Tuning the electronic properties of porphyrin dyes: Effects of meso substitution on their optical and electrochemical behaviour

Article abstract of DOI:10.1002/ejoc.201300124

Two series of unsymetrically functionalized, carboxyethynylphenyl- containing porphyrins, bearing either 2,4,6-triisopropylphenyl or triphenylamino substituents at three of the four meso positions, have been prepared by Sonogashira coupling from the corre

Full text of DOI:10.1002/ejoc.201300124

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FULL PAPER
DOI: 10.1002/ejoc.201300124
Tuning the Electronic Properties of Porphyrin Dyes: Effects of meso
Substitution on Their Optical and Electrochemical Behaviour
Maria-Eleni Ragoussi,[a] Gema de la Torre,*[a] and Tomás Torres*[a]
Dedicated to the memory of Professor Christian G. Claessens
Keywords: Porphyrinoids / Dyes / Electronic structure / Redox chemistry / Structure–activity relationships
Two series of unsymetrically functionalized, carboxyethynyl-
phenyl-containing porphyrins, bearing either 2,4,6-triiso-
propylphenyl or triphenylamino substituents at three of the
four meso positions, have been prepared by Sonogashira
coupling from the corresponding ethynyl- or iodo-function-
alized porphyrin precursors. UV/Vis and electrochemical
measurements have been performed to determine the elec-
tronic features of these new compounds and, hence, their
potential as dyes for dye-sensitized solar cells.
moiety (i.e., COOH) because it provides an optimal dis-
tance between the sensitizer and the semiconductor to re-
tard undesired charge recombination.[6] Regarding the ac-
ceptor/anchoring moiety itself, some papers have been pub-
lished in which the effect of double carboxylic acid substitu-
tion on porphyrins[7] and other chromophores[8] as a way
to increase the stability and, therefore, the performance of
the cell was explored.
Introduction
In the last few years, porphyrins have proved to be realis-
tic candidates for replacing the costly and environmentally
unfriendly ruthenium-based sensitizers in dye-sensitized so-
lar cells (DSSCs).[1] In addition to their well-known light-
harvesting properties, porphyrins have redox properties ap-
propriate for the sensitization of TiO2 films; the LUMO
level of the macrocycles lies above the TiO2 conduction
band, and the HOMO level is close to the redox potential
of the electrolyte, which ensures efficient dye regeneration.
Additionally, adjustment of the electronic levels of the
macrocycle is possible by changing the porphyrin substitu-
tion at the meso and β positions, and also by changing the
complexed metal, with ZnII proving to be the best choice
for obtaining efficient sensitizers.[2]
The best ZnII porphyrin sensitizers, showing efficiency
values of up to 12.3% (see Scheme 1),[3] have a “push–pull”
substitution pattern, with an electron-donating arylamino
group at one of the meso carbon atoms and an electron-
withdrawing carboxyphenylethynyl anchoring group at the
opposite meso position.[4] The beneficial effect of the substi-
tution with electron-donating diarylamino groups has been
rationalized in terms of broadening and redshifting of the
absorption features of the porphyrins, together with more
efficient electron-injection abilities.[5] The phenylethynyl
unit is well-established and widely used as a bridging moi-
ety between the porphyrin core and the acceptor/anchoring
[a] Departamento de Química Orgánica, Universidad Autónoma
de Madrid,
28049 Madrid, Spain
E-mail: tomas.torres@uam.es
Homepage: www.uam.es/phthalocyanines
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201300124
Scheme 1.
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Another structural feature that has been shown to have tron injection and dye regeneration. Other authors have ex-
a strong impact on the photovoltaic performance of ZnII plored the ortho-substitution approach using methyl radi-
porphyrins is the substitution with linear alkoxy chains at cals, which turned out to be too short to effectively protect
the ortho position of the phenyl groups linked at the macro- the porphyrins from dye aggregation.[11] Still, a “push–pull”
cyclic meso carbon atoms. The effect of these chains is two- derivative bearing ortho-methylphenyl rings has reached
fold: to protect the porphyrin core and so impede charge efficiencies as high as 7%.[12]
recombination processes,[9] and also to effectively decrease
In a search for new hints to the rational molecular design
the dye aggregation and so allow an efficient electron injec- and optimization routes, we are exploring ortho substitution
tion. Diau and co-workers have successfully used this ap- of the phenyl rings of ZnII tetraphenylporphyrins as a tool
proach.[2,10] In the meantime, ortho-alkoxy substitution to adjust the electronic levels of the sensitizer to the con-
raises both HOMO and LUMO levels, as can be seen, for duction band of TiO2 and to the redox potential of the
example, on going from YD2[3] to YD2-oC8[2] (Scheme 1), electrolytes, and also to hinder aggregation of the macro-
and this would seem to be beneficial for maximizing elec- cycles. In particular, we have prepared porphyrins function-
alized at the meso positions with 2,4,6-triisopropylphenyl
substituents. For the sake of comparison, we have also pre-
pared porphyrins substituted with three arylamino moieties,
which are well-established substituents for efficient DSSCs.
Also, mono- and double carboxylic acid substitution is
compared in the pursuit of compounds with better adsorp-
tion properties to the TiO2 (Scheme 2).
Results and Discussion
Our investigation started with the porphyrins bearing
2,4,6-triisopropylphenyl units at the meso-positions
(Scheme 3). For the sake of comparison, we prepared por-
phyrins having carboxyphenylethynyl anchoring moieties
(i.e., compounds 2 and 3), and also a porphyrin with a turn-
around connectivity between the COOH and the porphyrin
core (i.e., compound 1 bearing a p-carboxyethynylphenyl
group). The preparation of 1 involved initially the synthesis
of derivative 7 by reaction of 2,4,6-triisopropylbenzalde-
hyde,[13] 4-iodobenzaldehyde, and pyrrole, in the presence of
BF3·OEt2, under the standard conditions described in the
literature[14] (see Exp. Sect. for details). Compound 7 was
obtained in a rather low yield (7%), which, however, is not
surprising considering the significant steric effect of the iso-
propyl groups. The isolation of this free-base derivative was
Scheme 2.
followed by zinc(II) metalation with Zn(OAc)2, and Sono-
Scheme 3. (a) pyrrole, 4-iodobenzaldehyde, BF3·OEt2, CHCl3/EtOH, room temp., 1 h; followed by DDQ (2,3-dichloro-5,6-dicyano-1,4-
benzoquinone), room temp., 1.5 h, (b) Zn(OAc)2, CH2Cl2/MeOH, room temp., 1 h, (c) propiolic acid, CuI, PdCl2(PPh3)2, THF/Et3N,
room temp., 1 h.
2
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Tuning the Electronic Properties of Porphyrin Dyes
gashira coupling with propiolic acid to obtain the desired The yield of this step was equally low (7%). Compound 9
porphyrin. During this last step of the procedure, a fair was subsequently subjected to iodination with
amount of the starting material (compound 8) remained PhI(CF3COO)2 and I2, metallation with Zn(OAc)2, and
unreacted after several hours of reaction. Efforts to improve stepwise Sonogashira couplings to get to the final por-
the yield by varying the conditions and the catalyst of the phyrins bearing one (in 2) or two (in 3) carboxylic acid moi-
coupling proved fruitless. Nonetheless, it is noteworthy that eties. It is worth mentioning that even though the first
the yield based on the recovered starting material was mod- Sonogashira coupling to install the trimethylsilylethynyl
erate (55%).
group was carried out using the most common catalytic sys-
The synthesis of porphyrins 2 and 3 was originally at- tem of CuI/PdCl2(PPh3)2, the second coupling to attach the
tempted following the same strategy, but replacing 4-iodo- carboxyphenyl rings did not proceed under these condi-
benzaldehyde by trimethylsilylpropynal as a way to install tions. Therefore, Lindsey’s conditions[15] [i.e., Pd2(dba)3/
the alkyne moiety. However, this approach proved unsuc- AsPh3] were used, and the reaction took place smoothly.
cessful, since no trace of the desired porphyrin was de- Moderate to good yields were obtained in all of the steps
tected. To overcome this problem, an alternative pathway following the formation of the porphyrin ring.
was envisaged (Scheme 4). Condensation of 2,4,6-triiso-
The synthesis of the arylamino analogues turned out to
propylbenzaldehyde and paraformaldehyde in the appropri- be more straightforward and higher-yielding (Scheme 5).
ate ratio (see Exp. Sect.), led to porphyrin 9, which was Reaction of 4-(diphenylamino)benzaldehyde (14),[16] tri-
singled out for having one of the four meso positions free. methylsilylpropynal, and pyrrole under the usual conditions
Scheme 4. (a) pyrrole, paraformaldehyde, BF3·OEt2, CHCl3/EtOH, room temp., 1 h followed by DDQ, room temp., 1.5 h,
(b) PhI(CF3COO)2, I2, CHCl3, pyridine, 20 min, room temp., (c) Zn(OAc)2, CH2Cl2/MeOH, room temp., 2 h, (d) ethynyltrimethylsilane,
CuI, PdCl2(PPh3)2, THF/Et3N, room temp., 15 min, (e) TBAF (tetrabutylammonium fluoride), THF, 0 °C to room temp., 30 min, (f) 4-
iodobenzoic acid, AsPh3, Pd2(dba)3, THF/Et3N, room temp., 30 min, (g) dimethyl 4-bromophthalate, AsPh3, Pd2(dba)3, THF/Et3N, 60 °C,
20 min, (h) NaOH, THF/MeOH, 60 °C, 30 min.
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Scheme 5. (a) pyrrole, trimethylsilylpropynal, BF3·OEt2, CHCl3/EtOH, room temp., 1 h, followed by DDQ, room temp., 1.5 h,
(b) Zn(OAc)2, CH2Cl2/MeOH, room temp., 1 h, (c) TBAF, THF, 0 °C to room temp., 1 h, (d) 4-iodobenzoic acid, AsPh3, Pd2(dba)3, THF/
Et3N, room temp., 1 h, (e) dimethyl 4-bromophthalate, AsPh3, Pd2(dba)3, THF/Et3N, 60 °C, 18 h (f) NaOH, THF/MeOH, 60 °C, 30 min.
gave porphyrin derivative 15 in 13% yield. The conversion of magnitude lower than their monocarboxylic analogues,
to 4 and 5 was accomplished by metallation followed by probably due to the aggregation of these dyes in solution.
Sonogashira couplings, following the same procedure as de-
scribed above, with good yields in all steps.
The steady-state fluorescence spectra of compounds 1–5
were measured in CHCl3 by exciting at the maxima of the
corresponding Soret bands (Figure 2 and Figure S1 in the
Supporting Information). The wavelengths for the emission
maxima are listed in Table 1. The zero–zero excitation en-
ergy (E0–0) values were estimated from the intersection of
the normalized absorption and emission spectra, and are
also shown in Table 1.
The HOMO and LUMO energy levels of compounds 1–5
were determined by cyclic voltammetry measurements and
square-wave voltammetry, as shown in Figure 3 and Fig-
ure S2 in the Supporting Information. The electrochemical
and optical data, together with the HOMO/LUMO values,
are summarized in Table 1. The first oxidation reactions of
compounds 1–5 are observed in the range of 0.31–0.40 V
vs. Fc/Fc+, and are consistent with the formation of the
porphyrin radical cation. The second oxidative wave of
Spectroscopic and Electrochemical Studies
Figure 1 shows the UV/Vis absorption spectra of com-
pounds 1–5 in CHCl3. The monocarboxylic acid derivatives,
namely 1, 2, and 4, showed significantly higher extinction
coefficients than their dicarboxyl analogues, with 4 having
the highest. In addition, porphyrin 1, the only derivative
bearing a phenyl ring instead of an alkyne directly con-
nected to the porphyrin ring, was blueshifted in comparison
to the other porphyrins. The peak positions and molar ab-
sorption coefficients of Soret and Q-bands are listed in
Table 1. It is also noteworthy that 3 and 5, which bear two
anchoring groups, present very broad Soret and Q-bands,
and their extinction coefficients are more than one order
4
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Tuning the Electronic Properties of Porphyrin Dyes
Figure 2. Fluorescence spectra of porphyrins 2 and 4 in CHCl3.
Excitation wavelength for compound 2, 444 nm; compound 4,
446 nm.
Figure 1. UV/Vis spectra in CHCl3 of (a) monocarboxylic acid de-
rivatives (1, 2, and 4), and (b) dicarboxylic acid derivatives (3 and
5). An enlargement of the Q-band region is shown in the inset.
compounds 4 and 5 matches that of the reference tri-
phenylamine (TPA) (Figure 3 and Figure S2 in the Support-
ing Information) and, consequently, it can be assigned as a
redox event taking place at the triphenylamino substituents,
as previously established for other arylamino-substituted
derivatives.[18]
Remarkably, the first oxidation waves of the porphyrins
bearing 2,4,6-triisopropylphenyl substituents (i.e., com-
pounds 1–3) are cathodically shifted by 90–160 mV com-
pared to the first oxidation waves of the compounds func-
Figure 3. Square-wave voltammetry of porphyrins 2 and 4 and tri-
phenylamine in CH2Cl2 with 0.1 m tetrabutylammonium hexafluo-
rophosphate (TBAPF6) as electrolyte. Working electrode: Pt; refer-
ence electrode: Ag/AgNO3; calibrated with ferrocene/ferrocenium
(Fc/Fc+) as an external reference. Counter electrode: Pt.
tionalized with arylamino moieties (i.e., compounds 4 and these derivatives (Table 1). Although one would expect an
5). Binding energies of 0.90 and 1.06 eV, respectively, vs. increase in the energy of the HOMO level upon substitution
normal hydrogen electrode (NHE) were determined for of the porphyrin with strongly electron-donating amino
Table 1. Optical, electrochemical data and HOMO/LUMO levels for porphyrins 1–5.
Dye λabs[a] [nm] (ε [103 m–1 cm–1])
λem[b] [nm]
Eox1/2 [V]
HOMO [eV] E0–0[c] [eV]
(vs. NHE)
LUMO[d] [eV] ΔGinj [eV] ΔGreg [eV]
(vs. NHE)
(vs. Fc/Fc+)
1
2
3
4
5
403 (5.23), 551 (4.1), 591 (3.40)
444 (4.4), 568 (3.05), 617 (3.29)
444 (3.85), 568 (2.99), 616 (3.0)
446 (5.26), 571 (4.11), 622 (4.36)
445 (4.04), 577 (3.28), 629 (3.36)
608, 652
623
628
656
662
0.31
0.28
0.26
0.42
0.40
0.95
0.92
0.90
1.06
1.04
2.06
1.93
1.92
1.88
1.86
–1.11
–1.01
–1.02
–0.82
–0.82
–0.61
–0.51
–0.52
–0.32
–0.32
–0.42
–0.39
–0.37
–0.53
–0.51
[a] Wavelengths for Soret and Q-band maxima in CHCl3. [b] Wavelengths for emission maxima in CHCl3 by exciting at 440 nm. [c] E0–0
was estimated from the interception of the corresponding absorption and emission spectra. [d] LUMO was calculated using the equation
ELUMO = EHOMO – E0–0
.
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groups, it was recently reported that the HOMO levels of a
Figure 4 shows an energy-level diagram for the porphyrin
series of related ZnII porphyrins with an increasing number dyes, comparing their HOMO–LUMO levels with the stan-
of triphenylamino substituents (i.e., where the tri- dard potential for the conducting band (CB) of TiO2 vs.
–
phenylamine is bound to the meso position of the porphyrin NHE: ECB = –0.5 V, and for the iodide/triiodide (I–/I3 ) re-
core through the para position of one of the phenyl rings) dox couple vs. NHE: E = 0.53 V.[5,17] The driving forces for
are virtually identical.[18] This result indicates that function- electron injection from the porphyrin excited singlet state
alization with triphenylamine moieties causes an insignifi- to the CB of TiO2 (ΔGinj) and for the regeneration of the
–
cant variation of the HOMO energy, probably as a conse- porphyrin radical cation by the I–/I3 redox couple (ΔGreg
)
quence of the orthogonal disposition of the phenyl rings, in a conventional DSSC have been determined (Table 1).
and the resulting low level of conjugation between the elec- Both processes are thermodynamically feasible, and the
trons of the N atom and the aromatic cloud of the por- driving forces values (Ͻ –0.3 V) would allow efficient elec-
phyrin. In contrast, it was recently published that the pres- tron transfer in a solar cell.
ence of alkyl and alkoxy chains at the ortho positions of
phenyl rings linked to the porphyrin core has a strong im-
Conclusions
pact on the HOMO levels and, therefore, ortho-substituted
compounds show higher HOMO energy levels than related
meta- or para-functionalized derivatives.[10a] On the other
hand, substitution of the porphyrin core with two carbox-
ylic acids does not affect the HOMO energy compared to
the monosubstituted counterparts.
Two series of unsymetrically functionalized, carboxy-
ethynylphenyl-containing porphyrins (1–5) have been pre-
pared in the search for new structural parameters that can
bring about higher efficiencies in DSSCs based on por-
phyrin dyes. A comparison of the optical and electrochemi-
cal features and, therefore, of the HOMO–LUMO levels be-
tween triisopropylphenyl- (1–3) and triphenylamino-substi-
tuted (4 and 5) derivatives indicates that the former have
higher HOMO and LUMO levels, close to those of the best
porphyrin dyes reported in the literature with maximal elec-
tron-injection and dye-regeneration abilities. In addition,
the presence of bulky isopropyl groups hinders the aggrega-
tion of the macrocycles, which is also beneficial. In this way,
functionalization with triisopropylphenyl moieties at the
meso positions of carboxyporphyrins arises as a plausible
substitution pattern for obtaining efficient dyes for DSSCs.
The construction and measurements of DSSCs based on
these derivatives is currently underway.
As the reduction processes of compounds 1–5 could not
be recorded by cyclic voltammetry or by square-wave ex-
periments, the LUMO binding energies were estimated by
subtracting the E0–0 values from the electrochemically de-
termined HOMO binding energies. This yielded LUMO
binding energies ranging from –1.11 to –0.82 eV (vs. NHE).
In general, porphyrins bearing 2,4,6-triisopropylphenyl sub-
stituents (i.e., compounds 1–3) showed more negative
LUMO values than those functionalized with tri-
phenylamine groups. Remarkably, compound 1, with tris-
(isopropyl)phenyl moieties and a carboxyethynylphenyl an-
choring group (i.e., with a connectivity that is opposite to
that commonly used in reported porphyrin sensitizers)
showed the most negative LUMO value of the series, and
this would, in principle, contribute to a better electron injec-
tion from this dye to TiO2 in a DSSC cell. As for the
HOMO values, substitution of the porphyrin core with two
carboxylic acid moieties does not have an influence on the
LUMO energies compared to the monosubstituted counter-
parts.
Experimental Section
General Remarks: H and 13C NMR spectra were recorded at 300
1
and 75 MHz, respectively, at 25 °C with a BRUKER AC-300 in-
strument. Chemical shifts are given in parts per million, coupling
constants are given in Hertz. UV/Vis spectra were recorded with a
JASCO V-660 spectrophotometer. Fluorescence spectra were re-
corded with a JASCO J-810 spectropolarimeter equipped with a
JASCO PTC-4235 temperature controller, using Hellma® precision
cells made of Quartz Suprasil® (0.2 mm, 106-QS). IR spectra were
recorded with a Bruker Vector 22 spectrophotometer. HRMS spec-
tra were recorded with a VG AutoSpec instrument. MALDI-TOF
mass spectra were recorded with a Bruker Reflex III spectrometer.
Electrochemical measurements were performed at room tempera-
ture in a potentiostate/galvanostate Autolab PGSTAT30 using a
home-built one-compartment cell with a three-electrode configura-
tion, containing 0.1 m tetrabutylammonium hexafluorophosphate
(TBAPF6) as supporting electrolyte. Column chromatography was
carried out on silica gel Merck-60 (230–400 mesh, 60 Å), and TLC
was carried out on aluminum sheets pre-coated with silica gel 60
F254 (E. Merck). Chemicals were purchased from commercial sup-
pliers and used without further purification.
5-(4-Iodophenyl)-10,15,20-tris[(2,4,6-triisopropyl)phenyl]porphyrin
(7): Pyrrole (0.445 mL, 6.54 mmol), 4-iodobenzaldehyde (0.378 g,
1.63 mmol), and EtOH (4.9 mL) were added to a solution of 6
Figure 4. Schematic energy level diagram (HOMO–LUMO) for
dyes 1–5.
6
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Tuning the Electronic Properties of Porphyrin Dyes
(1.14 g, 4.91 mmol) in CHCl3 (654 mL). The mixture was deoxy-
genated by bubbling argon through it for 15 min, after which
BF3·OEt2 (0.290 mL, 2.30 mmol) was added, and the resulting mix-
ture was stirred at room temperature in the dark for 1 h. 2,3-
Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ; 1.11 g, 4.91 mmol)
was subsequently added, and the mixture was stirred for a further
1.5 h. Finally, addition of Et3N (1.5 mL) and filtration through sil-
ica gave a crude mixture, which was purified by column chromatog-
raphy (CH2Cl2/hexane, 1:2) and washing with MeOH, to give por-
phyrin 7 (0.13 g, 7 %) as a dark reddish powder. 1H NMR
(300 MHz, CDCl3): δ = –2.47 (s, 2 H, NH), 0.80–0.90 (m, 54 H,
CH3), 2.21–2.25 (m, 6 H, CH), 3.19–3.28 (m, 3 H, CH), 7.35 (d, J
= 6.0 Hz, 6 H, ArH), 7.96 (d, J = 6.0 Hz, 2 H, ArH), 8.08 (d, J =
6.0 Hz, 2 H, ArH), 8.59 (d, J = 6.0 Hz, 4 H, ArH), 8.73 (s, 4 H,
ArH) ppm. UV/Vis (CHCl3): λmax (logε) = 298 (3.77), 371 (3.84),
404 (4.37), 418 (4.74), 517 (3.77), 552 (3.44), 591 (3.26), 647 (3.14)
nm. MS (MALDI-TOF, dithranol): m/z = 1118.6 [M]+.
(2.83), 583 (2.93), 638.5 (2.25) nm. MS (MALDI-TOF, dithranol):
m/z = 916.6 [M]+.
5-Iodo-10,15,20-tris[(2,4,6-triisopropyl)phenyl]porphyrin (10): A
solution of PhI(CF3COO)2 (15 mg, 0.035 mmol) in CHCl3 was
added to a solution of porphyrin 9 (50 mg, 0.055 mmol) and I2
(8 mg, 0.031 mmol) in CHCl3 (6 mL), and then pyridine (1 drop)
was added to the mixture. The mixture was stirred at room tem-
perature for 1 h, after which it was quenched with Na2S2O3 and
extracted with CH2Cl2. Purification by column chromatography
(hexane/CH2Cl2, 2:1) gave compound 10 (56 mg, quant.) as a dark
1
pink solid. H NMR (300 MHz, CDCl3): δ = –2.34 (s, 2 H, NH),
0.83–0.95 (m, 54 H, CH3), 2.19–2.28 (m, 6 H, CH), 3.20–3.30 (m,
3 H, CH), 7.37 (d, J = 12.0 Hz, 6 H, ArH), 8.55–8.61 (m, 4 H,
ArH), 8.78 (d, J = 6.0 Hz, 2 H, ArH), 9.60 (d, J = 6.0 Hz, 2 H,
ArH) ppm. 13C NMR (75 MHz, CDCl3): δ = 28.81 (isopropyl),
31.50 (isopropyl), 34.40 (isopropyl), 34.71 (isopropyl), 114.22
(ArC), 119.02 (ArC), 120.39 (ArC), 122.17 (ArC), 130.35 (ArC),
131.24 (ArC), 135.57 (ArC), 137.59 (ArC), 139.43 (ArC), 147.67
(ArC), 148.80 (ArC), 149.63 (ArC), 149.89 (ArC), 150.00 (ArC)
ppm. UV/Vis (CHCl3): λmax (logε) = 310.5 (2.97), 434 (4.48), 519.5
(2.24), 564.5 (3.03), 605.5 (2.89), 618 (2.74) nm. MS (MALDI-TOF,
dithranol): m/z = 1042.5 [M]+.
5-(4-Carboxyethynylphenyl)-10,15,20-tris[(2,4,6-triisopropyl)phen-
yl]porphyrinatozinc(II) (1): Zn(OAc)2 (200 mg, 1.09 mmol) was
added to a solution of porphyrin 7 (110 mg, 0.098 mmol) in
CH2Cl2 (45 mL) and MeOH (15 mL). The mixture was stirred at
room temperature for 1 h, after which the solvents were evaporated
in vacuo. The crude was extracted with CH2Cl2 and, after evapora-
tion of the solvent, the solid residue was washed with MeOH. It
was then redissolved in THF (3 mL) and Et3N (1 mL), and CuI
(4 mg, 0.02 mmol) and PdCl2(PPh3)2 (6 mg, 0.0085 mmol) were
added. The mixture was deoxygenated, by bubbling argon through
it for 15 min, and then propiolic acid (6 μL, 0.098 mmol) was
added. After stirring at room temperature for 1 h, the solvents were
evaporated in vacuo, and the residue was extracted with CH2Cl2.
Purification by column chromatography and subsequent washing
with MeOH/H2O (4:1) gave porphyrin 1 (27 mg, 25%; yield based
on recovered starting material, 55%) as a dark pink solid. 1H NMR
(300 MHz, [D8]THF): δ = 0.79–0.89 (m, 34 H, CH3), 1.50 (t, J =
6.0 Hz, 20 H, CH3), 2.29–2.33 (m, 6 H, CH), 3.16–3.23 (m, 3 H,
CH), 7.39 (s, 6 H, ArH), 7.98 (d, J = 9.0 Hz, 2 H, ArH), 8.23 (d,
J = 6.0 Hz, 2 H, ArH), 8.50 (d, J = 4.5 Hz, 2 H, ArH), 8.54 (d, J
= 4.5 Hz, 2 H, ArH), 8.70 (d, J = 6.0 Hz, 2 H, ArH), 8.78 (d, J =
6.0 Hz, 2 H, ArH), 10.84 (s, 1 H, COOH) ppm. UV/Vis (CHCl3):
λmax (logε) = 306 (4.0), 403 (4.41), 422 (4.61), 517 (3.37), 551 (4.10),
591 (3.40) nm. HRMS (MALDI-TOF, dithranol): calcd. for
C74H82N4O2Zn 1122.5729; found 1122.5724.
5,10,15-Tris[(2,4,6-triisopropyl)phenyl]-20-(trimethylsilylethynyl)por-
phyrinatozinc(II) (12): Porphyrin 10 (56 mg, 0.055 mmol) was dis-
solved in CH2Cl2 (33 mL) and MeOH (11 mL), and Zn(OAc)2
(96 mg, 0.52 mmol) was added. The mixture was stirred at room
temperature for 30 min, after which the solvents were evaporated
in vacuo, and the residue was extracted with CH2Cl2. It was then
redissolved in THF (1 mL) and Et3N (1 mL), and CuI (0.8 mg,
0.004 mmol) and PdCl2(PPh3)2 (2 mg, 0.003 mmol) were added.
The mixture was deoxygenated by bubbling argon through it for
15 min, and then trimethylsilylacetylene (15 μL, 0.11 mmol) was
added. After stirring at room temperature for 20 min, the solvents
were evaporated in vacuo, and the residue was extracted with
CH2Cl2. Purification by column chromatography (hexane/THF,
4:1) gave porphyrin 12 (46 mg, 80%) as a dark pink solid. 1H NMR
(300 MHz, CDCl3): δ = 0.61 (s, 9 H, 3 CH3Si), 0.90–0.94 (m, 54
H, CH3), 2.82–2.94 (m, 6 H, CH), 3.50–3.66 (m, 3 H, CH), 7.35
(d, J = 12.0 Hz, 6 H, ArH), 8.54 (dd, J = 3.0, 15.0 Hz, 4 H, ArH),
8.79 (d, J = 6.0 Hz, 2 H, ArH), 9.62 (d, J = 6.0 Hz, 2 H, ArH)
ppm. 13C NMR (75 MHz, CDCl3): δ = 0.67 (SiC), 28.82 (iso-
propyl), 31.53 (isopropyl), 34.45 (isopropyl), 34.73 (isopropyl),
86.05 (alkyne), 88.24 (alkyne), 120.07 (ArC), 122.21 (ArC), 125.70
(ArC), 130.53 (ArC), 135.97 (ArC), 139.41 (ArC), 147.25 (ArC),
147.67 (ArC), 148.81 (ArC), 149.07 (ArC), 149.62 (ArC), 150.27
(ArC), 151.17 (ArC), 151.69 (ArC), 152.57 (ArC) ppm. UV/Vis
(CHCl3): λmax (logε) = 313 (2.96), 434 (4.46), 521 (2.24), 564 (3.01),
604 (2.85), 617.5 (2.73) nm. MS (MALDI-TOF, dithranol): m/z =
1074.6 [M]+.
5,10,15-Tris[(2,4,6-triisopropyl)phenyl]porphyrin (9): Pyrrole
(0.367 mL, 5.39 mmol), paraformaldehyde (40 mg, 1.33 mmol), and
EtOH (4.0 mL) were added to a solution of 6 (940 mg, 4.05 mmol)
in CHCl3 (540 mL). The mixture was deoxygenated by bubbling
argon through it for 15 min, after which BF3·OEt2 (0.226 mL,
1.80 mmol) was added, and the resulting mixture was stirred at
room temperature in the dark for 1 h. DDQ (920 mg, 4.05 mmol)
was subsequently added, and the mixture was stirred for a further
1.5 h. Finally, addition of Et3N (1.5 mL) and filtration through sil-
ica gave a crude mixture, which was purified by column chromatog-
raphy (CH2Cl2/hexane, 1:4) to give porphyrin 9 (0.103 g, 7%) as a
dark reddish powder. 1H NMR (300 MHz, CDCl3): δ = –2.69 (s, 2
H, NH), 0.81–0.91 (m, 54 H, CH3), 2.18–2.28 (m, 6 H, CH), 3.17–
5,10,15-Tris[(2,4,6-triisopropyl)phenyl]-20-(4-carboxyphenylethyn-
yl)porphyrinatozinc(II) (2): TBAF (1 m in THF; 0.15 mL,
0.15 mmol) was added to a solution of compound 12 (50 mg,
0.05 mmol) in dry THF (4 mL) at 0 °C, and the mixture was stirred
at room temperature for 15 min. The reaction was quenched with
3.29 (m, 3 H, CH), 7.36 (d, J = 12.0 Hz, 6 H, ArH), 8.61–8.65 (m, H2O, and the mixture was extracted with CH2Cl2. Without any
4 H, ArH), 8.86 (d, J = 6.0 Hz, 2 H, ArH), 9.23 (d, J = 6.0 Hz, 2 H, further purification, the deprotected derivative was redissolved in
ArH), 10.09 (s, 1 H, meso-H) ppm. 13C NMR (75 MHz, CDCl3): dry THF (4 mL), and Et3N (1.5 mL), and 4-iodobenzoic acid
δ = 28.87 (isopropyl), 31.50 (isopropyl), 34.04 (isopropyl), 34.72
(isopropyl), 104.13 (meso-CH), 117.55 (ArC), 120.30 (ArC), 122.21
(24 mg, 0.1 mmol) was added. The mixture was deoxygenated by
bubbling argon through it for 15 min, after which AsPh3 (30 mg,
(ArC), 130.43 (ArC), 130.87 (ArC), 135.60 (ArC), 139.52 (ArC), 0.1 mmol) and Pd2(dba)3 (10 mg, 0.01 mmol) were added, and the
147.59 (ArC), 149.48 (ArC), 150.05 (ArC) ppm. UV/Vis (CHCl3):
λmax (logε) = 300 (3.27), 365.5 (3.60), 416 (4.95), 510.5 (3.57), 543
reaction mixture was stirred at reflux for 30 min. The solvents were
then evaporated, and the residue was extracted with CH2Cl2. After
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Pages: 10
M.-E. Ragoussi, G. de la Torre, T. Torres
stirred for a further 1.5 h. Finally, addition of Et3N (1.5 mL) and
FULL PAPER
purification by column chromatography (CH2Cl2 followed by
CH2Cl2/MeOH, 10:1) and washing with MeOH, porphyrin 2 was filtration through silica gave a crude mixture, which was purified
obtained (47 mg, 85 %) as a bright green solid. 1H NMR by column chromatography (CH2Cl2/hexane, 1:1) and washing with
(300 MHz, [D8]THF): δ = 0.91–0.99 (m, 54 H, CH3), 2.30–2.41 (m,
6 H, CH), 3.34–3.48 (m, 3 H, CH), 7.76 (d, J = 3.0 Hz, 6 H, ArH),
8.08 (d, J = 9.0 Hz, 2 H, ArH), 8.24 (d, J = 9.0 Hz, 2 H, ArH),
8.49 (dd, J = 3.0, 15.0 Hz, 4 H, ArH), 8.76 (d, J = 6.0 Hz, 2 H,
ArH), 9.70 (d, J = 6.0 Hz, 2 H, ArH) ppm. UV/Vis (CHCl3): λmax
(logε) = 313 (3.12), 444 (4.4), 568 (3.05), 617 (3.29) nm. HRMS
(MALDI-TOF, dithranol): calcd. for C74H82N4O2Zn 1122.5729;
found 1122.5724.
MeOH to give porphyrin 15 (0.33 g, 13%) as a dark brown powder.
1H NMR (300 MHz, CDCl3): δ = –2.31 (s, 2 H, NH), 0.62 (s, 9 H,
3 CH3Si), 7.13–7.18 (m, 6 H, ArH), 7.41–7.48 (m, 30 H, ArH),
8.03–8.07 (m, 6 H, ArH), 8.92 (s, 4 H, ArH), 9.02 (d, J = 6.0 Hz, 2
H, ArH), 9.67 (d, J = 6.0 Hz, 2 H, ArH) ppm. 13C NMR (75 MHz,
CDCl3): δ = 0.51 (CH3Si), 98.79 (alkyne), 121.09 (ArC), 121.37
(ArC), 121.51 (ArC), 123.51 (ArC), 125.08 (ArC), 129.66 (ArC),
135.57 (ArC), 135.67 (ArC), 135.74 (ArC), 139.41 (ArC), 147.80
(ArC), 147.97 (ArC) ppm. IR (film): ν = 3329, 3059, 3036, 2953,
˜
5-(3,4-Dimethoxycarbonylphenylethynyl)-10,15,20-tris[(2,4,6-tri-
isopropyl)phenyl]porphyrinatozinc(II) (13): TBAF (1 m in THF;
0.12 mL, 0.12 mmol) was added to a solution of compound 12
(30 mg, 0.03 mmol) in dry THF (2 mL) at 0 °C, and the mixture
was stirred at room temperature for 15 min. The reaction was
quenched with H2O, and the mixture was extracted with CH2Cl2.
Without any further purification, the deprotected derivative was
redissolved in dry THF (2 mL) and Et3N (1 mL), and 4-bromo-
phthalate (24 mg, 0.09 mmol) was added. The mixture was deoxy-
genated by bubbling argon through it for 15 min, after which AsPh3
2143, 1593, 1491, 1281, 1157, 849, 754 cm–1. UV/Vis (CHCl3): λmax
(logε) = 303.5 (4.52), 439 (4.71), 537 (3.78), 580 (4.07), 668.5 (3.67)
nm. MS (MALDI-TOF, dithranol): m/z = 1135.5 [M]+.
5,10,15-Tris[(4-diphenylamino)phenyl]-20-(trimethylsilylethynyl)-
porphyrinatozinc(II) (16): Zn(OAc)2 (335 mg, 1.83 mmol) was
added to a solution of porphyrin 15 (190 mg, 0.17 mmol) in
CH2Cl2 (75 mL) and MeOH (25 mL). The mixture was stirred at
room temperature for 30 min, after which the solvents were evapo-
rated in vacuo, and the residue was extracted with CH2Cl2 and
(18 mg, 0.06 mmol) and Pd2(dba)3 (7 mg, 0.007 mmol) were added, washed with MeOH to give compound 16 (200 mg, quant.) as a
1
and the reaction mixture was stirred at reflux for 1 h. The solvents
were then evaporated and the residue was extracted with CH2Cl2.
After purification by column chromatography (hexane/CH2Cl2,
2:1), compound 13 was obtained as a dark green solid (30 mg,
85%). 1H NMR (300 MHz, [D8]THF): δ = 0.85–0.97 (m, 54 H,
CH3), 2.27–2.39 (m, 6 H, CH), 3.19–3.30 (m, 3 H, CH), 7.38 (d, J
= 3.0 Hz, 6 H, ArH), 7.97 (d, J = 9.0 Hz, 1 H, ArH), 8.22 (dd, J
= 3.0, 9.0 Hz, 1 H, ArH), 8.33 (s, 1 H, ArH), 8.50 (dd, J = 3.0,
15.0 Hz, 4 H, ArH), 8.77 (d, J = 6.0 Hz, 2 H, ArH), 9.69 (d, J =
6.0 Hz, 2 H, ArH) ppm. 13C NMR (75 MHz, [D8]THF): δ = 32.14
(isopropyl), 35.45 (isopropyl), 52.49 (COOCH3), 52.61 (COOCH3),
97.79 (alkyne), 120.12 (ArC), 120.61 (ArC), 125.85 (ArC), 126.37
(ArC), 128.89 (ArC), 129.43 (ArC), 131.52 (ArC), 132.28 (ArC),
132.54 (ArC), 134.55 (ArC), 135.22 (ArC), 136.14 (ArC), 137.60
(ArC), 142.86 (ArC), 149.88 (ArC), 150.07 (ArC), 150.19 (ArC),
150.73 (ArC), 150.83 (ArC), 151.79 (ArC), 152.98 (ArC), 187.94
(C=O) ppm. UV/Vis (CHCl3): λmax (log ε) = 328.5 (3.84), 443
(4.63), 567.5 (3.26), 617.5 (3.50) nm. MS (MALDI-TOF,
dithranol): m/z = 1194.6 [M]+.
dark green solid. H NMR (300 MHz, CDCl3): δ = 0.65 (s, 9 H, 3
CH3Si), 7.13–7.19 (m, 6 H, ArH), 7.42–7.50 (m, 30 H, ArH), 8.04–
8.08 (m, 6 H, ArH), 9.02–9.06 (m, 4 H, ArH), 9.12 (d, J = 6.0 Hz,
2 H, ArH), 9.78 (d, J = 6.0 Hz, 2 H, ArH) ppm. IR (film): ν =
˜
3340, 3051, 2924, 2137, 1589, 1489, 1333, 1281, 997, 854, 754,
692 cm–1. UV/Vis (CHCl3): λmax (logε) = 307 (4.20), 445 (4.71),
569.5 (3.59), 618.5 (3.64) nm. MS (MALDI-TOF, dithranol): m/z
= 1197.4 [M]+.
5,10,15-Tris[(4-diphenylamino)phenyl]-20-(4-carboxyphenyl-
ethynyl)porphyrinatozinc(II) (4): TBAF (1 m in THF; 0.64 mL,
0.64 mmol) was added to a solution of compound 16 (192 mg,
0.16 mmol) in dry THF (30 mL) at 0 °C, and the mixture was
stirred at room temperature for 15 min. The reaction was quenched
with H2O, and the mixture was extracted with CH2Cl2. Without
any further purification, the deprotected derivative was redissolved
in dry THF (20 mL) and Et3N (10 mL), and 4-iodobenzoic acid
(80 mg, 0.32 mmol) was added. The mixture was deoxygenated by
bubbling argon through it for 15 min, after which AsPh3 (98 mg,
0.32 mmol) and Pd2(dba)3 (37 mg, 0.04 mmol) were added, and the
5-(3,4-Dicarboxyphenylethynyl)-10,15,20-tris[(2,4,6-triisopropyl)- reaction mixture was stirred at reflux for 1 h. The solvents were
phenyl]porphyrinatozinc(II) (3): A mixture of compound 13 (30 mg,
0.025 mmol) and NaOH (0.5 m; 1.2 mL, 0.6 mmol) in THF (3 mL)
and MeOH (1.2 mL) was heated at reflux for 20 min. It was then
cooled to room temperature, extracted with CH2Cl2, and purified
by reverse-phase column chromatography (H2O/THF, 1:1) to give
porphyrin 3 (18 mg, 60 %) as a dark green solid. 1H NMR
(300 MHz, [D8]THF): δ = 0.9–1.0 (br. m, 54 H, CH3), 2.2–2.4 (br.
then evaporated, and the residue was extracted with CH2Cl2. After
purification by column chromatography (CH2Cl2 followed by
CH2Cl2/MeOH, 10:1) and washing with MeOH, porphyrin 4 was
obtained (170 mg, 85%) as a dark green solid. 1H NMR (300 MHz,
[D8]THF): δ = 7.10–7.15 (m, 6 H, ArH), 7.39–7.49 (m, 30 H, ArH),
8.07 (t, J = 9.0 Hz, 6 H, ArH), 8.16 (d, J = 9.0 Hz, 2 H, ArH),
8.26 (d, J = 9.0 Hz, 2 H, ArH), 8.93–8.97 (m, 4 H, ArH), 9.09 (d,
m, 6 H, CH), 3.1–3.4 (br. m, 3 H, CH), 7.1–7.5 (br. m, 6 H, ArH), J = 6.0 Hz, 2 H, ArH), 9.83 (d, J = 6.0 Hz, 2 H, ArH), 10.82 (br.
8.2–8.9 (br. m, 9 H, ArH), 9.5–9.9 (br. m, 2 H, ArH) ppm. UV/Vis s, 1 H, COOH) ppm. UV/Vis (CHCl3): λmax (logε) = 306 (4.73),
(CHCl3): λmax (logε) = 444 (3.85), 568 (2.99), 616 (3.0), 630 (2.95) 446 (5.26), 527 (3.56), 571 (4.11), 622 (4.36) nm. HRMS (MALDI-
nm. HRMS (MALDI-TOF, dithranol): calcd. for C75H82N4O4Zn TOF, dithranol): calcd. for C83H55N7O2Zn 1245.3709; found
1166.5628; found 1166.5622.
1245.3703.
5,10,15-Tris[(4-diphenylamino)phenyl]-20-(trimethylsilylyethynyl)por- 5-(3,4-Dimethoxycarbonylphenylethynyl)-10,15,20-tris[(4-diphenyl-
phyrin (15): Pyrrole (0.611 mL, 8.98 mmol), trimethylsilylpropynal
(0.333 mL, 2.24 mmol), and EtOH (6.5 mL) were added to a solu-
amino)phenyl]porphyrin (17): TBAF (1 m in THF; 0.27 mL,
0.27 mmol) was added to a solution of compound 16 (81 mg,
tion of 14 (1.84 g, 6.73 mmol) in CHCl3 (898 mL). The mixture was 0.068 mmol) in dry THF (10 mL) at 0 °C, and the mixture was
deoxygenated by bubbling argon through it for 15 min, after which
BF3·OEt2 (0.284 mL, 2.25 mmol) was added, and the resulting mix-
ture was stirred at room temperature in the dark for 1 h. DDQ
(1.53 g, 6.73 mmol) was subsequently added, and the mixture was
stirred at room temperature for 15 min. The reaction was quenched
with H2O, and the mixture was extracted with CH2Cl2. Without
any further purification, the deprotected derivative was redissolved
in dry THF (10 mL) and Et3N (5 mL), and 4-bromophthalate
8
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O30124
/KAP1
Date: 20-03-13 16:42:41
Pages: 10
Tuning the Electronic Properties of Porphyrin Dyes
[3] A. Yella, H. Lee, H. N. Tsao, C. Yi, A. K. Chandiran, M. K.
Nazeeruddin, E. W. Diau, C. Yeh, S. M. Zakeeruddin, M.
Grätzel, Science 2011, 334, 629.
[4] T. Bessho, S. M. Zakeeruddin, C. Y. Yeh, E. W. G. Diau, M.
Grätzel, Angew. Chem. 2010, 122, 6796–6799; Angew. Chem.
Int. Ed. 2010, 49, 6646–6649.
[5] a) S.-L. Wu, H.-P. Lu, H.-T. Yu, S.-H. Chuang, C.-L. Chiu, C.-
W. Lee, E. W.-G. Diau, C.-Y. Yeh, Energy Environ. Sci. 2010,
3, 949; b) C.-F. Lo, S.-J. Hsu, C.-L. Wang, Y.-H. Cheng, H.-P.
Lu, E. W.-G. Diau, C.-Y. Lin, J. Phys. Chem. C 2010, 114,
12018; c) H. Imahori, Y. Matsubara, H. Iijima, T. Umeyama,
Y. Matano, S. Ito, M. Niemi, N. V. Tkachenko, H. Lemme-
tyinen, J. Phys. Chem. C 2010, 114, 10656–10665.
[6] a) J. Rochford, D. Chu, A. Hagfeldt, E. Galoppini, J. Am.
Chem. Soc. 2007, 129, 4655–4665; b) J. R. Stromberg, A. Mar-
ton, H. L. Kee, C. Kirmaier, J. R. Diers, C. Muthiah, M. Tanig-
uchi, J. S. Lindsey, D. F. Bocian, G. J. Meye, D. Holten, J. Phys.
Chem. C 2007, 111, 15464–15478.
(40 mg, 0.14 mmol) was added. The mixture was deoxygenated by
bubbling argon through it for 15 min, after which AsPh3 (41 mg,
0.13 mmol) and Pd2(dba)3 (15 mg, 0.016 mmol) were added, and
the reaction mixture was stirred at reflux for 1 h. The solvents were
then evaporated and the residue was extracted with CH2Cl2. After
purification by column chromatography (hexane/THF, 4:1), com-
pound 17 was obtained (71 mg, 80%) as a dark green solid. 1H
NMR (300 MHz, [D8]THF): δ = 3.93 (s, 3 H, COOCH3), 3.98 (s,
3 H, COOCH3), 7.11–7.16 (m, 6 H, ArH), 7.40–7.47 (m, 30 H,
ArH), 8.00 (d, J = 9.0 Hz, 1 H, ArH), 8.05–8.13 (m, 6 H, ArH),
8.26 (dd, J = 1.6, 8.0 Hz, 1 H, ArH), 8.36 (d, J = 3.0 Hz, 1 H,
ArH), 8.94–8.97 (m, 4 H, ArH), 9.10 (d, J = 3.0 Hz, 2 H, ArH),
9.82 (d, J = 6.0 Hz, 2 H, ArH) ppm. 13C NMR (75 MHz, [D8]-
THF): δ = 49.95 (COOCH3), 52.00 (COOCH3), 114.40 (alkyne),
122.02 (ArC), 122.65 (ArC), 123.95 (ArC), 125.53 (ArC), 130.17
(ArC), 130.40 (ArC), 130.80 (ArC), 131.97 (ArC), 132.51 (ArC),
133.32 (ArC), 133.69 (ArC), 134.63 (ArC), 136.34 (ArC), 137.74
(ArC), 139.63 (ArC), 148.26 (ArC), 148.83 (ArC), 150.70 (ArC),
151.59 (ArC), 153.04 (ArC), 167.28 (C=O) ppm. UV/Vis (CHCl3):
λmax (logε) = 304.5 (4.47), 451.5 (5.00), 573 (3.74), 630 (4.05) nm.
MS (MALDI-TOF, dithranol): m/z = 1317.4 [M]+.
[7] W. M. Campbell, K. W. Jolley, P. Wagner, K. Wagner, P. J.
Walsh, K. C. Gordon, L. Schmidt-Mende, M. K. Nazeeruddin,
Q. Wang, M. Grätzel, D. L. Officer, J. Phys. Chem. C 2007,
111, 11760–11762.
[8] a) P. Y. Reddy, L. Giribabu, C. Lyness, H. J. Snaith, C. Vijayku-
mar, M. Chandrasekharam, M. Lakshmikantam, J.-H. Yum,
K. Kalyanasundaram, M. Grätzel, M. K. Nazeeruddin, Angew.
Chem. 2007, 119, 377–380; Angew. Chem. Int. Ed. 2007, 46,
373–376; b) S. Eu, T. Katoh, T. Umeyama, Y. Matano, H. Im-
ahori, Dalton Trans. 2008, 5476–5483; c) M. García-Iglesias, J.-
H. Yum, R. Humphry-Baker, S. M. Zakeeruddin, P. Péchy, P.
Vázquez, E. Palomares, M. Grätzel, M. K. Nazeeruddin, T.
Torres, Chem. Sci. 2011, 2, 1145; d) M.-E. Ragoussi, J.-J. Cid,
J.-H. Yum, G. de la Torre, D. Di Censo, M. Grätzel, M. K. Na-
zeeruddin, T. Torres, Angew. Chem. 2012, 124, 4451–4454; An-
gew. Chem. Int. Ed. 2012, 51, 4375–4378.
5-(3,4-Dicarboxyphenylethynyl)-10,15,20-tris[(4-diphenylamino)phen-
yl]porphyrin (5): A mixture of compound 17 (58 mg, 0.044 mmol)
and NaOH (0.5 m; 2.3 mL, 1.15 mmol) in THF (4 mL) and MeOH
(1.6 mL) was heated at reflux for 20 min. It was then cooled to
room temperature, extracted with CH2Cl2, and purified by reverse-
phase column chromatography (H2O/THF, 1:1) to give porphyrin
1
5 (34 mg, 60%) as a dark green solid. H NMR (300 MHz, [D6]-
DMSO): δ = 7.34–7.40 (m, 23 H, ArH), 7.44–7.50 (m, 16 H, ArH),
8.05 (t, J = 9.0 Hz, 6 H, ArH), 8.85–8.89 (m, 4 H, ArH), 9.00 (d,
J = 6.0 Hz, 2 H, ArH), 9.76 (d, J = 6.0 Hz, 2 H, ArH) ppm. UV/
Vis (CHCl3): λmax (logε) = 303 (3.90), 445 (4.04), 577 (3.28), 629
(3.36) nm. HRMS (MALDI-TOF, dithranol): calcd. for
C84H55N7O4Zn 1289.3607; found 1289.3602.
[9] A. J. Mozer, P. Wagner, D. L. Officer, G. G. Wallace, W. M.
Campbell, M. Miyashita, K. Sunahara, S. Mori, Chem. Com-
mun. 2008, 4741–4743.
[10] a) C.-L. Wang, C.-M. Lan, S.-H. Hong, Y.-F. Wang, T.-Y. Pan,
C.-W. Chang, H.-H. Kuo, M.-Y. Kuo, E. W.-G. Diau, C.-Y.
Lin, Energy Environ. Sci. 2012, 5, 6933–6940; b) C. Chang,
C. L. Wang, T. Y. Pan, S. H. Hong, C. M. Lan, H. H. Kuo,
C. F. Lo, H. Y. Hsu, C. Y. Lin, E. W. Diau, Chem. Commun.
2011, 47, 8910–8912; c) T. Ripolles-Sanchis, B. C. Guo, H. P.
Wu, T. Y. Pan, H. W. Lee, S. R. Raga, F. Fabregat-Santiago, J.
Bisquert, C. Y. Yeh, E. W. Diau, Chem. Commun. 2012, 48,
4368–4370.
Supporting Information (see footnote on the first page of this arti-
cle): 1H and 13C NMR spectra and MALDI-TOF mass spectra for
all new compounds are included, together with fluorescence and
square-wave voltammetry spectra for porphyrins 1–5.
Acknowledgments
[11] H. Imahori, S. Hayashi, H. Hayashi, A. Oguro, S. Eu, T. Ume-
yama, Y. Matano, J. Phys. Chem. C 2009, 113, 18406–18413.
[12] S. Mathew, H. Iijima, Y. Toude, T. Umeyama, Y. Matano, S.
Ito, N. V. Tkachenko, H. Lemmetyinen, H. Imahori, J. Phys.
Chem. C 2011, 115, 14415–14424.
Financial support from the Spanish Ministerio de Ciencia e Innov-
ación (MICINN) and the Ministerio de Educación y Ciencia
(MEC) (CTQ-2011-24187/BQU, PIB2010US-00652, CONSOL-
IDER-INGENIO 2010 CDS 2007-00010, Nanociencia Molecular,
PLE2009-0070), and from Comunidad de Madrid (CAM) (MAD-
RISOLAR-2, S2009/PPQ/1533) is acknowledged.
[13] D. Casarini, L. Lunazzi, A. Mazzanti, J. Org. Chem. 2008, 73,
2811–2818.
[14] R. W. Wagner, T. E. Johnson, J. S. Lindsey, J. Am. Chem. Soc.
1996, 118, 11166–11180.
[15] R. W. Wagner, T. E. Jonson, J. S. Lindsey, J. Org. Chem. 1995,
[1] a) W. M. Campbell, A. K. Burrell, D. L. Officer, K. W. Jolley,
Coord. Chem. Rev. 2004, 248, 1363–1379; b) H. Imahori, T.
Umeyama, S. Ito, Acc. Chem. Res. 2009, 42, 1809–1818; c)
M. V. Martínez-Díaz, G. de la Torre, T. Torres, Chem. Com-
mun. 2010, 46, 7090–7108.
60, 5266–5273.
[16] M. E. El-Khouly, J. B. Ryu, K.-Y. Kay, O. Ito, S. Fukuzumi, J.
Phys. Chem. C 2009, 113, 15444–15453.
[17] T. Meyer, D. Ogermann, A. Pankrath, K. Kleinermanns, T. J. J.
Müller, J. Org. Chem. 2012, 77, 3704–3715.
[2] T. Dos Santos, A. Morandeira, S. Koops, A. J. Mozer, G. Tsek-
ouras, Y. Dong, P. Wagner, G. Wallace, J. C. Earles, K. C. Gor-
don, D. Officer, J. R. Durrant, J. Phys. Chem. C 2010, 114,
3276–3279.
[18] B. Liu, W. Zhu, Y. Wang, W. Wu, X. Li, B. Chen, Y.-T. Long,
Y. X i e, J. Mater. Chem. 2012, 22, 7434.
Received: January 23, 2013
Published Online: ᭿
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9

Job/Unit: O30124
/KAP1
Date: 20-03-13 16:42:41
Pages: 10
M.-E. Ragoussi, G. de la Torre, T. Torres
FULL PAPER
Porphyrin Dyes
The synthesis of two series of unsymetri-
cally functionalized porphyrins, bearing
either 2,4,6-triisopropylphenyl or tri-
phenylamino substituents at three of the
four meso positions, is described. The elec-
tronic features of these new compounds
have been investigated by UV/Vis and elec-
trochemical measurements to determine
their potential as dyes for dye-sensitized so-
lar cells.
M.-E. Ragoussi, G. de la Torre,*
T. Torres* ........................................ 1–10
Tuning the Electronic Properties of Por-
phyrin Dyes: Effects of meso Substitution
on Their Optical and Electrochemical Be-
haviour
Keywords: Porphyrinoids / Dyes / Elec-
tronic structure / Redox chemistry / Struc-
ture–activity relationships
10
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Eur. J. Org. Chem. 0000, 0–0