Synthesis and physico-chemical properties of porphycenes

Article abstract of DOI:10.1142/S1088424612500563

A new and improved synthesis for porphycenes is presented. In particular, treating pyrroles with iodine monochloride results in quantitative yields and easier work up. This key step was employed for the synthesis of different 2,7,12,17-substituted porphycenes (TPrPc, TPPc, TtBPPc). The synthetic part of this project is followed by a global analysis of the physico-chemical properties of three exemplary porphycenes, including absorption, emission, and electrochemistry. In-situ UV-vis/nIR spectroelectrochemistry was used to determine the spectral signatures of the radical anion and cation species. Temperature-dependent fluorescence lifetimes were determined under air as well as under inert atmosphere.

Full text of DOI:10.1142/S1088424612500563

Journal of Porphyrins and Phthalocyanines
J. Porphyrins Phthalocyanines 2012; 16: 651–662
DOI: 10.1142/S1088424612500563
Published at http://www.worldscinet.com/jpp/
Synthesis and physico-chemical properties of porphycenes
a◊◊
a,b
b
b◊
Wolfgang Brenner , Jenny Malig , Christian Oelsner , Dirk M. Guldi*
and Norbert Jux*
a◊
a
Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-
Universität Erlangen-Nürnberg, Chair of Organic Chemistry II, Henkestraße 42, 91054 Erlangen, Germany
Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-
b
Universität Erlangen-Nürnberg, Chair of Physical Chemistry I, Egerlandstraße 3, 91058 Erlangen, Germany
Dedicated to Professor Emanuel Vogel in memoriam
Received 1 February 2012
Accepted 23 February 2012
ABSTRACT: A new and improved synthesis for porphycenes is presented. In particular, treating
pyrroles with iodine monochloride results in quantitative yields and easier work up. This key step was
employed for the synthesis of different 2,7,12,17-substituted porphycenes (TPrPc, TPPc, TtBPPc).
The synthetic part of this project is followed by a global analysis of the physico-chemical properties of
three exemplary porphycenes, including absorption, emission, and electrochemistry. In-situ UV-vis/nIR
spectroelectrochemistry was used to determine the spectral signatures of the radical anion and cation
species. Temperature-dependent fluorescence lifetimes were determined under air as well as under inert
atmosphere.
KEYWORDS: porphycene, synthesis, electrochemistry, spectroscopy, time-resolved spectroscopy.
therapy with a series of functionalized porphycenes was
INTRODUCTION
carried out in 1995 by Kimel et al. [4] Following a variety
Since their first synthesis in 1986 by Vogel and
of image analysis techniques they were able to document
coworkers [1] porphycenes have attracted considerable
a considerable constriction of blood vessel diameter, a
interest as archetypes of novel porphyrinoids. Due
to their poor solubility and yields, the main focus
reduction of blood perfusion, and shrinkage of tumors to
10% of its original size. In fact, the aforementioned work
concentrated on 2,7,12,17-tetrasubstituted porphycenes
with 2,7,12,17-tetra-n-propylporphycene [2] becoming
the most commonly studied porphycene. An important
feature that has attracted the interest of chemists is their
strong absorption in the red region of the absorption
spectrum rendering them a promising class of materials
for biomedical and photochemical applications.
Initial assays have given evidence that methoxy-
ethylporphycenes [3] give rise to enhanced uptake
characteristics in comparison to the more commonly
administered porphyrin mixture Photofrin. Photodynamic
sparked intense research efforts related to the biomedical
application of porphycenes, which have already been
highlighted in several reviews [5].
Research concerning porphycenes has been
multifaceted. Extensive research on the photophysical
[6, 7] and electrochemical [8, 9] properties of a
variety of porphycenes as well as investigations in the
tautomerism [10] of porphycene have been accompanied
by rather interesting work in the application of these
porphyrin-isomers — including catalysis [11], protein
mimicry [12] and material chemistry [13]. Especially
the relatively rare exploration of porphycenes in fields
of material science is somewhat surprising considering
their structural and spectroscopical similarity with other
pyrrole-based macrocycles — including porphyrins and
phthalocyanines — and the wide employment of the latter
SPP full and ◊◊student member in good standing
*
Correspondence to: Norbert Jux, tel: +49 9131-85-22976,
fax: +49 9131-85-26864, email: norbert.jux@chemie.
uni-erlangen.de
Copyright © 2012 World Scientific Publishing Company

6
52
W. BRENNER ET AL.
in different fields of research. For example, functionalized
porphyrins/phthalocyanines have been used in dye-
sensitized solar cells [14], in surface modification of
nanoparticles [15], in supramolecular dyads [16], in self-
organization studies [17], in layer-by-layer construction
of nanostructured porphyrin-fullerene electrodes [18],
and in various studies of carbon nanotube-porphyrin
interactions [19].
spectra, i.e. the difference between a spectrum with and
without an applied potential.
All chemicals were purchased by chemical suppliers
and used without further purification. All analytical
reagent-grade solvents were purified by distillation.
Thin layer chromatography (TLC): Merck silica gel 60
F254. Detection: UV lamp. Flash- chromatography (FC):
Macherey-Nagel silica gel 60 M (230–400 mesh, 0.04–
0
.063 mm). Solvents were purified by distillation prior to
use. High-resolution electrospray ionization (ESI) mass
spectrometry: Bruker micrOTOF II. NMR spectroscopy:
JEOL JNM EX 400 and JEOL JNM GX 400 and Bruker
Avance 300. The chemical shifts are given in ppm relative
to TMS. The resonance multiplicities are indicated as br
(broad), s (singlet), d (doublet), t (triplet), q (quartet) and
m (multiplet). 2,7,12,17-tetrapropylporphycene [2] and
2,7,12,17-tetraphenylporphycene [20] were synthesized
according to the literature. Procedure as well as the data
for the improved synthesis of the respective pyrrole,
iodopyrrole and bipyrrole of the latter porphycene are
listed below.
EXPERIMENTAL
General
All used solvents were spectroscopic grade (99.5%)
and were purchased from Sigma-Aldrich. The
experiments at room temperature in a 10 × 10 or 10 ×
2
mm quartz cuvette were split into investigations with
argon flushed solutions and under aerated conditions.
Steady state UV-vis/nIR absorption spectroscopy was
performed on a Cary 5000 spectrometer (Varian) in a
1
0 × 10 mm quartz cuvette. All absorption maxima lmax
are given in [nm]. The steady state emission studies in
the visible range were performed under standardized
condition at room temperature in a 10 × 10 mm quartz
cuvette on a FluoroMax3 fluorescence spectrometer
Synthesis
Diethyl 3-(4-(tert-butyl)phenyl)-1H-pyrrole-2,4-di-
carboxylate (2). To a mixture of tert-butylbenzaldehyde
(1) (10.0 g, 61.6 mmol) in THF (150 mL) ethyl
isocyanoacetate (13.5 mL, 123.2 mmol) was added. After
addition of DBU (27.6 mL, 184.8 mmol) the mixture was
stirred for 24 h at room temperature. It was diluted with
water (250 mL) and extracted with ethyl acetate several
times. The combined organic layers were stripped of
solvent and purified by column chromatography (40%
ethyl acetate in hexanes). The desired product was
recrystallized from methanol and obtained as white
(
Horiba JobinYvon) using 740 for excitation and 360 nm
for emission. For measurements in the nIR region a
FluoroLog3 spectrometer (Horiba Jobin Yvon) with an
IGA Symphony (512 × 1 × 1 μm) detector was used.
Emission lifetimes were determined via time correlated
single photon counting (TCPSC) on a FluoroLog3
emission spectrometer (Horiba Jobin Yvon) with a
MCP detector (R3809U-58). For excitation a laserdiode
(
NanoLED-405L, 403 nm, pulse width < 200 ps) was
used. Transient absorption studies were performed with
87 nm laser pulses (SHG) of an amplified Ti/sapphire
1
solid. Yield 5.10 g (14.9 mmol, 24.1%). H NMR (400
3
MHz, rt, CDCl ): d, ppm 9.72 (br, 1H, NH), 7.55 (d, 1H,
3
3
3
laser system (Model CPA 2101, Clark-MXR Inc. —
output: 775 nm, 1 kHz and 170 fs pulse width) in the
TAPPS-Transient Absorption Pump/Probe System —
Helios from Ultrafast Systems with 200 nJ laser
energy. Finally, the changes in optical density (DOD)
are measured against the wavelength in both visible
and near-infrared regions. The transient spectra were
recorded in a 2 mm quartz cuvette at room temperature.
Spectroelectrochemistry (SEC) and electrochemical
experiments were performed with a home-built cell and a
three-electrode setup: a light-transparent platinum gauze
J = 3.4 Hz, pyrrole-H), 7.35 (d, 2H, J = 8.5 Hz, Ar-H),
3
3
7.25 (d, 2H, J = 8.5 Hz, Ar-H), 4.11 (q, 4H, J = 7.1 Hz,
3
OCH CH ), 4.10 (q, 4H, J = 7.1 Hz, OCH CH ), 1.32 (s,
2
3
2
3
3
9H, -C(CH ) ), 1.09 (t, 3H, J = 7.2 Hz, OCH CH ), 1.03
3
3
2
3
3
13
(t, 3H, J = 7.1 Hz, OCH CH ). C NMR (100.5 MHz,
2
3
rt, CDCl ): d, ppm 164.0, 161.2, 149.9, 132.7, 130.6,
3
129.8, 127.0, 123.9, 121.0, 117.1, 60.5, 59.7, 34.4, 31.3,
13.9, 13.6. HR-MS (ESI): m/z calcd. for C H NO :
2
0
26
4
-1
344.18563; found 344.18503. IR (ATR, rt): n, cm 608,
762, 786, 829, 853, 1025, 1178, 1268, 1286, 1387, 1421,
1526, 1671, 1702, 2981, 3127, 3294.
(
SEC) or a glassy carbon electrode (cyclic voltammetry
Diethyl 3-phenyl-1H-pyrrole-2,4-dicarboxylate (3).
The product was obtained from benzaldehyde (3.14 g,
29.6 mmol) using the same procedure described above.
and square wave voltammetry) were used as working
electrodes, a platinum wire as counter electrode, and a
silver wire as quasi reference electrode. The pathlength
of the SEC cell was determined to 2.3 mm. Potentials
were applied and monitored with a METROHM-Autolab
Potentiostat/Galvanostat PGSTAT101 and spectra were
recorded with a UV-vis/NIR-spectrometer Cary 5000
1
Yield 1.93 g (6.72 mmol, 22.6%) H NMR (300 MHz,
rt, CDCl ): d, ppm 9.63 (br, 1H, NH), 7.56 (s, 1H, Ar-H),
3
3
7.31 (m, 4H, Ar-H), 4.12 (q, 2H, J = 7.2 Hz, OCH CH ),
4.10 (q, 2H, J = 7.2 Hz, OCH CH ), 1.09 (t, 3H, J =
7.2 Hz, OCH CH ), 1.05 (t, 3H, J = 7.2 Hz, OCH CH ).
C NMR (75.5 MHz, rt, CDCl ): d, ppm 163.8, 161.0,
2
3
3
3
2
3
3
2
3
2
3
1
3
(
Varian). The results are finally shown as differential
3
Copyright © 2012 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2012; 16: 652–662

SYNTHESIS AND PHYSICO-CHEMICAL PROPERTIES OF PORPHYCENES
653
3
3
1
6
33.7, 132.3, 130.1, 127.1, 126.9, 126.8, 120.9, 117.2,
0.5, 59.8, 14.0, 13.8. HR-MS (ESI): m/z calcd. for
J = 8.5 Hz, Ar-H), 7.17 (d, 4H, J = 8.3 Hz, Ar-H), 4.17
3
3
(q, 4H, J = 7.1 Hz, OCH CH ), 4.01 (q, 4H, J = 7.1
Hz, OCH CH ), 1.34 (s, 18H, -C(CH ) ), 1.11 (t, 6H, J =
2 3 3 3
2 3
3
C H NO Na: 310.10498; found 310.10354. IR (ATR,
rt): n, cm 700, 759, 782, 980, 1027, 1119, 1174, 1264,
1
1
6
17
4
1
-
3
7.1 Hz, OCH CH ), 0.70 (t, 6H, J = 7.2 Hz, OCH CH ).
2
3
2
3
1
3
282, 1384, 1404, 1445, 1476, 1517, 1685, 2987, 3290.
Diethyl 3-(4-(tert-butyl)phenyl)-5-iodo-1H-pyrrole-
,4-dicarboxylate (4). Diethyl 3-(4-(tert-butyl)phenyl)-
H-pyrrole-2,4-dicarboxylate (3) (5.00 g, 14.5 mmol)
C NMR (75.5 MHz, rt, CDCl ): d, ppm 167.7, 160.4,
3
149.6, 134.7, 132.4, 129.2, 123.9, 120.2, 114.1, 61.0,
60.4, 34.5, 31.4, 13.8, 12.8. HR-MS (ESI): m/z calcd.
for C H N O : 685.34834; found 685.34931. IR (ATR,
rt): n, cm 794, 827, 840, 871, 1027, 1112, 1164, 1185,
1251, 1303, 1382, 1417, 1471, 1514, 1655, 1724, 2870,
2905, 2963.
2
1
4
0
49
-1
2
8
and sodium acetate (7.14 g, 87.0 mmol) were dissolved in
acetic acid (80 mL), heated to 80 °C and a solution of ICl
(
2.21 mL, 43.5 mmol) in acetic acid (20 mL) was added.
The solution was kept at 80 °C overnight, allowed to cool
down and sodium thiosulfate was added to the mixture.
Water was added until a white precipitate formed. The
white solid was filtered off, washed with water and dried.
Tetraethyl 4,4′-bisphenyl-1H,1′H-[2,2′-bipyrrole]-
3,3′,5,5′-tetracarboxylate (7). The product was
obtained from diethyl 3-phenyl-5-iodo-1H-pyrrole-2,4-
dicarboxylate (5) (7.65 g, 18.5 mmol) using the above
1
Yield 6.60 g (14.1 mmol, 97.0%) H NMR (300 MHz,
mentioned procedure. Yield 1.39 g (2.43 mmol, 26.2%).
3
1
rt, CDCl ): d, ppm 10.24 (br, 1H, NH), 7.32 (d, 2H, J =
H NMR (400 MHz, rt, CDCl ): d, ppm 14.24 (br, 2H,
3
3
3
8
2
.5 Hz, Ar-H), 7.15 (d, 2H, J = 8.5 Hz, Ar-H), 4.14 (q,
H, J = 7.2 Hz, OCH CH ), 4.04 (q, 2H, J = 7.0 Hz,
OCH CH ), 1.32 (s, 9H, C(CH ) ), 1.00 (t, 3H, J = 7.2
Hz, OCH CH ), 0.92 (t, 3H, J = 7.2 Hz, OCH CH ). C
NH), 7.36 (m, 6H, Ar-H), 7.30 (m, 4H, Ar-H), 4.20 (q,
4H, J = 7.1 Hz, OCH CH ), 4.06 (q, 4H, J = 7.1 Hz,
OCH CH ), 1.15 (t, 6H, J = 7.1 Hz, OCH CH ), 0.79
2 3 2 3
(t, 6H, J = 7.1 Hz, OCH CH ). C NMR (100.5 MHz,
3
3
3
3
2
3
2 3
3
3
2
3
3 3
3
13
3
13
2
3
2
3
2 3
NMR (75.0 MHz, rt, CDCl ): d, ppm 163.3, 160.4, 150.0,
rt, CDCl ): d, ppm 167.6, 160.3, 135.6, 134.5, 129.6,
3
3
1
1
4
8
1
33.6, 129.4, 125.0, 123.8, 121.0, 61.0, 60.1, 34.5, 31.4,
129.2, 127.0, 126.7, 120.4, 114.0, 61.0, 60.5, 13.8, 13.0.
3.6, 13.4. HR-MS (ESI): m/z calcd. for C H INO Na:
HR-MS (ESI): m/z calcd. for C H N O Na: 595.20509;
2
0
24
4
32 32
2
8
-1
-1
92.06422; found 492.06351. IR (ATR, rt): n, cm 788,
31, 1030, 1117, 1180, 1259, 1363, 1385, 1420, 1448,
472, 1516, 1553, 1666, 1697, 2361, 2964, 3236.
found 595.20418. IR (ATR, rt): n, cm 700, 760, 788,
834, 1025, 1154, 1180, 1248, 1298, 1353, 1391, 1402,
1422, 1468, 1504, 1563, 1677, 1709, 2990.
Diethyl 3-phenyl-5-iodo-1H-pyrrole-2,4-dicarbo-
xylate (5). The product was obtained from diethyl
-phenyl-1H-pyrrole-2,4-dicarboxylate (6.70 g, 23.3
4,4′-bis(4-(tert-butyl)phenyl)-1H,1′H-2,2′-bipyr-
role (8). In a 100 mL round bottom flask equipped with
a reflux condenser and stirring bar tetraethyl 4,4’-bis(4-
(tert-butyl)phenyl)-1H,1′H-[2,2′-bipyrrole]-3,3′,5,5′-
tetracarboxylate (6) 4.00 g, 5.84 mmol), NaOH (2.35 g,
58.8 mmol) and ethylene glycol (60 mL) were heated
to 190 °C for 2 h under inert atmosphere. While it was
allowed to cool down to room temperature a grayish
precipitate formed, which was filtered off, washed
extensively with water and dried. The grayish solid was
3
mmol) following the same procedure as described above.
1
Yield 9.05 g (21.9 mmol, 94.0%) H NMR (400 MHz, rt,
CDCl ): d, ppm 10.02 (br, 1H, NH), 7.35 (m, 3H, Ar-H),
3
3
7
.27 (m. 2H, Ar-H), 4.17 (q, 2H, J = 7.1 Hz, OCH CH ),
.08 (q, 2H, J = 7.1 Hz, OCH CH ), 1.06 (t, 3H,
J = 7.1 Hz, OCH CH ), 1.00 (t, 3H, J = 7.1 Hz,
2
3
3
4
2 3
3
3
2
3
1
3
OCH CH ). C NMR (100.5 MHz, rt, CDCl ): d, ppm
2
3
3
1
7
63.2, 160.2, 134.0, 133.3, 129.8, 127.0, 125.0, 121.1,
used without further purification. Yield 2.30 g (5.80
1
7.6, 61.0, 60.1, 13.8, 12.6. HR-MS (ESI): m/z calcd. for
mmol, 99.3%). H NMR (300 MHz, rt, DMSO-d ): d,
6
3
C H INO : 436.00162; found 435.99954. IR (ATR, rt):
ppm 11.10 (br, 2H, NH), 7.44 (d, 4H, J = 8.5 Hz, Ar-H),
7.32 (d, 4H, J = 8.5 Hz, Ar-H), 7.14 (s, 2H, pyrrole-H),
6.62 (s, 2H, pyrrole-H), 1.28 (s, 18H, C(CH ) ).
1
6
16
4
-
1
3
n, cm 696, 792, 1018, 1041, 1176, 1259, 1276, 1356,
1
3
1
3
386, 1419, 1448, 1476, 1503, 1549, 1672, 1698, 2988,
219.
C
3
3
NMR (75.5 MHz, rt, DMSO-d ): d, ppm 147.2, 133.1,
6
Tetraethyl 4,4′-bis(4-(tert-butyl)phenyl)-1H,1′H-
126.8, 125.3, 124.0, 123.8, 114.4, 100.5, 34.1, 31.2.
[
2,2′-bipyrrole]-3,3′,5,5′-tetracarboxylate (6). Copper
HR-MS (ESI): m/z calcd. for C H N : 395.24927; found
28
-1
31
2
powder (7.02 g, 110.5 mmol) was added to a solution
of diethyl 3-(4-(tert-butyl)phenyl)-5-iodo-1H-pyrrole-
2
395.24853. IR (ATR, rt): n, cm 657, 740, 790, 837, 928,
1038, 1087, 1126, 1267, 1365, 1403, 1461, 1501, 1566,
2364, 2903, 2962, 3121, 3401.
,4-dicarboxylate (4) (6.48 g, 13.8 mmol) in toluene
(
100 mL) under nitrogen atmosphere. The mixture was
4,4′-bis(4-(tert-butyl)phenyl)-1H,1′H-[2,2′-
bipyrrole]-5,5′-dicarbaldehyde (9). 4,4′-bis(4-(tert-
butyl)phenyl)-1H,1′H-2,2′-bipyrrole (8) (1.20 g, 3.03
mmol) was dissolved in DMF (25 mL) and phosphoryl
chloride (1.40 mL, 15.1 mmol) was added at 0 °C. The
mixture was heated to 70 °C for 2 hours, allowed to cool
to room temperature and given into water. NaOH was
added till the smell of amine was apparent. The deep
yellow solid was filtered off, washed with water, and
then heated at reflux temperature for 72 hours. It was
allowed to cool to room temperature, filtered through a
celite pad and stripped off solvent. The crude product
was purified by column chromatography (silica gel, 8 ×
2
0 cm, 40% ethyl acetate in hexanes). The bipyrrole was
recrystallized from acetone and obtained as white solid.
Yield 2.50 g (3.65 mmol, 52.9%). H NMR (300 MHz,
rt, CDCl ): d, ppm 14.13 (br, 2H, NH), 7.35 (d, 4H,
1
3
Copyright © 2012 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2012; 16: 653–662

6
54
W. BRENNER ET AL.
carried on to the next step without further purification.
Yield 1.30 g (2.87 mmol, 94.7%). H NMR (300 MHz,
814, 841, 887, 964, 1024, 1062, 1107, 1140, 1229, 1264,
1293, 1362, 1406, 1460, 1504, 1545, 2866, 2962.
1
rt, CDCl ): d, ppm 12.58 (br, 2H, NH), 9.67 (s, 2H,
3
CHO), 7.45 (s, 8H, Ar-H), 6.73 (s, 2H, pyrrole-H), 1.36
RESULTS AND DISCUSSION
1
3
(
s, 18H, C(CH ) ). C NMR (100.5 MHz, rt, CDCl ):
3
3
3
d, ppm 180.0, 151.3, 131.3, 130.2, 129.7, 128.8, 127.1,
25.9, 111.2, 34.7, 31.3. HR-MS (ESI): m/z calcd. for
The aforementioned results encouraged us to revisit
the well-known tetra-n-propylporphycene (TPrPc)
and tetraphenylporphycene (TPPc). As a complement
we tested the potential of a newly synthesized
porphycenederivative,namelyapara-phenyl-substituted
porphycene — tetra-t-butylphenylporphycene (TtBPPc)
— as a prototype in terms of applicability in materials
science (Fig. 1).
1
C H N O : 451.23910; found 451.23795. IR (ATR, rt):
3
0
31
-
2
2
1
n, cm 724, 801, 825, 1005, 1113, 1271, 1344, 1362,
1
2
379, 1425, 1474, 1498, 1535, 1594, 1635, 2868, 2904,
962, 3269.
2
,7,12,17-tetrakis-(4′-tert-butylphenyl)-porphy-
cene (TtBPPc). Under nitrogen atmosphere titanium
tetrachloride (2.71 mL, 24.3 mmol) was added to a
mixture of zinc (2.89 g, 44.2 mmol) and CuCl (306 mg,
Parent porphycene was first synthesized by Vogel and
coworkers in 1986 [1], followed later by the synthesis
of 2,7,12,17-tetra-n-propylporphycene [2] and of the
first porphycene bearing aromatic substituents —
2,7,12,17-tetraphenylporphycene [21]. To this day,
different variations of the original synthesis by Vogel
have been published. Nonell and coworkers [20], for
example, replaced the sublimation of the tetracarboxylic
acid by heating a mixture of tetracarboxylic ester
and sodium hydroxide in ethylene glycol to 180 °C.
This alteration enabled proceeding directly from the
tetracarboxylic ester to the unsubstituted bipyrrole. Later
on, efforts were directed to circumvent the relatively
unstable unsubstituted bipyrrole during the synthesis. To
this end, a non-decarboxylative method was introduced
by Stockert et al. [22] However, employing this method
let to an increased number of synthetic steps. In 2006,
Borrell et al. [23] published the synthesis of a bipyrrole,
which allows introducing the substituents in the
4,4′-positions late in the synthesis. Again, such a method
goes hand in hand with an increased number of overall
steps to obtain the desired bipyrroles. Furthermore, the
employed starting material is very expensive or requires
preparation from thiophenes via multi-step synthesis.
More recently, a novel method regarding the synthesis
of bipyrroles was reported by Sanchez-Garcia et al. [24]
Here, the synthesis is based on the oxidative coupling
3
.09 mmol) in THF (400 mL). The mixture was heated
at reflux temperature for 3 hours. Then a suspension of
4
5
,4′-bis(4-(tert-butyl)phenyl)-1H,1′H-[2,2′-bipyrrole]-
,5′-dicarbaldehyde (9) (1.00 g, 2.21 mmol) in THF
(
80 mL) was added and the mixture heated at reflux
temperature for 45 min. The zinc was filtered off and the
reaction quenched with ammonia (37 mL) while keeping
the temperature at 0 °C. The solids were removed by a
celite plug using chloroform as eluent. The organic layer
was washed with water, dried over magnesium sulfate
and stripped off solvent. The residue was purified by
column chromatography (silica gel, 20 × 5 cm, hexanes/
methylene chloride = 2/1) to yield the product as bluish
1
powder. Yield 276 mg (0.33 mmol, 29.8%). H NMR
(
300 MHz, rt, CDCl ): d, ppm 9.86 (s, 4H, pyrrole-CH-
3
3
CH-pyrrole), 9.58 (s, 4H, pyrrole-H), 8.26 (d, 8H, J = 8.5
Hz, Ar-H), 7.83 (d, 8H, J = 8.3 Hz, Ar-H), 3.44 (br, 2H,
NH), 1.56 (s, 36H, C(CH ) ). C NMR (75.5 MHz, rt,
3
1
3
3
3
CDCl ): d, ppm 150.8, 144.6, 142.6, 134.2, 133.7, 131.2,
3
1
26.0, 123.4, 114.3, 34.9, 31.6. HR-MS (ESI): m/z calcd.
for C H N : 839.50472; found 839.50394; elemental
6
0
63
4
analysis calcd. (%) for C H N × H O: C 84.07, H 7.53,
6
0
62
4
2
N 6.54; found C 84.06, H 7.40, N 6.68. UV-vis (THF):
-
1
-1
lmax, nm (e, M .cm ) = 660 (37342), 628 (40107), 586
-1
(
29395), 377 (97480). IR (ATR, rt): n, cm 674, 729,
N
H
N
N
H
N
N
H
N
H
N
H
N
H
N
N
N
N
TPrPc
TPPc
TtBPPc (10)
Fig. 1. Investigated porphycenes
Copyright © 2012 World Scientific Publishing Company
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SYNTHESIS AND PHYSICO-CHEMICAL PROPERTIES OF PORPHYCENES
655
of a 2-trimethylstannylated pyrrole and, in turn, reduces
the number of synthetic steps for the synthesis of
Through a slight variation of the reaction conditions we
were able to isolate the desired iodopyrrole 4 in nearly
quantitative yields. Furthermore, it is easily accessible,
since it crystallizes upon adding water to the reaction
mixture. This allows 4 to be filtered, dried, and subjected
to Ullmann coupling without further purification. Finally,
after decarboxylation and Vilsmeier–Haack formylation,
McMurry coupling provided 2,7,12,17-tetrakis-(4′-tert-
butylphenyl)-porphycene 10 in excellent yields (30%,
see Scheme 1).
2
,7,12,17-substituted porphycenes to five.
While this is among the shortest possible routes to
obtain porphycenes, we decided to follow a modified
route based on Vogel’s procedure. Key points were the
variations of the pyrrole formation and the subsequent
iodination. In 1974 Matsumoto et al. [25] published the
synthesis of different substituted pyrroles by reacting
isocyanoacetates with aldehydes in the presence of DBU.
Therefore, we subjected tert-butyl benzaldehyde 1 to a
reaction with two equivalents of ethyl isocyanoacetate in
the presence of DBU and were able to obtain the desired
pyrrole 2 in reasonable yields. Notably, we never reached
the mentioned yields. But, it provides the noteworthy
advantage of circumventing the formation of nitroalkenes
during the synthesis [26] and as such it avoids the time-
consuming purification via column chromatography.
Several approaches towards the respective iodopyrroles
focus on the treatment with a mixture of iodine and
potassium iodide. However, we found this reaction is far
from being quantitative. Therefore, we decided to adapt a
procedure presented by Dolphin et al. [27] who performed
the iodination by treatment with iodine monochloride.
Typical for pyrrole-based macrocycles, the absorption
spectra (see Fig. 2) of metal-free porphycenes comprise
features in the low energy region (i.e. 500 to 680
nm), these are three intense Q-bands with high molar
extinction coefficients (Table 1), and in the high energy
region (i.e. 300 to 450 nm), namely two B- or Soret-
bands. Although the similarity to porphyrins with respect
to transition energies is obvious the intensity of the
Q-bands is much more distinct and the presence of two
close-lying electronic states in the Q-band as well as in
the Soret-band region hints to higher energy transitions
S –S and S –S or even higher for the Soret-band [28].
0
3
0
4
The latter are split, in contrast to what is known for
porphyrins, due to the lower symmetry of porphycenes.
CN
CO2Et
ICl, NaOAc
DBU, THF
rt
HOAc
Cu, toluene
reflux
EtO2C
EtO2C
I
80 ˚C
CO2Et
CO2Et
O
N
H
N
H
1
2
4
(
24%)
(97%)
KOH
ethylene glycol
CO2Et CO2Et
POCl , DMF
3
190 ˚C
70 ˚C
N
H
N
H
N
H
N
H
EtO2C
CO2Et
6
8
(
53%)
(99%)
TiCl4, Zn, CuCl
THF
N
H
N
H
N
reflux
N
N
N
H
H
O
O
9
TtBPPc (10)
(
95%)
(30%)
Scheme 1. Formation of 2,7,12,17-tetrakis-(4′-tert-butylphenyl)-porphycene TtBPPc
Copyright © 2012 World Scientific Publishing Company
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6
56
W. BRENNER ET AL.
Fig. 2. Molar extinction coefficients of TPrPc (black), TPPc (dark grey) and TtBPPc (light grey) in THF solution
Table 1. Maximum absorption and emission features of TPrPc, TPPc, and TtBPPc in THF.
Excitation wavelengths for steady state experiments and for TCSPC measurements were
3
50 nm and 403 nm, respectively, in degassed (deg) and aerated (aer) solutions. Emission was
recorded at the emission maximum
-3
-1
-1
l , nm (e × 10 , M .cm )
lem, nm
Fem
tem,298K, ns
tem,77K, ns
abs
TPrPc
TPPc
635 (39.8)
656 (41.7)
660 (37.3)
637
0.38
9.9aer
2.1deg
1
17.9deg
10.1deg
9.4deg
664
668
0.14
0.09
3.6aer
4
.1deg
2.4aer
.5deg
TtBPPc
2
Upon replacing the propyl-groups by phenyl-groups in
the 2,7,12,17-positions an overall bathochromic shift of
up to 30 nm is observed. Another shift of up to 5 nm is
noted, when tert-butyl groups are attached to the para-
position of the phenyl-rings.
In detail, the two reduction and the two oxidation
steps are quasi-reversible. Another difference is given by
the easier reduction and slightly more difficult oxidation
when introdcing electron-withdrawing groups like phenyl
substituents. The stabilization of the porphycene anions by
the phenyl rings through delocalization of the introduced
charges is likely to be responsible for the underlying trend.
Especially the first reduction of the phenyl porphycenes
is strongly influenced by the environment. In particular,
the reduction renders easier and easier, when changing
the solvent from less polar dichloromethane (-0.73 V,
TPPc) [30] to THF (-0.63 V, TPPc) and to very polar
dimethylformamide (-0.51 V, TPPc).
Further insights into the electronic ground state
properties came from electrochemical measurements.
The electrochemical characteristics of the porphycene
systems TPrPc, TPPc, and TtBPPc were measured
in dimethylformamide (DMF) and tetrahydrofurane
-
4
(
THF) (10 M) with 0.1 M tetrabutylammonium
hexafluorophosphate (TBAPF ) as supporting electrolyte
6
+
vs. Fc/Fc as internal standard. All of the metal-free
porphycenes exhibited similar redox characteristics,
including two reduction steps and two oxidation steps
In addition to the steady state absorption and standard
electrochemical investigations we performed in-situ
UV-vis/nIR spectroelectrochemistry (Fig. 3) to establish
the spectroscopic fingerprints of the oxidized and
reduced species. The latter are crucial in the context of
photoinduced electron transfer reactions. In particular,
we altered the potential from +1.0 to -1.0 V in 0.2 V steps
and vice versa and recorded the corresponding changes
(
see Table 2). Importantly, the half-wave potentials, as the
oxidation is much more difficult than the reduction, and
HOMO–LUMO gap differ drastically from other pyrrole
based macrocycles like porphyrins and phthalocyanines
—
compare 2.25 V for porphyrins and 1.90 V for
porphycene, respectively [29].
Copyright © 2012 World Scientific Publishing Company
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SYNTHESIS AND PHYSICO-CHEMICAL PROPERTIES OF PORPHYCENES
657
Table 2. Half-wave potentials of of TPrPc, TPPc, and TtBPPc
in THF with Fc/Fc as standard and silver wire as reference
electrode
are assigned as typical fingerprints of the radical anions
+
[8, 33, 34].
Initially, the excited state features were investigated
by steady-state and time-resolved fluorescence meas-
urements. In the case of TtBPPc, the fluorescence
spectrum is dominated by a single, intense fluorescence
band at 668 nm followed by a weaker band at 730 nm. In
agreement with the absorption assays an overall 30 nm
bathochromic shift is discernable with respect to TPrPc.
Comparing, nevertheless, the lowest energy absorption
and the highest energy fluorescence a small Stokes shift
of 8 nm evolves. Interestingly, the phenyl substitution
exerts a drastic impact on the quantum yields with
values that decrease from 0.38 (TPrPc) to 0.14 (TPPc)
and 0.09 (TtBPPc). The fluorescence quantum yields
obtained in aerated or degassed solutions for TPrPc
(0.35 ± 0.06 [35], 0.38 ± 0.06 [36] and 0.36 [37]) and
TPPc (0.14 [38]) are in excellent agreement with other
experimentally obtained values.
Compound Eox2, V Eox1, V Ered1, V Ered2, V Eox1-Ered1, V
TPrPc
TPPc
1.4
1.1
1.3
1.3
-0.9
-0.6
-0.6
-1.2
-0.9
-0.9
1.96
1.88
1.90
TtBPPc
in the absorption spectra. The spectral signatures of the
radical anion and cation species appear similar [30]. All
of the sharp ground state features are displaced by broad
bands in the visible and new features in the near-infrared
region. Overall, the characteristics of the radical cations
tend to be more featureless and much weaker than those
of the corresponding radical anions, which is in good
agreement with earlier pulse radiolytic experiments
[
31, 32]. In detail, a broad band between 430 and 565
+.
-.
nm is observed for the TPrPc , while TPrPc shows
a sharp feature at 329 nm and a broad signal with two
distinguishable maxima at 414 and 482 nm in the visible
and 744 and 842 nm in the near-infrared regions. On the
contrary, the transitions seen for the radical cation and
radical anion species of the phenyl-substituted system
appear more fine-structured. Moreover, they tend to be
in close agreement with the aforementioned steady-
state absorption measurements bathochromically shifted
by 30–40 nm relative to TPrPc. As the features in the
visible region are comparable for the radical cations and
radical anions, the near-infrared signatures with maxima
at 842 nm (TPrPc) and 883 nm (TPPc and TtBPPc)
The same tendency is seen when analyzing the
fluorescence decays of TPrPc, TPPc, and TtBPPc,
which are best fit mono-exponentially. In particular,
the fluorescence lifetimes in oxygen-free solutions are
12 ns for TPrPc (10.5 ± 0.5 ns [37], 9.76 ± 0.03 ns
[35]), 4 ns for TPPc (4.8 ns [38]), and 2 ns for TtBPPc.
Molecular oxygen impacts the radiative deactivation rate
through diffusion controlled reactions and scales with
an increased probability of collisions [39]. For instance,
while the lifetime of TPrPc is decreased from 12.2 to 9.9
ns under nitrogen and air, respectively, the influence on
the radiative kinetics is somewhat weaker for TPPc (4.0
vs. 3.7 ns) and for TtBPPc (2.5 vs. 2.4 ns).
-5
Fig. 3. Differential absorption map of spectroelectrochemical absorption measurements of TtBPPc in THF solution (10 M) with
alternating potentials from 1.0 V to - 1.0 V in 0.2 V steps vs. silver wire
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W. BRENNER ET AL.
Fig. 4. Differential absorption spectra (visible and near-infrared) obtained upon femtosecond flash photolysis (387 nm) of TtBPPc in
THF with several time delays between 0 and 7750 ps at room temperature — time evolution from black to grey to white. Inset shows
the time-absorption profiles (0 to 7750 ps) of the spectra shown above at 500 nm and 650 nm monitoring the excited state decay
Next to the oxygen dependency we investigated the
fluorescence lifetimes at different temperatures, namely
the excited state dynamics from transient absorption
measurements. Common to experiments with 387 and
605 nm photoexcitation are maxima that develop around
450 and 1000 nm as well as minima in the range between
525 and 675 nm (Fig. 4). The latter are attributed to
ground state bleaching. A multi-wavelength analysis of
the differential absorption changes in the range of the
minima resultedintwoshort-anda long-livedcomponent.
Importantly, the long lifetime correlates well with the
radiative ground state recovery with values of 12 ns for
TPrPc and 2 ns for TtBPPc and reflects the intersystem
crossing to the triplet excited state. The ultra-short
lifetime, on the other hand, with values of around 600 fs
is likely to originate from internal vibrational relaxation
processes, that is, an intrinsic decay from higher excited
states, a second short-lived component, with lifetimes
of around 150 ps, which is identified to correspond to
thermal equilibration due to energy exchange with the
solvent molecules [40] and are superimposed by the
corresponding long lived triplet manifolds, that affects
the maxima at 450–500 and 950–1000 nm [6, 36].
In addition, time resolved experiments on the
nanosecond timescale were conducted with photoex-
citation at 532 nm (Fig. 5). To this end, two different sets
of experiments were performed. Firstly, theTHF solutions
of the porphycene derivatives were degassed with argon.
Secondly, the THF solutions were purged with oxygen
prior to the measurements. Common to all experiments
are features of the triplet excited states that are in
agreement with the aforementioned results. In particular,
from maxima at 380 nm (TPrPc) and 420 nm (TPPc and
2
98 and 77 K. Upon decreasing the temperature from 298
to 77 K, the fluorescent excited state depopulates much
slower due to “frozen” vibrations. TtBPPc, which gives
rise to the fastest fluorescence decay, reveals the most
pronounced temperature dependence — the lifetime is
increased in this particular case by nearly a factor of four,
that is, from 2.4 to 9.4 ns.
Under ambient conditions the lifetimes of the two
fluorescent bands are nearly the same. Cooling the
sample yields distinguishable changes. TPPc reveals an
appreciably stronger increase of the fluorescence lifetime
for the higher energy band at 670 nm. Noteworthy, steady-
state experiments prompt to the fact that the radiative
deactivation is highest. The loss of photoexcitation energy
evolves from the lowest vibrational level of the excited
state, while excitation does not necessarily proceed from
the lowest vibrational level of the ground state. Such
a trend goes hand in hand with the already discussed
bathochromic shifted absorption and fluorescence
features of TtBPPc and TPPc when compared to TPrPc.
Introducing additional groups like tert-butyl promotes
the overall flexibility of the system and, in turn, increases
the vibronic levels. All together these trends suggest
that non-radiative deactivation processes of the excited
states are favored. In fact, Nonell et al. [30] have already
postulated a more efficient non-radiative decay for the
phenyl-substituted porphycenes.
As a complement to the aforementioned fluorescence
experiments we gathered additional information about
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SYNTHESIS AND PHYSICO-CHEMICAL PROPERTIES OF PORPHYCENES
659
Fig. 5. Differential absorption spectra in the visible region obtained upon nanosecond flash photolysis (532 nm) of TtBPPc
in THF with several time delays between 0 and 0.5 ms at room temperature — time evolution from black to grey to white.
Inset shows the time-absorption profiles (0 to 0.5 ms) of the spectra shown above at 420 nm and 620 nm monitoring the excited
state decay
Fig. 6. Singlet oxygen production (1270 nm) at 615 nm excitation wavelength (inset) and excitation spectrum of the corresponding
peak of TPPc in THF measured at 1270 nm
TtBPPc) and minima between 500 and 700 nm we have
derived triplet excited state lifetimes that decrease in the
following order TPrPc > TPPc > TtBPPc. In oxygen
saturated solutions the TPrPc, TPPc, and TtBPPc
centered transients disappear completely as a result of
oxygen induced quenching of the triplet excited states
and the subsequent formation of singlet oxygen (Fig. 6)
singlet oxygen peak at 1270 nm clarifies the origin of the
triplet states dominantly from intersystem crossing out
of the Q-bands. The singlet oxygen quantum yields were
measured by phosphorescence quenching methods and
found to be in the order of 0.5 for TPrPc (compare 0.4
± 0.1 [35, 36]), 0.2 for TPPc (compare 0.23 [38]), and
0.3 for TtBPPc in THF, which again reflects the trend of
decreasing lifetimes when substituting the propyl-chains
[
41]. The excitation spectrum at the corresponding
Copyright © 2012 World Scientific Publishing Company
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6
60
W. BRENNER ET AL.
by phenyl-rings in the periphery of the porphycenes.
The corresponding phosphorescence was measured by
low temperature experiments with maxima in the near-
infrared region.
structural flexibility of the porphycene, that is, when
substituting the propyl-groups by phenyl-groups and
adding extra tert-butyl groups, which favor non-radiative
deactivations through vibrational relaxation. The former
range from 12.1 to 2.4 ns at room temperature and
from 17.9 to 9.4 ns at 77 K. It is, however, not only
the fluorescence lifetimes that are impacted, but also
the fluorescence quantum yields with values as high
as 0.38 and as low as 0.09 at room temperature. Once
populated the triplet excited states decay in the absence
of molecular oxygen with dynamics in the range of 30 to
70 μs, while the presence of molecular oxygen leads to
accelerated decays. Here, singlet oxygen with quantum
yields of 0.2 up to 0.5 (TPPc and TPrPc) result as
diffusion controlled deactivations of all of the triplet
excited states.
Additionally, the versatility of TPrPc, TPPc, and
TtBPPc were documented in terms of their two photon
absorption properties [42], which were corroborated
by varying the laser power stepwise from 100–200 nJ
at different excitation wavelengths. Multiwavelength
analyses revealed that under one photon excitation
conditions, that is, 387 nm excitation, the optical density
doubled when going from 100 to 200 nJ. Comparing
the optical densities at different laser power when
conducting the same experiments at 605 nm excitation
wavelength drastic changes arise. Specifically, doubling
the laser power yields four times higher intensities,
which is a clear indicator for the occurrence of two
photon absorption processes in all studied porphycene
derivatives.
CONCLUSION
In summary, excitation of TPrPc, TPPc, and TtBPPc
into either their Soret- or into their Q-band features
with 387 and 600 nm excitation, respectively, generates
the second (2.7 eV) or the first singlet excited states
To
conclude,
tetra-(tert-butylphenyl)porphycene
TtBPPc has been synthesized for the first time. The
respective pyrrole precursor 2 as well as the pyrrole 3
required for the tetraphenylporphycene TTPc, were
synthesizedaccordingtoMatsumotoetal. [25]Quantitative
iodination was carried out by addition of iodine monoch-
loride to a solution of pyrrole 2 (and 3) in glacial acetic
acid. The desired iodopyrroles 4 and 5 were easily obtained
upon completion the reaction by adding water and filtrating
the precipitated solids. Advantages such as quantitative
yields and easy availability of the iodopyrroles constitute
a considerable improvement over the commonly used
I2/KI procedure.
While porphycenes have largely been tested in the field
of PDT, other areas of potential/interest/applications —
as outlined in the introduction — were barely explored. In
lightofthephotophysicalmeasurementspresentedherein,
namely two-photon absorptions, porphycenes exhibit
potential as powerful agents for dye-sensitized solar cells
(
1.8 eV). The energies of second singlet excited states
were derived exclusively from the absorption spectra,
while those of the first singlet excited states came
either from absorption/fluorescence assays or from
electrochemical measurements and are in excellent
agreement. The internal conversion between the Sn
multitude of states and the S state occurs within some
2
1
00 fs. From the correspondingly formed singlet excited
states fluorescence competes with intersystem crossing
to the corresponding triplet manifolds (1.2 eV). In
terms of optical fingerprints, maxima at around 450–
5
00 nm and 950–1000 nm evolved as markers for the
singlet and triplet excited states. The dynamics — both
fluorescence and intersystem crossing — reflect the
(DSSC) or for the functionalization of nanoparticles. In
this context, the high extinction coefficient in the visible
regionandthehighphotostabilityaretwoadditionalassets
for DSSCs. Furthermore, comparing the electrochemical
properties with those known for PDIs prompts to their
use as integrative components in p-type DSSC with, for
example, NiO.
To the best of our knowledge, so far only one
publication focused on the application of porphycenes
in solar cells [43]. Experimental expertise in our groups
exists on both topics and is now transferred to the field of
porphycenes. This is currently under way and will be the
topic of future work.
Acknowledgements
We gratefully acknowledge the DFG, ICMM and
the GSMS (Graduate School of Molecular Science) for
financial support.
Scheme 2. Schematic energy level diagram for porphycenes in
solution. S, T: Singlet, triplet states
Copyright © 2012 World Scientific Publishing Company
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SYNTHESIS AND PHYSICO-CHEMICAL PROPERTIES OF PORPHYCENES
661
Ikegami T, Hori H, Hisaeda Y and Hayashi T.
J. Am. Chem. Soc. 2004; 126: 16007–16017. d)
REFERENCES
1
. Vogel E, Köcher M, Schmickler H and Lex J.
Nakashima H, Hasegawa JY and Nakatsuji H. J.
Comput. Chem. 2006; 27: 1363–1372. e) Matsuo
T, Ikegami T, Sato H, Hisaeda Y and Hayashi T. J.
Inorg. Biochem. 2006; 100: 1265–1271. f) Matsuo
T, Tsuruta T, Maehara K, Sato H, Hisaeda Y and
Hayashi T. Inorg. Chem. 2005; 44: 9391–9396.
3. a) Saoiabi A, Maroufi N, Laghzizil A, Barbe JM
and Guilard R. J. Maro. Chim. Heterocycl. 2005;
Angew. Chem. 1986; 98: 262–264; Angew. Chem.
Int. Ed. 1986; 25: 257–259.
2
3
. Vogel E, Balci M, Pramod K, Koch P, Lex J and
Ermer O. Angew. Chem. 1987; 99: 909–912.
. Richert C, Wessels JM, Müller M, Kisters M, Ben-
ninghaus T and Goetz AE. J. Med. Chem. 1994; 37:
1
2
797–2807.
4
5
. Gottfried V, Davidi R, Avernbuj C and Kimel S. J.
Photochem. Photobiol. B 1995; 30: 115–121.
4
: 65–80. b) Barbe JM, Richard P, Aukauloo MA,
Lecomte C, Petit P and Guilard R. J. Chem. Soc.,
Chem. Commun. 1994; 2757–2758. c) Sánchez-
García D and Sessler JL. Chem. Soc. Rev. 2008; 37:
. a) O’Connor AE, Gallagher WM and Byrne AT.
Photochem. Photobiol. 2009; 85: 1053–1074. b)
Sessler JL, Gebauer A and Vogel E. The Porphy-
rin Handbook, Vol. 2, Kadish KM, Smith KM and
Guilard R. (Eds.)Academic Press: San Diego, 2000;
pp 1–54. c) Stockert JC, Canete M, Juarranz A, Vil-
lanueva A, Horobin RW, Borrell JI, Teixido J and
Nonell S. Curr. Med. Chem. 2007; 14: 997–1026.
. Levanon H, Toporowicz M, Ofir H, Fessenden RW,
Das PK, Vogel E, Köcher M and Pramot K. J. Phys.
Chem. 1988; 92: 2429–2433.
. See for example: a) Braslavsky SE, Müller M, Mar-
tire DO, Pörting S, Bertolotti SG, Chakravorti S,
Koc-Weier G, Knipp B and Schaffner K. J. Photo-
chem. Photobiol. B 1997; 40: 191–198. b) Ofir H,
Regev A, Levanon H, Vogel E, Köcher M and Balci
M. J. Phys. Chem. 1987; 91: 2686–2688.
2
15–232.
1
1
1
4. Gnichwitz JF, Marczak R, Werner F, Lang N, Jux N,
Guldi DM, Peukert W and Hirsch A. J. Am. Chem.
Soc. 2010; 132: 17910–17920.
5. Marczak R, Werner F, Gnichwitz JF, Hirsch A,
Guldi DM and Peukert W. J. Phys. Chem. C 2009;
6
7
1
13: 4669–4678.
6. a) Imahori H, Tamaki K, Guldi DM, Luo C, Fujit-
suka M, Ito O, Sakata Y and Fukuzumi S. J. Am.
Chem. Soc. 2001; 123: 2607–2617. b) Da Ros T,
Prato M, Guldi DM, Alessio E, Ruzzi M and Pasi-
meni L. Chem. Commun. 1999; 635–636. c) Hauke
F, Guldi DM and Hirsch A. J. Mater. Chem. 2002;
1
2: 2088–2094.
1
1
1
7. Guldi DM, Luo C, Swartz A, Scheloske M and
Hirsch A. Chem. Commun. 2001; 1066–1067.
8. Guldi DM, Pellarini F, Prato M, Granito C and
Troisi L. Nano Lett. 2002; 2: 965–968.
9. a) Guldi DM, Taieb H, Rahman GNA, Tagmatarchis
N and Prato M. Adv. Mater. 2005; 17: 871–875. b)
Ehli C, Rahman GMA, Jux N, Balbinot D, Guldi
DM, Paolucci F, Marcaccio M, Paolucci D, Melle-
Franco M, Zerbetto F, Campidelli S and Prato M. J.
Am. Chem. Soc. 2006; 128: 11222–11231.
8
9
. D’Souza F, Boulas P, Aukauloo AM, Guilard R,
Kisters M, Vogel E and Kadish KM. J. Phys. Chem.
1
994; 98: 11885–11891.
. See for example: a) Kadish KM, Caemelbecke EV,
Boulas P, D’Souza F, Vogel E, Kisters M, Medforth
CJ and Smith KM. Inorg. Chem. 1993; 32: 4177–
4
178. b) D’Souza F, Boulas PL, Kisters M, Sam-
brotta L, Aukauloo AM, Guilard R and Kadish KM.
Inorg. Chem. 1996; 35: 5743–5746.
1
0. See for example: a) Fita P, Urbanska N, Radzewicz
C and Waluk J. Chem. Eur. J. 2009; 15: 4851–4856.
b) Gil M, Dobkowski J, Wiosna-Salyga G, Urban-
ska N, Fita P, Radzewicz C, Pietraszkiewicz M,
Borowicz P, Marks D, Glasbeek M and Waluk J.
J. Am. Chem. Soc. 2010; 132: 13472–13485. c)
Langer U, Hoelger C, Wehrle B, Latanowicz L,
Vogel E and Limbach HH. J. Phys. Org. Chem.
2
0. Nonell S, Bou N, Borrell JI, Teixido J, Villanueva
A, Juarranz A and Canete M. Tetrahedron Lett.
1
995; 36: 3405–3408.
1. Hennig W. PhD Thesis, University of Cologne,
992.
2
2
1
2. Gavalda A, Borrell JI, Teixido J, Nonell S, Arad O,
Grau R, Canete M, Juarranz A, Villanueva A and
Stockert JC. J. Porphyrins Phthalocyanines 2001;
2
000; 13: 23–34.
5
: 846–852.
1
1
1. Hayashi T, Okazaki K, Urakawa N, Shimakoshi H,
2
2
2
2
2
3. Arad O, Morros J, Batllori X, Teixido J, Nonell S
and Borrell JI. Org. Lett. 2006; 8: 847–850.
4. Sánchez-García D, Borrell JI and Nonell S. Org.
Lett. 2009; 11: 77–79.
5. Suzuki M, Miyoshi M and Matsumoto K. J. Org.
Chem. 1974; 39: 1980.
6. Barton DHR, Kervagoret J and Zard SZ. Tetrahe-
dron 1990; 46: 7587–7598.
7. Paine III JB and Dolphin D. J. Org. Chem. 1988; 53:
Sessler JL, Vogel E and HisaedaY. Organometallics
2
001; 20: 3074; Lo WC, Che CM, Cheng KF and
Mak TCW. Chem. Commun. 1997; 1205–1206.
2. a) Hayashi T, Dejima H, Matsuo T, Sato H, Murata
D and Hisaeda Y. J. Am. Chem. Soc. 2002; 124:
1
1226–11227. b) Hayashi T, Murata D, Makino
M, Sugimoto H, Matsuo T, Sato H, Shiro Y and
Hisaeda Y. Inorg. Chem. 2006; 45: 10530–10536.
c) Matsuo T, Dejima H, Hirota S, Murata D, Sato H,
2
787–2795.
Copyright © 2012 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2012; 16: 661–662

6
62
W. BRENNER ET AL.
2
2
8. Waluk J, Müller M, Swiderek P, Köcher M, Vogel E,
35. Aramendia PF, Redmond RW, Nonell S, Schuster
W, Braslavsky SE, Schaffner K and Vogel E.
Photochem. Photobiol. 1986; 44: 555–559.
36. Nonell S, Aramendia PF, Heihoff K, Negri RM
and Braslavsky SE. J. Phys. Chem. 1990; 94:
5879–5883.
37. Redmond RW, Valduga G, Nonell S, Braslavsky SE,
Schaffner K, Vogel E, Pramod K and Köcher M. J.
Photochem. Photobiol. B 1989; 3: 193–207.
38. Rubio N, Prat F, Bou N, Borrell JI, Teixidó J,
Villanueva Á, Juarranz Á, Cañete M, Stockert JC
and Nonell S. New J. Chem. 2005; 29: 378–384.
39. Ware WR. J. Phys. Chem. 1962; 66: 455–458.
40. Fita P, Radzewicz C and Waluk J. J. Phys. Chem. A
2008; 112: 10753–10757.
Hohlneicher G and Michl J. J. Am. Chem. Soc.
1
991; 113: 5511–5527.
9. a) Kadish KM, Caemelbecke EV and Royal G.
In The Porphyrin Handbook, Vol. 8, Kadish KM,
Smith KM and Guilard R. (Eds.) Academic Press:
San Diego, 2000; pp 1–114. b) L’Her M and
Pondhaven A. In The Porphyrin Handbook, Vol.
1
6, Kadish KM, Smith KM and Guilard R (Eds.)
Academic Press: San Diego, 2000; pp 117–170.
0. Rubio N, Borrell JI, Teixido J, Canete M, Juarranz
A, Villanueva A, Stockert JC and Nonell S.
Photochem. Photobiol. Sci. 2006; 5: 376–380.
1. Guldi DM, Field J, Grodkowski J, Neta P and Vogel
E. J. Phys. Chem. 1996; 100: 13609–13614.
3
3
3
3
3
2. Guldi DM, Neta P, Heger A, Vogel E and Sessler JL.
J. Phys. Chem. A 1998; 102: 960–967.
41. Kawaoka K, Khan A and Kearns DR. J. Chem.
Phys. 1967; 46: 1842–1853.
42. Arnbjerg J, Jiménez-Banzo A, Paterson MJ, Nonell
S, Borrell JI, Christiansen O and Ogilby PR. J. Am.
Chem. Soc. 2007; 129: 5188–5199.
3. Bernard C, Gisselbrecht JP, Gross M, Jux N and
Vogel E. J. Electroanal. Chem. 1995; 381: 159–166.
4. Kadish KM, Boulas PL, Kisters M, Vogel E,
Aukauloo AM, D’Souza F and Guilard R. Inorg.
Chem. 1998; 37: 2693–2700.
43. Yamada Y, Okushima T, Ono N and Kuzuhara H.
Jpn. Kokai Tokkyo Koho 2010, JP 2010077054.
Copyright © 2012 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2012; 16: 662–662