Study on new quinacridone derivatives with enhanced third-order nonlinear optical properties

Article abstract of DOI:10.1016/j.tet.2020.131169

Seven new quinacridone derivatives were designed and synthesized. The relationship between molecular structure and nonlinear optical properties was studied by cyclic voltammetry, DFT calculation and Z-scan. By introducing strong electron donating groups at the two sides of the quinacridone, and then introducing a strong electron withdrawing group dicyanoethylene group, the band gap of the molecule can be effectively reduced, and the intramolecular charge transfer can be promoted. The results shown that the HOMO/LUMO band gaps of the target compounds are all reduced, and QA-F has the best third-order nonlinear optical performance, and its γ (γ = 5.32 × 10^?33 esu) is 4.38 times that of QA-1 (γ = 1.21 × 10^?33 esu).

Full text of DOI:10.1016/j.tet.2020.131169

Journal Pre-proof
Study on new quinacridone derivatives with enhanced third-order nonlinear optical
properties
Yanhong Cui, Guanqiu Liang, Jianhong Jia, Guoyi Yu, Yangcheng Sha, Chunsong
Zhou, Yuanbin She
PII:
S0040-4020(20)30304-5
https://doi.org/10.1016/j.tet.2020.131169
TET 131169
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 14 February 2020
Revised Date: 18 March 2020
Accepted Date: 31 March 2020
Please cite this article as: Cui Y, Liang G, Jia J, Yu G, Sha Y, Zhou C, She Y, Study on new
quinacridone derivatives with enhanced third-order nonlinear optical properties, Tetrahedron (2020), doi:
https://doi.org/10.1016/j.tet.2020.131169.
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Study on new quinacridone derivatives with enhanced
third-order nonlinear optical properties
Yanhong Cui, Guanqiu Liang, Jianhong Jia∗, Guoyi Yu, Yangcheng Sha, Chunsong Zhou,
Yuanbin She∗∗
College of Chemical Engineering, Zhejiang University of Technology, Hangzhou, 310032, PR
China
Abstract: Seven new quinacridone derivatives were designed and synthesized. The
relationship between molecular structure and nonlinear optical properties was studied by
cyclic voltammetry, DFT calculation and Z-scan. By introducing strong electron donating
groups at the two sides of the quinacridone, and then introducing a strong electron
withdrawing group dicyanoethylene group, the band gap of the molecule can be effectively
reduced, and the intramolecular charge transfer can be promoted. The results shown that the
HOMO/LUMO band gaps of the target compounds are all reduced, and QA-F has the best
third-order nonlinear optical performance, and its γ (γ =5.32×10-33 esu) is 4.38 times that of
QA-1 (γ =1.21×10-33 esu).
Keywords: Second-order hyperpolarizability; Quinacridone derivatives; NLO materials;
Z-scan technology.
1

1 Introduction
Nonlinear optical (NLO) materials have profound importance in some advanced
technologies of contemporary significance such as optical limiting, optical data storage, laser
medicine, image processing, all-optical switch and so on1-9. The molecular design and
synthesis of novel organic compounds with superior third-order NLO properties has drawn a
widely public attention10, 11. Compared with inorganic NLO materials, organic NLO materials
have the advantages of short response time, low dielectric constant, high optical damage
threshold, high molecular plasticity, excellent processing performance and high nonlinear
polarizability10-13. The polarization of the organic NLO materials results from the
delocalization of the π electrons in the backbone14-17. Partial π-conjugated polymers have
good electrochemical properties, photochemical properties, and good mechanical properties
and processing properties14, 18, 19. It is a good strategy to get high performance NLO materials
by modifying the molecular structure 20-22. Therefore, the organic conjugated compound
having a delocalized large π structure can be preferred as third-order nonlinear optical
materials12, 23-25
.
As organic chromophores, QA and its derivatives are widely used in organic photovoltaic
materials, organic light-emitting diodes, dye-sensitized solar cells and other fields because of
their high fluorescence quantum yield, good photostability and chemical stability. QA, as an
electron acceptor, has been used in molecular design of NLO materials together with some
electron donors because of its highly delocalized system, which exhibits high nonlinear
optical response26. At the same time, QA also has several modified active sites through which
appropriate molecular modification can be carried out to improve intramolecular charge
transfer (ICT) and reduce molecular band gap. It is helpful to improve the third-order
nonlinear optical response of molecules27-29
.
In previous works20, a series of D-A poly-quinacridone were applied to third-order
nonlinear optical materials. However, the relationship between molecular structure and
nonlinear response of quinacridone derivatives is still not very clear. According to the
previous work, we believe that improving the electron-absorbing ability of quinacridone
2

structure and the electron-supplying ability of electron donors in material molecules will be
beneficial to improving the third-order nonlinear response of materials. In this study,
dicyanoethylene (DCN) was introduced into quinacridone structure to enhance the electron
absorption ability of quinacridone structure, and triphenylamine and carbazole as electron
donors were introduced to enhance the molecular dipole moment of material molecules. The
purpose is to extend the p-π conjugate system to make QA derivatives have push-pull
structure, enhance intramolecular charge transfer, reduce molecular band gap, and improve
the third-order nonlinear optical properties of molecules. In addition, we analyzed the effect
of structure on the photophysical, electrochemical and third-order nonlinear optical properties
of materials by UV and fluorescence spectrophotometer, cyclic voltammetry and Z-scan
performance.
2 Experimental
2.1 Materials and Instruments
All chemicals and solvents, unless otherwise stated, are commercially available, and were
used without further purification.
1
The H nuclear magnetic-resonance (1H NMR) spectra were recorded on a Varian XL-200
spectrometer with tetramethylsilane (TMS) as the internal standard. Infrared spectra were
determined using a Vector 22 FT-IR spectrometer using KBr pellets. The Ultra-violete visible
(UV-vis) absorption spectra of the synthesized compounds were recorded on a Shimadzu
UV-2550 UV-visible spectrophotometer with a quartz cuvette (path length 1 cm).
2.2 Synthesis
The main synthesis scheme of the all materials were shown as Scheme 1. The synthesis
scheme of Z-1, Z-2 were shown as Scheme S1.
3

Scheme 1. The synthetic procedure of the quinacridone derivatives.
2.2.1 N, N′- dodecane quinacridone (QA-1)
Reference article to synthesize QA-120. Quinacridone (3.00 g, 9.60 mmol), Cs2CO3 (9.39 g,
28.80 mmol), and tetrabutylammonium bromide (TBAB) (0.62 g,1.92 mmol) were dissolved
in DMSO (80 mL) and stirred at 30 for 4 hours, and then 1-bromosodecane (8.38 g, 33.62
mmol) was slowly added dropwise. The resulting mixture was allowed to react at room
temperature for 20 h and then heated to 90 °C for 6 h. When cooled to room temperature, the
reaction solution was poured into 250 ml of saturated brine and filtered under reduced
pressure. The solvent was removed from filter cake by washing with methanol. The resulting
crude product was purified by recrystallization from ethyl acetate to give an orange-red solid
QA-1 (4.98 g, 80%). M.p.: 138-139 .1H NMR (500 MHz, CDCl3) δ 8.69 (s, 2H), 8.52 (dd, J
= 8.0, 1.6 Hz, 2H), 7.70 (m, J = 8.6, 6.9, 1.6 Hz, 2H), 7.46 (d, J = 8.8 Hz, 2H), 7.22 (t, J = 7.4
Hz, 2H), 4.61 – 4.27 (t, 4H), 2.07 – 1.88 (m, 4H), 1.62 (m, J = 15.4, 7.6 Hz, 4H), 1.47 (m, J =
4

15.2, 6.9 Hz, 4H), 1.42 – 1.26 (m, 12H), 0.91 (t, J = 6.9 Hz, 6H). 13C NMR (126 MHz, CDCl3)
δ 177.99, 142.15, 135.58, 134.46, 127.98, 126.16, 121.02, 120.72, 114.57, 113.40, 46.35,
31.93, 29.67, 29.63, 29.60, 29.48, 29.35, 27.13, 27.04, 22.70, 14.12. HRMS (ESI) m/z calcd
+
for C44H61N2O2 (M+H)+ 649.47276, found 649.47253.
2.2.2 N, N'-dodecane-2,9-dibromoquinacridone (QA-2)
Reference article to synthesize QA-220. Under a N2 atmosphere, QA-1 (0.50 g, 0.77
mmol) and N-bromosuccinimide (NBS) (0.48 g, 2.70 mmol) were add in 20 mL of DMF. The
mixture was stirred at 90
for 24 h in a dark environment and then cooled to room
temperature, and poured into a saturated aqueous solution of sodium chloride. After
precipitated, filtered and washed with methanol, the filter cake was recrystallized from
1
dichloromethane to give the dark-red solid QA-2 (0.49g, 79%). H NMR (500 MHz, CDCl3)
δ 8.41 (s, 2H), 8.39 (d, J = 2.5 Hz, 2H), 7.68 (dd, J = 9.2, 2.5 Hz, 2H), 7.23 (d, J = 9.3 Hz,
2H), 4.36 (t, J = 16.4, 8.5 Hz, 4H), 2.00 – 1.81 (m, 4H), 1.60 (m, J = 15.3, 7.5 Hz, 4H), 1.46
(m, J = 14.8, 6.7 Hz, 4H), 1.36 (m, J = 21.2, 10.4, 5.3 Hz, 12H), 0.92 (t, J = 6.9 Hz, 6H).
2.2.3 N, N'-dodecane -2,9-diborate quinacridone(QA-3)
QA-2 (2.01 g, 2.49 mmol), bornazolium diborate (2.21 g, 8.70 mmol), PdCl2(dppf) (0.17 g,
0.25 mmol), potassium acetate (0.85 g, 8.72 mmol) were add to 30 mL of 1,4-dioxane under
an atmosphere of N2. The mixture was stirred at 80 for 12 h and then poured into saturated
salt water. After filtered and washed with methanol, crude products were obtained by
decolorization with activated carbon in dichloroethane and recrystallization from ethyl acetate
to afford a dark-red solid QA-3 (1.17 g, 76%). 1H NMR (500 MHz, CDCl3) δ 9.00–8.93 (m, J
= 1.5 Hz, 2H), 8.63 (s, 2H), 7.99 (dd, J = 8.7, 1.4 Hz, 2H), 7.36 (d, J = 8.8 Hz, 2H), 4.49–4.42
(m, 4H), 1.98–1.90 (m, J = 15.6, 8.9 Hz, 4H), 1.66–1.57 (m, J = 15.2, 7.6 Hz, 4H), 1.49–1.43
(m, J = 14.3, 7.2 Hz, 4H), 1.41 (s, 24H), 1.36–1.25 (m, 28H), 0.89 (t, J = 6.9 Hz, 6H).
2.2.4 5,12-didodecyl-2,9-diphenyl-5,12-dihydroquinolino[2,3-b]acridine-7,14-dione (QA-A)
QA-3 (0.56 g, 0.62 mmol), bromobenzen (0.39 g, 2.48 mmol), K2CO3 (0.35 g, 2.48 mmol),
Pd(PPh3)4 (0.07 g, 0.06 mmol) were placed in 10mL of toluene and 50 mL of distilled water
as solvent. The solution was stirred for 24 h under a N2 atmosphere at 90 . After removal of
the solvent under reduced pressure, the crude product was purified by silica chromatography,
eluting with (V (petroleum ether) / V (dichloromethane) = 1/2) to obtain red solid QA-A (0.35
5

1
g, 70.5%). M.p.: 185.1-187.4 . H NMR (500 MHz, CDCl3) δ8.70 (d, J = 2.4 Hz, 1H), 8.61
(s, 1H), 7.82 (dd, J = 8.9, 2.3 Hz, 1H), 7.69–7.63 (m, 2H), 7.50 (dd, J = 10.5, 4.8 Hz, 2H),
7.44–7.36 (m, 2H), 4.59–4.23 (m, 2H), 1.72 (s, 1H), 1.65 (dt, J = 15.3, 7.6 Hz, 2H), 1.56–1.44
(m, 2H), 1.43–1.21 (m, 17H), 0.93–0.84 (m, 4H). 13C NMR (126 MHz, CDCl3) δ 177.84,
141.22, 139.36, 135.26, 133.09, 133.05, 128.94, 127.31, 126.69, 125.91, 125.27, 120.96,
115.26, 113.48, 46.41, 31.95, 29.70, 29.66, 29.63, 29.52, 29.37, 27.19, 27.08, 22.71, 14.12.
+
HRMS (ESI) m/z calcd for C56H69N2O2 (M+H)+ 801.53536, found 801.53564.
2.2.5
2,9-bis(4'-(diphenylamino)-[1,1'-biphenyl]-4-yl)-5,12-didodecyl-5,12-dihydroquinolino[2,3-b
]acridine-7,14-dione (QA-B)
The synthetic procedures were almost the same as that of QA-A, except that compound Z-1
(0.87 g, 2.17 mmol). The crude product was purified by silica gel column chromatography (V
(petroleum ether) /V (dichloromethane) = 3/1) to give the red solid QA-B (0.52 g, 65%). M.p.:
212.1-219.4 . 1H NMR (500 MHz, CDCl3) δ 8.81-8.73 (m, 1H), 8.69- 8.62 (m, 1H), 8.04 (dt,
J = 7.0, 3.5 Hz, 1H), 7.78 (d, J = 8.2 Hz, 2H), 7.72 (dd, J = 17.1, 8.0 Hz, 2H), 7.58 (d, J = 9.1
Hz, 1H), 7.55-7.48 (m, 2H), 7.29 (dd, J = 13.9, 6.4 Hz, 5H), 7.17 (d, J = 7.7 Hz, 5H), 7.06 (dd,
J = 20.1, 12.8 Hz, 2H), 4.66-4.40 (m, 2H), 1.69 (dt, J = 15.0, 7.6 Hz, 2H), 1.59 (s, 3H),
1.57-1.47 (m, 2H), 1.47 (s, 16H), 0.89 (t, J = 6.8 Hz, 3H). 13C NMR (126 MHz, CDCl3) δ
177.71, 147.68, 147.35, 141.13, 139.46, 137.52, 135.18, 134.34, 132.74, 132.44, 129.33,
127.60, 127.00, 126.86, 125.84, 124.91, 124.53, 123.86, 123.03, 120.94, 115.23, 113.43,
31.95, 29.72, 29.67, 29.65, 29.55, 29.38, 27.11, 22.71, 14.13. HRMS (ESI) m/z calcd for
+
C92H95N4O2 (M+H)+ 1287.74495, found 1287.74451.
2.2.6
2,9-bis(4-(9H-carbazol-9-yl)phenyl)-5,12-didodecyl-5,12-dihydroquinolino[2,3-b]acridine-7,
14-dione (QA-C)
The synthetic procedures were almost the same as that of QA-A, except that compound Z-2
(0.70 g, 2.17 mmol). The crude product was purified by silica gel column chromatography (V
(petroleum ether) /V (dichloromethane) = 1/2) to give the red solid QA-C (0.53 g, 75%). m.p.
245.1-246.4 .1H NMR (500 MHz, CDCl3) δ 8.83 (d, J = 2.1 Hz, 1H), 8.77–8.69 (m, 1H),
8.19 (d, J = 7.8 Hz, 2H), 8.02 (dd, J = 8.8, 2.1 Hz, 1H), 7.91 (t, J = 8.1 Hz, 2H), 7.70 (t, J =
6

6.5 Hz, 2H), 7.60 (t, J = 8.3 Hz, 1H), 7.56–7.47 (m, 3H), 7.42 (dt, J = 26.5, 7.6 Hz, 2H), 7.33
(t, J = 7.4 Hz, 2H), 4.73– 4.47 (m, 2H), 1.78–1.66 (m, 2H), 1.64 (s, 3H), 1.60–1.49 (m, 3H),
1.48–1.22 (m, 19H), 0.89 (t, J = 6.8 Hz, 4H). 13C NMR (126 MHz, CDCl3) δ 177.89, 140.83,
138.37, 136.96, 133.03, 128.00, 127.43, 126.04, 125.54, 123.53, 121.18, 120.38, 120.09,
115.55, 113.68, 109.85, 31.95, 29.72, 29.67, 29.56, 29.39, 27.14, 22.71, 14.13. HRMS (ESI)
+
m/z calcd for C80H83N4O2 (M+H)+ 1131.65105, found 1131.64844.
2.2.7
2,2'-(5,12-didodecyl-5,12-dihydroquinolino[2,3-b]acridine-7,14-diylidene)
dimalononitrile (QA-D)
Under a N2 atmosphere, QA-1 (0.20 g, 0.31 mmol), TiCl4 (0.17 g, 0.63 mmol),
malononitrile (0.24 g, 3.72 mmol), triethylamine (3 mL) were added to 20 mL of
dichloromethane and stirred for 24 h at room temperature. After removal of the solvent under
reduced pressure, the crude product was purified by silica chromatography, eluting with (V
(petroleum ether) / V (dichloromethane) = 1/3) to obtain dark green solid QA-D (0.19 g,
82%). M.p.: 173.1-176.4 . 1H NMR (500 MHz, CDCl3) δ8.67 (s, 1H), 8.51 (dd, J = 8.0, 1.6
Hz, 1H), 7.69 (ddd, J = 8.6, 7.0, 1.6 Hz, 1H), 7.45 (d, J = 8.8 Hz, 1H), 7.21 (t, J = 7.4 Hz, 1H),
4.79-4.23 (m, 2H), 1.81 (s, 1H), 1.62 (dt, J = 15.3, 7.6 Hz, 2H), 1.52–1.42 (m, 2H), 1.41-1.19
(m, 17H), 0.89 (t, J = 6.9 Hz, 3H). 13C NMR (126 MHz, CDCl3) δ 155.09, 139.29, 134.39,
133.61, 127.24, 122.82, 121.94, 117.55, 117.16, 116.76, 114.49, 111.63, 70.30, 49.23, 31.93,
29.70, 29.65, 29.62, 29.58, 29.37, 29.30, 27.05, 26.84, 22.70, 14.12. HRMS (ESI) m/z calcd
+
for C50H61N6 (M+H)+ 745.49522, found 745.49554.
2.2.8
2,2'-(5,12-didodecyl-2,9-diphenyl-5,12-dihydroquinolino[2,3-b]acridine-7,14-diylidene)dimal
ononitrile (QA-E)
The synthetic procedures were almost the same as that of QA-D, except that compound
QA-A (0.50 g, 0.62 mmol). The crude product was purified by silica gel column
chromatography (V (petroleum ether) /V (dichloromethane) = 1/2) to give the dark green
1
solid QA-E (0.40 g, 72%). M.p.: 202.1-204 . H NMR (500 MHz, CDCl3) δ8.75 (d, J = 2.0
Hz, 1H), 8.64 (d, J = 11.5 Hz, 1H), 8.02 (dd, J = 9.0, 2.0 Hz, 1H), 7.74 (d, J = 7.3 Hz, 2H),
7.58 (d, J = 9.0 Hz, 1H), 7.51 (t, J = 7.7 Hz, 2H), 7.40 (t, J = 7.4 Hz, 1H), 4.59-4.15 (m, 2H),
1.68 (dt, J = 15.1, 7.6 Hz, 2H), 1.58 (d, J = 14.6 Hz, 1H), 1.56-1.46 (m, 2H), 1.46 (s, 16H),
7

0.89 (t, J = 6.9 Hz, 3H). 13C NMR (126 MHz, CDCl3) δ 154.93, 139.04, 138.37, 135.04,
133.48, 133.32, 129.23, 127.90, 127.09, 125.11, 122.80, 117.63, 117.34, 117.19, 115.08,
111.75, 70.17, 49.21, 31.92, 29.71, 29.66, 29.62, 29.60, 29.37, 29.33, 27.16, 26.85, 22.69,
+
14.12. HRMS (ESI) m/z calcd for C62H69N6 (M+H)+ 897.55782, found 897.55707.
2.2.9
2,2'-(2,9-bis(4'-(diphenylamino)-[1,1'-biphenyl]-4-yl)-5,12-didodecyl-5,12-dihydroquinolino[
2,3-b]acridine-7,14-diylidene)dimalononitrile (QA-F)
The synthetic procedures were almost the same as that of QA-D, except that compound
QA-B (0.20 g, 0.16 mmol). The crude product was purified by silica gel column
chromatography (V (petroleum ether) /V (dichloromethane) = 1/2) to give the dark green
solid QA-F (0.14 g, 65%). M.p.: 230.1-234℃. 1H NMR (500 MHz, CDCl3) δ 8.78 (d, J = 1.8
Hz, 1H), 8.68–8.61 (m, 1H), 8.09–7.98 (m, 1H), 7.77 (t, J = 9.9 Hz, 2H), 7.75 (s, 2H), 7.58 (d,
J = 9.1 Hz, 1H), 7.55–7.47 (m, 2H), 7.29 (dd, J = 13.9, 6.4 Hz, 5H), 7.17 (d, J = 7.7 Hz, 5H),
7.06 (dd, J = 20.0, 12.8 Hz, 2H), 4.59–4.23 (m, 2H), 1.69 (dt, J = 15.0, 7.6 Hz, 2H), 1.62–1.47
(m, 5H), 1.44 –1.13 (m, 16H), 1.01–0.75 (m, 3H). 13C NMR (126 MHz, CDCl3) δ 147.63,
129.35, 127.62, 127.38, 127.32, 124.63, 123.69, 123.12, 31.94, 29.72, 29.67, 29.61, 29.39,
+
29.35, 26.86, 22.71, 14.13. HRMS (ESI) m/z calcd for C98H94N8 (M)+ 1382.75960, found
1382.75940.
3 Results and discussion
3.1 Synthesis and structure
The synthetic procedure of M-1, Z-1, Z-2 were shown in Scheme S1. The synthetic routes
for the compounds QA-1, QA-A, QA-B, QA-C, QA-D, QA-E and QA-F were shown in
Scheme 1. The synthesis of quinacridone derivatives was started from a commercially
available quinacridone precursor. The N-alkylation of quinacridone gave QA-1. Then the
bromination of QA-1 with N-bromosuccinimide (NBS) provided compound QA-2 in good
yield. Suzuki coupling reaction of bis(pinacolato)diboron with QA-2 and
4-bromotriphenylamine respectively gave compounds QA-3 and M-1. Then Suzuki coupling
reaction of bromoiodobenzene with M-1 gave compound Z-1 and Ullmann coupling reaction
of bromoiodobenzene with carbazole gave compound Z-2. In the next step, QA-A, QA-B and
8

QA-C were obtained Suzuki coupling reaction of bromobenzene, Z-1 and Z-2 with QA-2,
respectively. Finally, by Knoevenagel reaction, QA-1, QA-A and QA-B reacted with
malononitrile to obtain the target products QA-D, QA-E and QA-F, respectively. All
intermediates and target compounds were confirmed by stan-dard spectroscopic methods.
3.2 Photophysical properties
The UV-Vis absorption spectra of compounds (QA-1 and QA-A~F) in CH2Cl2 (ca. 10-5 M)
solution were shown in Fig. 1, and the absorption data were listed in Table 1. In the UV-Vis
spectra in Fig. 1, seven QA derivatives have multiple absorption peaks. The absorption peak
around 220-320 nm belongs to the n-π* transition of the electrons on the heterocycle and the
π-π* transition of the molecule at 450-650 nm. These absorption peaks are attributed to the
electron transfer of the electron donating group in the QA molecule to the
electron-withdrawing carbonyl group (C=O) or dicyandivinyl group. The maximum
absorption peaks of QA-1, QA-A, QA-B, and QA-C are located at 520 nm, 532 nm, 536 nm,
and 533 nm, respectively. Compared with QA-1, the maximum absorption peaks of the
compounds with electron donors are significantly red shifted due to intramolecular charge
transfer between electron donors and acceptors.
Compared with QA-1, the maximum absorption peaks of QA-A, QA-B and QA-C have a
larger red shift. Similarly, compared with QA-D, the maximum absorption peaks of QA-E
and QA-F have a larger red shift. These phenomena are caused by the introduction of electron
donors such as triphenylamine and carbazole, the increase of conjugate system of material
molecules, and the easier transition of off-domain electrons from low-energy state to
high-energy state. The absorption peaks of QA-D, QA-E and QA-F appeared at 650 nm,
which was due to the introduction of strong electron-absorbing group of dicyanoethylene into
quinacridone. QA-F has the largest absorption wavelength and the smallest band gap (Egap
=
1.79 eV) in seven target compounds. The introduction of electron-donating groups and strong
electron-withdrawing groups (DCN) can reduce the HOMO and LUMO band gap, which is
beneficial to intramolecular charge transfer, resulting in a significant red shift in the UV
absorption spectrum30.
The luminescence spectra have a consistent variation with the absorption spectra, as
showed in Fig. 2. The fluorescence quantum yields (ΦPL) of the compounds QA-A, QA-B,
9

and QA-C were 0.39, 0.03, and 0.48, respectively, which are lower than those of the
compound QA-1 (ΦPL = 0.96). It may be that the free rotation of the phenyl group leads to the
weakening of fluorescence. It could also be the result of the charge separation from
intramolecular charge transfer with the stronger electron donating group. QA-B molecule
contains more freely rotating phenyl groups, so the fluorescence quantum yield is minimal. ,
The fluorescence quantum yield of QA-C (ΦPL =0.48) is higher than that of QA-A (ΦPL
=0.39), because the steric hindrance of carbazole limits the free rotation of phenyl group. In
addition, the increase of Stokes shift of the compounds introduced to electron-donating
groups further proves the existence of non-radiative transition. The red emission peaks (λem)
of QA-A, QA-B and QA-C are 546.5, 555, and 549 nm, respectively, which show a
significant red shift compared with QA-1 (λem = 531.5 nm). The fluorescence of QA-D,
QA-E and QA-F is quenched in solvents of different polarities introducing DCN group. The
reason for fluorescence quenching is that the steric hindrance between DCN group and
quinacridone distorts the structure of the molecule, destroys the planar configuration of the
molecule and turns it into a butterfly-shaped molecule, resulting in the non-radiative transition
of the excited state in the molecule31. The solvatochromic effect is an important method to
study the polarity of a compound. The fluorescence emission spectra of QA-1, QA-A, QA-B
and QA-C in different polar solvents are shown in Fig 3. It can be seen from the figure that
the peak shape and peak position of QA-A and QA-C do not change significantly with the
increase of solvent polarity. This indicates that the introduction of phenyl group and carbazole
has little effect on the polarity of the compounds. However, QA-B exhibited fluorescent
properties in the non-polar solvent toluene and CHCl3, and exhibited fluorescence quenching
in the polar solvents CH3CN and DMSO. This phenomenon indicates that the introduction of
triphenylamine into the QA parent enhances molecular non-polarity.
10

Figure. 1 UV-vis absorption spectra of quinacridone derivatives in the dilute solution (1
× 10-5 M in CH2Cl2)
Table 1. The photophysical data of the quinacridone derivatives
Stokes shift
λonseta (nm)
ΦPL
Compd
λmax (nm)
λem (nm)
(nm)
487 520
545
552
561
556
674
687
692
0.96
0.39
0.03
0.48
-
531.5
146.5
QA-1
QA-A
QA-B
QA-C
QA-D
QA-E
QA-F
，
496 532
546.5
161.5
，
500 536
555
170
，
497 533
549
164
，
470 635
-
-
-
-
-
-
，
493 650
-
，
477 658
-
，
a The lowest-energy absorption edge of the absorption spectra.
11

Figure 2. Fluorescence spectra of quinacridone derivatives in the dilute solution
(2 × 10-7 M in CH2Cl2)
Figure 3. Fluorescence spectra of quinacridone derivatives in various solvents (2 × 10-7
M)
3.3 Electrochemical properties
12

The effect of substituents on the electrochemical properties of target compounds was
further studied by cyclic voltammetry using a standard three-electrode system (with platinum
carbon as the working electrode, platinum wire as the auxiliary electrode, Ag/AgCl electrode
as the reference electrode, and ferrocene as the internal standard) as the electrolytic cell,
tetrabutylammonium hexafluorophosphate (TBAPF6) as a supporting electrolyte, CH2Cl2 as
solvent, concentration being 1.0 × 10-3 M, and scanning speed being 100 mV/s. The cyclic
voltammograms of seven target compounds were shown in Fig 4, and the specific data were
listed in Table 2.
According to the cyclic voltammetry curve of the compounds, the initial oxidation potential
was obtained and the HOMO energy level was calculated. The LUMO energy level was
32
obtained by the HOMO value plus the band gap Egap , and the data was shown in Table 2.
The HOMO/LUMO energy levels of QA-1 and QA-A~F were calculated as -5.78/-3.50eV,
-5.77/-3.52eV, -5.61/-3.40eV, -5.65/ -3.42eV, -5.87/-4.03eV, -5.85/-4.05eV and
-5.65/-3.86eV, respectively showed from Fig. 4. When the carbonyl group is substituted by
DCN group, the oxidation potential of compounds QA-D, QA-E, QA-F increases, and the
LUMO level decreases significantly, so it's easier to get electronics, compared with that of
compound QA-1, QA-A, QA-B. It indicates that the introduction of donor and acceptor can
effectively reduce the band gap between HOMO and LUMO of the other compounds, which
is beneficial to ICT. Comparing the DFT-calculated HOMO/LUMO level in Table 5, we can
find that the value of the CV test is inconsistent with the theoretically calculated value.
However, the decrease trend of QA-1 and QA-A~F is consistent, thus, theoretical calculation
verify the experimental value of cyclic voltammetry, and have a good guiding value for the
design of compound.
Table 2. Cyclic voltammetric data of the quinacridone derivatives
Electrochemical (eV)
Compd
Egapa(eV)
ꢀꢅ
E
（eV）
ꢀꢁꢂꢃꢄ
HOMOb
-5.78
LUMOc
-3.50
2.28
2.25
2.21
QA-1
QA-A
QA-B
0.68
0.67
0.51
-5.77
-3.52
-5.61
-3.40
13

0.55
0.77
0.75
0.55
2.23
1.84
1.80
1.79
-5.65
-5.87
-5.85
-5.65
-3.42
-4.03
-4.05
-3.86
QA-C
QA-D
QA-E
QA-F
a Band gap estimated from λonset, Egap = 1240/λonset
b EHOMO = -(Eꢀꢀꢁꢅꢂꢃꢄ +5.1) eV. c ELUMO = EHOMO + Egap
.
.
Figure 4. Cyclic voltammograms of quinacridone derivatives are measured in CH2Cl2
14

3.4 Nonlinear optical properties
The third-order NLO properties of all compounds were determined by an open/closed-aperture
Z-scan technique. The solvent was CHCl3, the concentration was 1 mg/mL, the laser pulse energy
used was 0.4 μJ, the wavelength was 1030 nm, the pulse width was 190 fs, and focal length was
250 mm. The non-linearity of pure CHCl3 was also measured under the identical conditions and
found to negligible nonlinear response.
Fig.5 shown the normalized signal measured by the QA derivatives under open-cell conditions.
It was used to describe the absorption process of third-order nonlinear optics. The black circle
was the experimental data, and the red line was the curve after fitting. All compounds exhibited a
symmetric anti-saturation absorption curve with respect to the focus (Z=0), and the sample had
the lowest transmission intensity at the focal position.
When nonlinear absorption exists, open-cell curves and closed-cell curves can be obtained, and
the data measured by the closed-cell is divided by the open-hole data to obtain a single nonlinear
refractive property. It can be seen from Fig. 6 that all the patterns have the shape of the peak after
the valley, indicating that the nonlinear refractive index n2>0, which is the self-focusing
phenomenon, the difference between the peak and the valley (ΔTp-v) and the third-order non- The
linear refractive index n2 (m2/W) is related.
Nonlinear refractive index 33:
（3.4.1）
where S is the linear transmittance of the small aperture pupil, ΔTp-v is the peak-to-valley
difference of the sample, and n0 is the linear refractive index of the solvent (CHCl3 n0 = 1.4476).
The nonlinear optical coefficients n2 and β are obtained by calculation, and the effective
third-order nonlinear polarizability of the compound is calculated according to the following
ꢈ ꢊ
ꢈ ꢊ
ꢉ
34-36
ꢉ
equation (esu) χ(3), ꢆꢇ , ꢆꢋ
.
（3.4.2）
（3.4.3）
（3.4.4）
15

By the third-order nonlinear polarization coefficient χ(3), the second-order hyperpolarizability γ
of the sample can be obtained by the following formula:
（3.4.5）
where N is the molecular density of the solute, N=NAc, and c is the molar concentration of the
sample solution. The third-order nonlinear parameters obtained by the corresponding calculations
were summarized in Table 3.
16

QA-D
Figure 5. Normalized open-aperture Z-scan curves of the quinacridone derivatives solutions.
The open circles and solid lines represent the experimental data and theoretical fitting
curves, respectively
17

Figure 6. Normalized close-aperture Z-scan curves of the quinacridone derivatives solutions.
The open circles and solid lines represent the experimental data and theoretical fitting
curves, respectively.
According to the data in Table 3, the third-order nonlinear performance exhibited by this series
of compounds is roughly the same as the expected value of the initial design of the compound,
18

and the nonlinear absorption coefficient
polarizability χ(3) are between 4.38-13.26×10-12 esu. And the molecular second-order
hyperpolarizability
are between 1.21-5.32 × 10-33 esu. For the convenience of comparison, the
β
are between 1.23-3.09×10-13 m/W . The order nonlinear
γ
opening curves of QA-1 and QA-A~F were placed in the same picture as shown in Fig. 7. The
depth of the opening was from QA-F > QA-E > QA-B > QA-D > QA-C > QA-A > QA-1. It can
be seen from Fig. 7 that triphenylamine is acted as a strong electron donor to promote ICT, which
is very beneficial to improve the third-order nonlinear performance of materials. When the DCN
group with strong electron absorption is introduced into the conjugated system, the electron
mobility of the molecule is improved. The delocalization degree of
molecule increase, which reduce the transition energy of electron from ground state to excited
state. The of QA-F in the third-order nonlinear performance (
=5.32×10-33 esu) is nearly 4
times higher than the of QA-1, and is nealy 7823 times higher than the of urea (
=0.68×10-36
π electron and dipole torch of
γ
γ
γ
γ
γ
esu). Compound QA-F has the most excellent third-order nonlinear properties in these
compounds. It is attributed to the strong power supply of triphenylamine group and the strong
electricity absorption of DCN, which reduce the transition energy from ground state to excited
state. The energy level of the HOMO orbit can be increased by the electron donor group, and the
energy level of the LUMO orbit can be decreased by the electron acceptor group. Thus, the band
gap Egap of the molecule can be reduced and the nonlinear optical response of the material can be
enhanced.
Table 3. Third-order NLO parameters of quinacridone derivatives in CHCl3
β
(m/W)
n2 (m2/W)
χ(3)(esu)
γ(esu)
ꢆꢇꢈ ꢊ (esu)
ꢉ
ꢆꢋꢈ ꢊ (esu)
ꢉ
Compd
×10-13
×10-17
×10-12
×10-33
×10-13
×10-12
1.23
1.36
1.73
1.42
1.54
1.85
3.09
1.20
1.27
1.11
1.20
1.13
1.19
1.07
9.67
9.10
8.94
9.07
9.08
8.76
8.65
4.29
5.90
7.41
6.51
6.62
7.94
13.23
4.38
5.97
7.46
6.58
6.68
8.00
12.26
1.21
2.35
3.55
2.52
2.82
3.58
5.32
QA-1
QA-A
QA-B
QA-C
QA-D
QA-E
QA-F
19

Table 4. The NLO properties of organic and inorganic NLO materials
β (m/W)
×10-13
1.23
n2 (m2/W)
×10-17
1.20
χ(3)(esu)
×10-12
4.38
γ(esu)
×10-33
1.21
Sample
Reference
This work
This work
This work
This work
This work
This work
This work
QA-1
QA-A
QA-B
QA-C
QA-D
QA-E
QA-F
1.36
1.73
1.42
1.54
1.85
3.09
1.27
1.11
1.20
1.13
1.19
1.07
5.97
7.46
6.58
6.68
8.00
12.26
2.35
3.55
2.52
2.82
3.58
5.32
202.6
0.07
0.35
-
[37]
28.5
0.16
-
-
-
[38]
[39]
-
-
4.68 a
338.6
0.08
0.53
0.02 a
[40]
250
-
0.06
-
8.80
-
-
[41]
[42]
32
Graphene
a. γ was calculated by using solvatochromic data.
20

Figure 7. Normalized open-aperture Z-scan curves of quinacridone derivatives
3.5 Theoretical calculation
In order to gain a deep insight into the relationship between the molecular structure and
properties of the synthesized target compounds, density functional theory (DFT) calculations
were performed. DFT calculations were performed on the B3LYP/6-31G (d) level 43-46. The
structure optimization of the seven target compounds was shown in Fig. 8. It can be seen from
Fig. 8 that QA-1, QA-A, QA-B and QA-C have excellent molecular planarity. DCN groups
form a large steric hindrance effect with ortho hydrogen, which makes the center of
quinacridone twist into a "V" structure at the upper and lower sides in the molecular structure
of QA-D, QA-E and QA-F. The "V" structure of the molecule weakens π-π stacking between
molecules and makes the compounds have better solubility in solvents.
21

Figure 8. Optimized geometries of D-A-D quinacridone derivatives at the
B3LYP/6-31G(d) level
Table 5. DFT-calculated HOMO and LUMO energies
E
gap (eV)
Compd
HOMO（eV）
LUMO（eV）
-5.21
-5.18
-4.88
-5.33
-5.65
-5.59
-4.98
-2.11
-2.13
-2.16
-2.28
-3.20
-3.15
-3.16
3.10
3.05
2.72
3.04
2.45
2.44
1.81
QA-1
QA-A
QA-B
QA-C
QA-D
QA-E
QA-F
22

It is found that the distribution of HOMO and LUMO of QA-B and QA-F compounds
are quite different from that of other compounds by DFT calculation and simulation. The
HOMO is mainly distributed on the electron donor triphenylamine, while that of LUMO is on
the electron acceptor quinacridone. The phenomenon of several other compounds is not
obvious. The reason is that the triphenylamine group has a large electron supply capacity, and
the quinacridone structure has a large electron absorption capacity. The formation of "D-A-D"
type electronic push-pull structure in the molecule is conducive to the delocalization of π
electrons in the conjugated system. The triphenylaniline groups at both ends of the molecular
structure of QA-B and QA-F have more electron supplying ability than benzene ring, so the
difference between distribution in HOMO and in LUMO is greater than that in QA-A and
QA-E. This phenomenon is conducive to the delocalization of π electrons in the conjugated
system. Therefore, the second-order hyperpolarizability (γ) of compounds QA-B and QA-F
are higher than those of compounds QA-A and QA-E. In terms of molecular design of
nonlinear optical materials, triphenylamine is a better electron donor group than benzene ring.
In addition, the three benzene rings of triphenylamine in compound QA-B have larger degree
of freedom of rotation, so the angle between triphenylamine and quinacridone is smaller. This
is beneficial to the delocalization of π electron from triphenylamine to quinacridone, and to
the improvement of the nonlinear response of the material. The angle between carbazole
group and quinacridone in QA-C compound is larger because two benzene rings connected
together are not conducive to rotation. The difficulty of π electron delocalization from
carbazole to quinacridone increases, which is not conducive to the third-order nonlinear
response of materials. This is consistent with the third-order nonlinear performance test
results. The γ of QA-B compound is larger than that of QA-C. Compared with carbazole,
triphenylamine is a better electron donor group. On the other hand, when the quinacridone
structure of compounds QA-E and QA-F is connected to DCN group, the ability of electron
absorption is enhanced, and the dipole moment of the molecule is increased. It is
advantageous for π electron to be delocalized from the electron donor group at both ends to
the electron acceptor group in the middle. Compared with compound QA-B, the γ of
compound QA-F increases obviously. Similarly, the γ of compound QA-E is significantly
23

higher than that of compound QA-A. In conclusion, reducing the angle between the electron
donating groups at both ends of the molecule and quinacridone, enhancing the electron
donating ability of the electron donating groups at both ends of the molecule and the electron
absorbing ability of quinacridone structure are conducive to enhancing the third-order
nonlinear response of the material.
Figure 9. DFT-calculated frontier molecular orbitals of the quinacridone derivatives
4 Conclusion
Seven derivatives of D-A-D quinacridone were designed and synthesized. The
relationship between molecular structure and nonlinear optical properties was studied by
cyclic voltammetry, DFT calculation and Z-scan. The results show that the molecular
structure of D-A-D type push-pull structure can enhance the nonlinear optical response of the
material when the two sides of quinacridone are connected with electron donor groups. It is
beneficial to improve the nonlinear optical response of the material by enhancing the power
supply performance of the electronic groups on both sides of the molecule and adding DCN
groups to enhance the electronic absorption performance of quinacridone, reducing the angle
between the electronic group and quinacridone. Among the seven target compounds, QA-F
has excellent third-order nonlinear properties, and its γ (γ=5.32×10-33 esu) is 4.38 times that of
24

QA-1 (γ=1.21×10-33 esu). It provides a new idea for the molecular design and study on the
relationship between structure and properties of D-A-D organic nonlinear optical materials.
Acknowledgements
This work was supported by Yinglin Song from the College of Physical, Optoelectronics
and Energy in Soochow University in the Z-scan experiment and data analysis. We are
thankful for the National Natural Science Foundation of China (Synthesis and quantum theory
reveals of fused heterocyclic organic third-order nonlinear optical material, 21452001).
References
1. Jia, J.; Zhang, J.; Zhou, C.; Zheng, M.; Feng, D.; Liang, G.; She, Y., Extended
π-conjugated quinazolinone derivatives with enhanced third-order nonlinear optical response.
Dyes and Pigments 2019, 166, 314-322.
2. Ma, X.; Lin, C. S.; Zhang, H.; Lin, Y. J.; Hu, S. M.; Sheng, T. L.; Wu, X. T.,
Synthesis, spectral and redox switchable cubic NLO properties of chiral dinuclear iron
cyanide/isocyanide-bridged complexes. Dalton Trans 2013, 42 (34), 12452-9.
3. Luan, Y.; Yang, M.; Ma, Q.; Qi, Y.; Gao, H.; Wu, Z.; Wang, G., Introduction of an
organic acid phase changing material into metal–organic frameworks and the study of its
thermal properties. Journal of Materials Chemistry A 2016,
4. Loh, K. P.; Bao, Q.; Eda, G.; Chhowalla, M., Graphene oxide as a chemically tunable
platform for optical applications. Nat Chem 2010, (12), 1015-24.
4 (20), 7641-7649.
2
5. Kasel, T. W.; Deng, Z.; Mroz, A. M.; Hendon, C. H.; Butler, K. T.; Canepa, P.,
Metal-free perovskites for non linear optical materials. Chemical Science 2019.
25

6. Jia, J.; Li, Y.; Gao, J., A series of novel ferrocenyl derivatives: Schiff bases-like
push-pull systems with large third-order optical responses. Dyes and Pigments 2017, 137
,
342-351.
7. Helmchen, F.; Denk, W., Deep tissue two-photon microscopy. Nature Methods 2005,
(12), 932-940.
2
8. Han, P.; Wang, D.; Gao, H.; Zhang, J.; Xing, Y.; Yang, Z.; Cao, H.; He, W.,
Third-order nonlinear optical properties of cyanine dyes with click chemistry modification. Dyes
and Pigments 2018, 149, 8-15.
9. Feng, Q.; Li, Y.; Shi, G.; Wang, L.; Zhang, W.; Li, K.; Hou, H.; Song, Y., A
photo-controllable third-order nonlinear optical (NLO) switch based on a rhodamine B
salicylaldehyde hydrazone metal complex. Journal of Materials Chemistry C 2016,
8552-8558.
4 (36),
10. Ming Li, Y. L., Hui Zhang, Shiwei Wang, Yuhui Ao and Zhanchen Cui Molecular
engineering of organic chromophores and polymers for enhanced bulk second-order optical
nonlinearity. Journal of Materials Chemistry C 2017, 5, 4111-4122
.
11. Makhal, K.; Arora, S.; Kaur, P.; Goswami, D.; Singh, K., Third-order nonlinear optical
response and ultrafast dynamics of tetraoxa[22]porphyrin(2.1.2.1)s. Journal of Materials
Chemistry C 2016,
4 (40), 9445-9453.
12. Jia, J.-H.; Tao, X.-M.; Li, Y.-J.; Sheng, W.-J.; Han, L.; Gao, J.-R.; Zheng, Y.-F.,
Synthesis and third-order optical nonlinearities of ferrocenyl Schiff base. Chemical Physics
Letters 2011, 514 (1-3), 114-118.
13. Zhao, Y.; Li, H.; Shao, Z.; Xu, W.; Meng, X.; Song, Y.; Hou, H., Investigation of
26

Regulating Third-Order Nonlinear Optical Property by Coordination Interaction. Inorg Chem
2019, 58 (8), 4792-4801.
14. Harapriya Rath, J. S., Viswanathan PrabhuRaja, Tavarekere K. Chandrashekar, Amit
Nag, and Debabrata Goswami, Core-Modified Expanded Porphyrins with Large Third-Order
Nonlinear Optical Response. J Am Chem Soc 2005, 127, 11608-11609.
15. Jerca, F. A.; Jerca, V. V.; Kajzar, F.; Manea, A. M.; Rau, I.; Vuluga, D. M.,
Simultaneous two and three photon resonant enhancement of third-order NLO susceptibility in
an azo-dye functionalized polymer film. Phys Chem Chem Phys 2013, 15 (19), 7060-3.
16. Bhattacharya, S.; Biswas, C.; Raavi, S. S. K.; Venkata Suman Krishna, J.; Vamsi
Krishna, N.; Giribabu, L.; Soma, V. R., Synthesis, Optical, Electrochemical, DFT Studies,
NLO Properties, and Ultrafast Excited State Dynamics of Carbazole-Induced Phthalocyanine
Derivatives. The Journal of Physical Chemistry C 2019, 123 (17), 11118-11133.
17. Asokan, P.; Kalainathan, S., Bulk Crystal Growth, Optical, Electrical, Thermal, and Third
Order NLO Properties of 2-[4-(Diethylamino)benzylidene]malononitrile (DEBM) Single Crystal.
The Journal of Physical Chemistry C 2017, 121 (40), 22384-22395.
18. Li, H.; Gu, C.; Jiang, L.; Wei, L.; Hu, W.; Fu, H., Donor–acceptor copolymers
containing quinacridone and benzothiadiazole for thin film transistors. Journal of Materials
Chemistry C 2013,
1 (10).
19. Cho, M. J.; Choi, D. H.; Sullivan, P. A.; Akelaitis, A. J. P.; Dalton, L. R., Recent
progress in second-order nonlinear optical polymers and dendrimers. Progress in Polymer
Science 2008, 33 (11), 1013-1058.
20. Jia, J.; Li, T.; Cui, Y.; Li, Y.; Wang, W.; Han, L.; Li, Y.; Gao, J., Study on the
27

synthesis and third-order nonlinear optical properties of D-A poly-quinacridone optical
materials. Dyes and Pigments 2019, 162, 26-35.
21. Hongwei Hou , Y. S., Yaoting Fan , Linping Zhang , Chenxia Du, Yu Zhu A novel
coordination
polymer
[Co(NCS)2(bpms)2]n
(bpms=1,2-bis(4-pyridylmethyl)disulfenyl):
synthesis, crystal structure and third-order nonlinear optical properties. Inorganic Chimica Acta
2001, 316, 140-144.
22. I. Fuks-Janczarek, J. L., B. Sahraoui, F. Dumur, P. Hudhomme, J. Berdowski, I. V. Kityk,
Third-Order Nonlinear Optical Figure of Merits for Conjugated TTF-Quinone Molecules. J.
Phys. Chem. B 2005, 109, 10179-10183.
23. Biswal, B. P.; Valligatla, S.; Wang, M.; Banerjee, T.; Saad, N. A.; Mariserla, B. M.
K.; Chandrasekhar, N.; Becker, D.; Addicoat, M.; Senkovska, I.; Berger, R.; Rao, D.
N.; Kaskel, S.; Feng, X., Nonlinear Optical Switching in Regioregular Porphyrin Covalent
Organic Frameworks. Angew Chem Int Ed Engl 2019, 58 (21), 6896-6900.
24. Arturs Bundulis, E. N., Igors Mihailovs, Janis Busenbergs, and Martins Rutkis, Study of
Structure−Third-Order Susceptibility Relation of Indandione Derivatives. J. Phys. Chem. C
2016, 120, 27515−27522.
25. Baili Chen, S. N., Laixi Sun, Xuan Luo, Qingjun Zhang, Yinglin Song, Quanjie Zhong, Yu
Fang, Chuanqun Huang, Shufan Chen, Weidong Wu, Intramolecular charge transfer tuning of
azo dyes: Spectroscopic characteristic and third-order nonlinear optical properties. Dyes and
Pigments 2018, 158, 474–481.
26. Dogukan Hazar Apaydin, E. D. G., Engelbert Portenkirchner, and Niyazi Serdar Sariciftci,
Direct Electrochemical Capture and Release of Carbon Dioxide Using an Industrial Organic
28