New synthesis of zinc tetrakis(arylethynyl)porphyrins and substituent effects on their redox chemistry

Article abstract of DOI:10.1039/b617170b

Sonogashira coupling of zinc 5,10,15,20-tetraethynylporphyrin with various phenyl iodides under mild conditions afforded good yields of the corresponding zinc porphyrins. This method is applicable to a variety of aryl iodides including meso-substituted iodoporphyrin to form a conjugated star-shaped multiporphyrin. The UV-Vis spectra show that peak broadening, red shifts, and changes in the oscillator strength of absorptions increase with the extension of π-conjugation. In the electrochemical measurements, the first oxidation of porphyrins 4-9 occurs at potentials in the range +0.89 to +1.08 V, which are comparable to that of ZnTPP (TPP = tetraphenylporphyrin). The first reduction was observed at potentials from -0.73 to -0.89 V, which is anodically shifted by 390-550 mV as compared to that of ZnTPP, and the second reduction occurs at potentials in the range -1.12 to -1.33 V. The para-substituted tetrakis(phenylethynyl)porphyrins show substituent effects on their redox chemistry and exhibit only slight substituent effects in their emission and absorption maxima. The Royal Society of Chemistry.

Full text of DOI:10.1039/b617170b

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www.rsc.org/dalton | Dalton Transactions
New synthesis of zinc tetrakis(arylethynyl)porphyrins and substituent effects
on their redox chemistry
Ming-Cheng Kuo, Long-An Li, Wei-Nan Yen, Shang-Shih Lo, Cheng-Wei Lee and Chen-Yu Yeh*
Received 23rd November 2006, Accepted 13th February 2007
First published as an Advance Article on the web 5th March 2007
DOI: 10.1039/b617170b
Sonogashira coupling of zinc 5,10,15,20-tetraethynylporphyrin with various phenyl iodides under mild
conditions afforded good yields of the corresponding zinc porphyrins. This method is applicable to a
variety of aryl iodides including meso-substituted iodoporphyrin to form a conjugated star-shaped
multiporphyrin. The UV-Vis spectra show that peak broadening, red shifts, and changes in the
oscillator strength of absorptions increase with the extension of p-conjugation. In the electrochemical
measurements, the first oxidation of porphyrins 4–9 occurs at potentials in the range +0.89 to +1.08 V,
which are comparable to that of ZnTPP (TPP = tetraphenylporphyrin). The first reduction was
observed at potentials from −0.73 to −0.89 V, which is anodically shifted by 390–550 mV as compared
to that of ZnTPP, and the second reduction occurs at potentials in the range −1.12 to −1.33 V. The
para-substituted tetrakis(phenylethynyl)porphyrins show substituent effects on their redox chemistry
and exhibit only slight substituent effects in their emission and absorption maxima.
catalyzed coupling of 5,10,15,20-tetraethynylporphyrin with aryl
Introduction
iodides. The substituent effects on the spectroscopic and electro-
Porphyrins have peculiar optical and electronic properties that
chemical properties of these porphyrins have been studied to elicit
allow them to play important roles in biological systems1 and in
a structure–property relationship.
a variety of applications.2 Recently, porphyrins with conjugated
connections on the meso-positions have attracted great attention
Results and discussion
because of their potential applications in electronic materials. To
extend the conjugation of the porphyrin core, a number of linkages
such as ethyne,3 polyyne,4 ethylene,5 alkane6 and aromatic entities7
have been examined. In general, acetylenic types of bridges provide
the most efficient way of extending the conjugated p-system.3,4 For
example, ethyne- or butadiyne-linked porphyrin dimers exhibit
stronger interporphyrin interactions than the corresponding aryl-
or alkene-linked analogues.3,4
The synthesis and properties of meso-substituted tetraaryl-
porphyrins have been intensively studied. In contrast, the
studies on the corresponding tetrakis(arylethynyl)porphyrins
are relatively rare.8–11 The first examples of 5,10,15,20-meso-
tetraalkynylporphyrins were synthesized from the reaction of
pyrrole with propargylic selenoacetals in poor yield.8 In 1995,
Milgrom and Yahioglu reported the synthesis of tetraalkynylpor-
phyrins in low yield under Lindsey’s conditions.9 Modification
of the procedure by protecting the ethynyl group with Co2(CO)6
at the aldehyde stage increased the yield of tetraalkynylpor-
phyrins up to 35%.10 Anderson et al. independently reported an
improved Lindsey’s method by performing the cyclization step
at −30 ◦C to afford the corresponding tetraalkynylporphyrin
in 20% yield.11 One major drawback of these methods is the
commercial unavailability of the substituted arylpropynals. This
prompted us to design an efficient and facile procedure for the
synthesis of such porphyrins. We present here an alternative route
to the tetrakis(arylethynyl)porphyrins by employing palladium-
Synthesis
The palladium-catalyzed coupling of terminal alkynes with aryl
or alkenyl halide was reported for the first time by Sono-
12
gashira et al. Although Sonogashira coupling has been widely
applied to porphyrin systems,13 such reactions performed on
all four meso-ethynyl groups of a porphyrin ring with aryl
halides are rare.14 The key step in our synthetic approach to
tetrakis(arylethynyl)porphyrins is the preparation of porphyrin 2
with four ethynyl groups available for subsequent cross-coupling
reaction (Scheme 1). It has been reported that desilylation of
the free base of porphyrin 1 gives an intractable material.9
Surprisingly, deprotection of porphyrin 111 by TBAF (tetrabuty-
lammonium fluoride) can be carried out efficiently in a mixture
of CH2Cl2 and THF in our hands.15,16 To determine the optimum
coupling reaction conditions, 4-butyliodobenzene was chosen to
perform an initial set of experiments. We found that the desired
products were formed with good or fair yields when the coupling
reactions of porphyrin 214 with substituted phenyl iodides were
performed in a mixture of NEt3 and THF at 50 ◦C using Pd2(dba)3
(dba = dibenzylideneacetone) as the catalyst and AsPh3 as the
ligand. When phenyl bromides instead of phenyl iodides were used
to couple with porphyrin 2, an inseparable porphyrin mixture was
obtained. The use of CuI as the cocatalyst resulted in the formation
of an insoluble solid, presumably, produced by homocoupling of
porphyrin 2.
Under optimized reaction conditions, the coupling preceded
smoothly with both the electron-rich and electron-deficient para-
substituted phenyl iodides (scheme 1). As for phenyl iodides with
Department of Chemistry and Center of Nanoscience and Nanotechnol-
ogy, National Chung Hsing University, Taichung 402, Taiwan. E-mail:
cyyeh@dragon.nchu.edu.tw
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Scheme 1 Synthesis of porphyrins 3–13.
Scheme 2 Synthesis of porphyrins 14–17.
Table 1 Yield, and absorption and emission data for 3–17a
synthesized and applied in light-harvesting systems.18 We also
examined the coupling reaction between porphyrin 2 with 2-
iodothiophene, which afforded the desired product in 50% yield.
Our procedure can also be applied to the synthesis of conjugated
star-shaped multiporphyrin 17 which was previously prepared
by stepwise Sonogashira coupling reactions.19 In this case, the
coupling reaction was carried out at an elevated temperature to
give the product in 55% yield.
Yield (%)
B-Bandbnm
Q-Bandb/nm
kemc/nm
3
81
44
58
46
46
69
75
70
81
38
76
61
65
50
55
479
477
478
481
476
479
480
480
478
482
477
487
497
484
424, 518
629, 684
625, 679
627, 684
633, 690
623, 677
626, 680
624, 676
630, 685
626, 680
626, 678
622, 675
634, 690
642, 705
691
693, 761
688, 758
692, 760
700, 774
686, 755
689, 757
685, 751
694, 763
688, 757
684, 753
682, 750
702, 768
723, 801
703, 774
810
4
5
6
7
8
9
10
11
12
13
14
15d
16
17e
Spectroscopic properties
The electron-donating or electron-withdrawing substituents on the
peripheral aryl groups of 5,10,15,20-tetraarylporphyrins have been
shown to influence their physical and chemical properties such
as absorption spectra, NMR chemical shifts, EPR parameters,
electron transfer rates, association constants for axial ligation,
and redox potentials.20 It would be interesting to study the
substituent effects of these porphyrins on their physical and
chemical properties because of the efficient conjugation between
the porphyrin ring and the para-substituted phenyl groups.
Substituent effects on the optical properties of porphyrins 3–9 were
investigated by UV-Vis absorption and emission spectroscopy.
In general, introduction of electron-donating substituents to the
para-positions of the phenyl groups evoke a red shift of the
absorption and emission maxima. Similar to the case of the
para-substituted 5,10,15,20-tetraphenylporphyrins, porphyrins 3–
9 exhibit only slight substituent effects in the absorption and
emission properties.21
Electronic absorption spectroscopy can be used to determine
the magnitude of the electronic interactions between the porphyrin
core and peripheral aryl groups. In these conjugated porphyrins,
both the absorption and emission maxima exhibit large red
shifts as compared to those of 5,10,15,20-tetraphenylporphyrins.
Such trends are larger upon an increase in the extension of p-
conjugation. As an example, Fig. 1 shows the absorption and
emission spectra for porphyrins 4, 14, and 15, and reference
570, 618, 787
a The absorption and emission spectra were taken in THF. b Absorption
maximum. c Emission maximum. d Reference 14. e Reference 19.
an ortho- or meta-substituent, the expected products were also
obtained in good or fair yields (Table 1). However, the desired
porphyrins were not obtained for some substituents such as para-
cyano and para-nitro groups due to the poor solubility of the
intermediates produced from incomplete coupling.
To demonstrate the scope of our new procedures, we further
evaluated the coupling of porphyrin 2 with various aryl iodides as
shown in Scheme 2. Again, the reactions gave coupling products
with good or fair yields. Triarylamines are of current interest
because of their wide applications in hole transporting materials,
dyes, and polymers. Previous studies showed that introduction of
triarylamine units into a porphyrin core significantly influences
the optical and electrochemical properties of the porphyrin
ring.14,17 We previously prepared porphyrin 15 from the reaction
of porphyrin 2 and 4-(diphenylamino)phenyl iodide using this
coupling method.14 Thiophene has the weaker resonance energy as
compared to benzene, thus exhibiting longer effective conjugation.
A number of porphyrins bearing thiophene units have been
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retards reduction of the porphyrin ring. In contrast, the addition
of electron-withdrawing groups to the macrocycle results in anodic
shifts for both oxidation and reduction. The redox potentials were
taken for both oxidation and reduction reactions of porphyrins 4–
9 in THF at −40 ◦C since the oxidation reactions were irreversible
when the electrochemical measurements were conducted at room
temperature. Table 2 presents the electrochemical data for 4–9
and Fig. 2 shows the cyclic voltammogram of porphyrins 4, 6,
and 9. The first oxidation of 4 occurred at E1/2(ox1) = +1.03 V
and the second oxidation is an irreversible reaction under these
electrochemical conditions. The reductive waves corresponding to
the formation of the anion radical and dianion were observed
at E1/2(red1) = −0.84 and E1/2(red2) = −1.28 V, respectively.
The first reduction is anodically shifted by 440 mV compared to
that of ZnTPP. This can be ascribed to the electron-withdrawing
nature of the ethynyl groups and the extension of p-conjugation
in 4 with respect to ZnTPP. In the cases of porphyrins 5–9, the
cyclic voltammograms are similar in shape and reversibility. As
expected, the redox potentials shift anodically for the porphyrins
with electron-withdrawing groups and shift cathodically for the
porphyrins with electron-donating groups. It is noteworthy that
the potential difference between the HOMO and LUMO gap
Fig. 1 Absorption and normalized emission (inset) spectra for porphyrins
1 (solid), 4 (dash), 14 (dot), and 15 (dash dot) in THF.
porphyrin 1. The absorption spectra of porphyrins 4, 14, and 15 are
very different from the sum of their respective components, i.e., the
porphyrin ring and the aryl substituents. In addition, the spectra
show peak broadening, peak shifts, and changes in the oscillator
strength of the absorptions.22,23 Both the Soret- and Q-bands of
porphyrins 4, 14, and 15 lie approximately 20–50 nm to the red of
those in the reference porphyrin 1. The large red shifts of both the
Soret- and Q-bands reflect very effective electronic communication
between the porphyrin core and the peripheral aryl groups, and a
decreased energy gap between the HOMO and LUMO orbitals as
a consequence of the expanded p-conjugation.18a,24 The full width
at half maximum height (fwhm) of the Soret-bands is larger by
237, 299, and 556 cm−1 for 4, 14, and 15, respectively, as compared
to that for 1 (423 cm−1), indicative of strong interchromophore
electronic interactions. It should be noted that these conjugated
porphyrins exhibit a significantly enhanced oscillator strength of
the Q-band relative to that of the Soret-band as the p-conjugation
is extended, which is consistent with an enhanced energy splitting
between the a1u and a2u orbitals, or the Eg orbitals.18a,23 The
absorption spectra suggest that incorporation of aryl units via
the carbon–carbon triple bonds produces profound perturbation
in the ground state properties of the porphyrin. The fluorescence
spectra of porphyrins 1, 4, 14, and 15 are shown in the inset of
Fig. 1. The enlargement of the p-conjugation results in a red shift of
the emission maximum. This finding is consistent with the similar
trend observed in the absorption spectra.
(estimated
by DE = E1/2(ox1) − E1/2(red1)) decreases with
increasing p-conjugation. The voltammetric HOMO − LUMO
Fig. 2 The cyclic voltammograms of 4, 6, and 9 in THF containing 0.1 M
TBAPF6 at −40 ◦C.
Table 2 Half-wave potentials for 4–9a
Electrochemistry
Oxidation/V
Reduction/V
Our investigations of the optical properties of porphyrins 3–9
showed that the substituents have small effects. Further insight into
the influence of substituents on the redox potentials and electronic
properties were studied by cyclic voltammetry. The substituent
effects can be described by the Hammett linear free-energy equa-
tion, DE(X) = 4rq, where DE(X) is the difference in the observed
half-wave potentials between the porphyrin having substituent X
and the reference porphyrin, r is the substituent constant,25 and
q is the reaction constant. In general, attachment of electron-
releasing groups to the porphyrin core facilitates oxidation and
4
+1.03
−0.84, −1.28
−0.89, −1.33
−0.89, −1.32
−0.82, −1.25
−0.79, −1.20
−0.73, −1.12
−1.28, −1.74
5
+0.99
6
+0.89
7
+1.03
8
+1.05
9
+1.08
ZnTPPb
+1.02, +1.34
a The electrochemical data were taken in THF containing 0.1 M TBAPF6
at −40 ◦C. b Zinc tetraphenylporphyrin.
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gap of 1.87 V for 4 is smaller by 430 mV than that of ZnTPP
(Table 2). This is consistent with the large red shifts in both
absorption and emission spectra. Furthermore, the half-wave
potential for the first oxidation of 4 is only slightly changed as
compared to that of ZnTPP, suggesting that the HOMO energy
is nearly unperturbed as the p-conjugation is expanded. In a
comparison of 4 with ZnTPP, the contraction of the HOMO −
LUMO energy gap is attributed to the lowered LUMO energy.
Fig. 3 shows the plot of E1/2 vs. 4r for the first oxidation and
two reductions of 4–9. The linear relationship between E1/2 and
4r indicates a constant reaction mechanism throughout this series
of compounds. The reaction constants (q) are calculated to be
0.05, 0.05, and 0.07 for the first oxidation, and first and second
reduction, respectively. These values are comparable to those of the
zinc complexes of para-substituted tetraphenylporphyrins.26 The
substituent effects of our zinc tetrakis(phenylethynyl)porphyrins
on the redox potentials of the porphyrin ring are remarkable
Experimental
Materials and methods
All reagents were used as received unless otherwise noted and
solvents were dried according to standard procedures. Compounds
1,11,27 2,14 and 1514 were prepared according to the reported
methods. Column chromatography was performed on silica gel
(Merck, 70–230 Mesh ASTM).1H NMR spectra were recorded at
400 or 600 MHz, 13C NMR spectra were recorded at 100.56 or
150.81 MHz using a Varian spectrometer. UV-Vis spectra were
taken on a Varian Carey 50 spectrometer and emission spectra
were measured on a AMINCO-Bowman Series 2 spectrofluorime-
ter. MALDI-TOF-MS and FAB-MS mass spectra were obtained
with a BrukerAPEX II spectrometer and a JMS-SX/SX102A
Tandem Mass Spectrometer, respectively, operating in the positive
ion detection mode. Electrochemistry was performed with a three-
electrode potentiostat (CH Instruments, Model 750A) in THF
with 0.1 M TBAPF6 deoxygenated by purging with purified
nitrogen gas. Cyclic voltammetry was conducted with the use of
a home-made three-electrode cell equipped with a BAS glassy
carbon (0.07 cm2) or platinum (0.02 cm2) disk as the working
electrode, a platinum wire as the auxiliary electrode, and a home-
made Ag–AgCl (sat’d) reference electrode. The reference electrode
is separated from the bulk solution by a double junction filled with
electrolyte solution. Potentials are reported vs. Ag–AgCl (sat’d)
and referenced to the ferrocene–ferrocenium (Fc–Fc+) couple
which occurs at E1/2 = +0.62 V vs. Ag–AgCl (sat’d). The working
electrode was polished with 0.03 lm aluminium on Buehler felt
pads. The reproducibility of individual potential values was within
5 mV.
˚
when considering the longer distance (by about 2.6 A) from the
substituents to the porphyrin macrocycle than that in zinc para-
substituted tetraphenylporphyrins. These results demonstrate that
the transmission of electronic effects from the periphery of the
porphyrin ring though the C–C triple bond is efficient.
Synthesis
Zinc 5,10,15,20-tetrakis(4-butylphenylethynyl)porphyrin (3)11.
To a degassed solution of 4-butyliodobenzene (55 mg, 0.21 mmol),
porphyrin 2 (10 mg, 0.021 mmol), and AsPh3 (10 mg, 0.033 mmol)
in a mixture of dry THF (10 mL) and Et3N (5 mL) was added
Pd2(dba)3 (2 mg, 0.002 mmol). The reaction mixture was stirred
at 50 ◦C for 3 h. The solvent was evaporated to dryness under
vacuum. The product was purified by recrystallization from a
mixture of THF, CH3OH, and Et3N to give a pure solid (17.2 mg,
81%). 1H NMR (400 MHz, CDCl3) dH = 8.88 (s, 8H), 7.85 (d, J =
7.6, 8H), 7.31 (d, J = 7.6, 8H), 2.75 (t, J = 7.6, 8H), 1.76 (m, 8H),
1.53 (m, 8H), 1.07 (t, J = 7.6, 12H); UV-Vis (THF) kmax/nm (log
e) = 479 (5.74), 629 (4.22), 684 (4.86); MS(FAB): 996 m/z (M+).
Fig. 3 Plot of E1/2 vs. 4r for the first oxidation (ꢀ), first reduction (᭹),
and second reduction (ꢁ) of 4–9 in THF containing 0.1 M TBAPF6.
Conclusions
Zinc 5,10,15,20-tetrakis(phenylethynyl)porphyrin (4). To a de-
gassed solution of phenyl iodide (43 mg, 0.21 mmol), porphyrin 2
(10 mg, 0.021 mmol), and AsPh3 (10 mg, 0.033 mmol) in a mixture
of dry THF (10 mL) and Et3N (5 mL) was added Pd2(dba)3 (2 mg,
We have presented an efficient preparation of a series of
tetrakis(arylethynyl)porphyrins and the synthetic route is more
versatile than previously reported methods.8–11 Our improved
method is also applicable to a wide range of aryl iodides and shows
broad functional group tolerance which makes the method useful
and attractive. These conjugated porphyrins exhibit significant
peak broadening and red shifts of absorptions and they may find
application in dye-sensitized solar cells and photodynamic therapy
upon suitable modification. Substituent effects of porphyrins 4–
9 on their redox potentials were observed. We are currently
investigating the scope of our procedures and substituent effects
of this type of porphyrin on the physical and chemical properties.
◦
0.002 mmol). The reaction mixture was stirred at 50 C for 3 h.
The solvent was evaporated to dryness under vacuum. The product
was purified by recrystallization from a mixture of THF, CH3OH,
and Et3N to give a pure solid (7.3 mg, 44%). 1H NMR (400 MHz,
DMSO-d6) dH = 9.65 (s, 8H), 8.17 (d, J = 7.2, 8H), 7.68 (t, J =
7.2, 8H), 7.61 (t, J = 7.2, 4H); 13C NMR (150.81 MHz, DMSO-d6)
dC = 151.12, 131.71, 129.25, 129.12, 122.90, 102.33, 96.91, 91.86;
UV-Vis (THF) kmax/nm (log e) = 477 (5.88), 625 (4.39), 679 (4.97);
MS(FAB): 772 m/z (M+).
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Zinc 5,10,15,20-tetrakis(4-methylphenylethynyl)porphyrin (5).
To a degassed solution of 4-iodotoluene (46 mg, 0.21 mmol),
porphyrin 2 (10 mg, 0.021 mmol), and AsPh3 (10 mg, 0.033 mmol)
in a mixture of dry THF (10 mL) and Et3N (5 mL) was added
Pd2(dba)3 (2 mg, 0.002 mmol). The reaction mixture was stirred
at 50 ◦C for 3 h. The solvent was evaporated to dryness under
vacuum. The product was purified by recrystallization from a
mixture of THF, CH3OH, and Et3N to give a pure solid (10.3 mg,
AsPh3 (10 mg, 0.033 mmol) in a mixture of dry THF (10 mL)
and Et3N (5 mL) was added Pd2(dba)3 (2 mg, 0.002 mmol). The
reaction mixture was stirred at 50 ◦C for 3 h. The solvent was
evaporated to dryness under vacuum. The product was purified
by recrystallization from a mixture of THF, CH3OH, and Et3N to
1
give a pure solid (16.4 mg, 75%). H NMR (400 MHz, THF-d8)
dH = 9.58 (s, 8H), 8.28 (d, J = 8.0, 8H), 7.93 (d, J = 8.0, 8H);
13C NMR (150.87 MHz, THF-d8) dC = 152.26, 132.87, 132.00,
128.95, 126.58, 126.20, 124.40, 102.73, 96.18, 95.57; UV-Vis (THF)
kmax/nm (log e) = 480 (5.67), 624 (4.24), 676 (4.74); MS(FAB): 1045
m/z (MH+).
1
58%). H NMR (400 MHz, THF-d8) dH = 9.71 (s, 8H), 7.99 (d,
J = 7.6, 8H), 7.44 (d, J = 7.6 8H), 2.51 (s, 12H); 13C NMR
(150.87 MHz, THF-d8) dC = 152.53, 139.72, 132.36, 132.03,
130.32, 122.03, 103.89, 97.87, 92.61, 21.68; UV-Vis (THF) kmax/nm
(log e) = 478 (5.66), 627 (4.17), 684 (4.78); MS(FAB): 828 m/z
(M+).
Zinc 5,10,15,20-tetrakis(2-methylphenylethynyl)porphyrin (10).
To a degassed solution of 2-iodotoluene (46 mg, 0.21 mmol),
porphyrin 2 (10 mg, 0.021 mmol), and AsPh3 (10 mg, 0.033 mmol)
in a mixture of dry THF (10 mL) and Et3N (5 mL) was added
Pd2(dba)3 (2 mg, 0.002 mmol). The reaction mixture was stirred
at 50 ◦C for 3 h. The solvent was evaporated to dryness under
vacuum. The product was purified by recrystallization from a
mixture of THF, CH3OH, and Et3N to give a pure solid (12.3 mg,
70%). 1H NMR (400 MHz, THF-d8) dH = 9.65 (s, 8H), 8.11
(t, J = 6.4, 4H), 7.41–7.47 (m, 12H), 3.07 (s, 12H); 13C NMR
(100.56 MHz, THF-d8) dC = 151.42, 141.06, 133.06, 131.97,
130.66, 129.41, 123.20, 126.86, 103.91, 97.23, 96.77, 21.84; UV-
Vis (THF) kmax/nm (log e) = 480 (5.71), 630 (4.23), 685 (4.86);
MS(FAB): 829 m/z (MH+).
Zinc 5,10,15,20-tetrakis(4-methoxyphenylethynyl)porphyrin (6).
To a degassed solution of 4-iodoanisol (49 mg, 0.21 mmol),
porphyrin 2 (10 mg, 0.021 mmol), and AsPh3 (10 mg, 0.033 mmol)
in a mixture of dry THF (10 mL) and Et3N (5 mL) was added
Pd2(dba)3 (2 mg, 0.002 mmol). The reaction mixture was stirred
at 50 ◦C for 3 h. The solvent was evaporated to dryness under
vacuum. The product was purified by recrystallization from a
mixture of THF, CH3OH, and Et3N to give a pure solid (8.7 mg,
1
46%). H NMR (400 MHz, DMSO-d6) dH = 9.66 (s, 8H), 8.12
(d, J = 8.8, 8H), 7.24 (d, J = 8.8, 8H), 3.93 (s, 12H); 13C NMR
(150.87 MHz, DMSO-d6) dC = 160.03, 150.88, 133.35, 131.49,
114.88, 114.80, 102.80, 97.17, 90.74, 55.48; UV-Vis (THF) kmax/nm
(log e) = 481 (5.71), 633 (4.17), 690 (4.85); MS(FAB): 893 m/z
(MH+).
Zinc 5,10,15,20-tetrakis(3-methylphenylethynyl)porphyrin (11).
To a degassed solution of 3-iodotoluene (46 mg, 0.21 mmol),
porphyrin 2 (10 mg, 0.021 mmol), and AsPh3 (10 mg, 0.033 mmol)
in a mixture of dry THF (10 mL) and Et3N (5 mL) was added
Pd2(dba)3 (2 mg, 0.002 mmol). The reaction mixture was stirred
at 50 ◦C for 3 h. The solvent was evaporated to dryness under
vacuum. The product was purified by recrystallization from a
mixture of THF, CH3OH, and Et3N to give a pure solid (12.3 mg,
Zinc 5,10,15,20-tetrakis(4-fluorophenylethynyl)porphyrin (7).
To a degassed solution of 1-fluoro-4-iodobenzene (47 mg,
0.21 mmol), porphyrin 2 (10 mg, 0.021 mmol), and AsPh3 (10 mg,
0.033 mmol) in a mixture of dry THF (10 mL) and Et3N (5 mL)
was added Pd2(dba)3 (2 mg, 0.002 mmol). The reaction mixture
was stirred at 50 ◦C for 3 h. The solvent was evaporated to dryness
under vacuum. The product was purified by recrystallization from
a mixture of THF, CH3OH, and Et3N to give a pure solid (8.3 mg,
1
70%). H NMR (400 MHz, DMSO-d6) dH = 9.70 (s, 8H), 8.02
(s, 4H), 7.97 (d, J = 7.6, 4H), 7.57 (t, J = 7.6, 4H), 7.43 (d,
J = 7.6, 4H), 2.53 (s, 12H); 13C NMR (150.87 MHz, DMSO-d6)
dC = 151.10, 138.49, 132.07, 131.70, 130.03, 129.00, 128.78, 122.74,
102.43, 97.13, 91.59, 20.93; UV-Vis (THF) kmax/nm (log e) = 478
(5.79), 626 (4.32), 680 (4.91); MS(FAB): 829 m/z (MH+).
1
46%). H NMR (400 MHz, DMSO-d6) dH = 9.66 (s, 8H), 8.24
(t, J = 8.8, 8H), 7.51 (t, J = 8.8, 8H); 13C NMR (150.87 MHz,
DMSO-d6) dC = 151.13, 134.14, 131.81, 116.49, 116.33, 102.241,
95.86, 91.57, 69.78; UV-Vis (THF) kmax/nm (log e) = 476 (5.77),
623 (4.29), 677 (4.84); MS(FAB): 844 m/z (M+).
Zinc 5,10,15,20-tetrakis(2-(trifluoromethyl)phenylethynyl)por-
phyrin (12). To a degassed solution of 2-iodobenzotrifluoride
(57 mg, 0.21 mmol), porphyrin 2 (10 mg, 0.021 mmol), and
AsPh3 (10 mg, 0.033 mmol) in a mixture of dry THF (10 mL)
and Et3N (5 mL) was added Pd2(dba)3 (2 mg, 0.002 mmol). The
reaction mixture was stirred at 50 ◦C for 3 h. The solvent was
evaporated to dryness under vacuum. The product was purified
by recrystallization from a mixture of THF, CH3OH, and Et3N to
give a pure solid (8.5 mg, 38%). 1H NMR (400 MHz, THF-d8) dH =
9.78 (s, 8H), 8.47 (d, J = 7.6, 4H), 7.99 (d, J = 7.6, 4H), 7.88 (t,
J = 7.6, 4H), 7.69 (t, J = 7.6, 4H); 13C NMR (150.87 MHz, THF-
d8) dC = 152.75, 135.49, 133.18, 132.31, 129.39, 129.11, 127.03,
126.38, 123.02, 103.10, 98.89, 93.40; UV-Vis (THF) kmax/nm (log
e) = 482 (5.46), 626 (4.12), 678 (4.58); MS(FAB): 1044 m/z (M+).
Zinc 5,10,15,20-tetrakis(4-chlorophenylethynyl)porphyrin (8).
To a degassed solution of 1-chloro-4-iodobenzene (50 mg,
0.21 mmol), porphyrin 2 (10 mg, 0.021 mmol), and AsPh3 (10 mg,
0.033 mmol) in a mixture of dry THF (10 mL) and Et3N (5 mL)
was added Pd2(dba)3 (2 mg, 0.002 mmol). The reaction mixture
was stirred at 50 ◦C for 3 h. The solvent was evaporated to dryness
under vacuum. The product was purified by recrystallization from
a mixture of THF, CH3OH, and Et3N to give a pure solid (13.3 mg,
69%). 1H NMR (400 MHz, THF-d8) dH = 9.69 (s, 8H), 8.10 (d, J =
8.0, 8H), 7.66 (d, J = 8.0, 8H); 13C NMR (150.87 MHz, THF-d8)
dC = 152.54, 135.37, 133.89, 132.07, 130.01, 123.61, 103.37, 96.40,
94.13; UV-Vis (THF) kmax/nm (log e) = 479 (5.56), 626 (4.10), 680
(4.66); MS(MALDI-TOF): 908 m/z (M+).
Zinc 5,10,15,20-tetrakis(3-(trifluoromethyl)phenylethynyl)por-
phyrin (13). To a degassed solution of 3-iodobenzotrifluoride
(57 mg, 0.21 mmol), porphyrin 2 (10 mg, 0.021 mmol), and
AsPh3 (10 mg, 0.033 mmol) in a mixture of dry THF (10 mL)
Zinc 5,10,15,20-tetrakis(4-(trifluoromethyl)phenylethynyl)por-
phyrin (9). To a degassed solution of 4-iodobenzotrifluoride
(57 mg, 0.21 mmol), porphyrin 2 (10 mg, 0.021 mmol), and
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and Et3N (5 mL) was added Pd2(dba)3 (2 mg, 0.002 mmol). The
reaction mixture was stirred at 50 ◦C for 3 h. The solvent was
evaporated to dryness under vacuum. The product was purified
by recrystallization from a mixture of THF, CH3OH, and Et3N to
Acknowledgements
We thank the National Science Council of Taiwan for financial
support.
1
give a pure solid (16.7 mg, 76%). H NMR (400 MHz, THF-d8)
dH = 9.61 (s, 8H), 8.41 (s, 4H), 8.35 (d, J = 7.2, 4H), 7.81–7.84
(m, 8H); 13C NMR (150.87 MHz, THF-d8) dC = 152.38, 135.92,
132.14, 131.89, 130.60, 129.02, 126.05, 125.97, 124.28, 102.82,
95.92, 94.68; UV-Vis (THF) kmax/nm (log e) = 477 (5.65), 622
(4.22), 675 (4.73); MS(FAB): 1044 m/z (M+).
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m/z (M+).
Zinc 5,10,15,20-tetrakis(thiophen-2-ylethynyl)porphyrin (16).
To a degassed solution of 2-iodothiophene (44 mg, 0.21 mmol),
porphyrin 2 (10 mg, 0.021 mmol), and AsPh3 (10 mg, 0.033 mmol)
in a mixture of dry THF (10 mL) and Et3N (5 mL) was added
Pd2(dba)3 (2 mg, 0.002 mmol). The reaction mixture was stirred
at 50 ◦C for 3 h. The solvent was evaporated to dryness under
vacuum. The product was purified by recrystallization from a
mixture of THF, CH3OH, and Et3N to give a pure solid (8.5 mg,
50%). 1H NMR (400 MHz, DMSO-d6) dH = 9.59 (s, 8H), 8.00 (d,
J = 4.4, 4H), 7.92 (d, J = 4.4, 4H), 7.38 (t, J = 4.4, 4H); 13C NMR
(150.87 MHz, DMSO-d6) dC = 150.80, 133.55, 131.59, 129.80,
128.34, 122.35, 102.30, 95.423, 90.44; UV-Vis (THF) kmax/nm (log
e) = 484 (5.01), 691 (4.22); MS(FAB): 797 m/z (MH+).
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a degassed solution of
5-iodo-10,15,20-tris(3,5-di-tert-butylphenyl)porphyrin (138 mg,
0.13 mmol), porphyrin 2 (10 mg, 0.021 mmol), and AsPh3 (26 mg,
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under vacuum. the crude product was purified by chromatography
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mixture of CH2Cl2, and CH3OH to give a pure solid (49 mg,
55%). 1H NMR (400 MHz, CDCl3) dH = 10.61 (s, 8H), 10.60 (d,
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