2,7,12,17-Tetra(2,5-thienylene)-substituted porphycenes

Article abstract of DOI:10.1142/S1088424619500743

We report syntheses of thiophene and dithiophene-substituted porphycenes (ThPc and DThPc) at 2,7,12,17-positions by McMurry coupling. The crystal structure of ThPc revealed that the porphycene plane shows a highly planar structure, and the dihedral angles between the porphycene core and thiophene are relatively small at 21deg and 18deg. ThPc and DThPc exhibit red-shifted and broadened absorption because of the extension of I conjugations through porphycene to the substituted thiophenes. We found that introduction of thiophene units onto porphycene results in decreasing the HOMO-LUMO differences effectively.

Full text of DOI:10.1142/S1088424619500743

Journal of Porphyrins and Phthalocyanines
J. Porphyrins Phthalocyanines 2019; 23: 898–907
DOI: 10.1142/S1088424619500743
Published at http://www.worldscinet.com/jpp/
2,7,12,17-Tetra(2,5-thienylene)-substituted porphycenes
Daiki Kuzuhara*a◊, Haruka Nakaokab, Kyohei Matsuob, Naoki Aratanib
and HirokoYamada*b◊
aFaculty of Science and Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551, Japan
bGraduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5 Takayama-cho,
Ikoma, Nara 630-0192, Japan
This paper is part of the 2019 Women in Porphyrin Science special issue.
Received 26 May 2019
Accepted 21 June 2019
ABSTRACT: We report syntheses of thiophene and dithiophene-substituted porphycenes (ThPc and
DThPc) at 2,7,12,17-positions by McMurry coupling. The crystal structure of ThPc revealed that the
porphycene plane shows a highly planar structure, and the dihedral angles between the porphycene core
and thiophene are relatively small at 21° and 18°. ThPc and DThPc exhibit red-shifted and broadened
absorption because of the extension of p conjugations through porphycene to the substituted thiophenes.
We found that introduction of thiophene units onto porphycene results in decreasing the HOMO–LUMO
differences effectively.
KEYWORDS: porphycene, thiophene, NIR absorption.
which is suitable for the synthesis of b-substituted por-
phycenes. The other is an acid-catalyzed homocoupling of
dipyrrolyl-ethane derivatives [24, 64], which is suitable for
thesynthesisofmeso-substitutedporphycenes.Amongthese,
the introduction of aryl groups to porphycene is simple and
effective to control the optical and electronic properties of
porphycenes. 2,7,12,17-Tetraphenylporphycene (b-PhPc)
[65, 66] and 9,10,19,20-tetraphenylporphycene (m-PhPc)
[67] have been reported. Comparing these two porphycenes,
absorption and fluorescence of b-PhPc are slightly red
shifted compared to m-PhPc because the phenyl rings of
m-PhPc are perpendicularly tilted in the crystal structure,
whereas b-PhPc forms relatively small dihedral angles
between porphycene and phenyl rings at 33° and 48°.
Inspired by these phenomena, we designed 2,7,12,17-
thiophene- and dithiophene-substituted porphycenes
(ThPc and DThPc, respectively) to achieve the creation
of p-expanded porphycenes (Fig. 1). Introductions of
thiophene units to porphyrins [68–70] and subporphyrins
[71, 72] are known to extend their p conjugations
efficiently to give unique optical and electrochemical
properties. In contrast, thiophene-substituted porphy-
cenes have not yet been reported except as core-modified
porphycenes. In this context, we report the synthesis
of ThPc and DThPc from corresponding diformylated
INTRODUCTION
Porphycene, which consists of two bipyrroles and
two ethylene bridges, is the first constitutional isomer of
porphyrin, as reported by Vogel in 1986 [1]. Compared to
porphyrin, porphycene shows specific optical properties
such as red-shifted absorption, relatively strong red-colored
fluorescence and efficient singlet oxygen generation [2,
3]. These properties allow us to apply it to photodynamic
therapy [4, 5], protein mimicry [6–9], catalysis [10, 11] and
materials sciences [12–18]. The mechanism of tautomerism
of the NH in the cavity has also been studied [19–24]. In
order to modify the optical and electronic properties of
porphycenes, various modification methods have been
reported [25, 26], such as metallations [27–35], alkylations
at pyrrolic b-positions and/or meso-positions [36–40],
dimerizations [18, 41], p expansions [42–47], introduc-
tions of functional groups [48–57], and core modifications
[58–63]. Porphycene is mainly synthesized by two methods.
One is the McMurry coupling of diformylated bipyrroles,
◊ SPP full member in good standing
*Correspondence to: Daiki Kuzuhara, tel.: +81-19-621-6351,
email: kuzuhara@iwate-u.ac.jp; Hiroko Yamada, tel.: +81 743-
72-6041, email: hyamada@ms.naist.jp.
Copyright © 2019 World Scientific Publishing Company

2,7,12,17-TETRA(2,5-THIENYLENE)-SUBSTITUTED PORPHYCENES
899
C6H13
NH
N
N
S
C6H13
N
H
N
N
H
N
n
S
n
HN
N
H
N
N
H
N
porphyrin
β-PhPc
S
N
H
N
N
H
N
C6H13
n
S
n
N
H
N
N
H
N
C6H13
ThPc: n = 1
DThPc: n = 2
porphycene
m-PhPc
Fig. 1. Structure of 2,7,12,17-tetrathienyl-porphycenes with reference compounds
EtO2C
X
EtO2C
EtO2C
H
I2, HIO3
Cu
toluene
N
EtO2C
CO2E
N
1,2-dichloroethane
AcOH, H2O
60%
CO2Et
I
CO2Et
N
N
H
H
H
X
CO2Et
3 (X = H)
4 (X = Br)
40%
1
2
NBS, DMF
71%
C6H13
C6H
EtO2C
S
n
S
n
C6H13
nBuMe3
S
H
H
N
Pd(PPh3)4
toluene
N
NaOH
(CH2OH)2
EtO2C
S
CO2Et
N
N
H
H
CO2Et
S
n
n
C6H13
C6H13
5 (79%): n = 1
6 (76%): n = 2
7 (96%): n = 1
8 (quant.): n = 2
C6H13
S
C6H13
C6H13
n
S
n
S
n
H
N
H
N
N
H
N
DMF, POCl3
Zn, TiCl4, CuCl
THF
N
OHC
S
CHO
N
H
S
n
C6H13
C6H13
n
S
n
9 (95%): n = 1
10 (89%): n = 2
C6H13
ThPc (18%): n = 1
DThPc (17%): n = 2
Scheme 1. Synthesis of 2,7,12,17-tetrathienyl-porphycenes
bipyrroles by McMurry coupling. The substitution of
thiophenes induces the efficient p extensions leading to
the NIR absorption properties
The starting material of diethyl 1H-pyrrole-2,4-dicar-
boxylate 1 was synthesized from ethyl propiolate and
ethyl 2-isocyanoacetate by a copper(I) oxide and 1,10-
phenanthroline mediated cyclization method [73]. The
iodination of 1 with iodine and HIO3 gave pyrrole 2 in
60% yield. Ullmann coupling of 2 provided 2,2-bipyrrole
3 in 40%, and then bromination with N-bromosuccinimide
(NBS) in DMF afforded 4 in 71% yield. The brominated
bipyrrole 4 is a key intermediate for introduction of the
thiophene and bithiophene moieties onto the bipyrrole
RESULTS AND DISCUSSION
Synthesis and characterization
The synthetic procedure of thiophene- and dithio-
phene-substituted porphycenes is shown in Scheme 1.
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J. Porphyrins Phthalocyanines 2019; 23: 899–907

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D. KUZUHARA ET AL.
Fig. 2. Crystal structure of ThPc. (a) top view and (b) side view. In the side view, the alkyl chains and hydrogen atoms are
omitted clarity. Thermal ellipsoids are shown at the 50% probability level. (c) packing structure, (d) transfer integrals for the nearest
neighboring molecular pairs
units. The crystal structure of 4 is shown in Fig. S1 in
the Supporting information. The Stille coupling of 4
with 5-hexyl-2-tributylstannyl-thiophene or tributyl(5′-
hexyl-[2,2′-bithiophen]-5-yl)stannane in the presence of
Pd(PPh3)4 gave 5 or 6 in 79% or 76% yields, respectively.
Bipyrroles 5 and 6 were decarboxylated with NaOH in
ethylene glycol at 170°C and formylated by Vilsmeier–
Haack reaction to give 9 and 10 in 95 and 89% yield,
respectively. Finally, McMurry coupling of 9 and 10 gave
the thiophene- and dithiophene-substituted porphycenes
ThPc and DThPc in 18% and 17% yields, respectively.
The synthesized porphycenes were characterized with
1H and 13C NMR spectroscopy and high-resolution mass
spectroscopy (HRMS), Figs S2–S13.
Figure2showsthecrystalstructureofThPc.Thesingle
crystal was obtained from a slow diffusion of isopropanol
into a chlorobenzene solution of ThPc. Thiophenes are
positioned as propeller-like structures. The porphycene
core forms a highly planar macrocyclic structure with
mean–plane deviation with respect to the macrocyclic
atoms of 0.021 Å. The dihedral angles between thienyl
groups and porphycene are 21° and 18°. Previously, we
reported the crystal structure of b-PhPc, with dihedral
angles between phenyl groups and porphycene core
at 48° and 33° [66]. These results indicated that the
whole of the molecular planarity of ThPc increases
compared with that of b-PhPc due to the small five-
membered ring unit of thiophene relative to benzene.
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2,7,12,17-TETRA(2,5-THIENYLENE)-SUBSTITUTED PORPHYCENES
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The inside N–N distances are 2.642 and 2.838 Å, which
degenerated HOMO and HOMO-1, and non-degenerated
LUMO and LUMO+1 because of its lower symmetric
structure. When thienyl groups are introduced on por-
phycene at 2,7,12,17-positions, the LUMO level is
comparable and the HOMO level increases to that of the
parent porphycene because the HOMO orbital of ThPc
is distributed on porphycene and thiophenes, resulting
in a decrease in the HOMO–LUMO difference. In the
case of DThPc, HOMO and LUMO levels are slightly
up and down, respectively, giving a smaller HOMO–
LUMO difference than that of ThPc. These trends are
consistent with results of the absorption spectra of ThPc
and DThPc. We also measured fluorescence spectra;
however, both ThPc and DThPc have no fluorescence,
even in degassed solutions.
To investigate the electrochemical properties of
ThPc and DThPc, cyclic voltammetry was measured
in benzonitrile containing 0.1 M tetrabutylammonium
hexafluorophosphate (TBAPF6) as a supporting electro-
lyte at room temperature (Fig. 5). ThPc shows one
irreversible oxidation peak at 0.52 V and two reversible
reduction peaks at -1.12 and -1.37 V (vs. ferrocene/
ferrocenium cation). DThPc also shows one irreversible
oxidation peak at 0.32 V and two reversible reduction
peaks at -1.05 and -1.27 V (vs. ferrocene/ferrocenium
cation). The resulting band-gap energies of ThPc
(1.60 V) and DThPc (1.37 V) are much smaller than
that of b-PhPc (1.80 V), indicating the extension of the
p conjugations through porphycene and thiophene units.
In conclusion, thiophene- and dithiophene-substituted
porphycenes, ThPc and DThPc, were successfully
synthesized by McMurry coupling from corresponding
diformyl-bipyrroles. The crystal structure revealed
that ThPc forms a highly planar structure through the
porphycene core to thiophenes because of less steric
hinderance between porphycene and thiophene units.
ThPc and DThPc exhibit the extension of the p
conjugations between porphycene and thiophene units,
resulting in the red-shifted absorption in NIR regions.
These results demonstrate that porphycene-based NIR
absorbing dyes can be used in practical applications for
PDT and non-linear optical materials. The optical and
electrochemical properties and herringbone-type packing
structures with high one-dimensional transfer integrals
of ThPc and DThPc signal superior performance as
organic semiconducting materials for organic solar cells
and transistors. Fabrication of solution-processed organic
field effect transistors to evaluate the charge carrier
mobility of Pc and DThPc is underway.
are comparable to that of b-PhPc (2.635 and 2.843 Å).
The stacking structure of ThPc is a herringbone pattern
and the intermolecular distance of each porphycene core
is 3.39 Å, which is slightly shorter than the sum of van
der Waals radii of carbon atoms. Intermolecular transfer
integral values between the HOMOs of neighboring
molecules were calculated with the Amsterdam density
functional (ADF) program package [74, 75]. Calculated
values are shown in Fig. 2d. The transfer integral value
is correlated to the charge carrier mobility and the
possibility of application for organic thin-film transistors.
Transfer integral values in the stacking direction (A and
E) are large (ca. 72 meV), whereas other directions are
negligible, indicating that ThPc is expected to exhibit
a one-dimensional transportation property. The transfer
integral of ThPc is similar to that of pentacene (79 meV)
[76], so that ThPc may work as a good semiconducting
material.
Electronic properties
Absorption spectra of ThPc and DThPc in CH2Cl2
are shown in Fig. 3. Generally, porphycene exhibits
slightly split strong Soret bands and three Q-band peaks
in the visible regions. ThPc and DThPc keep typical
porphycene-type absorption features. The ThPc shows
absorption peaks at 403 nm as broadened Soret bands and
at 601, 658 and 694 nm as Q-like bands. With additional
thiophene rings, DThPc shows red-shifted and broadened
absorption at 363, 424, 684 nm. In comparison of the
absorption property of b-PhPc, both Soret and Q bands
of ThPc and DThPc are significantly red shifted and
broadened because of the extension of the p conjugations.
These results indicate that thiophene moieties strongly
perturb the electronic property of porphycene. To evaluate
the electronic structures, DFT calculation was examined
at the B3LYP/6-31G** level. Geometry optimization
calculations were carried out using the structure of
ThPc′ and DThPc′ with methyl groups instead of hexyl
groups for simplicity. The molecular orbitals and energy
levels are illustrated in Fig. 4. The parent porphycene has
EXPERIMENTAL
General
Absorption spectra were measured with a JASCO
UV/vis/NIR Spectrophotometer V-670. H NMR and
Fig. 3. UV-vis-NIR absorption spectra of ThPc (red), DThPc
(blue) and b-PhPc (black dotted) in CH2Cl2
1
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D. KUZUHARA ET AL.
Pc
ThPc'
DThPc'
Fig. 4. Calculated energy diagrams and Kohn–Sham molecular orbitals of porphycene (Pc), ThPc′, and DThPc′ at the B3LYP/
6-31G** level
a JEOL JMS-700 MStation spectrometer. CV measure-
ment was conducted in a solution of 0.1 M TBAPF6
in dry benzonitrile with a scan rate of 100 mV s-1
in an argon-filled cell. A glassy carbon electrode and
a platinum wire were used as a working and a counter
electrode, respectively. Ag/AgNO3 electrodes were used
as reference electrodes, which were normalized with
the half-wave potential of the ferrocene/ferrocenium
(Fc/Fc+) redox couple. All solvents and chemicals were
reagent-grade quality, obtained commercially, and
used without further purification except as noted. For
spectral measurements, spectral-grade dichloromethane
was purchased from Nakalai Tesque Co. Thin-layer
chromatography (TLC), flush column chromatography,
and gravity column chromatography were performed on
Art. 5554 (Merck KGaA), Silica Gel 60 (Merck KGaA)
Fig. 5. Cyclic voltammograms of ThPc, DThPc and b-PhPc in
and Silica Gel 60N (Kanto Chemical Co.), respectively.
benzonitrile containing 0.1 M TBAPF6. Scan rate = 100 mV s-1
X-ray analysis
13C NMR spectra were recorded on a JNM-ECX 400
spectrometer (operating as 400 MHz for 1H and 100 MHz
for13C)usingtheresidualsolventastheinternalreference
for 1H (d = 7.26 ppm in CDCl3, d = 5.32 ppm in CD2Cl2,
and d = 2.50 ppm in DMSO-d6). Electrospray ionization
(ESI) mass spectra were recorded on a JEOL JMS-MS
T100LC spectrometer. Matrix-assisted laser desorption/
ionization (MALDI)-TOF-MS spectra were recorded
on a JEOL SpiralTOF JMS-S3000 spectrometer (JEOL
Akishima, Japan). FAB mass spectra were measured on
X-ray crystallographic data for ThPc was recorded
at 103 K on a Rigaku R-AXIS RAPID/S using Mo−Kα
radiation from the corresponding set of confocal optics.
The structures were solved by direct methods and refined
on F2 by full-matrix least-squares using the CrystalClear
and SHELXS−2000 programs [77].
Theoretical calculations
All density functional theory calculations were
achieved with the Gaussian 09 program package. The
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2,7,12,17-TETRA(2,5-THIENYLENE)-SUBSTITUTED PORPHYCENES
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geometry was optimized at the Becke’s three-parameter
(CH2Cl2) and recrystallized from CHCl3/MeOH to give
3 as white solids. Yield: 40% (3.53 g, 8.40 mmol). H
1
hybrid functional combined with the Lee−Yang−Parr
correlation functional abbreviated as the B3LYP level of
density functional theory with the 6-31G(d,p) basis set.
NMR (CDCl3; 400 MHz; Me4Si) dH, ppm 14.33 (s, 2H),
7.46 (s, 2H), 4.45–4.37 (m, 8H), 1.43–1.40 (t, 12H).
13C NMR (CDCl3; 100 MHz; Me4Si) dC, ppm 166.75,
160.40, 130.18, 122.65, 118.99, 113.76, 61.52, 60.94,
14.39, 14.30. HRMS (ESI): m/z = 443.1430. calcd for
C20H24N2NaO8: 443.14380 [M + Na]+.
Charge transfer integral calculation
Charge transfer integrals were calculated by the
fragment orbital method with the PW91/DZ2P level of
theory using the Amsterdam Density Functional (ADF)
program. Charge transfer integrals were obtained from
one of the disordered structures of ThPc with a larger
occupancy rate.
Tetraethyl 4,4′-dibromo-1H,1′H-[2,2′-bipyrrole]-3,-
3′,5,5′-tetracarboxylate (4). A solution of bipyrrole
3 (3.5 g, 8.4 mmol) and N-bromosuccinimide (4.5 g,
25 mmol) in DMF (170 ml) was heated at 100°C for
48 h under argon atmosphere. After cooling to room
temperature, the reaction was quenched with aqueous
NaHSO3. After removal of the solvent, the residue was
extracted with CH2Cl2. The extract was washed with 1 M
HCl, water and brine, and then dried over Na2SO4. After
removal of the solvent, the residue was purified by silica
gel column chromatography (CH2Cl2) and recrystallized
from CHCl3/hexane to give 4 as greenish-white solids.
Yield: 71% (3.4 g, 5.9 mmol). 1H NMR (CDCl3;
400 MHz; Me4Si) dH, ppm 14.31 (brs, 2H), 4.48 (q, J =
7 Hz, 4H), 4.43 (q, J = 7 Hz, 4H), 1.47 (t, J = 7 Hz, 6H),
1.44 (t, J = 7 Hz, 6H). 13C NMR (CDCl3; 100 MHz;
Me4Si) dC, ppm 166.63, 159.37, 129.21, 121.61, 114.72,
106.18, 62.38, 61.39, 14.33, 14.16. HRMS (ESI): m/z =
607.11848. calcd. for C28H28N2O8S2Na: 607.11867
[M + Na]+. Crystal data: C20H22Br2N2O8, Fw 578.21,
monoclinic, space group P21/c, a = 14.2510 (5), b =
5.51633 (16), c = 14.7039 (5) Å, b = 109.8223 (9),
V = 1087.43 (6) Å3, Z = 2, T = 103 K, Dcalc = 1.766 g cm-3,
GOF = 1.086, R1 (I > 2s(I)) = 0.0292 and wR2 = 0.0737
(all data), CCDC 1917992.
Tetraethyl 4,4′-bis(5-hexylthiophen-2-yl)-1H,1′H-
[2,2′-bipyrrole]-3,3′,5,5′-tetracarboxylate (5). A solution
of 4 (1.74 g, 3.0 mmol) and 5-hexyl-2-tributylstannyl-
thiophene (8.23 g, 18 mmol) in toluene (45 mL) was
degassed by bubbling with argon for 30 min. To the
resulting mixture was added Pd(PPh3)4 (376 mg,
0.30 mmol) and refluxed for 18 h. The solvent was
removed under reduced pressure. The crude product
was purified by column chromatography (10% K2CO3
in silica gel, hexane/CH2Cl2 9:1 to 1:9) to give 5 as
yellowish-white solids. Yield: 79% (1.78 g, 2.37 mmol).
1H NMR (CDCl3; 400 MHz; Me4Si) dH, ppm 14.10 (brs,
2H, –NH), 6.72 (d, 2H, J = 4 Hz), 6.70 (d, 2H, J = 4 Hz)
4.25 (q, 4H, J = 7 Hz), 4.14 (q, 4H, J = 7 Hz), 2.83 (t, 4H,
J = 7 Hz), 1.73–1.65 (m, 4H), 1.43–1.30 (m, 12H) 1.22
(t, 6H, J = 7 Hz), 0.97 (t, 6H, J = 7 Hz), 0.90 (t, 6H, J =
7.3 Hz). 13C NMR (CDCl3; 100 MHz; Me4Si) dC, ppm
167.50, 160.08, 145.96, 132.22, 128.92, 127.17, 126.36,
123.13, 121.73, 115.23, 61.33, 60.71, 31.99, 31.65,
30.16, 28.85, 22.65, 14.12, 13.96, 13.26. HRMS (ESI) :
m/z = 775.30628. calcd. for C40H52N2O8S2Na: 775.30472
[M + Na]+.
Synthesis
Diethyl 1H-pyrrole-2,4-dicarboxylate (1). To a 1,4-
dioxane solution (200 ml) of Cu2O (0.74 g, 5.1 mmol)
and 1,10-phenanthroline (1.82 g, 10 mmol) were
added ethyl propiolate (10.2 ml, 100 mmol) and ethyl
isocyanoacetate (12.0 ml, 110 mmol) under argon
atmosphere. The solution was stirred at 100°C for 1 h.
The reaction mixture was cooled to room temperature
and filtered through a short Florisil pad and concentrated.
The residue was purified by flash silica gel column
chromatography (hexane/AcOEt 20:1 to 3:1) to give 1
1
as white powder. Yield: 83% (17.5 g, 82.7 mmol). H
NMR (DMSO-d6; 400 MHz; Me4Si) dH, ppm 12.53 (brs,
1H), 7.56 (s, 1H), 7.07 (s, 1H), 4.28–4.17 (q + q, 4H),
1.31–1.25 (t + t, 6H). 13C NMR (DMSO-d6; 100 MHz;
Me4Si) dC, ppm 163.16, 159.90, 127.76, 123.40, 116.56,
115.09, 60.04, 59.38, 14.22, 14.18. HRMS (ESI): m/z =
211.09228. calcd for C10H14NO4:211.09299 [M + H]+.
Diethyl 5-iodo-1H-pyrrole-2,4-dicarboxylate (2). A
solution of 1 (12.1 g, 57.1 mmol), iodine (14.5 g,
57.2 mmol), HIO3 (2.63 g, 15.0 mmol), AcOH (78 ml) and
H2O (10 ml) in DCE (183 ml) was refluxed for 15 h. The
reaction was quenched with NaHSO3 aq. The separated
organic layer was washed with water, sat. NaHCO3 aq.
and brine, and then dried over Na2SO4. The solution was
removed under reduced pressure, then filtrated and rinsed
with 2-propanol. The crude product was purified by silica
gel column chromatography (CH2Cl2) and recrystallized
from CHCl3/2-propanol to give 2 as white crystals. Yield:
60% (11.56 g, 34.3 mmol). 1H NMR (DMSO-d6; 400 MHz;
Me4Si) dH, ppm 13.08 (s, 1H), 7.09 (s, 1H), 4.28–4.18 (m,
4H), 1.31–1.08 (t, 6H). 13C NMR (DMSO-d6; 100 MHz;
Me4Si) dC, ppm 162.30, 159.02, 127.05, 119.43, 116.98,
82.06, 60.17, 59.53, 14.13. HRMS (ESI): m/z = 359.97087.
calcd for C10H12INNaO4:359.97162 [M + Na]+.
Tetraethyl 1H,1′H-[2,2′-bipyrrole]-3,3′,5,5′-tetracar-
boxylate (3). A mixture of 2 (14.1 g, 42.4 mmol) and
activated Cu (18.1 g) in toluene (90 ml) was refluxed for
24 h under argon atmosphere. The precipitate was filtered
out on a Celite pad and washed with CH2Cl2. The solvent
was concentrated under a reduced pressure. The crude
product was purified by silica gel column chromatography
Tetraethyl 4,4′-bis(5′-hexyl-[2,2′-bithiophen]-5-yl)-
1H,1′H-[2,2′-bipyrrole]-3,3′,5,5′-tetracarboxylate
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D. KUZUHARA ET AL.
(6). A solution of 4 (1.74 g, 3.0 mmol) and 5-hexyl-2-
tributylstannyl-thiophene (8.23 g, 18 mmol) in toluene
(45 mL) was degassed by bubbling with argon for 30 min.
To the resulting mixture was added Pd(PPh3)4 (376 mg,
0.30 mmol) and refluxed for 18 h. The solvent was
removed under reduced pressure. The crude product was
purified by column chromatography (10% K2CO3 in silica
gel, hexane/CH2Cl2 9:1 to 1:9) to give 6 as yellowish-
white solids. Yield: 79% (1.78 g, 2.37 mmol). 1H NMR
(CDCl3; 400 MHz; Me4Si) dH, ppm 14.24 (brs, 2H), 7.05
(d, J = 4 Hz, 2H), 6.97 (d, J = 4 Hz, 2H), 6.82 (d, J = 4 Hz,
2H), 6.69 (d, J = 4 Hz, 2H), 4.26 (q, J = 7 Hz, 4H),
4.18 (q, J = 7 Hz, 4H), 2.80 (t, J = 7 Hz, 4H), 1.70 (m,
4H), 1.44–1.30 (m, 12H), 1.23 (t, J = 7 Hz, 6H), 1.00 (t,
J = 7 Hz, 6H), 0.90 (t, J = 7 Hz, 6H). 13C NMR (CDCl3;
100 MHz; Me4Si) dC, ppm 167.50, 160.08, 145.96,
132.22, 128.92, 127.17, 126.36, 123.13, 121.73, 115.23,
61.33, 60.71, 31.99, 31.65, 30.16, 28.85, 22.65, 14.12,
13.96, 13.26; HRMS (ESI) : m/z = 775.30628. calcd. for
C40H52N2O8S2Na : 775.30472 [M + Na]+.
MHz; Me4Si) dC, ppm 144.38, 138.80, 135.01, 132.69,
127.08, 125.93, 124.39, 123.16, 121.67, 118.46, 115.65,
101.78, 31.60, 31.49, 29.86, 28.62, 22.58, 14.49. HRMS
(MALDI-TOF): m/z = 628.2066. calcd for C36H41N2S4 :
628.2069[M]+.
4,4′-Bis(5-hexylthiophen-2-yl)-1H,1′H-[2,2′-bi-
pyrrole]-5,5′-dicarbaldehyde (9). To a solution of 7
(507 mg, 1.09 mmol) in DMF (11 ml) was slowly
added POCl3 (0.45 ml, 4.95 mmol) at 0°C under argon
atmosphere. The reaction mixture was heated at 60°C for
2 h.After cooling to room temperature, NaOAc aq. (1.2 g/
16 ml) was carefully added. The mixture was heated
at 85°C for another 1 h. The solution was poured into
cold water, the resulting precipitate was filtrated and
rinsed with water and MeOH. The product was dried
in vacuo with P2O5 to give 9 as yellowish-green solids.
This product was used for the next step without any
further purification. Yield: 95% (539 mg, 1.03 mmol).
1H NMR (DMSO-d6; 400 MHz; Me4Si) dH, ppm 12.41
(brs, 2H), 9.79 (s, 2H), 7.24 (d, J = 3 Hz, 2H), 7.18 (d,
J = 3 Hz, 2H), 6.97 (d, J = 3 Hz, 2H), 2.81 (t, J = 7
Hz, 4H), 1.64 (m, 4H), 1.38–1.28 (m, 12H), 0.87 (t, J =
7 Hz, 6H). 13C NMR (DMSO-d6; 100 MHz; Me4Si) dC,
ppm 178.55, 146.45, 132.75, 130.67, 129.41, 129.13,
126.94, 126.05, 110.18, 31.62, 31.50, 29.86, 28.67,
22.58, 14.49. HRMS (ESI): m/z = 543.21159. calcd for
C30H36N2O2S2Na:543.21194 [M]+.
4,4′-Bis(5′-hexyl-[2,2′-bithiophen]-5-yl)-1H,1′H-
[2,2′-bipyrrole]-5,5′-dicarbaldehyde (10). To a solution
of 8 (694 mg, 1.10 mmol) in DMF (11.5 ml) was slowly
added POCl3 (0.45 ml, 4.95 mmol) at 0°C under argon
atmosphere. The reaction mixture was heated at 60°C for
1h.Aftercoolingtoroomtemperature, NaOAcaq. (1.16g/
16 ml) was carefully added. The mixture was heated at
85°C for another 1 h. The solution was poured into cold
water, the resulting precipitate was filtrated and rinsed
with water and MeOH. The product was dried in vacuo
with P2O5 to give 10 as yellowish-green solids. This
product was used for the next step without any further
purification. Yield: 89% (670 mg, 0.98 mmol). 1H NMR
(DMSO-d6; 400 MHz; Me4Si) dH, ppm 12.53 (brs, 2H),
9.85 (s, 2H), 7.42 (d, J = 4 Hz, 2H), 7.26 (s, 2H), 7.26
(d, J = 4 Hz, 2H), 7.17 (d, J = 4 Hz, 2H), 6.84 (d, J = 4
Hz, 2H), 2.80 (t, J = 7 Hz, 4H), 1.63 (m, 4H), 1.38–1.24
(m, 12H), 0.87 (t, J = 7 Hz, 6H). 13C NMR could not
be recorded because of low solubility. HRMS (MALDI-
TOF): m/z = 684.1960. calcd for C38H41N2O2S4: 684.1967
[M+H]+.
4,4′-Bis(5-hexylthiophen-2-yl)-1H,1′H-2,2′-
bipyrrole (7). A mixture of 5 (926 mg, 1.23 mmol)
and NaOH (395 mg, 8.0 mmol) in degassed ethylene
glycol (17 ml), which was connected to a vacuum line
for 20 min, was heated at 170°C for 2 h under argon
atmosphere. After cooling to room temperature, the
reaction mixture was diluted with cold water. The
resulting precipitate was filtrated and washed with water
and MeOH. The product was dried in vacuo with P2O5 to
give 7 as greenish gray solids. This product was directly
used for the next step without any further purification.
Yield: 96% (549 mg, 1.18 mmol). 1H NMR (CDCl3; 400
MHz; Me4Si) dH, ppm 8.18 (brs, 2H), 6.93 (m, 2H), 6.85
(d, J = 3.7 Hz, 2H), 6.65 (d, J = 3.7 Hz, 2H), 6.38 (m,
2H), 2.78 (t, J = 7.3 Hz, 4H), 1.67 (quint, J = 7.3 Hz, 4H),
1.39–1.28 (m, 12H), 0.89 (t, J = 7.3 Hz, 6H). 13C NMR
(CDCl3; 100 MHz; Me4Si) dC, ppm 142.90, 136.23,
126.17, 124.38, 120.92, 120.58, 114.26, 102.33, 31.78,
31.71, 30.23, 28.89, 22.69, 14.20. HRMS (ESI): m/z =
465.23981. calcd for C28H37N2S2:465.23879 [M + H]+.
4,4′-Bis(5′-hexyl-[2,2′-bithiophen]-5-yl)-1H,1′H-
2,2′-bipyrrole (8).A mixture of 6 (1.12 g, 1.23 mmol) and
NaOH (380 mg, 9.5 mmol) in degassed ethylene glycol
(17 ml), which was connected to vacuum line for 20 min,
was heated at 170°C for 2 h under an argon atmosphere.
After cooling to room temperature, the reaction mixture
was diluted with cold water. The resulting precipitate was
filtrated and washed with water and MeOH. The product
was dried in vacuo with P2O5 to give 8 as greenish-gray
solids. This product was directly used for the next step
without any further purification. Yield: quant. (773 mg,
2,7,12,17-Tetra(5-hexyl-thien-2-yl)porphycene
(ThPc). TiCl4 (1.10 ml, 10 mmol) was added dropwise
to a THF (80 mL) solution containing Zn dust (1.31 g)
and CuCl (499 mg, 5.0 mmol) at room temperature
under argon atmosphere, and then the mixture was
refluxed for 3 h. The resulting mixture was added
pyridine (0.8 ml). Subsequently a solution of 9 (520 mg,
1.0 mmol) in THF (40 mL) was added dropwise to the
boiling reaction mixture. The mixture was stirred at
1
1.23 mmol). H NMR (DMSO-d6; 400 MHz; Me4Si)
dH, ppm 11.29 (brs, 2H), 7.14 (d, J = 1 Hz, 2H), 7.08
(d, J = 4 Hz, 2H), 7.02 (d, J = 4 Hz, 2H), 7.00 (d, J =
4 Hz, 2H), 6.78 (d, J = 4 Hz, 2H), 6.55 (d, J = 1 Hz,
2H), 2.77 (t, J = 7 Hz, 4H), 1.62 (m, 4H), 1.36–1.26 (m,
12H), 0.87 (t, J = 7 Hz, 6H); 13C NMR (DMSO-d6; 100
Copyright © 2019 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2019; 23: 904–907

2,7,12,17-TETRA(2,5-THIENYLENE)-SUBSTITUTED PORPHYCENES
905
same temperature for another 30 min. After cooling to
calculations in this research were obtained using super-
computing resources at Cyberscience Center, Tohoku
University. The authors thank Ms. Y. Nishikawa,
Mr. F. Asanoma and Mr. S. Katao for the measurement of
mass spectra, NMR spectra and single-crystal structure
analysis, respectively. The authors thank to Leigh
McDowell in NAIST for checking the English.
0°C, an aqueous 10% K2CO3 solution (140 ml) was
added dropwise. After filtration the precipitate was
washed with CH2Cl2, the combined organic layer was
then dried with Na2SO4, and the solution was removed
under reduced pressure. The crude product was purified
by alumina column chromatography (CH2Cl2) and silica
gel column chromatography (20% CH2Cl2 in hexane).
Recrystallization from CHCl3/MeOH gave ThPc as
greenish-purple powder.Yield: 18% (87 mg, 0.09 mmol).
1H NMR (CD2Cl2; 400 MHz; Me4Si) dH, ppm 9.77 (s,
4H), 9.23 (s, 4H), 7.82 (d, J = 4 Hz, 4H), 7.23 (d, J = 4
Hz, 4H), 3.15 (t, J = 7 Hz, 8H), 2.59 (brs, 2H), 1.98 (m,
8H), 1.67–1.46 (m, 24H), 1.01 (t, J = 7 Hz, 12H). 13C
NMR (CDCl3; 100 MHz; Me4Si) dC, ppm 148.24, 140.88,
136.32, 135.65, 133.06, 127.82, 125.74, 121.74, 113.27,
32.09, 31.86, 30.59, 29.19, 22.84, 14.06. HRMS (FAB):
m/z = 975.4556 calcd for C60H71N4S4: 975.4568 [M+H]+.
Crystal data: C60H70BN4S4, Fw 975.48, monoclinic,
space group P2/c, a = 25.6267 (13), b = 5.2743 (2), c
= 20.2390 (10) Å, b = 107.6630 (10), V = 2606.6 (2) Å3,
Z = 2, T = 103 K, Dcalc = 1.243 g cm-3, GOF = 1.048, R1
(I > 2s(I)) = 0.0680 and wR2 = 0.1890 (all data), CCDC
1917993.
2,7,12,17-Tetra(5′-hexyl-[2,2′-bithiophen]-5-yl)
porphycene (DThPc). TiCl4 (0.80 ml, 7.3 mmol) was
added dropwise to a THF (70 mL) solution containing
Zn dust (0.963 g) and CuCl (753 mg, 7.4 mmol) at
room temperature under argon atmosphere, and then
the mixture was refluxed for 3 h. The resulting mixture
was added pyridine (0.6 ml). Subsequently a solution
of bipyrrole 10 (506 mg, 0.73 mmol) in THF (50 mL)
was added dropwise to the boiling reaction mixture.
The mixture was stirred at same temperature for another
30 min. After cooling to 0°C, an aqueous 10% K2CO3
solution (140 mL) was added dropwise. After filtration
the precipitate was washed with CH2Cl2, the combined
organic layer was then dried with Na2SO4, and the
solution was removed under reduced pressure. The crude
product was purified by alumina column chromatography
(CH2Cl2) and silica gel column chromatography (20%
CH2Cl2 in hexane). Recrystallization from CHCl3/
MeOH gave DThPc as greenish purple powder. Yield:
17% (83 mg, 0.06 mmol). 1H NMR (CD2Cl2; 400 MHz;
Me4Si) dH, ppm 8.93 (s, 4H), 9.42 (s, 4H), 7.55 (d, J =
4 Hz, 4H), 7.36 (d, J = 4 Hz, 4H), 7.21 (d, J = 4 Hz, 4H),
6.79 (d, J = 4 Hz, 4H), 2.89 (t, J = 7 Hz, 8H), 2.66 (brs,
2H), 1.78 (m, 8H), 1.40–1.31 (m, 24H), 0.93 (t, J = 7 Hz,
12H); 13C NMR spectrum were not recorded because of
poor solubility; HRMS (MALDI-TOF): m/z = 1303.4075
calcd for C76H79N4S8: 1303.4065 [M + H]+.
Supporting information
Crystal structure for compound 4 and spectral data for
Compounds 1–10 and ThPc and DThPc are given in the
supplementary material. This material is available free of
charge via the Internet at http://www.worldscinet.com/
jpp/jpp.shtml.
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