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

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.


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-.

-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

3.1.2.2. 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

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


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


TCNQF4

2

-2/-1

TCNQF4

1

i (A)

0
-1
-2
-3

0/-1

TCNQF4

-4

-1/-2

TCNQF4

TCNQF4


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


Ep

GC

277

345

311

-255

-185

-220

531

-331

68

-131.5

399

Au

277


-186

-221

531

-133

59

-37

192

ITO

201

406

303.5

-335

-157

-246

549.5


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,

+

[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.

1501
1532
1627

2210
2195
2221

971

1593

TCNQF4

1395
972
1190

1493
2225

1000

1500
2000
-1
Wavenumber/cm

2500


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-•.

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

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

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


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

+


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