Nghiên cứu tổng hợp vật liệu mới từ TCNQ và TCNQF4 tt tiếng anh

MINSTRY OF EDUCATION AND TRAINING
THE UNIVERSITY OF DANANG

RESEARCH ON THE SYNTHESIS OF
NEW TCNQ AND TCNQF4 – BASED
MATERIAL

Major: Organic Chemistry
Code: 60.44.01.14

Summary of Doctoral Thesis in Chemistry

Danang - 2019
1


The work was completed in
THE UNIVERSITY OF DANANG

Supervisor: 1. Assoc. Prof Le Tu Hai
Supervisor: 2. Assoc. Prof Lisa Martin

Reviewers 1:
Reviewers 2:
Reviewers 2:

The dissertation is protected before the Council meeting
marked PhD thesis at the University of Danang in day month
year 2019

Thesis can be found at

- National library of Vietnam
- Center for learning information resources and communications
2


A. DESSRTATION INTRODUCTION
1. The significances of the research
TCNQ-based materials (tetracyanoquinondimetan) have been
studied since the 1960s. Especially, a semiconductor compound was
chemically synthesized from TCNQ with TTF. Since then, there have
been many researches on chemical synthesis and characterization of
TCNQ-based materials.
The synthesis of TCNQ with nitrogen-containing organic
compounds such as amine derivatives, amino acids has not been
studied widely. Especially, there have been not many publications on
the chemistry and the synthesis of materials from TCNQFn derivatives.
The use of electrochemical method in synthesis and
characterization of the materials has not been properly investigated.
Therefore, the thesis title: "Research on the synthesis of new TCNQ
and TCNQF4 – based materials" has been chosen
2. Subjects and tasks of the dissertation
- Chemically synthesize new materials from TCNQ, TCNQF4 with
amino acid compounds and transition metal cations.
- Use electrochemical method to study the conditions to synthesize
TCNQF4 – based materials and provide suitable conditions for the
electrochemical synthesis.
- Characterize the new materials with spectroscopic methods.
- Contribute to the research on the application of conductive organic
polymers.

3. New findings of the dissertation
- Novel materials of TCNQ with amino acid Proline, Leucine and their
methyl derivatives has been successfully synthesized and chacracterze

1


- Novel TCNQF42- - based materials with metal cations (Ag+, Cu+,
Zn2+, Co2+, Mn2+) has been successfully synthesized and characterized.
- Electrochemical method has been used to study the synthesis the
characterization of TCNQF4 – based materials an
- The materials of TCNQ and amino acid derivatives have shown
interesting conductive properties.
Chapter 1. Overview
1. Conductive Polymer
Literature review on the conductive polymers and its
applications.
2. TCNQ and TCNQF4
- In the world, there have been many researches on TCNQ-based
materials. At first, it was the result of the synthesis of semiconductor
compounds from TCNQ and TTF, then the group of Prof. Kim Dunbar
and colleagues has also reported the chemical synthesis of TCNQbased materials with metal cations in different solvents. The
application of these products in the field of conductivity, optical
transformation, sensors has been studied in depth. Alan Bond and Lisa
Martin research group has started to investigate the electrochemical
synthesis as well as analyzing the reaction mechanism of these TCNQbased materials with metal cations.
- There have been less reports on the formation of TCNQ-based
materials with organic cations, compared to with transition metal
cations. Also, the research on TCNQFn derivatives has only been
started recently and there are not many significant results.

2


- The use of electrochemical methods to study the electrochemical
properties and electrochemical synthesis of materials of TCNQ and
TCNQF4 should be studied.
- The characterization of TCNQ, TCNQF4 and their anions in solid and
solution states has been described.
Chapter 2: Content and research methods
2.1. Equipment, tools and chemicals
2.1.1. Chemicals
7,7,8,8-tetracyanoquinondimethane (TCNQ)
2,3,5,6-tetrafloro-7,7,8,8-tetracyanoquinondimethane (TCNQF4)
L–Proline
N,N-dimethyl-D-Proline methyl ester
N,N,N-trimetyl Leucin metyl ester
Tetrakis(acetonitrin) Silve(I) tetrafloborat Ag(CH3CN)4BF4
Tetrakis(acetonitrin) copper (I) hexafloborat [Cu(CH3CN)4]PF6
Zince perclorat hexahydrat Zn(ClO4)2·6H2O
2.1.2. Experimental equipment and tools
Bioanalytical Systems (BAS) 100 W and Bioanalytical
devices (BAS) Epsilon is a versatile system used to study the
electrochemical properties of materials.
2.2. Research Methods
2.2.1. Physical method
2.2.2. Chemical synthesis method
2.2.3. Electrochemical method
2.3. Research on synthesizing and characterizing properties of
TCNQ with organic ions

3


2.3.1. TCNQ- Proline
2.3.2. TCNQ - N, N- dimetyl –proline este
2.3.3. Leucin(CH3)3 – TCNQ
2.4. Study on electrochemical properties and synthesis of TCNQF4
with metal cations.
2.4.1. Electrochemical properties of TCNQF4 in the presence of
Cu(CH3CN)4+ and Ag(CH3CN)4+
2.4.2. Synthesis materials of TCNQF4 with Ag+, Cu+ in CH3CN
2.4.3. Synthesis M-TCNQF4 (M = Zn, Co, Mn) in mix solvent of
CH3CN and DMF.
Chapter 3: Results and Discussion
3.1. Materials of TCNQ with amino acides
3.1.1. Material of Proline with TCNQ
3.1.1.1. Structure of product

The

Figure 3.3. Structure of ProTCNQ
asymmetric unit of the product contains

two

crystallographically independent proline molecules and three halves of
TCNQ species. There are two groups of TCNQ are anionic radicals
TCNQ-, the other TCNQ group is a neutral molecule of TCNQ0
alternating between 2 TCNQ-.

4


3.1.1.2. Spectral properties of the product
Raman spectrum of TCNQ0 shows the vibrational bands of C≡N,
ring C=C, exocyclic C=C and C-H bonds at 2227, 1601, 1454 and
1205 cm-1 respectively. Raman spectrum of the crystal represents the
vibrational band of C≡N stretch at 2194 cm-1 and of exo-ring C=C
stretch at 1387 cm-1. These bands shift towards the lower energy
showing the presence of TCNQ-. Infrared and UV-Vis spectra also
confirm the existence of two TCNQ- moieties and 1 TCNQ0 moieties.
3.1.1.3. Electrochemical properties of the product
The steady state voltammogram of ProTCNQ dissolved in
CH3CN is shown in Figure 3.7. The voltammogram illustrates that the
magnitude of oxidation current doubles that of reduction one, implying
the presence of two TCNQ.- and one TCNQ0 moieties in the solution.
0.4
0.3
0.2

ProTCNQ

i/[nA]

0.1
0.0

TCNQ

-0.1
-0.2
-0.3
-0.4
0.0

0.1

0.3

0.2

0.4

0.5

0.6

+

E/[V] vs Ag/Ag

Figure 3.7. Steady state voltammogram of ProTCNQ and TCNQ in
CH3CN
3.1.1.4. Conductivity of ProTCNQ
The solid state conductivity of ProTCNQ is measured at
2.5mS.cm-1 at 295K. That indicates it is within the semiconductor
range (10-5 to 106 mS.cm-1).

5

3.1.2. Product of N,N-dimetyl- Proline methyl este with TCNQ
3.1.2.1. Crystall structure
- ProCH3TCNQ (1:1) material

Figure 3.10. Structure of Pro(CH3)3TCNQ (1:1)
The product crystallizes in the monoclinic space group P21, with
the asymmetric unit cell comprising of one Pro(CH3)3+ and an anionic
TCNQ- (Figure 3.10). The structure of this crystal shows that it is a
layer structure. The charge of TCNQ moieties derived from the bond
length in TCNQ is -1,07, indicating the presence of anionic mono
TCNQ-.
- Material (ProCH3)2(TCNQ)3
Single crystals of ProCH3TCNQ (2:3) belong to the monoclinic
space group P21/c with the asymmetric unit cells containing a
Pro(CH3)3+ cation with two TCNQ moieties (Figure 3.11).
The structure includes alternating layers of Pro(CH3)3+ and
(TCNQ)32-. From the results of analyzing the bond length of each
TCNQ moieties, the charge (ρ) can be calculated as -0.30 for TCNQA and -0.94 for TCNQ-B. Therefore TCNQ-A is considered almost as
a TCNQ0 molecule, whereas TCNQ-B is close to the anion TCNQ-.

6


TCNQ-B

TCNQ-A

Figure 3.11. Structure of (ProCH3)2( TCNQ)3 2:3

3.1.2.2. Raman spectroscopy of ProCH3TCNQ (1:1 và 2:3)
Raman spectra are shown in Figure 3.25. The four characteristic
peaks of TCNQ, C=C-H, C-CN, C=C (round) and C≡N are at 1206,
1454, 1602 and 2227 cm-1, respectively. Raman spectra of 1:1
ProCH3TCNQ and 2:3 (ProCH3)2(TCNQ)3 shows these vibrational
bands with a shift to lower energy levels. The shift of these pic confirm
the existence of monoanion TCNQ-.

Figure 3.12. Raman spectra for (a) TCNQ0, (b) 1:1 ProCH3TCNQ
and(c) 2:3 (ProCH3)2( TCNQ)3
In addition, in the Raman spectrum of (ProCH3)2(TCNQ)3, there
are three peaks of the CN stretch at 2192, 2207, and 2225 cm-1 and 3
peaks for C-CN stretch at 1296, 1350 and 1388 cm-1. This may be due
to the special structure of (ProCH3)2(TCNQ)3, in which the three

7


TCNQ moieties share the two negative charges, leading to the
emergence of new vibrations.
3.1.2.3. Electrochemical properties of the product
Steady-state voltammogram of ProCH3TCNQ (1:1) (Figure
3.14) shows that it dissolves completely (nearly 100%) into
monoanion TCNQ-. TCNQ- can be oxidized to form TCNQ0, leading
to a positive current or reduced to TCNQ2-, leading to a negative
current, so the position of zero current is exactly between TCNQ0/and TCNQ-/2- processes.

0.32

2.8

(ProCH3)TCNQ (1:1)

1.4

I/[nA]

I/[nA]

0.16
0.00

(ProCH3)TCNQ (2:3)

0.0
-1.4

-0.16

-2.8

-0.32
-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

-0.6

+

-0.4

-0.2

0.0

0.2

0.4

0.6

+

E/[V] vs Ag/Ag

E/[V] vs Ag/Ag

Figure 3.14. Curve line i-E of 1:1 ProCH3TCNQ (1:1 and 2:3) (0,2
mM) in CH3CN (0,1 M Bu4NBF6) , 10 µm Pt electrode diameter,
100 mV / s
Steady-state voltammogram ProCH3TCNQ (2:3) shows the
presence of TCNQ0 and TCNQ-. Quantitative analysis of current
magnitude related to the first process shows that the oxidative current
derived from monoanion TCNQ- accounts for about 67% (about 2/3)
of the total current, while the rest (1/3) is the reducing current
generated from TCNQ. The rate of oxidation/reduction currents shows
that the ratio of this crystal is 2: 3.
3.1.2.4. Conductivity of Pro(CH3)TCNQ

8


The solid state conductivity of Pro(CH3)TCNQ is measured at 3.1
x 10-2 S.cm-1 at 295K which indicates that it is within the
semiconductor range (10-5 to 106 mS.cm-1).
3.1.3. Product of Leucin with TCNQ
3.1.3.1. Structure of [Leu(CH3)3][TCNQ]
Crystals crystallize in the space group P212121 containing 1 cation
[Leu (CH3)3]+ and one anion TCNQ-. The charge (ρ) of the TCNQ is
calculated as -1.07 from the associated bond lengths and this value
corresponds to the existence of TCNQ- (Figure 3.17)

Hình 3.17. Structure of [Leu(CH3)3][TCNQ]
3.1.3.2. Spectral properties of [Leu(CH3)3][TCNQ]

Figure 3.18. Raman spectrum of Leu(CH3)TCNQ
Raman spectra (Figure 3.18) show that the peaks of the
characteristic groups shift towards lower energy than neutralized

9


TCNQ. This represents the presence of the TCNQ anion radical in
complex.
3.1.3.3. Electrochemical properties of the product
The steady state voltammetry result of the product is perfectly
consistent with the structural data determined at 1:1 ratio of
Leu(CH3)TCNQ.
0.6

LeuTCNQ

0.4

i (nA)

0.2
0.0
-0.2
-0.4
-0.6
-1.0

-0.5
0.0

+
E (V) vs. Ag/Ag

0.5

Figure 3.19. Steady state voltammogram of Leu(CH3)TCNQ in
CH3CN (0.1 M Bu4NPF6)
Conculsion 1:
Successfully synthesized materials from Prolin, Prolin ester,
Leucin ester with TCNQ. In which, Leu(CH3)TCNQ material is the
new material, firstly synthesized. The obtained results determine the
existence of different types of TCNQ in materials.
The methylation ability of amino groups in amino acids affects the
structure of the obtained products.
The resulting materials exhibit the properties of semiconductor
materials.

10


3.2. Products of [Ag(CH3CN)4]+, Cu(CH3CN)4+ với TCNQF4
3.2.1. Cyclicvoltammetry of TCNQF4, [Ag(CH3CN)4]+ and
Cu(CH3CN)4+ in CH3CN (0.1 M Bu4NPF6)
The voltammogram of 1.0 mM TCNQF4 in CH3CN (0.1 M
Bu4NPF6) is shown in Figure 3.20. The peak values are shown in Table
3.7 (Em1 = (Ep1kh + Ep1ox)/2 and Em2 = (Ep2kh + Ep2ox)/2). It is clear fro
the table that the value of Em does not depend on the material of the
electrode.
3
-1/0

TCNQF4

2

-2/-1

TCNQF4

1

i (A)

0
-1
-2
-3

0/-1

TCNQF4

-4

-1/-2

TCNQF4

TCNQF4

-5
-600

-300

0

300

600

+

E (mV) vs. Ag/Ag

Figure 3.20. CV with GC 3 mm) v =100 mV/s for 1.0 mM TCNQF4
in CH3CN (0.1 M Bu4NPF6).
120

i (A)

80
40

GC
Au
Pt
ITO
(chu ky 1)

Ag

0/+

0
-40

Ag

+/0
+

Ag(CH3CN)4

-80
-600

-300

0

E / mV vs. Ag/Ag

300

600

+

Figure 3.21 CV of 2.0 mM Ag(CH3CN)4+ in CH3CN (0,1 M

Bu4NPF6), v = 100 mV/s

11


Table 3.7. The obtained potential values (mV) for CV scan of
TCNQF4 and Ag (CH3CN)4+
Compounds
Ag(MeCN)4+ ( chu kỳ 1)

TCNQF4
Ep(kh1)

Ep(ox1)

Em1

Ep(kh2)

Ep(ox2)

Em2

∆E0

Epkh

Epox

Em

Ep

GC

277

345

311

-255

-185

-220

531

-331

68

-131.5

399

Au

277

343

310

-255

-185

-220

530

-99

79

-10

178

Pt

277

343

310

-256

-186

-221

531

-133

59

-37

192

ITO

201

406

303.5

-335

-157

-246

549.5

-447

34

-206.5

481

Cyclic voltammetry of solution containing 2.0 mM Ag(CH3CN)4+
in CH3CN (0.1 M Bu4NPF6) is shown in Figure 3.21. The reduction of
Ag(CH3CN)4+ to Ag metal depends significantly on the electrode
material. It can be seen that cation Ag(CH3CN)4+ is easily reduced in
order of Au Ag(CH3CN)4+ reduction process in the first potential scan cycle is
always negative than the subsequent cycles.
Table 3.8. The average potential (Em = (Eox + Ekh)0/2) of TCNQF4
and [Cu(CH3CN)4]+ in CH3CN solution (0,1 M Bu4NPF6)
0/

GC
Au
Pt
ITO

TCNQF4
311
310
310
303.5

process
TCNQF4/2
220
220
221
246

Cu+/0
706
630
659
640

Cu+/2+
748
560
545
725

AgTCNQF4 can easily be synthesized. However Ag2TCNQF4
cannot be synthesized on Au or Pt electrode, because Ag(CH3CN)4+ is
reduced simultaneously with TCNQF4-/2- reduction process. However,

12


GC or ITO electrodes can be used to synthesize Ag2TCNQF4 , because
the reduction process of TCNQF4- into TCNQF42- happens at slightly
more positive than the Ag(CH3CN)4+ reduction process. However,

Ag2TCNQF4 cannot be experimentally synthesized on GC or ITO
electrodes.
Cylic voltammetry of [Cu(CH3CN)4]+ is more complicated
(Table 3.8). However, the potential of two reduction and oxidation
processes of Cu+(CH3CN) is outside that of the reduction process of
TCNQF4 into TCNQF4- and TCNQF4- into TCNQF42-. Therefore, it
is theoretically possible to synthesize Cu+ products with the anions of
TCNQF4.
3.2.2. Synthesis of materials AgTCNQF4, CuTCNQF4, Ag2TCNQF4,
and Cu2TCNQF4
From the investigation of electrochemical properties, the method
of synthesis is proposed for AgTCNQF4, CuTCNQF4, Ag2TCNQF4,
Cu2TCNQF4
- Electrochemical crystallization:
AgTCNQF4 and CuTCNQF4 were electrically crystallized on the
surface of the ITO electrode by reducing 2.0 mM TCNQF4 in CH3CN
(0.1M

Bu4NPF6)

containing

10.0

mM

[Ag(CH3CN)4]+

or

+

[Cu(CH3CN)4] . The E on the ITO electrode was kept at 100 mV for
15 minutes. The crystallized solids were washed with ethanol, dried
under N2 gas flow for 10 minutes and finally stored in vacuum
overnight before characterization.
Cu2TCNQF4 was crystallized on the ITO electrode surface from
a solution containing 1.0 mM TCNQF4 and 2.0 mM [Cu(CH3CN)4]+ in
CH3CN (0.1M Bu4NPF6). TCNQF4 was reduced to TCNQF42- when

13


the potential was held at -500 mV for 15 minutes. The crystallized
product on ITO electrode was then washed with 3 x 3 mL CH3CN,
dried with N2 gas stream within 10 minutes, then store in vacuum
overnight before analysis.
- Electrochemical synthesis


Products of TCNQF4•-: Bulk electrolysis of a solution (5.0 mL)

containing 10 mM TCNQF4 in CH3CN (0.1M Bu4NPF6) was done
with a Pt electrode potential of 100 mV (compared with Ag/Ag+) to
obtain TCNQF4•-. Then 0.25 mL solution containing 100 mM
[Cu(CH3CN)4]+ or Ag(CH3CN)4+(CH3CN) was added to the obtained
TCNQF4•- solution. The dark blue precipitate was immediately
formed, then centrifuged and washed several times with excess
CH3CN (8mL) to remove reactant residues. The obtained products
were dried under the vacuum overnight before characterization.



Products TCNQF42-: Bulk electrolysis of 2.0 mL solution

containing 5.0 mM TCNQF4 (CH3CN, 0.1 M Bu4NPF6) was done with
Pt electrode at -400 mV (compared to Ag/Ag+), to form 5.0 mM
TCNQF42-. 2.0 mL of the solution containing 10.0 mM Ag (CH3CN)4+
or [Cu(CH3CN)4]+ (CH3CN) was added into the obtained solution. The
white precipitate of Ag2TCNQF4 or Cu2TCNQF4 formed immediately.
Particularly, Ag2TCNQF4 gradually changed to green in a few
minutes. The precipitate was collected by centrifugation and washed
three times with CH3CN before filtration. The washed solids were
dried under the N2 stream for 10 minutes then store in a vacuum for 1
hour before IR spectrocopy.
3.2.3. Characteristic properties of synthetic materials

3.2.3.1. Spectrocopy of TCNQF4•- materials
14


- FT IR spectrocopy
1369

(a)
Absorbance

1205

AgTCNQF4

1501
1532
1627

2210
2195
2221

971

1593

TCNQF4

1395
972
1190

1493
2225

1000

1500
2000
-1
Wavenumber/cm

2500

Figure 3.34. FT-IR spectrum of AgTCNQF4 and CuTCNQF4
IR spectrocopy of CuTCNQF4 and AgTCNQF4 material is shown
in Figure 3.34. The IR spectrum of the two products shows the peaks
at 2221; 2210 and 2195 cm-1 (AgTCNQF4) and at 2214 and 2187 cm-1
(CuTCNQF4), which corresponds to the vibration of of the C≡N group
(TCNQF4)•-. The peak split (compared to 1 peak in TCNQF4) is the
result of coordination TCNQF4-• with metal cations through the CN
group. At the same time the vibration of ring π (C = C) (at 1493 cm-1
in TCNQF4) appears at 1501 cm-1 (AgTCNQF4) and at 1496 cm-1
(CuTCNQF4) implying the existence of the anion form TCNQF4-•.
Similarly, the out-of-plane C-F stretch shows peaks at 1205 cm-1
(AgTCNQF4) and 1216 cm-1 (CuTCNQF4), shifting towards higher
wave numbers than TCNQF4 (1190 cm-1)
- Raman spectrocopy
Raman spectra of CuTCNQF4 shows peaks at 2221 (C≡N), 1641 (C =
C ring), 1439 (C = C outside ring) and 1273 cm-1 (C-F and C-C ring).
The Raman peak at 1273 cm-1 shifts to a higher energy level than the
peak at 1193 cm-1 of TCNQF4.

15


1449

(a)

AgTCNQF4
1642
2221

1275

TCNQF4

1457

2226
1665
1193

1000

1500
2000
-1
Raman shift/cm

2500

Figure 3.35: Raman spectrum of AgTCNQF4 and CuTCNQF4
While the other three bands have lower energies indicating the
presence of monoanion TCNQF4-• in CuTCNQF4. Similarly, Raman
spectrum of AgTCNQF4 shows three peaks at 2221; 1642 and 1449
cm-1, corresponding to the vibration of the group C≡N, C=C and C-CN
outside the ring. Compared with TCNQF4 (2226; 1665 and 1457 cm1

), all peaks in the Raman spectrum of AgTCNQF4 appear at a lower

wavenumber than in TCNQF4, which is due to the existence of
TCNQF4-•.

- UV- Vis spectrum
UV- Vis spectra of AgTCNQF4 và CuTCNQF4 (Figure 3.36) show
all peaks at λmax of 411, 686 and 752 nm, respectively, for TCNQF4-•
386

1.6
Absorbance

411

1.2
0.8

TCNQF4
AgTCNQF4
Ag(MeCN)4BF4

365
752

0.4
686

0.0
200

400
600
Wavelength/nm

800

Figure 3.36. UV-Vis of AgTCNQF4 and CuTCNQF4

16


3.2.3.2. Spectroscopy of TCNQF42- materials

- FT-IR spectrum

Figure 0.38. IR spectrum of Ag2TCNQF4
In the IR spectrum of the product Ag2TCNQF4 (Figure 3.38), band
for CN stretch appears at 2212; 2193 cm-1 (typical for TCNQF4-•);
2159 and 2127 cm-1 (typical for TCNQF42-). This suggests that
although Ag2TCNQF4 was synthesized from the reaction between
TCNQF42- cation Ag+ in CH3CN, this solid was not stable and
gradually decomposed by redox reaction into AgTCNQF4 and Ag
metal.

Figure 3.39: FT-IR of (a) Cu2TCNQF4 synthesis by chemistry, (b)
Cu2TCNQF4 Electric crystallization on ITO

17


IR spectrum of Cu2TCNQF4 product (Figure 3.39) shows the
vibrational band of C≡N group at 2162 and 2135 cm-1, indicating the
presence of TCNQF42- dianion. However, there is still peaks at 2204
which is typical for TCNQF4-•. This implies the internal molecular

oxidation from TCNQF42- to TCNQF4-• under light conditions.
However, this change is slow which is evident from UV-Vis spectrum.
- Raman spectrum
The Raman spectrum of Cu2TCNQF4 shows the vibrational band
of the CN group at 2218, 2179, and 2141 cm-1. Band at 2218 cm-1,
characteristic for TCNQF4-•, again confirms the photochemical
transformation from TCNQF42- to TCNQF4-•. Meanwhile 2 peaks at
lower energy is consistent with the presence of TCNQF42-. The Raman
peaks at 1655, 1435 and 1246 cm-1 are characteristic for the C = C
outside the ring, CF and CC ring vibrations in TCNQF42-, while the
peaks at 1643, 1443, 1273 cm-1 are characteristic for TCNQF4-• (Figure
3.40).

Figure 3.40. Raman spectrum of Cu2TCNQF4 synthesis by
chemistry and electrochemistry

18


3.2.4. Conclusion 2
AgTCNQF4, CuTCNQF4 and Cu2TCNQF4 have been
successfully synthesized electrochemically. Cu2TCNQF4 can be
crystallized on the electrode surface from TCNQF4 and Cu(CH3CN)4]+
at low concentrations, while AgTCNQF4, CuTCNQF4 can be
synthesized with high concentration of reactants. The spectral data
confirmed the presence of TCNQF4.- and TCNQF42- in products,
consistent

with

the

synthesis

pathway.

Cu2TCNQF4

photochemical conditions will be convert into Cu

I

TCNQF4I-

under
and Cu

metal through redox reaction.
3.3. Products of TCNQF4 with M2+ (M= Zn, Co, Mn)
3.3.1. Cyclic voltammetry TCNQF4 in CH3CN/ DMF solution
containing M2+
In CH3CN/DMF 5% solvent mixture, TCNQF4 undergoes two
one electron reversible processes. The corresponding potential for two
processes TCNQF40/TCNQF4-• and TCNQF4-•/TCNQF42- is 253.5 mV
and -217.5 mV, similar to TCNQF4 in CH3CN. M2+ meanwhile is not
active electrically over this range.

Current (A)

0.2

0.0

-0.2
2+

M
CH3CN

-0.4

CH3CN- DMF(5%)

-600 -400 -200

0

200

400

600

+

E (mV) vs. Ag/Ag

Figure 3.46. CV of TCNQF4 in CH3CN and CH3CN/DMF(5%)
(0.1M Bu4NBF6), GC, v = 50mV/s and of 0.1M M2+

19


In a solution containing Zn2+ (0.1M), the cyclic voltammetry over
the potential range from 600 mV to 50 mV is unchanged TCNQF40/-•
process (Figure 3.47). This indicates that Zn2+TCNQF4- does not
crystallize electrochemically under these conditions. Therefore it can
be seen that Zn2+-TCNQF4- cannot be synthesized
3
2mM TCNQF4

2

0.1 M Zn

2+

1

i(A)

0
-1
-2
-3
-4
0

100

200

300

400

500

600

+

E (mV) vs. Ag/Ag

Hình 3.47. Cyclic voltammetry in CH3CN/DMF(5%) of 2,0 mM
TCNQF4 in 0,1M Zn2+
However, there was a change in the process of TCNQF4-•/2- (Figure
3.48).
15
10

Ox 2

2+

[Zn ]/ mM
0.5
1
2

i(A)

Ox 1

5
0

Ox 3

-5

Kh 1

Kh 3 Kh 2

-10
-600 -400 -200

0

200

E (V) vs. Ag/Ag

400

600

+

Figure 3.48. Cyclic voltammetry of solution contain 2,0 mM
TCNQF4 with different concentrations of Zn2+.

20


When the potential is swept towards the negative potential, three
reduction processes appear. The processes of Kh1 and Kh3 correspond
to the reduction processes of TCNQF4 to TCNQF4-• and TCNQF4-• to
TCNQF42-. A second reduction process occurs at -166mV. And when
the concentration of Zn2+ increases from 0.5 mM to 2.0 mM, the
process of Kh3 disappeared (Figure 3.48). This indicates that
Zn2+TCNQF42- can be synthesized.
3.3.2. Synthesis ZnTCNQF4(DMF)2.2DMF
3.3.2.1. Chemical synthesis
The solution of Li2TCNQF4 (43,4mg, 0,15 mmol) in CH3OH (10
mL) was gently injected with a needle into the Zn(ClO4)2.6H2O (0.15
mmol) solution in DMF (10 mL). Colorless crystals were obtained
after one day
3.3.2.2. Electrochemical synthesis
Bulk electrolysis of a solution containing 0.1 mM TCNQF4
(CH3CN) was done at 160 mV respectively to form TCNQF4•- and then
at -350 mV to form TCNQF42-. The process of electrolysis ends when
the current decreases to 0.1% of the initial current. Meanwhile, the
solution contains an equivalent amount of Zn2+ dissolved in DMF was
prepared so that after mixing the two solutions, the DMF ratio is 5%.
The two above solutions were mixed together and the white precipitate
appeared immediately. Continue stirring this solution for 10 minutes,
then centrifuge to collect the precipitate. The precipitate was washed
with CH3CN/DMF 5% solvent mixture 3 times to remove residual

electrolyte and dried in vacuum.
3.3.3. Structure of ZnTCNQF4(DMF)2.2DMF

21


The asymmetric cell unit consists of two halves of the
TCNQF42- with different orientation in the crystal lattice, two
coordinated DMF molecules and two free DMF molecules. TCNQF42forms two different TCNQF42- layers in the crystal lattice (Figure
3.57). The charge calculated from bond length for TCNQF4 is -2.18

Figure 3.57. Structure of [ZnTCNQF (DMF) ].2DMF
4

2

3.3.4. Properties of materials
3.3.4.1. Spectral properties
- IR spectra of ZnTCNQF4(DMF)2.2DMF are shown in Figure
3.54.

Figure 3.62. IR spectrum of [ZnTCNQF4(DMF)2].2DMF

22


Both chemical and electrochemical synthesis methods
produce the same product, which is shown by the consistence of the
spectrum. The vibration of the CN group at 2142, 2146 and 2211 cm-1
indicates the presence of TCNQF42-, peak at 1688 cm-1 corresponding

to the free DMF and at 1647 corresponding to the coordinated DMF
(Figure 3.62).
IR spectroscopy of products was theoretically calculated and
compared with the experimental one (Figure 3.63). Via these results,
it was able to identify the characteristic vibration bands in the IR
spectrum of the material.

Figure 3.63. Experimental IR spectra of
[ZnTCNQF4(DMF)2]·2DMF (black line) and theoretically
calculated (DFT) frequencies (red lines)
UV-Vis

spectrum

obtained

when

dissolved

[Zn(DMF)2TCNQF4].2DMF in DMF with λmax = 330 nm shows the
existence of dianion TCNQF42-. The current-potential curve of the
solution in DMF (0.1M Bu4NPF6) also shows the two oxidation
processes of TCNQF42-

23