Synthesis and photophysical properties of phosphorus(v) porphyrins functionalized with axial carbazolylvinylnaphthalimides

Article abstract of DOI:10.1039/c2ob26478a

We have synthesized new D-A-D type phosphorus(v) porphyrin derivatives 1 and 2 functionalized with axial carbazolylvinylnaphthalimide units. The absorption bands of the obtained phosphorus(v) porphyrins were in the range 250-640 nm with high molar absorption coefficients, meaning strong light-harvesting abilities. Notably, it is found that the devices based on phosphorus(v) porphyrins with a configuration structure of [ITO/PEDOT:PSS/ organic active film/LiF/Al] give an incident-photon-to-current conversion efficiency (IPCE) response. The maximal IPCE value reaches 2.76% for the device based on compound 2, which is much higher than that of 0.20% for compound 1. The reason might be due to the low oxidation potential and the strong light-harvesting ability of the enlarged conjugation of the axial units in compound 2. Therefore, we deduced that photo-induced electron transfer happened in phosphorus(v) porphyrins bearing axial conjugated donor units, which would make them good candidates for photovoltaic materials that could be applied in solar cells.

Full text of DOI:10.1039/c2ob26478a

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PAPER
Synthesis and photophysical properties of phosphorus(V) porphyrins
functionalized with axial carbazolylvinylnaphthalimides†
Yong Zhan,a Kaiyu Cao,a Chenguang Wang,a Junhui Jia,a Pengchong Xue,a Xingliang Liu,a Xuemei Duanb
and Ran Lu*a
Received 28th July 2012, Accepted 12th September 2012
DOI: 10.1039/c2ob26478a
We have synthesized new D-A-D type phosphorus(V) porphyrin derivatives 1 and 2 functionalized with
axial carbazolylvinylnaphthalimide units. The absorption bands of the obtained phosphorus(V) porphyrins
were in the range 250–640 nm with high molar absorption coefficients, meaning strong light-harvesting
abilities. Notably, it is found that the devices based on phosphorus(V) porphyrins with a configuration
structure of [ITO/PEDOT : PSS/organic active film/LiF/Al] give an incident-photon-to-current conversion
efficiency (IPCE) response. The maximal IPCE value reaches 2.76% for the device based on compound
2, which is much higher than that of 0.20% for compound 1. The reason might be due to the low
oxidation potential and the strong light-harvesting ability of the enlarged conjugation of the axial units in
compound 2. Therefore, we deduced that photo-induced electron transfer happened in phosphorus(V)
porphyrins bearing axial conjugated donor units, which would make them good candidates for
photovoltaic materials that could be applied in solar cells.
that dichloride 5,10,15,20-tetraphenyl phosphorus(V) porphyrin
Introduction
[P(TPP)Cl2]+ is an axial-bonding block, in which the phos-
In recent years, various conjugated porphyrins have been widely
employed as building blocks for photo-active and electro-active
materials due to their excellent light-harvesting abilities and
potential applications in molecular electronics, photochemical
energy conversion and storage.1–3 In order to realize artificial
molecular systems for photoenergy conversion and photo-
electronic operation, natural photosynthesis systems are very
useful examples, and various mimetic systems containing
porphyrins have been synthesized.4–6 So far most of the por-
phyrin arrays reported have been synthesized via typical organic
reaction sequences carried out at meso- or/and β-positions in
porphyrin rings.7–13 However, less attention has been paid to an
“axial covalent bonding” strategy in fabricating functional por-
phyrins, although novel photoelectric properties and functional-
ities would be afforded when the conjugated groups are attached
to the axial positions of the porphyrin ring. It has been known
phorus(V) porphyrin core is a strong electron acceptor and the
P–Cl bonds are reactive toward phenols and alcohols.14 There-
fore, the central phosphorus atom could be connected to desired
conjugated moieties in order to construct novel porphyrin arrays.
For example, Segawa and co-workers reported the competition
between photo-induced energy transfer and electron transfer
from an excited pyrene to the phosphorus(V) porphyrin core.15
Maiya and co-workers have investigated the intramolecular elec-
tron and energy transfer processes in D-A type phosphorus(V)
porphyrins.16 Our group has prepared phosphorus(V) porphyrins
bearing carbazole-based dendrons in axial positions, which are
nonfluorescent due to the electron transfer from dendritic carba-
zoles to the phosphorus(V) porphyrin core.17 However, the
absorption of the oligocarbazole is located in the high-energy
region,18,19 which would limit its light-harvesting ability towards
most visible light. In order to enlarge the absorption wavelength
range of phosphorus(V) porphyrins, herein, naphthalimide units
are introduced as the linker between carbazole and phosphorus(V)
porphyrin. In this work, new D-A-D type phosphorus(V)
porphyrins 1 and 2 (Chart 1) with strong light-harvesting abi-
lities have been synthesized. It is interesting that the device
based on phosphorus(V) porphyrin 2 with a configuration struc-
ture of [ITO/PEDOT : PSS/organic active film/LiF/Al] gives an
obvious incident-photon-to-current conversion efficiency (IPCE)
response to the visible light. We suggested that photo-induced
electron transfer occurred in the synthesized phosphorus(V)
porphyrins bearing axial conjugated donor units, which would
aState Key Laboratory of Supramolecular Structure and Materials,
College of Chemistry, Jilin University, Changchun 130012, P. R. China.
E-mail: luran@mail.jlu.edu.cn; Fax: +86-431-88923907;
Tel: +86-431-88499179
bState Key Laboratory of Theoretical and Computational Chemistry,
Institute of Theoretical Chemistry, Jilin University, Changchun 130021,
P. R. China
†Electronic supplementary information (ESI) available: UV-vis absorp-
tion and fluorescence spectra; cyclic voltammetry diagrams; 1H NMR,
13C NMR, and MALDI/TOF MS spectra of new compounds. See DOI:
10.1039/c2ob26478a
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compounds 4 and 5 afforded compound 6, catalyzed by
Pd(OAc)2 at 110 °C for 12 h in a yield of 76%.21 Similarly, com-
pound 7 was obtained through a Wittig reaction between com-
pound 6 and methyltriphenylphosphoniumiodine in a yield of
78%. After that, compounds 8 and 9 with methoxy terminal
groups were generated from compounds 5 and 7, respectively, by
Heck reactions with 4-bromo-N-(4′-methoxyphenyl)-1,8-
naphthalimide22 in yields of 72% and 65%.23 The precursors 10
and 11 for the syntheses of phosphorus(V) porphyrin derivatives
1 and 2 were easily prepared from compounds 8 and 9, respect-
ively, by the cleavage of methoxy in the presence of tribromo-
borane at −78 °C in dry dichloromethane in yields of 92% and
65%.24a Finally, the nucleophilic substitution reactions of the
phenols 10 and 11 with dichloride 5,10,15,20-tetraphenyl phos-
phorus(V) porphyrin24b–e in dry pyridine afforded phosphorus(V)
porphyrins functionalized with axial carbazolylvinylnaphthali-
mides 1 and 2 in yields of 71% and 60%.25 Similarly, reference
compound 12 was prepared from phenol and dichloride
5,10,15,20-tetraphenyl phosphorus(V) porphyrin in dry pyri-
dine.26 All the intermediates and the final products were purified
by column chromatography, and the new compounds were
Chart 1 The molecular structures of phosphorus(V) porphyrins 1
and 2.
make them become good candidates for photovoltaic materials
that could be applied in solar cells.
Result and discussion
Synthesis and characterizations
The synthetic routes for phosphorus(V) porphyrins functionalized
with axial carbazolylvinylnaphthalimides (1 and 2) are sketched
in Schemes 1 and 2. Firstly, 9-octyl-9H-carbazole-3-carbalde-
hyde (3) was prepared from 9-octyl-9H-carbazole under Vilsme-
ier reaction condition,20a and the iodination of compound 3 gave
6-iodo-9-octyl-9H-carbazole-3-carbaldehyde (4).20b Meanwhile,
compound 3 was transformed into 9-octyl-3-vinyl-9H-carbazole
(5) via Wittig reaction with methyltriphenylphosphoniumiodine
in a yield of 90%.20c Then, the Heck reaction between
1
characterized with FT-IR, H NMR, 13C NMR, elemental analy-
sis, and MALDI/TOF mass or HRMS spectroscopy. From the
FT-IR spectra of the compounds 1, 2, 8–11, we could find the
vibration absorption bands appeared at ca. 960 cm−1 arising
from the wagging vibration of the trans-double bond (CHvCH),
and the bands at ca. 860 cm−1 for compounds 1 and 2
were ascribed to the wagging vibration of P–O. In addition, the
Scheme 1 Syntheses of carbazolylvinylnaphthalimides 10 and 11. (a) POCl3, DMF, ClCH2CH2Cl, reflux; (b) KI, KIO3, AcOH, 80 °C; (c)
[Ph3PCH3]+I−, t-BuOK, THF, 0 °C to rt; (d) Pd(OAc)2, K2CO3, DMF, Bu4NBr, 110 °C; (e) BBr3, CH2Cl2, −78 °C to rt.
8702 | Org. Biomol. Chem., 2012, 10, 8701–8709
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obvious absorptions in the range of 300–400 nm for compounds
1 and 2 compared with the very weak ones for compound 1229b
mainly originate from the units of carbazolylvinylnaphthali-
mides. The other absorption bands in the range of 460–540 nm
for compounds 1 and 2 are due to the intramolecular charge
transfer (ICT) transition from carbazole to naphthalimide in the
axial positions of the phosphorus(V) porphyrins, which can be
confirmed by the solvent-dependent absorption and fluorescent
emission spectra of compound 8, the axial-functionalized moiety
in compound 1. As shown in Fig. S1 (see ESI†), it is clear that
the absorption band of compound 8 at ca. 420 nm in hexane red-
shifts with increasing the polarity of the solvents, and reaches
ca. 455 nm in DMF. On the other hand, in the nonpolar solvents,
such as hexane and cyclohexane, the fluorescence spectra of
compound 8 give vibration structures, and the maximal emission
bands are located at ca. 485 nm. As the polarity of the solvents
increases, the emission band becomes broader and obviously
red-shifts, for instance, the emission red-shifts to ca. 650 nm in
DMF. Therefore, it indicates an intramolecular charge-transfer
(ICT) character for the excited state of the axial-functionalized
moieties in the synthesized phosphorus(V) porphyrins.29c
Notably, the synthesized phosphorus(V) porphyrins 1 and 2 show
several absorption bands in the range 250–640 nm with high
molar absorption coefficients (Table S1†, for example, ε (M−1
cm−1) = 7.69 × 104 for 300 nm, 8.20 × 104 for 350 nm, 1.66 ×
105 for 440 nm), meaning strong light-harvesting abilities, which
is of importance in photovoltaic materials. In addition, we can
find from Fig. S2a† that the UV-vis absorption spectrum for
compound 1 can be regarded as the superposition of the ones of
compounds 8 and 12. Similar absorption spectral behavior can
also be detected for compound 2 (Fig. S2b†). It indicates that the
electronic coupling between the axial substituted chromophores
and the phosphorus(V) porphyrin cores in compounds 1 and 2 in
the ground state should be neglected. Notably, there is no distinct
shift of the Soret and Q bands of compounds 1 and 2 compared
with those of 12, meaning that the electronic structures of the
phosphorus(V) porphyrin cores may not change with increasing
the conjugation of the axial functional groups. The absorption
spectra of 1 and 2 in the films obtained through spinning the
chloroform solutions (2.0 × 10–3 M) onto quartz slides are
Scheme 2 Syntheses of phosphorus(V) porphyrins 1, 2 and 12.
1H NMR spectra of compounds 1 and 2 also confirmed that
the vinyl groups adopted the trans-conformation on account of
the absence of the signal at ∼6.5 ppm assigned to the proton
in the cis-double bond (CHvCH).27,28 On the other hand, the
disappearance of the internal H signal of the porphyrin rings
indicated the formation of the phosphorus(V) porphyrins. The
obtained phosphorus(V) porphyrins 1 and 2 were readily dis-
solved in common organic solvents, including dichloromethane,
chloroform, toluene, tetrahydrofuran, etc.
UV-vis absorption and fluorescent spectra
The normalized UV-vis absorption spectra of the phosphorus(V)
porphyrins 1, 2 and 12 in chloroform are shown in Fig. 1 and
the data are listed in Table S1 (ESI†). We can find two Q-bands
at ca. 564 nm and 610 nm for compounds 1 and 2, which are
similar to those of the reference compound 12, suggesting the
formation of phosphorus(V) porphyrins.29a In addition, the Soret
bands for compounds 1, 2 and 12 appear at ca. 440 nm. The
Fig. 1 Normalized UV-vis absorption spectra of the phosphorus(V)
porphyrins 1, 2 and 12 in chloroform (5.0 × 10−6 M).
Fig. 2 Fluorescence emission spectra of the phosphorus(V) porphyrins
1, 2 and 12 in CHCl3 (5.0 × 10−6 M, λex = 570 nm).
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shown in Fig. S3 (see ESI†). It is clear that the Soret bands of
compounds 1 and 2 in the films red-shift to 450 nm and 448 nm,
respectively, from 440 nm in chloroform, which might be due to
the aggregation in the solid state. The smaller red-shift of the
Soret band in compound 2 compared with that in compound 1
might result from a larger site-isolation effect of the more extended
conjugated carbazolylvinylene units on the porphyrin core.30
Fig. 2 shows the fluorescence emission spectra of 1, 2 and 12
in CHCl3 (5.0 × 10−6 M). When excited at 570 nm, which can
selectively excite the phosphorus(V) porphyrin core instead of
the carbazolylvinylnaphthalimide units, compound 12 gives
strong emission at 618 nm and 669 nm. However, the emission
at ca. 619 nm and ca. 670 nm coming from the phosphorus(V)
porphyrin cores in compounds 1 and 2 at the same concentration
is obviously weaker than that of compound 12, suggesting that
the attachment of carbazolylvinylnaphthalimides to the axial
positions of phosphorus(V) porphyrins might impart a fast deacti-
vation of the porphyrin’s singlet excited state through electron
transfer,31 which will be discussed below.
and LUMO in the synthesized D-A-D type phosphorus(V)
porphyrins makes it possible that photo-induced electron transfer
might occur from the donors to the phosphorus(V) porphyrin
rings.32
Electrochemical properties
To estimate the HOMO level of the phosphorus(V) porphyrins,
cyclic voltammetry has been employed using a three-electrode
cell and an electrochemistry workstation (CHI 604). A platinum
button is used as the working electrode, a platinum wire as the
counter electrode and Ag/AgCl as the reference electrode under
a N2 atmosphere. The cyclic voltammetry (CV) diagrams of
compounds 1 and 2 in dichloromethane with Bu4NBF4 as the
supporting electrolyte are shown in Fig. S4†, and the corres-
ponding electrochemical data are listed in Table 1. The redox
potential of Fc/Fc+, which possesses an absolute energy level of
−4.8 eV relative to the vacuum level for calibration, is located at
0.66 eV at a scan rate of 100 mV s−1. Therefore, the evaluation
of the HOMO and LUMO energy levels could be estimated
according to the following equations:
Molecular orbital calculations
HOMO ðeVÞ ¼ ꢀðEox þ 4:14Þ eV
LUMO ðeVÞ ¼ ꢀðEred þ 4:14Þ eV
where Eox and Ered are the measured potentials relative to the
standard calomel electrode (SCE). As a result, the HOMO
energy levels are −5.35 eV and −5.13 eV for compounds 1 and
2, respectively. The higher HOMO energy level for compound 2
compared with that of compound 1 suggests that the electron-
donating ability would be enhanced by increasing the length of
the conjugation in axial functional carbazolylvinylnaphthalimide
units.
ð1Þ
ð2Þ
The frontier orbital plots of the highest occupied molecular
orbital (HOMO and HOMO − 1) and the lowest unoccupied
molecular orbital (LUMO) of compounds 1 and 2 have been cal-
culated on the optimized structure by using density functional
theory (DFT). As shown in Fig. 3 and Table 1, the orbital distri-
butions of HOMO and HOMO − 1 for compounds 1 and 2 are
localized on the carbazole units and the neighboring naphthal-
imide rings, and the energy difference between HOMO and
HOMO − 1 is very small (0.03 eV for compound 1, 0 eV for
compound 2). The electron densities of the LUMO are primarily
located on the phosphorus(V) porphyrin cores. Therefore, the
strong electron density relocation between HOMO (or HOMO − 1)
Photovoltaic characterizations
To confirm the occurrence of the photo-induced electron transfer
in D-A-D type phosphorus(V) porphyrins 1 and 2, devices with a
configuration structure of [ITO/PEDOT : PSS/organic active film/
LiF/Al] have been fabricated. The photovoltaic data are obtained
using a 150 W xenon light source that is focused to give
100 mW cm−2, the equivalent of one sun at AM 1.5, at the
surface of the test device. The IPCE values are determined with
2 nm intervals. The IPCE spectrum is recorded as a function of
the excitation wavelength. As shown in Fig. 4, the IPCE
response of the device based on compound 1 is quite low, and
Fig. 3 The frontier orbital plots of the HOMO − 1, HOMO and
LUMO for compounds 1 and 2.
Table 1 Electrochemical data and energy levels of phosphorus(V) porphyrins 1 and 2
Potential (E1/2) V versus SCE
Compound
Oxidationa
Reductionb
Egc (eV)
HOMOd (eV)
HOMO − 1/HOMO/LUMOe (eV)
1
2
1.21
0.99
0.59
0.59
1.95
1.96
−5.35
−5.13
−6.32/−6.29/−4.64
−5.61/−5.61/−4.72
a Ground state oxidation potential (first oxidation peak) of the compounds were measured in CH2Cl2 with ferrocene/ferrocenium (Fc/Fc+) as an
internal reference. b Ground state reduction potential (first reduction peak). c Eg was determined from the edge of the absorption spectrum. d HOMO
(eV) = −(Eox + 4.14) eV. e The energy levels of HOMO − 1, HOMO and LUMO versus vacuum were given after geometrical optimization.
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solvent and tetramethylsilane (TMS) as the standard. UV-vis
absorption spectra were determined on a Shimadzu UV-1601PC
spectrophotometer. Photoluminescence (PL) spectra were carried
out on a Shimadzu RF-5301 luminescence spectrometer. FT-IR
spectra were measured using a Germany Bruker vertex 80v
FT-IR spectrometer by incorporating samples in KBr disks.
Mass spectra were performed on Agilent 1100 MS series and
AXIMA CFR MALDI/TOF (Matrix assisted laser desorption
ionization/Time-of-flight) MS (COMPACT). HRMS spectra were
determined on a 1290-microTOF Q II spectrograph (Agilent).
C, H and N analyses were taken on a Perkin–Elmer 240C
elemental analyzer. Cyclic voltammetry (CV) was performed
using a CHI 604B electrochemical working station in CH2Cl2
containing 0.1 M Bu4NBF4 as a supporting electrolyte at room
temperature. A platinum button was used as a working electron
and a platinum wire as a counter electrode. The potentials were
recorded versus Ag/AgCl (saturated) as a reference electrode.
The scan rate was maintained at 100 mV s−1. The IPCE spectral
output of the lamp was matched with the aid of a Mega-9 AM
1.5 sunlight filter so as to reduce the mismatch between the
simulated and the true solar spectrum. A similar data acquisition
system was used to control the IPCE measurement. Under full
computer control, light from a 250 W halogen lamp was focused
through a high throughput monochromator (Omni-150) onto the
photovoltaic device under test. THF was refluxed with sodium
and benzophenone. DMF was distilled from phosphorous
pentoxide. Pyridine and dichloromethane were dried by CaH2,
and other chemicals were used as received without further
purification.
Fig. 4 IPCE spectra of the devices based on the phosphorus(V) por-
phyrins 1 and 2.
the highest IPCE value is 0.20% at the Soret band. However, the
device based on compound 2 gives an obvious photovoltaic
response, the IPCE spectrum is similar to the absorption one,
and the highest IPCE value reaches 2.76% at the Soret band.
The reason that the device based on compound 2 shows a more
efficient photovoltaic response to visible light than 1 might be
due to the lower oxidation potential of the more extended conju-
gated axial carbazolylvinylnaphthalimide units, which might
lower the energy level of the charge separated state.33 In
addition, the stronger light-harvesting ability of compound 2
than 1 might be helpful for the enhanced IPCE response.
Notably, the IPCE response of the devices suggests that the elec-
tron transfer from the axial carbazolylvinylnaphthalimide
units to the phosphorus(V) porphyrin cores in compounds 1
and 2 indeed happens under illumination.34 Therefore, the
phosphorus(V) porphyrins might be good candidates for photo-
voltaic materials that could be applied in solar cells due to their
broad absorption in the visible region.35
Synthetic procedures and characterizations
4-Bromo-N-(4′-methoxyphenyl)-1,8-naphthalimide, dichloride
5,10,15,20-tetraphenyl phosphorus(V) porphyrin and compound
12 were synthesized according to the reported procedures.22,36,37
9-Octyl-9H-carbazole-3-carbaldehyde (3). Phosphoryl chlo-
ride (6.12 g, 40 mmol) was added slowly to dry DMF (5 mL) at
0 °C, and the mixture was stirred for 1 h at room temperature.
Then, a solution of 9-octyl-9H-carbazole (5.6 g, 20 mmol) in
1,2-dichloroethane (30 mL) was added. After stirring at room
temperature for another 1 h, the mixture was refluxed for 10 h.
Finally, the solution was cooled to room temperature and poured
into 300 mL water. The mixture was extracted with CH2Cl2 (3 ×
50 mL), the organic phase was collected and washed with brine,
and then dried with anhydrous MgSO4. After the solvent was
removed, the crude product was purified by column chromato-
graphy (silica gel) with petroleum ether/ethyl acetate (v/v = 6/1)
as eluent, followed by recrystallization in petroleum ether
(60–90 °C) to give a pale yellow solid in a yield of 75%. Mp:
Conclusions
In summary, the phosphorus(V) porphyrins 1 and 2 bearing axial
carbazolylvinylnaphthalimide moieties have been synthesized.
It is found that a photo-induced electron transfer occurs from
the donors of the carbazolylvinylnaphthalimide to the acceptor
of the phosphorus(V) porphyrin core. The IPCE maximum of
2.76% is achieved for the device based on compound 2, which is
much higher than that of 1 due to the lower oxidation potential
and the strong light-harvesting ability of the extended conju-
gation of the axial units. Therefore, phosphorus(V) porphyrins
functionalized with axial conjugated units might become good
candidates for photovoltaic materials that could be applied in
solar cells.
1
60.0–62.0 °C. H NMR (300 MHz, TMS, CDCl3): δ = 10.07 (s,
1H), 8.58 (s, 1H), 8.13 (d, J = 7.5 Hz, 1H), 7.98 (d, J = 8.7 Hz,
1H), 7.54–7.49 (m, 1H), 7.43 (d, J = 7.8 Hz, 2H), 7.33–7.28 (m,
1H), 4.31–4.27 (m, 2H), 1.91–1.81 (m, 2H), 1.33–1.23 (m,
10H), 0.85 (t, J = 6.6 Hz, 3H) (see Fig. S5†); IR (KBr, cm−1):
2920, 2360, 2030, 1600, 1380, 1140, 1070, 995, 864, 619, 515;
Elemental analysis calculated for C21H25NO: C 82.04, H 8.20,
N 4.56. Found C 81.86, H 8.26, N 4.65; MS, m/z: cal: 307.4,
found 308.5 (Fig. S6†).
Experimental section
Materials and measurements
1H NMR spectra were recorded on a Mercury plus 500 MHz and
600 MHz, and Varian 300 MHz using CDCl3 or DMSO-d6 as
the solvents. 13C NMR spectra were recorded on a Mercury plus
125 MHz and Varian 75 MHz at 298 K using CDCl3 as the
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6-Iodo-9-octyl-9H-carbazole-3-carbaldehyde (4). Compound
3 (3.07 g, 10 mmol) was dissolved in 50 mL glacial acetic acid,
and then KI (1.1 g, 6.7 mmol) and KIO3 (0.86 g, 4 mmol) were
added. The mixture was stirred at 80 °C until I2 was fully con-
sumed. After that, the mixture was cooled to room temperature,
and a yellow solid appeared. The solid was collected by fil-
tration, and then poured into 5% NaHSO3 (300 mL) to clear
KIO3. The resulting precipitate was filtered off, followed by
recrystallization in ethanol to afford white solid in a yield of
8.27 (d, J = 1.0 Hz, 1H), 8.15 (d, J = 8.0 Hz, 1H), 8.02–8.00
(m, 1H), 7.76 (m, 1H), 7.72 (m, 1H), 7.49–7.32 (m, 7H), 7.25
(s, 1H), 4.33–4.28 (m, 4H), 1.92–1.84 (m, 4H), 1.40–1.24 (m,
20H), 0.88–0.85 (m, 6H) (see Fig. S9†); IR (KBr, cm−1): 3130,
2920, 2030, 1600, 1380, 1070, 995, 951, 862, 621, 515;
Elemental analysis calculated for C43H50N2O: C 84.55, H 8.25,
N 4.59. Found C 84.37, H 8.17, N 4.43; MS, m/z: cal: 610.9,
found 610.8 (Fig. S10†).
1
9-Octyl-3-((E)-2-(9-octyl-9H-carbazol-6-yl)vinyl)-6-vinyl-9H-
carbazole (7). Compound 7 was prepared from compound 6 fol-
lowing the similar procedure for compound 5 in a yield of 78%
as a white solid. Mp: 110.0–112.0 °C. 1H NMR (500 MHz,
TMS, CDCl3): δ = 8.27 (s, 2H), 8.16 (m, 2H), 7.72 (m, 2H),
7.58 (m, 1H), 7.47 (m, 1H), 7.40 (m, 3H), 7.36 (t, J = 5.5 Hz,
3H), 7.33 (s, 1H), 6.96–6.90 (m, 1H), 5.80 (d, J = 17.5 Hz, 1H),
5.22 (d, J = 11.5 Hz, 1H), 4.31–4.26 (m, 4H), 1.86 (m, 4H),
1.35–1.25 (m, 20H), 0.88–0.85 (m, 6H) (see Fig. S11); IR (KBr,
cm−1): 3130, 2360, 2020, 1600, 1380, 1070, 951, 860, 619, 515;
Elemental analysis calculated for C44H52N2: C 86.79, H 8.61,
N 4.60. Found C 86.53, H 8.52, N 4.63; MS, m/z: cal: 608.9,
found 608.5 (Fig. S12†).
76%. Mp: 106.0–108.0 °C. H NMR (300 MHz, TMS, CDCl3):
δ = 10.08 (s, 1H), 8.52 (d, J = 1.2 Hz, 1H), 8.44 (d, J = 1.5 Hz,
1H), 8.02 (m, 1H), 7.76 (m, 1H), 7.46 (d, J = 8.7 Hz, 1H), 7.22
(d, J = 8.7 Hz, 1H), 4.28 (t, J = 7.2 Hz, 2H), 1.90–1.80 (m, 2H),
1.34–1.22 (m, 10H), 0.85 (t, J = 3.6 Hz, 3H); IR (KBr, cm−1):
2920, 1690, 1620, 1590, 1280, 1130, 885, 808, 775; Elemental
analysis calculated for C21H24INO: C 58.21, H 5.58, N 3.23.
Found C 57.96, H 5.44, N 3.35; MS, m/z: cal: 433.3, found
434.0.
9-Octyl-3-vinyl-9H-carbazole (5). Potassium tert-butoxide
(1.75 g, 15.6 mmol) was added to a solution of triphenylmethyl-
phosphonium iodine (7.9 g, 19.5 mmol) in anhydrous THF
(40 mL). After the mixture was stirred for 20 min at room
temperature, 9-octyl-9H-carbazole-3-carbaldehyde 3 (4.00 g,
13.0 mmol) was added at 0 °C. Then, the mixture was stirred at
room temperature for another 2 h, followed by pouring into
300 mL water. The mixture was extracted with CH2Cl2 (3 ×
50 mL), and the organic phase was collected and washed with
brine. Then, it was dried with anhydrous MgSO4. After the
solvent was removed, the residue was purified by column
chromatography (silica gel) with petroleum ether (60–90 °C) as
eluent to afford 3.58 g (90%) of compound 5 as colorless oil.
1H NMR (300 MHz, TMS, CDCl3): δ = 8.16 (t, J = 7.5 Hz, 2H),
7.63 (d, J = 7.8 Hz, 1H), 7.51 (d, J = 4.8 Hz, 1H), 7.52–7.42
(m, 2H), 7.29 (d, J = 2.7 Hz, 1H), 7.03–6.93 (m, 1H), 5.85 (d,
J = 17.4 Hz, 1H), 5.27 (d, J = 11.1 Hz, 1H), 4.30 (t, J = 7.2 Hz,
2H), 1.92–1.88 (m, 2H), 1.38–1.25 (m, 10H), 0.94 (t, J =
4.8 Hz, 3H) (see Fig. S7†); IR (KBr, cm−1): 3050, 2930, 2850,
1600, 1490, 1350, 1230, 1150, 987, 887, 806, 748, 735, 546;
Elemental analysis calculated for C22H27N: C 86.51, H 8.91,
N 4.59. Found C 86.40, H 8.78, N 4.80; MS, m/z: cal: 305.5,
found 305.2 (Fig. S8†).
4-[(E)-2-(9-Octyl-9H-carbazol-3-yl)vinyl]-N-(4′-methoxyphenyl)-
1,8-naphthalimide (8). A mixture of 9-octyl-3-vinyl-9H-carba-
zole 5 (1.45 g, 4.75 mmol), 4-bromo-N-(4′-methoxy phenyl)-
1,8-naphthalimide (1.65 g, 4.32 mmol), anhydrous potassium
carbonate (1.19 g, 8.64 mmol), tetrabutylammonium bromide
(1.53 g, 4.75 mmol), and Pd(OAc)2 (12 mg) in dry DMF
(10 mL) was stirred under nitrogen atmosphere at 110 °C for
12 h. Then, the mixture was cooled to room temperature and
poured into 300 mL water with stirring. The resulting precipitate
was filtered off and washed with water. The crude product was
purified by column chromatography (silica gel) with dichloro-
methane/petroleum ether (60–90 °C) (v/v = 3/1) as eluent, fol-
lowed by recrystallization in a dichloromethane/petroleum ether
(60–90 °C) mixture to afford an orange-yellow solid in a yield of
1
72%. Mp: 216.0–218.0 °C. H NMR (300 MHz, TMS, CDCl3):
δ = 8.74–8.63 (m, 3H), 8.37 (d, J = 1.2 Hz, 1H), 8.16 (d, J =
7.8 Hz, 1H), 8.07 (d, J = 7.8 Hz, 1H), 7.96 (d, J = 15.9 Hz, 1H),
7.85–7.79 (m, 2H), 7.60 (d, J = 15.9 Hz, 1H), 7.54–7.43 (m,
3H), 7.29 (m, 2H), 7.24 (m, 1H), 7.09 (m, 1H), 7.06 (t, J =
2.4 Hz, 1H), 4.33 (t, J = 7.2 Hz, 2H), 3.88 (d, J = 2.1 Hz, 3H),
1.96–1.86 (m, 2H), 1.46–1.26 (m, 10H), 0.89–0.82 (m, 3H) (see
Fig. S13†); IR (KBr, cm−1): 3130, 2920, 2030, 1600, 1380,
1170, 1070, 995, 953, 862, 619, 517; Elemental analysis calcu-
lated for C41H38N2O3; C 81.16, H 6.31, N 4.62. Found C 81.08,
H 6.25, N 4.73; MS, m/z: cal: 606.8, found 607.6 (Fig. S14†).
9-Octyl-6-((E)-2-(9-octyl-9H-carbazol-6-yl)vinyl)-9H-carbazole-
3-carbaldehyde (6). A mixture of 6-iodo-9-octyl-9H-carbazole-
3-carbaldehyde 4 (2.0 g, 4.62 mmol), 9-octyl-3-vinyl-9H-carba-
zole 5 (1.55 g, 5.08 mmol), anhydrous potassium carbonate
(1.28 g, 9.24 mmol), tetrabutylammonium bromide (1.64 g,
5.08 mmol), and Pd(OAc)2 (12 mg) in dry DMF (30 mL) under
nitrogen atmosphere was stirred at 110 °C for 12 h. Then, the
mixture was cooled to room temperature and poured into
300 mL water with stirring. After extraction with CH2Cl2 (3 ×
50 mL), the organic phase was washed with brine and dried with
anhydrous MgSO4. The solvent was removed and the residue
was purified by column chromatography (silica gel) with petro-
leum ether/CH2Cl2 (v/v = 2/3) as eluent, followed by recrystalli-
zation in THF/EtOH to afford a yellow solid in a yield of 76%.
4-[(E)-2-(9-Octyl-9H-6-((E)-2-(9-octyl-9H-carbazol-3-yl)vinyl)-
carbazol-3-yl)vinyl]-N-(4′-methoxyphenyl)-1,8-naphthalimide (9).
According to the synthetic procedure of compound 8, compound
9 was prepared from compound 7 and 4-bromo-N-(4′-methoxy
phenyl)-1,8-naphthalimide in a yield of 65% as a deep red solid.
1
Mp: 228.0–230.0 °C. H NMR (300 MHz, TMS, CDCl3): δ =
8.75 (d, J = 8.4 Hz, 1H), 8.69 (d, J = 6.9 Hz, 1H), 8.65 (d, J =
3.9 Hz, 1H), 8.42 (s, 1H), 8.33 (s, 1H), 8.28 (d, J = 1.2 Hz, 1H),
8.14 (d, J = 7.5 Hz, 1H), 8.09 (d, J = 7.8 Hz, 1H), 7.98 (d, J =
15.9 Hz, 1H), 7.86–7.71 (m, 4H), 7.61 (d, J = 15.9 Hz, 1H),
7.51–7.46 (m, 2H), 7.51–7.38 (m, 7H), 7.28 (d, J = 2.1 Hz, 1H),
1
Mp: 109.0–111.0 °C. H NMR (500 MHz, TMS, CDCl3): δ =
10.11 (s, 1H), 8.64 (d, J = 1.0 Hz, 1H), 8.31 (d, J = 1.0 Hz, 1H),
8706 | Org. Biomol. Chem., 2012, 10, 8701–8709
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7.25–7.23 (m, 2H), 4.35–4.28 (m, 4H), 3.88 (s, 3H), 1.94–1.87
(m, 4H), 1.41–1.26 (m, 20H), 0.90–0.85 (m, 6H) (see
Fig. S15†); IR (KBr, cm−1): 3130, 2920, 2030, 1600, 1380,
1170, 1070, 995, 951, 860, 621, 517; Elemental analysis calcu-
lated for C63H63N3O3: C 83.13, H 6.98, N 4.62. Found C 82.89,
H 6.76, N 4.74; MS, m/z: cal: 910.2, found 910.8 (Fig. S16†).
8.50 (d, J = 7.2 Hz, 2H), 8.45 (d, J = 7.8 Hz, 2H), 8.33 (s, 2H),
8.14 (d, J = 7.8 Hz, 2H), 8.00 (d, J = 7.8 Hz, 2H), 7.91–7.88
(m, 10H), 7.82 (d, J = 3.6 Hz, 12H), 7.79–7.75 (m, 4H),
7.73–7.71 (m, 1H), 7.56 (d, J = 15.6 Hz, 2H), 7.53–7.51 (m,
1H), 7.50 (s, 1H), 7.49 (s, 1H), 7.44 (t, J = 7.2 Hz, 4H), 7.28 (d,
J = 7.2 Hz, 4H), 5.97 (d, J = 7.8 Hz, 4H), 4.33–4.30 (m, 4H),
1.92–1.88 (m, 4H), 1.34–1.24 (m, 20H), 0.86 (t, J = 6.9 Hz, 6H)
(see Fig. S21†); 13C NMR (75 MHz, CDCl3): δ = 163.9, 163.7,
149.0, 148.8, 142.8, 141.0, 140.9, 139.4, 137.0, 134.6, 134.1,
133.5, 133.4, 131.4, 130.8, 130.7, 130.0, 129.6, 129.5, 128.9,
128.7, 128.4, 127.5, 126.5, 126.1, 125.0, 123.3, 123.2, 122.7,
122.6, 120.4, 120.1, 120.0, 119.7, 119.3, 117.5, 115.1, 115.0,
109.2, 109.0, 43.2, 31.7, 29.3, 29.0, 28.9, 27.2, 22.5, 14.0 (see
Fig. S22†); IR (KBr, cm−1): 3140, 2910, 2440, 2030, 1600,
1380, 1170, 1070, 951, 860, 546, 515; Elemental analysis calcu-
lated for C124H98ClN8O6P: C 79.96, H 5.30, N 6.02. Found
C 79.78, H 5.26, N 6.12; MS, m/z: cal: 1827.1 [M+ − Cl],
found 1827.6 [M+ − Cl] (Fig. S23†); HRMS cal: 1827.1287
[M+ − Cl], found: 1826.7260 [M+ − Cl] (Fig. S24†).
4-[(E)-2-(9-Octyl-9H-carbazol-3-yl)vinyl]-N-(4′-hydroxyphenyl)-
1,8-naphthalimide (10). A solution of BBr3 in anhydrous
CH2Cl2 (1 M, 4 mL) was added dropwise to a solution of com-
pound 8 (1.5 g, 2.47 mmol) in dry CH2Cl2 (50 mL) at −78 °C
under a nitrogen atmosphere. The resulting solution was stirred
at −78 °C for 2 h, and was then gradually warmed to room temp-
erature. After the mixture was stirring at room temperature for
another 15 h, it was poured into 300 mL water with stirring to
quench excess BBr3. After extraction with CH2Cl2 (3 × 50 mL),
the organic phase was washed with water and dried with anhy-
drous MgSO4. The solvent was removed and the residue was
purified by column chromatography (silica gel) with dichloro-
methane/methanol (v/v = 40/1) to afford a red power in a yield
of 92%. Mp: 222.0–224.0 °C. 1H NMR (300 MHz, TMS,
CDCl3): δ = 8.72–8.62 (m, 3H), 8.36 (s, 1H), 8.15 (d, J =
7.5 Hz, 1H), 8.06 (d, J = 7.8 Hz, 1H), 7.94 (d, J = 15.9 Hz, 1H),
7.83–7.78 (m, 2H), 7.60 (d, J = 15.6 Hz, 1H), 7.54–7.48 (m,
1H), 7.43 (d, J = 8.4 Hz, 2H), 7.17–7.11 (m, 2H), 6.89–6.87 (m,
1H), 6.85–6.84 (m, 1H), 6.21 (s, 1H), 4.31 (t, J = 7.5 Hz, 2H),
1.94–1.85 (m, 2H), 1.40–1.26 (m, 10H), 0.87 (t, J = 6.9 Hz, 3H)
(see Fig. S17†); IR (KBr, cm−1): 3380, 3130, 2360, 2020, 1600,
1380, 1070, 995, 953, 862, 620, 515; Elemental analysis calcu-
lated for C40H36N2O3: C 81.05, H 6.21, N 4.73. Found C 80.87,
H 6.12, N 4.65; MS, m/z: cal: 592.7, found 593.3 (Fig. S18†).
Di[4-[(E)-2-(9-Octyl-9H-6-((E)-2-(9-octyl-9H-carbazol-3-yl)vinyl)-
carbazol-3-yl)vinyl]-N-(4′-hydroxyphenyl)-1,8-naphthalimide]-
5,10,15,20-tetraphenylporphyrinato phosphorus(V) chloride (2).
Compound 2 was prepared from compounds 11 (1.2 g,
1.33 mmol) and dichloride 5,10,15,20-tetraphenyl phosphorus(V)
porphyrin (0.1 g, 0.13 mmol) under similar reaction conditions
for the synthesis of compound 1 except the reaction time was
prolonged to 12 h, and the crude product was purified by
column chromatography (silica gel) with dichloromethane/
methanol (v/v = 12/1) as eluent to afford a black solid in a yield
1
of 60%. Mp: >250 °C. H NMR (600 MHz, TMS, CDCl3): δ =
9.16 (s, 8H), 8.70 (d, J = 8.4 Hz, 2H), 8.50 (d, J = 7.2 Hz, 2H),
8.46 (d, J = 7.2 Hz, 2H), 8.37 (s, 2H), 8.30 (s, 2H), 8.25 (s, 2H),
8.12 (d, J = 7.8 Hz, 2H), 8.01 (d, J = 7.2 Hz, 2H), 7.90 (s, 10H),
7.82 (s, 14H), 7.76 (t, J = 10.2 Hz, 4H), 7.72 (t, J = 10.2 Hz,
4H), 7.56 (d, J = 15.6 Hz, 2H), 7.47 (t, J = 7.2 Hz, 3H),
7.43–7.40 (m, 9H), 7.36 (d, J = 6.0 Hz, 4H), 7.23 (d, J = 7.2 Hz,
2H), 5.98 (d, J = 8.4 Hz, 4H), 4.30 (m, 8H), 1.93–1.86 (m, 8H),
1.33–1.25 (m, 40H), 0.86 (t, J = 7.2 Hz, 12H) (see Fig. S25†);
13C NMR (125 MHz, CDCl3): δ = 164.0, 163.8, 149.1, 148.9,
142.8, 141.4, 140.9, 140.4, 140.1, 139.5, 137.1, 134.7, 134.2,
133.6, 131.5, 131.4, 130.8, 130.1, 129.7, 129.6, 129.0, 128.8,
128.5, 127.7, 127.6, 126.7, 125.3, 124.9, 124.2, 123.5, 123.3,
123.2, 122.9, 120.4, 120.2, 120.1, 119.7, 118.9, 118.9, 118.3,
118.2, 117.6, 115.2, 109.4, 108.9, 43.4, 43.2, 31.8, 29.7, 29.4,
29.2, 29.0, 27.3, 22.6, 14.1 (see Fig. S26†); IR (KBr, cm−1):
3140, 2920, 2440, 2020, 1600, 1380, 1170, 1070, 951, 860, 546,
515; Elemental analysis calculated for C68H148ClN10O6P:
C 81.71, H 6.04, N 5.67. Found C 81.59, H 5.86, N 5.69; MS,
m/z: cal: 2434.0 [M+ − Cl], found 2434.5 [M+ − Cl] (Fig. S27†);
HRMS cal: 2434.0099 [M+ − Cl], found: 2434.0588 [M+ − Cl]
(Fig. S28†).
4-[(E)-2-(9-Octyl-9H-6-((E)-2-(9-octyl-9H-carbazol-3-yl)vinyl)-
carbazol-3-yl)vinyl]-N-(4′-hydroxyphenyl)-1,8-naphthalimide (11).
By following the synthetic procedure for compound 10, com-
pound 11 was prepared from compound 9 (2.2 g, 2.4 mmol),
and the crude product was purified by column chromatography
(silica gel) with CH2Cl2/MeOH (v/v = 35/1) as eluent to afford a
1
red powder in a yield of 65%. Mp: 224.0–226.0 °C. H NMR
(300 MHz, TMS, DMSO-d6): δ = 9.65 (s, 1H), 8.70 (d, J =
9.6 Hz, 1H), 8.39–8.31 (m, 2H), 8.22 (d, J = 6.9 Hz, 1H), 8.19
(s, 1H), 8.07 (s, 1H), 7.93–7.55 (m, 7H), 7.41–7.25 (m, 6H),
7.06 (s, 4H), 6.86 (s, 4H), 4.09 (s, 4H), 1.71–1.48 (m, 4H), 1.10
(s, 20H), 0.75–0.67 (m, 6H) (see Fig. S19†); IR (KBr, cm−1):
3380, 3130, 2920, 2020, 1600, 1380, 1170, 1070, 995, 953, 860,
619, 515; Elemental analysis calculated for C62H61N3O3:C
83.09, H 6.86, N 4.69. Found C 82.78, H 6.67, N 4.87; MS,
m/z: cal: 896.2, found 896.5 (Fig. S20†).
Di[4-[(E)-2-(9-Octyl-9H-carbazol-3-yl)vinyl]-N-(4′ hydroxy-
phenyl)-1,8-naphthalimide]5,10,15,20-tetraphenylporphyrinato
phosphorus(V) chloride (1). Compound 10 (0.77 g, 1.3 mmol)
and dichloride 5,10,15,20-tetraphenyl phosphorus(V) porphyrin
(0.1 g, 0.13 mmol) were dissolved in dry pyridine (30 mL). The
mixture was refluxed for 8 h under a nitrogen atmosphere. The
solvent was evaporated, and the crude product was purified by
column chromatography (silica gel) with dichloromethane/
methanol (v/v = 15/1) as eluent to afford a black solid in a
yield of 71%. Mp: >250 °C. 1H NMR (600 MHz, TMS,
CDCl3): δ = 9.16 (d, J = 3.0 Hz, 8H), 8.69 (d, J = 8.4 Hz, 2H),
Theoretical calculation methods
The geometrical structures of compounds 1 and 2 were opti-
mized by employing the density functional theory at the B3LYP/
6-31 level with the Gaussian 03W program package. Molecular
orbitals were visualized using Gaussview.
This journal is © The Royal Society of Chemistry 2012
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Preparation of photovoltaic devices
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The device was fabricated on glass substrates pre-coated with
indium tin oxide (ITO) modified by a PEDOT : PSS (Clevios
P VP Al 4083) layer. The ITO-coated glass substrates were ultra-
sonicated for 20 min in toluene, acetone and Hellmanex soap
water (2%), followed by extensive rinsing and ultrasonication in
deionized water and isopropyl alcohol. The substrates were then
dried under IR radiation. After that, the ITO glass substrates
were spin-coated (3000 rpm, 60 s) with a PEDOT : PSS layer of
thickness about 20 nm and dried for 1 h at 90 °C in air on a hot
plate. The solutions for the active layer were prepared by dissol-
ving compounds 1 and 2 (10 mg) in chloroform (1 mL). The sol-
ution was then spin-cast at 1000 rpm on top of the PEDOT : PSS
layer. The optimized thicknesses of the active layers are 75 nm
for compound 1 and 60 nm for compound 2. Then, LiF (3 nm)
and Al (100 nm) layers were subsequently deposited on the
active layer under vacuum (5 × 10−4 Pa). The devices were
removed into a nitrogen glove-box and annealed by placing on
hot plates for 20 min at 70 °C. After annealing, the samples were
cooled to room temperature. Finally, the device of [ITO/PEDOT :
PSS/organic active film/LiF/Al] was fabricated.
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This work is financially supported by the National Natural
Science Foundation of China (20874034 and 51073068),
973 Program (2009CB939701), NSFC-JSPS Scientific
Cooperation Program (21011140069) and Open Project of State
Key Laboratory of Supramolecular Structure and Materials
(SKLSSM201203).
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