Alkyl- and aryl-substituted benzo[ghi]perylenetriimides: Synthesis, characterization and comparison of electrochemical and spectroscopic properties

Article abstract of DOI:10.1016/j.dyepig.2016.07.031

Benzo[ghi]peryleneimides constitute a unique class of fluorescent perylene dyes which possesses great synthetic diversity due to the presence of a large number of reactive active sites (availability of third imide region). Taking advantage of this additio

Full text of DOI:10.1016/j.dyepig.2016.07.031

Dyes and Pigments 134 (2016) 453e458
Contents lists available at ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Alkyl- and aryl-substituted benzo[ghi]perylenetriimides: Synthesis,
characterization and comparison of electrochemical and spectroscopic
properties
,
Lakshmi C. Kasi Viswanath a *, Jeremy Bernhardt a, Krishna Kumar Gnanasekaran b,
Colton Want a, Joshua Frank a, Jantzen Faulkner a, Sadagopan Krishnan b
a Department of Chemistry, Oklahoma Baptist University, Shawnee, OK, 74804, USA
b Department of Chemistry, Oklahoma State University, Stillwater, OK, 74074, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Benzo[ghi]peryleneimides constitute a unique class of fluorescent perylene dyes which possesses great
synthetic diversity due to the presence of a large number of reactive active sites (availability of third
imide region). Taking advantage of this additional active site we synthesized a new series of benzo[ghi]
perylenetriimides comprised of alkyl- and aryl-substituents in the third imide region. The core extension
of perylene diimides was performed using a Diels-Alder reaction to afford diimido anhydride (3) which
provided access to the various triimides with yields ranging from 58% to 69%. The combined spectro-
scopic and electrochemical studies revealed strong electron accepting properties of the triimides. Po-
tential application of the synthesized triimides for various optoelectronic devices and as non-fullerene
electron acceptors in photovoltaics is evident from this study.
Received 29 April 2016
Received in revised form
6 June 2016
Accepted 22 July 2016
Available online 26 July 2016
Keywords:
Benzo[ghi]perylenetriimide
Perylene diimides
Diels-Alder
© 2016 Published by Elsevier Ltd.
Organic solar cells
Electron transfer
1. Introduction
not highly appreciable when compared to the fullerene-based ac-
ceptors. Such low efficiency could be attributed to the charge loss
In recent years, Perylene-3,4:9,10-tetracarboxylic acid diimides
(PDI) have received a great deal of attention due to their wide-
spread industrial applications [1]. The exceptional thermal and
photochemical stability of PDIs in combination with their remark-
able optoelectronic properties with large fluorescence quantum
yields and high molar absorptivities make them as promising
organic n-type semiconductors [2]. Today, PDIs are extensively
used in field-effect transistors [3], light-emitting diodes [4,5], liquid
crystal displays [6,7], biosensors [8], light-harvesting materials [9],
optical switches [10], molecular wires [11,12] and as dyes in
photodynamic therapy [13]. As a means to replace fullerene elec-
tron acceptors in organic solar cells, several efforts were made to-
wards the construction of electron-rich aromatic cores that are
capable of acting as good electron acceptors in photovoltaic cells
[14e20]. One such electron acceptor is PDI [1,21e23]. Nevertheless,
the solar energy conversion efficiencies achieved for PDI comprised
of conjugated polymers and small molecule photovoltaic blends are
existing in PDI molecules [24]. Additionally, one of the drawbacks of
PDIs is their low solubility in most organic solvents which adds
difficulties in processing and thus limits their use in material sci-
ence applications. In order to circumvent the solubility issues and
increase the potential use of PDIs, various synthetic strategies have
been explored with the goal to obtain new soluble PDI derivatives.
Recently benzo[ghi]perylenes, representing a more expanded
p
conjugated system than PDI, have attracted scientists owing to their
high photostability and interesting electronic properties [24e28].
Comparison of the skeletal structures of benzo[ghi]perylene-
triimide (BPTI) and PDI suggests that BPTI offers more synthetic
diversity owing to the fact that it has three imide regions
[24,29e32]. This paves a way for fine-tuning the spectroscopic and
electrochemical properties based on the nature and type of sub-
stituents. Taking into consideration the synthetic versatility of BPTI
and their applications in organic solar cells, we intended to
synthesize and examine the properties of a series of benzo[ghi]
perylenetriimides containing either an alkyl- or aryl-substituent in
the third imide region.
* Corresponding author.
E-mail address: lakshmi.viswanath@okbu.edu (L.C.K. Viswanath).
http://dx.doi.org/10.1016/j.dyepig.2016.07.031
0143-7208/© 2016 Published by Elsevier Ltd.

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L.C.K. Viswanath et al. / Dyes and Pigments 134 (2016) 453e458
Table 1
2. Results and discussion
Reaction conditions and isolated yields of benzo[gho]perylenetriimides.
2.1. Synthesis
Entry
Amine
Time
6 h
Yield %
63
4a
The chemical structures of benzo[ghi]perylenetriimides (4a-4g)
and the synthetic routes to obtain such are shown in Scheme 1. The
synthesis originated from an imidization of perylene dianhydride
(1) by reaction with 3-aminopentane in imidazole at 140 ꢀC to
afford 2 in an isolated yield of 89%.
4b
4c
4d
6 h
6 h
7 h
68
69
62
A Diels-Alder reaction of PDI (2) with maleic anhydride in the
presence of p-chloranil as an oxidizing agent and nitrobenzene as
the solvent resulted in the formation of the diimido anhydride 3
[24,31]. Attempts were made to obtain the dianhydride (5) under
two different reaction conditions: (i) increasing the molar equiva-
lents of maleic anhydride and p-chloranil used and (ii) reacting the
formed benzo[ghi]perylenetriimide again with maleic anhydride
using similar reaction conditions. Unfortunately, no product was
realized in either of the reaction conditions performed. This was
presumably due to the presence of the electron-withdrawing group
in the 1,12 position that deactivates the benzo[ghi]perylene nucleus
preventing the formation of the dianhydride [33]. Additional efforts
were also taken towards the bromination of benzo[ghi]perylene-
triimide at the 6 or 7 position by refluxing with chlorinated sol-
vents and using a catalytic amount of Lewis acids such as AlCl3,
Silica or FeCl3. However, no conditions resulted in the formation of
the desired product. This could also be attributed to the deactivated
aromatic core. The solid monoanhydride (3) obtained from the
Diels-Alder reaction was poorly soluble in common organic sol-
vents at room temperature and hence used directly in the next step
after being washed with copious amount of methanol, ethyl acetate
and acetone. The condensation reaction with the amines was per-
formed in DMF and imidazole as the solvent at 140 ꢀC and 160 ꢀC
respectively. A relatively higher yield was obtained when DMF was
used owing to the higher solubility of the anhydride 3 (Table 1). All
of the compounds (4a-4g) were isolated as a yellow solid and were
readily soluble in chlorinated solvents, ethyl acetate, THF and DMF
at room temperature. The synthesized compounds were charac-
terized by 1H NMR spectroscopy. The optical and electrochemical
properties of the target compounds were determined by UVeVis,
fluorescence and cyclic voltammetric studies.
4e
4f
10 h
3 h
58
63
4g
3 h
64
2.2. NMR spectroscopy
The 1H NMR spectra for the target compounds (4a-4g) recorded
in CDCl3 are shown in Fig 1. The structure of substituted BPTIs was
confirmed by the presence of three distinct downfield signals
characteristic of the benzoperylene core. The “Ha” protons appear
as a singlet between 10.07 and 10.45 ppm. The chemical shift of the
Ha protons for alkyl-substituted BPTIs appear slightly downfield
relative to those of the aryl-substituted BPTIs. The “Hb” and “Hc”
protons of all the BPTIs exhibit two separate doublets existing be-
tween 8.96 and 9.37 ppm with 4c being an exception in which case
a singlet peak equivalent to four protons was obtained. The aro-
matic proton signals for the corresponding R group were dispersed
between 7.0 and 8.7 ppm depending on the substituents attached
in the para position of the phenyl group. Compounds 4a-4f display
one common multiplet at 5.2 ppm for the methine protons present
in 3-aminopentane group. However, the two methine protons
present in 4g can be clearly distinguished by the existence of two
separate multiplets (Hd ¼ 5.7 ppm e R) and (He ¼ 5.2 ppm, 3-
Scheme 1. Synthesis of benzo[ghi]perylenetriimides.

L.C.K. Viswanath et al. / Dyes and Pigments 134 (2016) 453e458
455
Fig. 1. 1H NMR spectra of benzo[ghi]perylenetriimide derivatives in CDCl3.
aminopentane) in the spectra. Compound 4f also showed an
additional singlet at 5.15 ppm corresponding to the methylene
protons of benzylamine.
imide region has only a slight effect on the optical properties of the
benzo[ghi]perylenetriimides.
2.4. Fluorescence spectroscopy
2.3. Steady-state absorption spectroscopy
Emission spectra of the target compounds were measured upon
excitation at the lmax of the compounds (4a-4d: l463; 4e: l464; 4f,
4g: l461). The emission spectra of compounds 4a, 4e and 4g, along
with PDI in THF are shown in Fig. 2b and summarized in Table 2
(emission spectra of 4b, 4c, 4d and 4f are provided in the
Supplementary Information). As expected from the absorption re-
sults, compounds 4a-4g exhibited similar emission characteristics.
The emission bands were approximate mirror images of the cor-
responding absorption bands with a Stokes shift of approximately
20 nm. The aryl-substituted imides (4a-4e) showed a maximum
emission peak at 485 nm while the alkyl-substituted compounds
display a slight red shift of ~4 nm (481 nm). Moreover the emission
spectra reveal another intense band centered around 505 nm along
with a shoulder peak existing around 545 nm. No significant effects
were realized in the emission spectra by changing the solvent.
Combining the absorption and emission spectral data, it can be
concluded that the properties of the benzo[ghi]perylenetriimides
are not drastically affected by the nature of the substituents
attached in the imide region.
The electronic absorption data of compounds 4a-4g were
measured in CH2Cl2 or THF and were compiled in Table 2. Fig. 2a
compares the electronic absorption spectra of BPTIs 4a, 4e and 4g
to that of free PDI, 2. PDI exhibits an absorption spectrum with two
intense bands at 523 nm and 488 nm along with a shoulder peak at
457 nm. Compared to the absorption spectral pattern of PDI, the
BPTIs exhibited a hypsochromic shift of about 58 nm. All of the
target compounds exhibited three bands characteristic of the benzo
[ghi]perylene core (l at 465, 435 and 410 nm). A small hyp-
sochromic shift of about 2 nm occurred for alkyl substituted BPTIs
4f and 4g, which could be attributed to the extended conjugation
present in the aryl-substituted compounds. Changing to a relatively
polar solvent, CH2Cl2 had only a minor effect on the absorption
maximum (lmax) displaying a slight bathochromic shift (aryl
substituted ¼ 465 nm; alkyl substituted ¼ 464 nm). Hence, it can be
concluded that incorporation of an alkyl- or aryl-substituent in the
Table 2
2.5. Electrochemical measurements
Spectroscopic data of benzo[ghi]perylenetriimides.
Entry lmax (CH2Cl2) nm lmax (THF) nm lemi (CH2Cl2) nm lemi (THF) nm
As a means to identify and compare the redox properties of the
benzo[ghi]perylenetriimides, electrochemical measurements were
performed using cyclic voltammetry. The respective values for the
corresponding reductions, optical band gap, and HOMO and LUMO
values are depicted in Table 3. Fig. 3 gives the typical voltammo-
grams of compounds 4c, 4e, 4f and PDI. All of the benzo[ghi]per-
ylenetriimides exhibited three reversible reductions with the
exception of NO2 substituted BPTI showing additional reduction
4a
4b
4c
465
465
465
465
464
464
464
523
463
463
463
463
464
461
461
521
485
485
485
485
484
484
484
476
481
481
571
4d
4e
4f
485
488
481
4g
PDI
481
537,573

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L.C.K. Viswanath et al. / Dyes and Pigments 134 (2016) 453e458
a)
b)
1200
1
0.8
0.6
0.4
0.2
0
1000
800
4a
4a
600
4e
4e
4g
4g
PDI
400
PDI
200
0
400
450
500
550
600
650
700
750
350
400
450
500
550
600
Wavelength/nm
Wavelength/nm
Fig. 2. (a) UVeVis spectra (b) emission spectra of benzo[ghi]perylenetriimides in CH2Cl2 at room temperature.
Table 3
Electrochemical potentials and electronic energy levels of benzo[ghi]perylenetriimides.
1E1/2 (V vs Ag/AgCl)
2E1/2 (V vs Ag/AgCl)
3E1/2 (V vs Ag/AgCl)
4E1/2 (V vs Ag/AgCl)
ELUMOb (eV)
EHOMO (eV)
a
c
Entry
Eg (eV)
4a
4b
4c
4d
4e
4f
2.6
2.6
2.6
2.6
2.5
2.6
2.6
2.3
ꢁ0.574
ꢁ0.571
ꢁ0.589
ꢁ0.643
ꢁ0.616
ꢁ0.564
ꢁ0.562
ꢁ0.444
ꢁ0.820
ꢁ0.822
ꢁ0.719
ꢁ0.838
ꢁ0.841
ꢁ0.819
ꢁ0.726
ꢁ0.642
e
ꢁ1.265
ꢁ1.293
ꢁ1.178
ꢁ1.297
ꢁ1.323
ꢁ1.280
ꢁ1.297
e
ꢁ3.82
ꢁ3.82
ꢁ3.89
ꢁ3.75
ꢁ3.78
ꢁ3.83
ꢁ3.88
ꢁ3.96
ꢁ6.42
ꢁ6.42
ꢁ6.49
ꢁ6.35
ꢁ6.28
ꢁ6.43
ꢁ6.48
ꢁ6.26
ꢁ0.918
e
ꢁ1.028
ꢁ0.998
e
e
e
4g
PDI
a
Eg ¼ (Eabs þ Eem)/2 ¼ optical band gap [22].
ELUMO ¼ 4.4eV-Ered1.
b
c
EHOMO ¼ ELUMO-Eg.
peaks. Two of the reversible reductions (ꢁ0.4 V and ꢁ0.64 V) can be
attributed to the PDI core and are slightly negatively shifted with
respect to those of PDI.
Organics), were purchased from commercial suppliers and used as
received or as specified. Reactions were monitored by thin layer
chromatography (TLC) on silica gel GF plates (Analtech, No. 21521)
and visualized using a hand-held UV lamp. Column chromatog-
raphy was carried out on silica gel (Sorbent Technologies, 230e400
mesh). Elemental analyses ( 0.4%) were performed by Atlantic
Microlabs, Inc., Norcross, GA 30071.
The difference in the reduction potential between PDI and BPTI
ranges from 0.06 V (4c) to 0.19 V (4d). A gradual shift of the onset
potential to a more positive value was realized while moving from
aryl-substituted BPTIs (ꢁ0.64 V) to alkyl-substituted BPTIs
(ꢁ0.56 V). This indicates that the alkyl-substituted derivatives
possess a stronger electron accepting properties than the aryl-
substituted derivatives. Of all the haloaryl-substituted BPTIs, the
bromophenyl derivative exhibited a more positive onset potential
(ꢁ0.50 V) demonstrating a relatively more efficient electron
acceptor behavior. The band gaps for all of the BPTI derivatives were
calculated to be 2.6 eV with an exception for 4e, the nitrophenyl
derivative (2.5 eV) in which case, additional reduction peaks were
observed. Based on the obtained electrochemical measurements, it
can be confirmed that the benzo[ghi]triimides exhibit excellent
acceptor properties that could be potentially applicable in the
development of organic solar cells.
Spectroscopic measurements
1H NMR spectra was measured at 400 MHz in CDCl3. Chemical
shifts (d) are referenced to internal (CH3)4Si and coupling constants
(J) are given in Hz. FT-IR spectra were run as thin film on NaCl disks
using dichloromethane. UV/Vis absorption and Fluorescence
emission spectra were recorded on a Cary Eclipse UVeViseNIR
spectrophotometer in dichloromethane and THF.
Electrochemical measurements
Cyclic voltammograms were recorded on a CH instrument
(Model: CHI 6017E) by using a three-electrode system. A glassy
carbon was used as the working electrode. A platinum wire served
as the counter electrode, and Ag/AgNO3 was used as the reference
electrode. Ferroceneꢁferrocenium redox couple was used as an
internal standard. The voltammograms were performed in CH2Cl2
with 0.1 M TBPF6 as the supporting electrolyte and at 100 mVꢁ1
scan rate. All solutions were purged prior to electrochemical
measurements using nitrogen gas.
3. Experimental section
General
Compounds perylenetetracarboxylic dianhydride, benzylamine,
3-aminopentane, phenylethylamine (Sigma Aldrich), p-fluoroani-
line, p-bromoaniline, p-chloroaniline, p-iodoaniline, p-nitroaniline,
(TCI America), nitrobenzene, (Alfa Aeser), imidazole (Acros

L.C.K. Viswanath et al. / Dyes and Pigments 134 (2016) 453e458
457
2.90E-04
2.40E-04
1.90E-04
1.40E-04
9.00E-05
4.00E-05
-1.00E-05
-6.00E-05
-1.10E-04
4c
4f
4e
PDI
0.8
0.3
-0.2
-0.7
-1.2
-1.7
-2.2
Potential V vs Ag/AgNO3
Fig. 3. Cyclic Voltammograms of BPTIs and PDI in CH2Cl2 with 0.1 M TBPF6 as supporting electrolyte at scan rate 100 mVꢁ1
.
4. Synthesis of compound 3
7.43e7.34 (m, 2H), 5.30e5.15 (m, 2H), 2.46e2.32 (m, 4H),
2.12e2.02 (m, 4H), 1.04 (t, J ¼ 7.2 Hz, 12H); Anal. Calcd for
To a stirred mixture of compound 2 (0.5 g, 9.0 mmol) in
nitrobenzene (10 mL) in a 50 mL round bottomed flask were
charged p-chloranil (1.75 g, 7.0 mmol), maleic anhydride (13.3 g,
130.0 mmol) and heated to 220 ꢀC under argon atmosphere for
24 h. The progress of the reaction was continuously monitored by
UVevis spectroscopy for the disappearance of the absorption
band at 523 nm in CH2 Cl2 corresponding to the starting material
2. The reaction mixture was cooled to room temperature and
filtered. The resulting solid was made into a slurry with a 1:1
mixture of methanol and ethyl acetate (250 mL) for 30 min and
collected the solid by filtration. The filter cake thus obtained was
washed with acetone to yield a yellow solid. The yellow crude
material was directly taken to the next step without any
purification.
C44H32FN3O6: C, 73.63; H, 4.49; N, 5.85. Found: C, 73.29; H, 4.10; N,
5.32.
N1,N2-Bis(3-pentyl)-N3-(4-chlorophenyl)-benzo[ghi]perylene-2,3,
8,9,11,12-hexacarboxylic triimide BPTI-4b: Reaction time: 6 h;
Yield: 93 mg (68%) as a yellow solid, m.p > 300 ꢀC; IR: 1713, 1665,
1317, 811 cmꢁ1; 1H NMR (CD2Cl2, 400 MHz):
d (ppm) 10.07 (s, 2H),
9.03 (d, J ¼ 8.2 Hz, 2H), 8.96 (d, J ¼ 8.2 Hz, 2H), 7.77 (d, J ¼ 8.2 Hz,
2H), 7.66 (d, J ¼ 8.2 Hz, 2H), 5.17 (quintet, J ¼ 7.2 Hz, 2H), 2.43e2.32
(m, 4H), 2.14e2.04 (m, 4H), 1.07 (t, J ¼ 7.2 Hz, 12H); Anal. Calcd for
C44H32ClN3O6: C, 71.98; H, 4.39; N, 5.72. Found: C, 71.75; H, 4.25; N,
5.92.
N1,N2-Bis(3-pentyl)-N3-(4-bromophenyl)-benzo[ghi]perylene-2,3,
8,9,11,12-hexacarboxylic triimide BPTI-4c: Reaction time: 6 h;
Yield: 99 mg (69%) as a yellow solid, m.p > 300 ꢀC; IR: 1712, 1664,
1317, 811 cmꢁ1; 1H NMR (CD2Cl2, 400 MHz):
d (ppm) 10.14 (s, 2H),
9.09 (s, 4H), 7.81 (d, J ¼ 8.2 Hz, 2H), 7.69 (d, J ¼ 8.2 Hz, 2H), 5.18
(quintet, J ¼ 7.2 Hz, 2H), 2.43e2.32 (m, 4H), 2.12e2.03 (m, 4H), 1.06
(t, J ¼ 7.4 Hz, 12H); Anal. Calcd for C44H32BrN3O6: C, 67.87; H, 4.14;
N, 5.40. Found: C, 67.96; H, 3.98; N, 5.25.
4.1. A general procedure for the synthesis of substituted benzo[ghi]
perylenetriimides (4a-4g)
The anhydride (0.24 mmol) and the corresponding amines
(0.72 mmol) were dissolved in 5 mL of DMF and heated in a round
bottomed flask at 140 ꢀC for 3e10 h. The progress of the reaction
was monitored by TLC using hexane:CH2Cl2 as the eluent. After
completion of the reaction, the reaction mixture was evaporated to
dryness. The solid obtained was dissolved in CH2Cl2 and washed
with brine, dried with Na2SO4, filtered and evaporated to yield a
yellow solid.
N1,N2-Bis(3-pentyl)-N3-(4-iodophenyl)-benzo[ghi]perylene-2,3,
8,9,11,12-hexacarboxylic triimide BPTI-4d: Reaction time: 7 h;
Yield: 96 mg (62%) as a yellow solid, m.p > 300 ꢀC; IR: 1713, 1664,
1317, 810 cmꢁ1; 1H NMR (CD2Cl2, 400 MHz):
d (ppm) 10.25 (s, 2H),
9.17 (d, J ¼ 8.1 Hz, 2H), 9.10 (d, J ¼ 8.1 Hz, 2H), 8.01 (d, J ¼ 8.1 Hz, 2H),
7.55 (d, J ¼ 8.1 Hz, 2H), 5.19 (quintet, J ¼ 7.1 Hz, 2H), 2.45e2.32 (m,
4H), 2.13e2.02 (m, 4H), 1.04 (t, J ¼ 7.3 Hz, 12H); Anal. Calcd for
C44H32IN3O6: C, 64.01; H, 3.91; N, 5.09. Found: C, 64.21; H, 3.75; N,
N1,N2-Bis(3-pentyl)-N3-(4-fluorophenyl)-benzo[ghi]perylene-2,3,
8,9,11,12-hexacarboxylic triimide BPTI-4a: Reaction time: 6 h;
Yield: 86 mg (63%) as a yellow solid, m.p > 300 ꢀC; IR: 1712, 1667,
5.15.
N1,N2-Bis(3-pentyl)-N3-(4-nitrophenyl)-benzo[ghi]perylene-2,3,
8,9,11,12-hexacarboxylic triimide BPTI-4e: Reaction time: 10 h;
Yield: 81 mg (58%) as a yellow solid, m.p > 300 ꢀC; IR: 1720, 1661,
1317, 811 cmꢁ1; 1H NMR (CD2Cl2, 400 MHz):
d
(ppm) 10.29 (s, 2H),
9.19 (d, J ¼ 8.0 Hz, 2H), 9.12 (d, J ¼ 8.0 Hz, 2H), 7.70e7.73 (m, 2H),

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L.C.K. Viswanath et al. / Dyes and Pigments 134 (2016) 453e458
1521, 1350, 1318, 812 cmꢁ1 1H NMR (CD2Cl2, 400 MHz):
; d (ppm)
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10.28 (s, 2H), 9.21 (d, J ¼ 8.5 Hz, 2H), 9.14 (d, J ¼ 8.5 Hz, 2H), 8.56 (d,
J ¼ 8.6 Hz, 2H), 8.09 (d, J ¼ 8.6 Hz, 2H), 5.20 (quintet, J ¼ 7.3 Hz, 2H),
2.44e2.33 (m, 4H), 2.11e2.03 (m, 4H), 1.05 (t, J ¼ 7.4 Hz, 12H); Anal.
Calcd for C44H32N4O8: C, 70.96; H, 4.33; N, 7.52. Found: C, 71.22; H,
4.19; N, 7.26.
N1,N2-Bis(3-pentyl)-N3-(benzyl)-benzo[ghi]perylene-2,3,8,9,11,12-
hexacarboxylic triimide BPTI-4f: Reaction time: 3 h; Yield: 84 mg
(63%) as a yellow solid, m.p > 300 ꢀC; IR: 1709,1664,1317, 811 cmꢁ1
;
1H NMR (CD2Cl2, 400 MHz):
d (ppm) 10.38 (s, 2H), 9.34 (d,
J ¼ 8.4 Hz, 2H), 9.15 (d, J ¼ 8.4 Hz, 2H), 7.63 (d, J ¼ 7.6 Hz, 2H), 7.38
(d, J ¼ 7.6 Hz, 2H), 7.31 (t, J ¼ 7.0 Hz, 1H), 5.22e5.18 (m, 2H), 5.15 (s,
2H), 2.44e2.33 (m, 4H), 2.10e2.0 (m, 4H), 1.01 (t, J ¼ 7.4 Hz, 12H);
Anal. Calcd for C45H35N3O6: C, 75.72; H, 4.94; N, 5.89. Found: C,
75.46; H, 5.03; N, 5.66.
N1,N2-Bis(3-pentyl)-N3-(1-phenylethyl)-benzo[ghi]perylene-2,3,8,
9,11,12-hexacarboxylic triimide BPTI-4g: Reaction time: 3 h; Yield:
87 mg (64%) as a yellow solid, m.p > 300 ꢀC; IR: 1717, 1664,
1317 cmꢁ1; 1H NMR (CD2Cl2, 400 MHz):
d (ppm) 10.45 (s, 2H), 9.37
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(d, J ¼ 8.4 Hz, 2H), 9.16 (d, J ¼ 8.4 Hz, 2H), 7.70 (d, J ¼ 7.7 Hz, 2H),
7.39 (d, J ¼ 7.5 Hz, 2H), 7.27 (t, J ¼ 7.0 Hz, 1H), 5.86 (q, J ¼ 7.3 Hz, 1H),
5.23e5.15 (m, 2H), 2.43e2.31 (m, 4H), 2.18 (d, J ¼ 8.5 Hz, 3H),
2.08e2.00 (m, 4H), 1.00 (t, J ¼ 7.4 Hz, 12H); Anal. Calcd for
C
46H37N3O6: C, 75.91; H, 5.12; N, 5.77. Found: C, 75.78; H, 5.36; N,
5.92.
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5. Conclusion
In conclusion, we have successfully synthesized a novel series of
benzo[ghi]perylenetriimides incorporating an alkyl- or aryl-
substituent in the third imide region. The optical properties of
the BPTIs as examined by steady state spectroscopic peak mea-
surements revealed a maximum absorption around 465 nm. The
electron transfer abilities as estimated by cyclic voltammetric ex-
periments revealed a more positive onset potential for alkyl-
substituted derivatives relative to the aryl-substituted BPTIs. The
synthesized BPTIs demonstrated better solubility than perylene
diimides in common organic solvents such as ethyl acetate,
dichloromethane, methanol, DMF and THF. The synthesized benzo
[ghi]perylenetriimides could be of considerable importance in the
development of organic solar cells.
Acknowledgements
This work was supported by the Faculty Development Grants
from Oklahoma Baptist University. The authors greatly acknowl-
edge the support provided by Department of Chemistry at Okla-
homa State University for accessing the NMR facilities. The authors
also thank Dr. K.D. Berlin for his valuable guidance towards this
research work.
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Appendix A. Supplementary data
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Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.dyepig.2016.07.031.
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