New soluble near-infrared dyes based on terrylene diimides with four aromatic heterocycles

Article abstract of DOI:10.1002/cjoc.201400175

Terrylene diimides with four aromatic heterocycles (AHTDIs) were synthesized under Stille Cross-coupling conditions and fully characterized by NMR and mass spectrometry. The aggregation of the terrylene diimide (TDI) was suppressed by four heterocycles substituents on the bay region, and these AHTDIs exhibited good solubility in common organic solvents. The effects of the substituted groups on the optical and electrochemical properties were also investigated. The introduction of four aromatic heterocycles on the bay of TDI resulted in significant red-shifts of the absorption peak (100 nm), corresponding to a decrease in the band gap from 1.82 to 1.50 eV. Furthermore, with four rich electron aromatic heterocycles, the AHTDIs showed 280 mV negative-shifts of first oxidation potentials and a new oxidation wave, corresponding to an increase in the HOMO levels from?-5.60 to?-5.28 eV. Two soluble NIR dyes based on terrylene diimides were synthesized by the introduction of aromatic heterocycles substituents on the bay region. The effects of the substituted groups on the optical and electrochemical properties were further investigated. Copyright

Full text of DOI:10.1002/cjoc.201400175

FULL PAPER
DOI: 10.1002/cjoc.201400175
New Soluble Near-Infrared Dyes Based on Terrylene Diimides
with Four Aromatic Heterocycles
Huimin Wei,a Nan Jiang,a Nan Zhao,a Ying Zhang,a and Baoxiang Gao*,a,b
a College of Chemistry and Environmental Science, Hebei University, Baoding, Hebei 071002, China
b Key Laboratory of Medicinal Chemistry and Molecular Diagnosis, Hebei University,
Baoding, Hebei 071002, China
Terrylene diimides with four aromatic heterocycles (AHTDIs) were synthesized under Stille Cross-coupling
conditions and fully characterized by NMR and mass spectrometry. The aggregation of the terrylene diimide (TDI)
was suppressed by four heterocycles substituents on the bay region, and these AHTDIs exhibited good solubility in
common organic solvents. The effects of the substituted groups on the optical and electrochemical properties were
also investigated. The introduction of four aromatic heterocycles on the bay of TDI resulted in significant red-shifts
of the absorption peak (100 nm), corresponding to a decrease in the band gap from 1.82 to 1.50 eV. Furthermore,
with four rich electron aromatic heterocycles, the AHTDIs showed 280 mV negative-shifts of first oxidation poten-
tials and a new oxidation wave, corresponding to an increase in the HOMO levels from −5.60 to −5.28 eV.
Keywords terrylene diimides, aromatic heterocycles, near-infrared dyes, optoelectronic properties
Introduction
reported novel soluble near infrared dyes based on
terrylene diimides (TDI) carring four aromatic hetero-
cycles (AHTDIs) on the bay region, and their optical
and electrochemical properties were further investigated.
Since the first discovery of dyes active in the near
infrared region in the early twentieth century, consider-
able effort has been made to develop various types of
near infrared organic compounds because of their po-
tential applications in optical recording,[1] laser print-
ers,[2] photodynamic therapy,[3] OLED,[4] and numerous
other applications.[5,6] With respect to their practical
implementation, these near infrared dyes must be easy
to produce in a small number of steps and are required
to have high stability.[7]
Rylenes and their dicarboxylic imide derivatives are
key chromophores in dye chemistry due to their excel-
lent chemical and photostability.[8,9] The absorption, and
emission behavior of this class of materials can be effi-
ciently controlled by functionalization using a variety of
different synthetic procedures.[10] Up to now, perylene-
bis(dicarboximide) and higher rylenes, namely terrylene,
quaterrylene, pentarylene, and hexarylene, have been
synthesized, and the higher order rylene bis(dicarboxi-
mide)s can serve as good near infrared dyes due to ex-
tended π-conjugation.[11,12] These higher order rylene
dyes have poor solubility even though some bulky
groups are attached to the peri-positions of the terminal
naphthalene units.[13]
Experimental
Materials
Solvents were purchased from Sinopharm Chemical
Reagent Co., Ltd. Solvents used for precipitation and
column chromatography were distilled under normal
atmosphere. The NMR spectra were recorded at 20 ℃
on 600 MHz NMR spectrometer (Bruker). Chemical
shifts are reported at room temperature using CDCl3 as
solvent and tetramethylsilane as internal standard unless
indicated otherwise. Mass spectra were carried out using
MALDI-TOF/TOF matrix assisted laser desorption
ionization mass spectrometry with autoflex III smart-
beam (Bruker Daltonics Inc). UV-Vis spectra were re-
corded with a Shimadzu WV-2550 spectrophotometer.
Cyclic voltammetry (CV) was performed on a Ivium
CompactStat electrochemical analyzer with a three-
electrode cell in 2－3 mg/mL compound dichloro-
methane solution with 0.1 mol/L tetrabutylammonium
hexafluorophosphate at a scan rate of 100 mV/s. A Pt
disk (2-mm diameter) was used as working electrode
with a Pt wire as the counter electrode and an Calomel
electrode as the reference electrode.
Our interests are in the development of the core-
enlarged terrylene diimide on the bay region for use as
stable near infrared dyes.[14] In the current study, we
*
E-mail: bxgao@hbu.edu.cn; Tel.: 0086-0312-3382004; Fax: 0086-0312-5079317
Received March 23, 2014; accepted April 6, 2014; published online April 22, 2014.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201400175 or from the author.
356
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Chin. J. Chem. 2014, 32, 356—360

New Soluble Near-Infrared Dyes Based on Terrylene Diimides with Four Aromatic Heterocycles
Synthesis and characterization of terrylene diimides
with four aromatic heterocycles
Scheme 1 Chemical structures of terrylene diimide (TDI) and
AHTDIs
Tetrabromo terrylene dicarboximide was prepared
according to literature procedures.[15] The detailed syn-
thetic procedures and route were shown in Supporting
Information. Acylation reaction between 4-bromo-1,8-
naphthalic anhydride and 2,6-diisopropylaniline gave
the intermediate compound 4. Imidazole melting
method in autoclave between 3,4,9,10-perylenetetra-
carboxylic acid dianhydride and 2,6-diisopropylaniline
gave compound 5 which was brominated to afford com-
pound 6. Conversion of 6 into diboronate ester 7 was
achieved under Miyaura reaction conditions in the
presence of bis(pinacolato)diborane, Pd(dppf)2Cl2 and
KOAc with dry DMF as the solvent, in a yield of
40%.[16] Compound 8 was obtained by Pd-catalyzed
Suzuki coupling reaction between compound 4 and
compound 7. Intramolecular oxidative cyclodehydroge-
nation reactions were then performed on compound 8
with ethanolamine and 50 equiv. of K2CO3 to give
compound 1 (TDI), which was brominated to afford
tetrabromo terrylenedicarboximide. The synthetic ap-
proach for AHTDIs is outlined in Scheme 2. Under
Stille Cross-coupling conditions, the reaction of com-
pound 9 with tributyl(5-hexylthiophen-2-yl)stannane
yielded the AHTDI 2 with a 63% yield. Compound 9
with tributyl(5-methylfuran-2-yl)stannane produced
AHTDI 3 in a good yield of 80%, under the same reac-
tion conditions.
O
N
O
S
S
S
O
N
O
O
N
O
S
O
N
O
AHTDI 2
TDI
O
O
N
O
O
N
O
O
AHTDI 3
Scheme 2 Synthetic of aromatic heterocycles terrylene diimides
SnBu3
S
S
S
S
O
N
O
O
N
O
O
N
O
S
Br
Br
Br
Br
O
SnBu3
O
O
O
O
N
O
O
N
O
N
O
AH
TD
I 3
(80
%)
Chin. J. Chem. 2014, 32, 356—360
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Wei et al.
FULL PAPER
N,N'-Bis(2,6-diisopropylphenyl)-1,6,9,13-tetra(5-
hexylthiophen-2-yl)-terrylene-3,4:11,12-tetracar-
boxidiimide (AHTDI 2) In a glove box filled with
dry nitrogen, tetrabromoterrylenedicarboximide (150
mg, 0.13 mmol), tributyl(5-hexylthiophen-2-yl)stannane
(596 mg, 1.30 mmol), toluene (25 mL) and DMF (5 mL)
were mixed. Then Pd(PPh3)4 (18 mg, 0.016 mmol) was
added. The mixture was stirred under nitrogen for 24 h
at 90 ℃. After cooling to room temperature, the reac-
tion mixture was poured into a 500 mL separatory fun-
nel, and extracted with 100 mL 5% (by mass) potassium
fluoride solution and 80 mL dichloromethane. The or-
ganic layer was collected and separated with 5% (by
mass) potassium fluoride solution and the solvent was
removed under reduced pressure. The residue was puri-
fied by column chromatography eluting with CH2Cl2
dichloromethane are shown in Figure 1 and the photo-
physical data are summarized in Table 1. The UV-Vis
spectra of the AHTDIs show a multipeak band with de-
fined structures. The absorption maximum of TDI ap-
peared at 652 nm, along with two higher vibronic tran-
sitions located at 598 and 550 nm. The absorption bands
of AHTDIs are red-shifted after connected with four
aromatic heterocycles in the bay region of the terrylene
diimide core. With four thiofuran units in the bay region,
AHTDI 2 has a significantly red-shifted absorbance
maximum at 752 nm, with three low absorption bands at
680, 509 and 400 nm. Replacing four thiofuran units in
the bay region of the terrylene by four furan units, the
π-π* transition absorption of AHTDI 3 is red shifted to
762 nm. Both the absorbance maximums of AHTDIs
were red-shifted by more than 100 nm to near-infrared
region compared with TDI. The large red-shifted maxi-
mum absorbance of AHTDIs may be attributed to small
dihedral angle and the reinforcing of the conjugation
between terrylene diimides core and the aromatic het-
erocycles on the bay region.[17] The dihedral angle of
1,2-diaryl-benzene is usually larger than the dihedral
angle of 1,2-diaryl-thiophene.[18,19] Furthermore, the
introduction of aryl substituents on the TDI core pro-
duces line broadening in the absorption spectrum and
less pronounced vibronic fine structure (Figure 1).[20]
The spectral-broadening phenomena have been reported
elsewhere for a twisted perylene bisimide[21] and
hexaazatriphenylene.[22]
1
and hexane to get dark green solid. 122 mg, 63%; H
NMR (600 MHz, CDCl3) δ: 8.67 (s, 4H), 7.92 (s, 4H),
7.51 (t, J＝7.8 Hz, 2H), 7.38 (d, J＝7.8 Hz, 4H), 7.11 (d,
J＝3.6 Hz, 4H), 6.79 (d, J＝3.0 Hz, 4H), 2.83 (t, J＝7.2
Hz, 8H), 2.80－2.78 (m, 4H), 1.70－1.65 (m, 8H), 1.39
－1.36 (m, 8H), 1.32－1.29 (m, 16H), 1.21 (d, J＝6.6
Hz, 24H), 0.89－0.87 (m, 12H); 13C NMR (150 MHz,
CDCl3) δ: 163.7, 148.5, 145.7, 141.9, 136.2, 135.0,
132.9, 130.9, 130.8, 130.0, 129.6, 129.2, 128.5, 128.2,
126.8, 125.3, 124.1, 120.5, 31.6, 31.6, 30.3, 29.2, 28.7,
24.0, 22.6, 14.1; MS (MALDI-TOF) cacld for MH＋:
1500.13, found 1499.6455.
N,N'-Bis(2,6-diisopropylphenyl)-1,6,9,13-tetra-
(5-methylfuran-2-yl)-terrylene-3,4:11,12-tetracarboxi-
diimide (AHTDI 3) In a glove box filled with dry
nitrogen, tetrabromoterrylenedicarboximide (300 mg,
0.26 mmol), tributyl(5-methylfuran-2-yl)stannane (774
mg, 2.09 mmol), toluene (50 mL), and DMF (5 mL)
were mixed. Then Pd(PPh3)4 (36 mg, 0.031 mmol) was
added. The mixture was stirred under nitrogen for 24 h
at 90 ℃. After cooling to room temperature, the reac-
tion mixture was poured into a 500 mL separatory fun-
nel, and extracted with 100 mL 5% (by mass) potassium
fluoride solution and 80 mL dichloromethane. The or-
ganic layer was collected and separated with 5% (by
mass) potassium fluoride solution and the solvent was
removed under reduced pressure. The residue was puri-
fied by column chromatography eluting with CH2Cl2
1.5
TDI
AHTDI 2
AHTDI 3
1.0
0.5
0.0
400
500
600
700
800
900
Wavelength/nm
1
and hexane to get dark purple solid. 242 mg, 80%; H
Figure 1 UV-Vis absorption spectra of the TDI and AHTDIs in
dichloromethane.
NMR (600 MHz, CDCl3) δ: 8.76 (s, 4H), 7.54 (t, J＝7.8
Hz, 2H), 7.42 (s, 4H), 7.39 (d, J＝7.8 Hz, 4H), 6.81 (d,
J＝3.6 Hz, 4H), 6.23 (d, J＝2.4 Hz, 4H), 2.82－2.77 (m,
4H), 2.21 (s, 12H), 1.22 (d, J＝7.2 Hz, 24H); 13C NMR
(150 MHz, CDCl3) δ: 163.7, 153.0, 152.6, 145.7, 134.7,
133.8, 130.8, 130.7, 130.4, 129.6, 129.3, 128.4, 128.1,
127.4, 124.1, 120.8, 110.9, 108.7, 29.2, 24.0, 13.6; MS
The aggregation behavior of TDI and AHTDIs in
toluene solution was studied by the changes in the ab-
sorption extinction coefficient at different concentra-
tions, and the concentration-dependent UV-Vis absorp-
tion spectroscopy as shown in Figure 2.
＋
Due to the aggregation, a non-Lambert-Beer law
behavior was observed for the investigated compound
TDI. Upon increasing the concentration from 1.0×10−6
to 1.0×10−4 mol•L−1, the extinction coefficient (0－0
transition) of TDI decreased by 27% (7.3×10−4 to 5.3×
10−4 L•mol−1•cm−1). This indicates that the TDI
(MALDI-TOF) cacld for MH : 1155.34, found
1155.5187.
Results and Discussion
The UV-Vis absorption spectra of the AHTDIs in
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Chin. J. Chem. 2014, 32, 356—360

New Soluble Near-Infrared Dyes Based on Terrylene Diimides with Four Aromatic Heterocycles
affinity essentially unchanged after the introduction of
10
8
1X10-4 mol/L
1X10-5 mol/L
1X10-6 mol/L
four aromatic heterocycles units in the bay region.
However, scanning from 0 to 2 V, both AHTDI 2 and
AHTDI 3 exhibit two reversible oxidation potentials at
0.93, 1.12 and 0.88, 1.05 V, respectively. Compared
with TDI, with four rich electron aromatic heterocycles,
AHTDIs show enhanced first oxidation potential levels
and a new oxidation wave, suggesting that the elec-
tron-donating properties of AHTDIs become stronger.
TDI
6
.
.
4
2
10
8
1X10-4 mol/L
1X10-5 mol/L
1X10-6 mol/L
AHTDI 2
AHTDI 3
6
4
2
10
8
TDI
1X10-4 mol/L
1X10-5 mol/L
1X10-6 mol/L
6
4
2
AHTDI 2
0
400
500
600
700
800
900
Wavelength/nm
Figure 2 Concentration-dependent UV-Vis absorption spectra
of TDI and AHTDIs in toluene.
AHTDI 3
molecule exhibited aggregation behavior in a relatively
high concentration. However, in the same concentration
range, the extinction coefficients of AHTDIs 2 and 3
were essentially unchanged. It suggests that the aggre-
gation behavior of the TDI is partly suppressed by four
aromatic heterocycles groups.[23] Compared with TDI,
the extinction coefficients of AHTDI 2 and AHTDI 3
were reduced slightly. However, the photoluminescence
was not detectable for the both AHTDIs from 300 to
900 nm. This fluorescence quenching might be due to
the efficient intramolecular electron transfer between
the electron donor (thiophene or furan) and the electron
acceptor (TDI core).[24] Both AHTDIs show broad ab-
sorption spectra with relatively high molar absorption
coefficient and better solubility in common organic
solvents than TDI molecule.
The CV curves of the TDI and AHTDIs are shown in
Figure 3. The corresponding data are collected in Table
1. TDI shows one reversible reduction potential at −0.53
V and one reversible oxidation potential at 1.16 V ver-
sus Calomel. On cathodic scanning, AHTDI 2 exhibits
one reversible reduction potential at −0.55 V. AHTDI 3
also exhibits one reversible reduction wave, which is
shifted by 30 mV to more negative potential at −0.56 V
compared to that of TDI. Both the reduction waves of
AHTDIs were reduced slightly, indicating that electron
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5
Potential/V (vs. calomel electrode)
Figure 3 The CV curves of the TDI and AHTDIs in CH2Cl2 at a
scan rate of 0.1 V/s.
The lowest unoccupied molecular orbital (LUMO)
and the highest occupied molecular orbital (HOMO)
were estimated from the onset of the reduction poten-
tials and first oxidation potentials.[25] The electrochemi-
cal band gap was obtained from Ege ＝1240/λonset. The
LUMO, HOMO and Ege levels of TDI are –3.87, –5.56
and 1.69 eV, respectively. With four electron-rich thio-
phene rings on the bay region, LUMO, HOMO and Ege
levels of AHTDI 2 are shifted to –3.85, –5.33 and 1.48
eV. In comparison, AHTDI 2 has essentially unchanged
LUMO, higher HOMO and small band gap. Whereas,
replacing four electron-rich thiophene rings by four
electron-rich furan rings, the LUMO, HOMO and Ege
levels of AHTDI 3 are −3.86, –5.28 and 1.42 eV, re-
spectively. AHTDI 3 also has essentially unchanged
LUMO, higher HOMO and small band gap compared
with TDI. The introduction of aromatic heterocycles
units reinforced the conjugation between terrylene
diimides core and the aromatic heterocycles on the bay
region, and improved the electrochemical properties.
Table 1 Optical and electrochemical properties and band gap data of TDI and AHTDIs
Ego a/eV
Ege d/eV
Eo1x /V
Eo2x /V
Compd.
TDI
λmax/nm
λonset/nm
Ered/V
LUMOb/eV
HOMOc/eV
652
752
761
680
828
832
1.82
1.50
1.49
−0.53
−0.55
−0.56
1.16
0.93
−3.87
−3.85
−5.56
−5.33
−5.28
1.69
1.48
1.42
AHTDI 2
1.12
1.05
AHTDI 3
0.88
c
−3.86
a
b
d
Optical band gap Ego ＝1240/λonset
.
LUMO ＝−(4.40＋Ered).
HOMO＝ −(4.40+ Eo1x ). Electrochemical band gap Ego ＝
LUMO − HOMO.
Chin. J. Chem. 2014, 32, 356—360
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359

Wei et al.
FULL PAPER
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In conclusion, we reported the synthesis of the novel
soluble NIR dyes based on terrylene diimides with aro-
matic heterocycles on the bay region. The aggregation
of the TDI was suppressed by four aromatic heterocy-
cles substituents on the bay region, and these AHTDIs
exhibited good solubility in common organic solvents.
The longest absorbance maximums of AHTDIs are sig-
nificantly red-shifted by more than 100 nm to near-in-
frared spectrum band (from 652 to 752 and 761 nm)
with relatively high molar absorption coefficients
(52500 and 65600 mol•L−1•cm−1, respectively) due to
the introduction of four aromatic heterocycles substitu-
ents in the bay region of the terrylene diimides. Fur-
thermore, the oxidation process of the AHTDIs in-
creased from one to two waves, and the HOMO levels
were enhanced from −5.56 to −5.28 eV due to the ex-
tended conjugation between the aromatic heterocycles
substituents and the terrylene diimides core.
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21274036), the Program for New Century Excellent
Talents in University (No. NCET-12-0684), Training
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