This presentation is a report from the PLMMP-2018 conference. For any information contact me here: dmitrynovikovs@gmail.com Abstract This work is a continuation of the systematic study of unsymmetrical electrolytes in non-aqueous media, carried out at the Department of Inorganic Chemistry of V.N. Karazin Kharkiv National University [1]. Here we report the results of the conductometric study of diluted solutions of Cu(BF4)2, Zn(BF4)2 and Co(BF4)2 in acetonitrile (AN) at 5-55 oC. The extended Lee-Wheaton equation was used to procced conductometric data and obtain primary association constants, limiting equivalent conductance of electrolytes and limiting ionic conductivities. The primary association constants were then used to interpret the contribution of the ionic solvation and association in terms of contact ionic pairs, solvent-separated ionic pairs and short-range non-Coulomb interionic potential. Obtained values of total limiting equivalent conductivity of electrolyte and the limiting conventional transference numbers allowed us to divide the equivalent conductivity on ionic constituents. These data were later proceeded to evaluate the parameter of dynamics of ionic solvation, within the modified theory of the dielectric friction. Additionally, densimetric study was carried out to derive structural parameters of ion solvation of Cu(BF4)2, Zn(BF4)2 and Co(BF4)2 in AN at 5-55 oC. Finally, molecular dynamics simulations were performed on the same electrolyte/AN systems by means of MDNAES package [2] to elucidate particle dynamics and microscopic structure within the first and second co-ordination shells of copper (II), cobalt (II) and zinc (II) cations in AN at 25 °C. References [1] O.N. Kalugin, V.N. Agieienko and N.A. Otroshko, J. Molec. Liquids, 165, 78-86 (2012). [2] O. N. Kalugin, M. N. Volobuev, and Y. V. Kolesnik, Khar. Univ. Bull., Chem. Ser. 454, 58-80 (1999).

1. INTERPARTICLE INTERACTIONS AND DYNAMICS IN SOLUTIONS OF COPPER (II),
COBALT (II) AND ZINC (II) TETRAFLUOROBORATES IN ACETONITRILE AT 5-55°C
V. N. Karazin Kharkiv national university
Chemistry faculty
PHYSICS OF LIQUID MATTER: MODERN PROBLEMS (PLMMP-2018)
report
Dmytro Novikov, Oleg Kalugin, Tatiana Chernozhuk,
V. Moiseenko, D. Abrosimova, K. Donchik
KYIV 2018 1

2. THE STRUCTURE OF THE REPORT
1. Objects and methods of the study
2. Concductometric experiment
a. Existing equilibria and the data treatment approach
b. The results of the conductometric study
c. Contributions of the ionic conductivities
d. Stokes radii and the thickness of the ionic solvation shells
3. Molecular modelling experiment
a. Details of the molecular dynamic simulations
b. Determination of the solvation shell boundaries and identification of the contact ion
pair formation
c. Dynamic properties of the copper cation and the contact ion pair
d. Solvation dynamics (translational)
e. Solation dynamics (dipole momentum re-orientation)
4. Conclusions
2

3. OBJECTS AND METHODS OF THE STUDY
3 2( ) 4( ) 4 2( ) 2( ) 2 ( )( ) 2 ( ) 2 2s aq aq g lCu HCO HBF Cu BF CO H O   
•Synthesized from copper hydrogen carbonate with 40% HBF4;
•Purified and dried at 70oC (40 h) and 130oC (80 h) under vacuum;
•Re-crystallized from acetonitrile multiple times;
•Solvate Cu(BF4)2·6H2O collected and dried under vacuum at 55oC for 40 h.
CH3CN
Physical properties of CH3CN
molar mass 41.05 g mol-1
density 0.786 g cm-3
dielectric constant 37.5
boiling point 82oC
•purified by multiple distillations with
P2O5;
•water content was controlled by the
Karl Fisher titration (no more than
0.01%);
Liquid solutions of Cu(BF4)2
in acetonitrile
concentration range 4·10-4 … 4·10-3 mol dm-3
temperature range 5, 15, 25, 35, 45 and 55oC
3

4. CONDUCTOMETRY
4

5. EXISTING EQUILIBRIA AND THE DATA TREATMENT APPROACH
Fig 1. Equivalent conductivity of copper tetrafluoroborate
in acetonitrile as a function of square root of
concentration
(4)
(5)
(6)
(7)
(8)
2
4 4Cu BF CoBF  

 4 4 4 2
CuBF BF Cu BF 

   0 0 2
4 42
1 1
, ,lg ,lg , ,
2 2
aI aIIA Cu BF CuBF K K t Cu R       
     
    
  
2
, ,
1
min
N
exp theor
eq k eq k
k
Q

     A
 
1
ln
2 1 R


  

1
m
st
j il kl
j
c c

 
1
il
q
Ai ki ki kl
l
K c y a 

 
 0
, ,( , ) 1 ( ) ( )eq i eq i i iI A E I H I   
(1)
(2)
(3)
0.001 0.002 0.003 0.004 0.005 0.006 0.007
100
120
140
160
180
200
220
240
at 5o
C
at 15o
C
at 25o
C
at 35o
C
at 45o
C
at 55o
C
eq
/Om-1
cm2
mol-1
(c / mol dm-3
)1/2
5

6. 5 0C 173.9±0.1 39±2 2.180.01 0.4590.002 0.09
15 0C 192.3±0.1 15±1 2.070.01 0.4550.002 0.11
25 0C 209.4±0.2 53±1 2.130.01 0.4550.001 0.23
35 0C 231.0±0.1 51±2 2.130.01 0.4540.002 0.15
45 0C 251.2±0.1 69±1 2.160.01 0.4570.001 0.17
55 0C 267.0±0.2 132±1 2.170.01 0.4550.001 0.12
,o
t C  0
4 2
1
2
Cu BF
 
  
 
 0
4CuBF 
lg aIK
21
2
t Cu  
 
 

Table 1. Limiting equivalent conductivity of Cu(BF4)2, limiting conductivity of associate, logarithm of the
first step association constant and conventional transfer number for the system studied.
(11)   0 0 2
4 42
1 1
, ,lg ,
2 2
aIA Cu BF CuBF K t Cu       
     
    
2
4 4Cu BF CuBF  

 4 4 4 2
CuBF BF Cu BF 

6
(10)
(9)
THE RESULTS OF THE CONDUCTOMETRIC STUDY

7. CONTRIBUTIONS OF THE IONIC CONDUCTIVITIES
0 10 20 30 40 50 60
75
90
105
120
135
150
0
(1/2Cu2+
)
0
(BF4
-
)
0
/Smcm2
mol-1
t, o
C
Dividing equivalent conductivity on ionic conductivities
   0 2 0 2
4 2
1 1
*
2 2
Cu Cu BF t Cu      
     
   
     0 0 0 2
4 4 2
1
2
BF Cu BF Cu   
   
 
Table 2. Limiting ionic conductivities
t,oC *
5 79.8 94.1 94.1
15 87.5 104.8 105.0
25 95.3 114.1 115.4
35 104.9 126.1 126.0
45 114.8 136.4 137.7
55 121.4 145.6 149.9
 0 2
Cu 
 0
4BF 
 0
4BF 
* - O.N. Kalugin et al. / ElectrochimicaActa105 (2013) 188– 1997
Fig 2. Equivalent electrical conductivity of Cu2+
and BF4
- as a function of concentration
(12)
(13)

8. STOKES RADII AND THE THICKNESS OF THE IONIC SOLVATION SHELL
Fig 3. Temperature function of thicknesses of ionic
solvation shells
(14)
04
st
zeF
R


0 10 20 30 40 50 60
0,5
1,0
1,5
2,0
2,5
3,0
Cu2+
BF4
-
Rst
-Ri
/1010
m
t, o
C
8

9. MOLECULAR DYNAMIC SIMULATIONS
9

10. DETAILS OF THE MOLECULAR DYNAMIC SIMULATIONS
Atom type Mass Charge σ, nm ε, kJ/mol
#atom C1
12.0112 -0.5503 0.3400 0.45729
#atom H 1.0079 0.1904 0.2500 0.03000
#atom C2
12.0112 0.4917 0.3546 0.056054
#atom N 14.0067 -0.5126 0.3100 0.556360
#atom Cu 63.5460 2.0000 0.135 17.0
#atom B 10.81 1.198328 0.000 0.000
#atom F 18.9984 -0.549582 0.3 0.2845
Table 3. Force field parameters of modelled particles *
STEPS OF MODELLING:
1. System initiation (1 ps)
2. System equilibration (250 ps)
3. Study of structure (500 ps)
4. Study of dynamic properties (500 ps)
Cut-off radius: 1.34 nm
Ensemble: NVT
Thermostat relaxation time: 0.05 ps
Dielectric constant: 36.0
Temperature: 298.15 К
Density of the system: 776.8 kg/m3
System (I) System (II) System (III)
*- AN: Nikitin A., J. Copm. Chem. – 2007 – Vol. 28, P. 2020-2026.
Cu: Torras J.,J. Phys. Chem. – 2013 –Vol. 117. – P. 10513-10522
10
216 CH3CN 215 CH3CN
1 Cu2+
215 CH3CN
1 Cu2+
1 BF4
-
Program package: MDNAES

11. DETERMINATION OF THE SOLVATION SHELLS BOUNDARIES AND
IDENTIFICATION OF THE CONTACT ION PAIR FORMATION
Table 4. Running coordination numbers of Cu2+
in systems (II) and (III)
System Coordination number of
Cu2+ by AN molecules
(II) 6
(III) 5
0,2 0,4 0,6 0,8
0
2
4
6
8
10
0
2
4
6
8
10
g(r)/rcn(r)
r, nm
(II) Cu...N
(III) Cu...N
(III) Cu...B
(II) rcn(r)
(III) rcn(r)
FSS Cu...N
0.243 nm
d(CIP) Cu...B
0.357 nm
11
Fig. 4. Radial density function of Cu2+ and BF4
- in
acetonitrile

12. (15) (16)
DYNAMIC PROPERTIES OF THE COPPER CATION AND THE CONTACT ION PAIR
0,0 0,5 1,0 1,5 2,0
0,0
0,4
0,8
Cvv
(t)
t, ps
(II) Cu2+
(III) Cu2+
(III) CuBF-
4
0 50 100 150
0,00
0,02
0,04
0,06
Svv
()
, THz
(II) Cu2+
(III) Cu2+
(III) CuBF-
4
Fig 6. Spectra of linear velocity of Cu2+ in systems (II) and (III)
and CuBF4
- in system (III)
Fig 5. ACF of linear velocity of Cu2+ in systems (II) and (III)
and CuBF4
- in system (III)
12
2
(0) ( ) (0) ( )
( )
(0) 3
VV
B
t t m
C t
k T
 
V V V V
V 0
( ) ( )cos( )VV VVS C t t dt 

 

13. SOLVATION DYNAMICS (TRANSLATIONAL)
Table 5. Coefficients of translational self-diffusion of
acetonitrile molecules by solvation shells in the systems studiedFig 7. Linear velocity ACF for acetonitrile by solvation shells
Fig 8. Linear velocity ACF spectra for acetonitrile by solvation shells
D·1010, m2s-1
(I) (II) (III)
Bulk 3.63 3.65 3.65
SSS - 2.56 -
FSS - 1.24 0.65
Cu2+
- 0.78 0.64
CuBF4
-
- - 0.68
(12)
(13)
(14)
0,0 0,5 1,0 1,5
0,0
0,4
0,8Cvv
(t)
t, ps
System (I)
System (II)
System (III)
0 25 50 75
0,00
0,04
0,08
0,12
Svv
()
, THz
System (I)
System (II)
System (III)
13
2
(0) ( ) (0) ( )
( )
(0) 3
VV
B
t t m
C t
k T
 
V V V V
V
0
( ) ( )cos( )VV VVS C t t dt 

 
0
1
( )
3
VVD C t dt

 

14. SOLVATION DYNAMICS (DIPOLE MOMENTUM RE-ORIENTATION)
(II) Dipole momentum
reorientation time
Lifetime by solvation
shells
Bulk 3.1 ps -
SSS 18.5 ps 13 ps
FSS 70.9 ps 3000 ps
(III) Dipole momentum
reorientation time
Lifetime by solvation
shells
Bulk 3.2 ps -
FSS 110.3 ps 22 ps
Fig 10. Dipole momentum reorientation time ACF
Fig 11. Lifetime ACF by solvation shells
Table 5. Results of dipole momentum reorientation time
and lifetime ACF study
(15)
(16)
10
0 4 8
-4
-2
0
II (Bulk)
II (SSS)
II (FSS)
III (Bulk)
III (FSS)
lnC1
(t)
t, ps
14
1
1
( ) exp
t
C t const

 
    
 
( ) exprt
rt
t
C t const

 
   
 
0,0 0,5 1,0 1,5 2,0
0,6
0,8
1,0
(II) SSS
(II) FSS
(III) FSS
C1
(t)
t, ps

15. CONCLUSIONS
15
1. The conductometric study had shown that the association of copper tetrafluoroborate in acetonitrile
is limited by the first step (CuBF4
- formation). The association constants calculated are quite high and
are constant at the studied temperatures;
2. The copper cation forms dynamically stable first solvation shell in acetonitrile. The thickness of the
solvation shell is constant at the temperatures studied;
3. Based on the analysis of radial distribution functions and running coordination numbers, it was found
that the copper cation keeps its coordination number constant ([Cu(AN)6]2+ and [Cu(AN)5(BF4)]+);
4. Translational and re-orientational dynamics of the acetonitrile molecules is significantly slowed down
when the solvent molecule is transferred from the bulk solvent to the first solvation shell of the
copper cation;
5. The analysis of the ACF of copper cation had shown the formation of strong and stable solvation shell.
This evidence was confirmed by the conductometric study.