies of normal vibrations of the reacting species MO and V4O10 in their ground (singlet) states using DFT M0634, CCSD(T)35, and CCSD(T)F1236 methods. Only the ground states of the reacting species were under consideration. Their excited states would be of interest for our investigation if they were distant from the ground ones by less than 0.2 eV (~ 2300 K). The ground state of germanium oxide is 1Σ+ and its first excited state is situated 21 117 cm-1 (~2.6 eV) higher on the energy scale.37 The ground state of tin monoxide is also 1Σ+ and its first excited state lies 24 333 cm-1 (~ 3.0 eV) above the ground state.37 Therefore, we can reasonably confine ourselves to the analysis of the reacting species GeO and SnO only in their ground states. The results of electronic and vibrational structure calculations of these molecules are given in Table 1. Ogden et al38 reported the results of experimental study of gaseous tin dioxide. Quantum chemical investigation of SnmOn (m=1-4; n=1-10) clusters was undertaken by Mazzone and Morandi.39

Dalton Transactions Accepted Manuscript

For reactions (15) and (16) involving gaseous tin vanadates we succeeded to measure the

Dalton Transactions

Page 8 of 18 View Article Online

DOI: 10.1039/C5DT00660K

8

On the Potential Energy Surface (PES) of Sn2O2 ground state two isomers were found. They

O

O

Sn

Sn

Sn

O

Sn

O

Structure I (D2h)

Structure II (C2v)

Fig.3 Singlet isomers of Sn2O2. Structure II is situated ~3.8 eV above structure I one on the energy scale and therefore was out of our consideration. For the same reason states of Sn2O2 corresponding to nontrivial spins were also out of our scope. From Table 2 it is seen that our results are in a very good correspondence with the experimental data. Table 1. Energies, equilibrium bond distances, harmonic frequencies of GeO and SnO molecules calculated by DFT M06 method (in parenthesis the experimental data from37 are given); CCSD(T) and CCSD(T)-F12 energies were calculated at M06 equilibrium geometries. GeO -1

State

RGe-O (Å)

ω (cm )

1 +

1.624 (1.625)

1011 (985)

Σ

EM06 (a.u.) −2152.219006

ECCSD(T) (a.u.) −2150.606564

ECCSD(T)+f12 (a.u.) −2150.638512

SnO 1 +

Σ

Table 2.

1.828 (1.832)

865 (815)

−289.598721

−288.562563

−288.593169

Equilibrium geometry parameters, vibrational frequencies, and total energies of

energetically favorable isomer of Sn2O2

Dalton Transactions Accepted Manuscript

Published on 21 April 2015. Downloaded by Freie Universitaet Berlin on 06/05/2015 18:29:38.

are displayed in Fig. 3.

Page 9 of 18

Dalton Transactions View Article Online

DOI: 10.1039/C5DT00660K

9

2.013

Experiment (in argon) 2.045±0.025

83

80

127(B3u)

-

230(Ag)

-

440(B3g)

-

528(B2u)

522(B2u)

605(Ag)

-

623(B1u)

611(B1u)

EM06

−579.314277

-

ECCSD(T)

−577.230959

-

ECCSD(T)+F12

−577.296580

-

Present work

∠(O-Sn-O)

Published on 21 April 2015. Downloaded by Freie Universitaet Berlin on 06/05/2015 18:29:38.

Frequencies (cm-1)

Total energies (a.u.)

Considerably less has been reported about the properties of gaseous tetravanadium decaoxide. It is believed that its geometric structure is close to that of tetraphosphorus decaoxide which possesses Td point symmetry. Our calculations support this suggestion. Geometric structure of V4O10 ground state is displayed in Fig. 4. The first ionization potential (IP) and electron affinity (EA) for gaseous V4O10 were experimentally determined.40,41 In accordance to these works IPexpt = 11.8±0.1 eV and EAexpt = 4.26±0.03 eV. Our calculations at the DFT M06 level of theory give IPM06 = 11.9 eV and EAM06 = 4.13 eV.

O

V O O

O

V

V

O

O

O

O

V O

O

Fig. 4 Equilibrium geometry of V4O10 ground state calculated at the DFT M06 level of theory.

Dalton Transactions Accepted Manuscript

Geometric parameters (Å, deg) r(Sn-O)

38

Dalton Transactions

Page 10 of 18 View Article Online

DOI: 10.1039/C5DT00660K

10

A summary concerning geometric and electronic structure of V4O10 is given in Table S3 (ESI). On the ground (singlet) PES of MV2O6 (M = Ge, Sn) three equilibrium structures were found (see Fig. 5). The energetically favorable both at the DFT M06 and CCSD(T) levels of theory is Structure I of symmetry C2v. The remainder structures have Cs symmetry and are enantiomers.

Published on 21 April 2015. Downloaded by Freie Universitaet Berlin on 06/05/2015 18:29:38.

for high temperature gas phase reactions. We therefore concentrate our attention on the structures with the minimal energy.

X X O1

X

O1

O2

O3

V1

O3

V2 O6

O2

O1

V2

V2

V1

O4

O2

O6

O6

O4

O3

V1

O4

O5

Structure I (C2v)

O5

Structure II (Cs)

O5

Structure III (Cs)

Fig. 5 Equilibrium geometry of MV2O6 (M = Ge, Sn) isomers calculated at the DFT M06 level of theory. A summary concerning details of geometric and electronic structure of MV2O6 molecules is given in Table S4 (ESI). Energies of molecules MV2O6 calculated at different levels of theory and required for estimation of reaction (15)-(16) enthalpies are listed in Table 3. NBO42 atomic charges, bond orders and valence indices may be found in Table S5 (ESI).

Table 3. Total energies of energetically favorable isomers of molecules MV2O6 (M = Ge, Sn) calculated at DFT M06, CCSD(T), and CCSD(T)-F12 levels of theory. Method

GeV2O6 (Structure I)

SnV2O6 (Structure I)

Dalton Transactions Accepted Manuscript

Minima corresponding to these structures are very shallow and can hardly be of any importance

Page 11 of 18

Dalton Transactions View Article Online

DOI: 10.1039/C5DT00660K

M06

Total energy (a.u.) −4416.553039

Total energy (a.u.) −2553.9981751

CCSD(T)

−4412.69969279

−2550.67156318

CCSD(T)+F12

−4412.89959428

−2550.87079137

Zero point energy (a.u.)

Zero point energy (a.u.)

0.023388

0.022997

M06

Using data from Tables 1-3 it is easy to estimate theoretical enthalpies of the aforementioned reaction and compare them with the experimental results. The corresponding enthalpy values (at 0 K) are presented in Table 4. From this table it is seen that theoretical and experimental values are in reasonably good agreement.

Table 4. Calculated and experimental enthalpies of reactions (15)-(16) at 0 K. −∆rH0(0), kJ mol-1

Reaction

DFT

CCSD(T)

CCSD(T) +F12

M06

Expt

GeO(1Σ+)+1/2V4O10(1A1)→ GeV2O6(1A1)

71

69

72

72±12

SnO(1Σ+)+1/2V4O10(1A1)→ SnV2O6(1A1)

144

111

115

134±5

302

273

284

294±9

−13

−50

−53

−38±5

1 +

1 +

1

SnO( Σ )+ SnO( Σ )→Sn2O2( Ag) 1

1

1

Sn2O2( Ag)+ V4O10( A1)→2 SnV2O6( A1)

Values of enthalpies of reactions (15) and (16) at 298 K obtained in the present paper are given in Table 5. It is to be noted that values of enthalpies of reactions (15) and (16) calculated according to equations (13) and (17) are in good mutual agreement which testifies that the thermodynamic functions of gaseous vanadates were calculated correctly. An additional point to emphasize is that enthalpies obtained experimentally and calculated by several quantum chemical methods are also in a good accordance.

Table 5. Values of enthalpies of reactions (15)-(16) and standard formation enthalpies of gaseous molecules GeV2O6 and SnV2O6 Reaction

−∆rH0(298 K), kJ

−∆fH0(298 K)

recommended

Dalton Transactions Accepted Manuscript

Published on 21 April 2015. Downloaded by Freie Universitaet Berlin on 06/05/2015 18:29:38.

11

Dalton Transactions

Page 12 of 18 View Article Online

DOI: 10.1039/C5DT00660K

12

value

GeO + 1/2 V4O10

2nd law

3th law

recommended

(eq 17)

(eq 13)

value

=

-

71±12

71±12

=

129±12

135±5

133±8

= 2

-51±17

-28±5

-33±10

1520±42

Published on 21 April 2015. Downloaded by Freie Universitaet Berlin on 06/05/2015 18:29:38.

SnO + 1/2 V4O10 SnV2O6 Sn2O2 + V4O10

1520±43

SnV2O6

The obtained enthalpies of reactions (15) and (16) recalculated to the standard temperature 298 K together with the available data on the standard formation enthalpies of GeO (-37±4), SnO (21.9±4), Sn2O2 (-238±25), and V4O10 (-2825±40) kJ/mol taken from33 made it possible to determine standard formation enthalpies of gaseous germanium and tin vanadates which are also listed in Table 5. Evaluated earlier in paper19 standard formation enthalpy of lead vanadate amounts to -1477±45 kJ/mol. Comparing this value with the data obtained in the present paper one can come to the conclusion that the formation enthalpies of the molecules under discussion are close to one another. In the isocation series of gaseous oxyacid salts the atomization enthalpy of gaseous salts has been shown43 to be linearly dependent on the atomization enthalpy of gaseous anion-forming oxides, with the dependence being represented by the eq 18. ∆atΗ 0(salt, gas, 298) = k⋅∆atΗ 0(anion-forming oxide, gas, 298) + b

(18)

To plot the data obtained on the dependence graph plotted earlier9,12 for gaseous salts of germanium and tin it is necessary to know atomization enthalpy of gaseous oxide V2O5 whose existence has so far not been recognized and whose thermodynamic characteristics have not been determined. Using the dependence equation (18) it is easy to calculate standard atomization enthalpy and formation enthalpy of a given oxide on the basis of data obtained in the present paper and data obtained earlier19 for gaseous lead vanadate. This value is equal to -1170 kJ/mol and can be used to evaluate formation and atomization enthalpies of so far unexplored gaseous vanadates.

3. Experimental

Dalton Transactions Accepted Manuscript

GeV2O6

Page 13 of 18

Dalton Transactions View Article Online

DOI: 10.1039/C5DT00660K

13

3.1. Samples V2O5, SnO2, and GeO2 (grade puriss, p.a.) were used in the present study. Oxides taken in equimolar proportion were mixed thoroughly and grinded in agate mortar with subsequent

Published on 21 April 2015. Downloaded by Freie Universitaet Berlin on 06/05/2015 18:29:38.

3.2. Mass spectrometry The Knudsen effusion technique combined with mass spectrometric analysis (standard model MS-1301 Construction Bureau, Academy of Science, St. Petersburg) of the vapor composition was employed. This mass spectrometer has a homogeneous magnetic sector analyzer with the radius of the central trajectory equal to 300 mm, and with the deflection angle of ions equal to 90°. The design of the MS-1301 provides a mutually perpendicular arrangement of the molecular, electron and ion beams. The mass resolution of this instrument is not less then 500 using the 10% peak height definition. The instrument allows ions to be measured in the range from m/z 1 to 500 at an accelerating voltage of 3.0 kV, and in the range from m/z 2 to 1000 at an accelerating voltage of 1.5 kV. The ion current was amplified by secondary electron multiplier. Ionization of vapor species was made by electron impact, with the energy of ionizing electrons being 30 eV. One of few methods, which are still applicable in high temperature chemistry, is the molecular effusion method suggested by Knudsen44. Following this method, small vapor pressures are determined by means of effusion of vaporized sample out of an isothermal vessel which is called "Knudsen cell". If thermodynamic equilibrium between the condensed sample and its vapor phase is established inside the Knudsen cell, then the pressure in the escaping molecular beam can be determined. The Knudsen cell serves as the "gas source" of high-temperature mass spectrometer, the effusing molecular beam from which is directed into the ionization chamber of the mass spectrometer. The effusion cell which we used had the ratio effusion orifice – evaporation area less then 1:200. The cell was placed into molybdenum block and heated by electron bombardment. The temperature was measured by disappearing filament one wave optical pyrometer EOP-66 in the temperature range 1500−1800 K, the accuracy of measurements being 5 K. Testing the instrument was performed by measuring the vapor pressures of the gold metal and comparing the measured values with the reference data.30 The appearance energies (AE) of ions were measured by the vanishing current method with Au as energy standard,27 which was found to be accurate within ±0.3 eV.

3.3. Quantum chemical calculations

Dalton Transactions Accepted Manuscript

loading the mixture obtained into effusion cell.

Dalton Transactions

Page 14 of 18 View Article Online

DOI: 10.1039/C5DT00660K

14

Two different approaches to quantum chemical calculations of reaction enthalpies were employed. The first one is purely ab initio wave function based approach using explicitly correlated CCSD(T)-F12 method developed by Werner group.36 In this method trial wave function includes explicitly interelectronic distances to account correlation effects for

Published on 21 April 2015. Downloaded by Freie Universitaet Berlin on 06/05/2015 18:29:38.

poor convergence of Slater determinant configuration interaction expansions. Efficiency of explicitly correlated methods for calculation of enthalpies of atomization of molecules including transition metals was recently demonstrated.45 All calculations were carried out with the MOLPRO suite of ab initio programs.46 The second approach is density based and exploits DFT M06 method developed by Truhlar group.34 All DFT calculations were performed with the GAUSSIAN’09 program set.47 Def2-TZVP basis sets48 with the corresponding relativistic small core effective potential for tin was chosen.49 Localization of energy stationary points and subsequent vibrational analysis were performed in the framework of DFT M06 method. At the equilibrium geometries obtained CCSD(T) and CCSD(T)-F12 calculations were carried out to get energy correlation corrections. Molecular structures and normal vibrations were visualized with the aid of Chemcraft50 and Avogadro51 graphical programs. Natural Population Analysis35 was employed to evaluate atomic charges and bond orders.

4. Conclusions The existence of two novel gaseous oxyacid salts (GeV2O6 and SnV2O6) was proven by means of Knudsen effusion mass spectrometry. The gas phase over GeO2-V2O5 and SnO2-V2O5 consist of MO, V4O10 and MV2O6 (M = Ge, Sn). The enthalpies of formation of these gaseous oxyacid salts were determined experimentally by Knudsen effusion mass spectrometry. The structures of gaseous GeV2O6 and SnV2O6 were calculated by quantum chemical methods. GeV2O6 and SnV2O6 proved to have similar geometric structure identical to that of PbV2O6.8 The data obtained allowed to estimate the standard enthalpies of formation of the gaseous V2O5 molecule. Several quantum chemistry methods were used to evaluate enthalpies of reactions involving the aforementioned gaseous oxyacid salts. The theoretical results are self-consistent and agree well with the experimental data.

Acknowledgments The present research was carried out using computer resources provided by Resource Center "Computer Center of SPbU" (http://cc.spbu.ru).

References

Dalton Transactions Accepted Manuscript

intermediate values of r12 which are difficult to handle in terms of orbital products due to very

Page 15 of 18

Dalton Transactions View Article Online

DOI: 10.1039/C5DT00660K

15

1

A.A. Fotiev, B.V. Slobodin and M.Ya. Khodos “Vanadates. Composition, synthesis, structure, properties”. Moscow, Nauka, 1988. 272 p.

2

T.D. Manning, I.P. Parkin, R.J.H. Clark, D. Sheel, M.E. Pemble and D. Vernadou, J.

3

M.H. Lee, M.G. Kim and H.K. Song, Thin Solid Films, 1996, 290-291, 30.

4

G.N. Jorgenson and J.C. Lee, Solar Energy Mater., 1986, 14, 205.

5

S.I. Lopatin and G.A. Semenov, Rus. J. Gen. Chem., 1995, 65, 1060.

6

V. Plies, Z. anorg. allg. Chem., 1982, 484, 165.

7

S.I. Lopatin, G.A. Semenov and T.S. Pilyugina, Rus. J. Gen. Chem., 2000, 70, 529.

8

S.I. Lopatin, S.M. Shugurov and G.A. Semenov, Vestnik SPbGU, Physic and Chemistry (Rus.), Gazette of St. Petersburg St. Univ., 2003, 2, 50.

9

S.I. Lopatin, A.I. Panin, S.M. Shugurov, K.A. Emelyanova, RSC Advances, 2014, 4, 39725.

10 S.I. Lopatin and G.A. Semenov, Rus. J. Gen. Chem., 1996, 66, 180. 11 M.N. Bulova, A.S. Alikhanyan, and A.M. Gas' kov, Inorganic materials, 2002, 38, 688. 12 S.I. Lopatin, S.M. Shugurov, Rus. J. Gen. Chem 2008, 78, 705. 13 G. Balducci, L. Bardi, G. Gigli, M. Guido , S. Nunziante Cesaro and F. Ramondo, High Temp.-High Pres., 1988, 20, 141.

14 G. Balducci, G. De Maria, G. Gigli and M. Guido, High Temp. Sci., 1988 (Publ. 1989), 28, 153. 15 G.A. Semenov, N.V. Kozyukova, B.V. Slobodin and V.M. Ushakov, Mass Spectrometric Study of Vaporization Behavior of Molten Cesium and Rubidium Metavanadates. // Abstr. XIV Intern. Mass Spectrometric Conf. Tampere, Finland. 1997. N ThPo 43. p. 234. 16 L.S. Kudin and A.M. Pogrebnoi, Rus. J. Phys. Chem., 1996, 70, 1758. 17 S.M. Shugurov and S.I. Lopatin, Electrochem. Soc. Transactions., 2013, 46, 211. 18 G.A. Semenov, S.I. Lopatin, N.V. Kozyukova and L.A. Kuligina, High Temp.-High Pres., 1988, 20, 637. 19 S.I. Lopatin, I.Ya. Mittova, F.S. Gerasimov, V.F. Kostryukov, S.M. Skorokhodova and S.M. Shugurov, Rus. J. Inorg. Chem., 2006, 51, 1749. 20 G. Balducci, G. Gigli and M. Guido, J. Chem. Phys., 1983, 79, 5623. 21 M. Farber and R.D. Srivastava, Combus. Flame, 1973, 20, 43. 22 S.M. Shugurov and S.I. Lopatin, Rapid Commun. Mass Spectrom., 2011, 25, 3464. 23 A.O. Gunina, S.I. Lopatin and S.M. Shugurov, Inorg. Chem., 2012, 51, 4918. 24 E. K. Kazenas, Yu. V. Tsvetkov “Vaporization of oxides (Isparenie oksidov)”. Nauka, Moscow, 1997, 544.

Dalton Transactions Accepted Manuscript

Published on 21 April 2015. Downloaded by Freie Universitaet Berlin on 06/05/2015 18:29:38.

Mater. Chem., 2002, 12, 2936.

Dalton Transactions

Page 16 of 18 View Article Online

DOI: 10.1039/C5DT00660K

16

25 J. Berkowitz, W.A. Chupka and M.G Inghram, J. Chem. Phys., 1957, 27, 87. 26 D.M. Chizikov, Y.A. Pavlov, Y.V. Tsvetkov, E.K. Kazenas and P.A. Nesterenko, Izvestiya Vysshikh Uchebnykh Zavedenii (Rus.), Ferrous metallurgy, 1970, 7, 5. 27 Energii razryva khimicheskikh svyazey: potentsialy ionizatsii i srodstvo k elektronu.

Published on 21 April 2015. Downloaded by Freie Universitaet Berlin on 06/05/2015 18:29:38.

Potentials and Electron Affinities); Kondrat’ev, V. N., Ed.; Nauka: Moscow, 1974.

28 F. H. Field and J. L. Franklin. “Electron impact phenomena: and the properties of gaseous ions”. Academic Press, 2013. 546 p. 29 V. L. Stolyarova, G. A. Semenov “Mass Spectrometric Study of the Vaporization of Oxide Systems” Beynon, J. H., Ed.; Wiley, N.Y. 1994, 434 p. 30 R. C. Paule and J .Mandel, Pure Appl. Chem., 1972, 31, 371. 31 In Recent Development in Mass Spectrometry; Ogata, K., Hayakawa, T., Eds.; University Park Press: Baltimore, 1970; p. 814. 32 M. Guido and G.Gigli, High Temp. Sci., 1975, 7, 122. 33 Termodinamicheskie Svoistva Individual’nykh Veschestv (Thermodynamic Properties of Individual Substances); Glushko, V. P., Ed.; Nauka: Moscow, 1978−1982; vol. 1−4.

34 Y. Zhao, D.G.Truhlar, Theor. Chem. Account, 2008, 120, 215. 35 R.J.Bartlett, M. Musial, Rev. Mod. Phys. 2007, 79, 291 (and references cited therein). 36 G. Knizia, T. B. Adler, H.-J. Werner, J. Chem. Phys. 2009. 130, 054104. 37 K.P. Huber and G. Herzberg "Constants of Diatomic Molecules" by (data prepared by J.W. Gallagher and R.D. Johnson, III) in NIST Chemistry WebBook, NIST Standard Reference Database Number 69, Eds. P.J. Linstrom and W.G. Mallard, National Institute of Standards and Technology, Gaithersburg MD, 20899, http://webbook.nist.gov, (retrieved April 14, 2014). 38 J. S. Ogden and M. J. Ricks, J. Chem. Phys. 1970, 53, 896. 39 A. M. Mazzone and V. Morandi, Eur. Phys. J. B, 2006, 51, 307. 40 H. J. Zhai, J. Dobler, J. Sauer, L. S. Wang, J. Am. Chem. Soc., 2007, 129, 13270. 41 S. L. Bennett, S.-S. Lin and P.W. Gilles, J. Phys. Chem., 1974, 78, 266. 42 A.E. Reed, L.A. Curtiss, F. Weinholt, Chem. Rev., 1988, 88, 899. 43 S.I. Lopatin, Rus. J. Gen. Chem., 2007, 77, 1761. 44 K. Hilpert "Chemistry of inorganic vapors." in “Noble Gas and High Temperature Chemistry”. Springer Berlin Heidelberg, 1990. p. 97-198. 45 D. H. Bross, J. G. Hill, H.–J. Werner, K.A. Peterson, J. Chem. Phys., 2013, 139, 094302. 46 MOLPRO, version 2010.1, a package of ab initio programs, H.–J.Werner, P. J. Knowles, G. Knizia, F. R. Manby, M. Schutz, and others, see http://www.molpro.net.

Dalton Transactions Accepted Manuscript

Spravochnik. (Handbook on the Dissociation Energies of Chemical Bonds: Ionization

Page 17 of 18

Dalton Transactions View Article Online

DOI: 10.1039/C5DT00660K

17

47 M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G.A. Petersson, H. Nakatsuji, M. Caricato, X. Li, H.P. Hratchian, A.F. Izmaylov, J. Bloino, G. Zheng, J.L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai,

Published on 21 April 2015. Downloaded by Freie Universitaet Berlin on 06/05/2015 18:29:38.

Brothers, K.N. Kudin, V.N. Staroverov, T. Keith, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, J.C. Burant, S.S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J.M. Millam, M. Klene, J.E. Knox, J.B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, R.L. Martin, K. Morokuma, V.G. Zakrzewski, G.A. Voth, P. Salvador, J.J. Dannenberg, S. Dapprich, A.D. Daniels, O. Farkas, J.B. Foresman, J.V. Ortiz, J. Cioslowski, and D. J. Fox, GAUSSIAN 09, (Revision D.01), Gaussian, Inc., Wallingford CT, 2010. 48 F. Weigend and R. Ahlrichs, Phys. Chem. Chem. Phys., 2005,7, 3297. 49 B. Metz, H. Stoll, M. Dolg, J. Chem. Phys., 2000, 113, 2563. 50 http://www.chemcraftprog.com (Last visited March 3, 2015). 51 M.D. Hanwell, D.E. Curtis, D.C. Lonie, T. Vandermeersch, E. Zurek and G.R. Hutchison, J. Cheminform., 2012, 4, 17.

Dalton Transactions Accepted Manuscript

T. Vreven, J.A. Montgomery, Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, J.J. Heyd, E.

Dalton Transactions

Page 18 of 18 View Article Online

DOI: 10.1039/C5DT00660K

18

The stability of gaseous GeV2O6 and SnV2O6 were confirmed by Knudsen effusion mass spectrometry. To get structure parameters of these gaseous salts quantum chemical investigation of molecules was undertaken.

Dalton Transactions Accepted Manuscript

Published on 21 April 2015. Downloaded by Freie Universitaet Berlin on 06/05/2015 18:29:38.

Table of contents:

Formation and thermodynamics of gaseous germanium and tin vanadates: a mass spectrometric and quantum chemical study.

The stabilities of gaseous germanium and tin vanadates were confirmed by high temperature mass spectrometry, and its structures were determined by qua...
799KB Sizes 1 Downloads 7 Views