Synthesis and characterization of new ferrocene, porphyrin and C60 triads, connected by triple bonds

Article abstract of DOI:10.1016/j.jorganchem.2015.04.006

The 2,12 pyrrole positions of meso-tetraphenylporphyrin were functionalized through triple carbon-carbon bonds by ferrocene and C₆₀ giving new electron donor-acceptor triads which have been characterized and studied by photophysical methods.

Full text of DOI:10.1016/j.jorganchem.2015.04.006

Journal of Organometallic Chemistry 787 (2015) 27e32
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and characterization of new ferrocene, porphyrin and C60
triads, connected by triple bonds
Pietro Tagliatesta , Roberto Pizzoferrato b
a
,
*
, *
a
Dipartimento di Scienze e Tecnologie Chimiche, University of Rome-Tor Vergata, Via della Ricerca Scientifica, 00133 Rome, Italy
Dipartimento di Ingegneria Industriale, University of Rome-Tor Vergata, Via della Ricerca Scientifica, 00133 Rome, Italy
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 16 February 2015
Received in revised form
The 2,12 pyrrole positions of meso-tetraphenylporphyrin were functionalized through triple carbonecarbon
bonds by ferrocene and C60 giving new electron donor-acceptor triads which have been characterized and
studied by photophysical methods.
1
April 2015
©
2015 Elsevier B.V. All rights reserved.
Accepted 7 April 2015
Available online 20 April 2015
Keywords:
Porphyrins
Ferrocene
C
60
Electron transfer
Introduction
of one or more triple bonds, we found that it was very convenient
and important to have a large delocalization of the electrons
p
Electron and energy transfer are important topics in the
chemistry of biological and artificial systems and have been
extensively studied over the past twenty years [1]. Photosynthesis
in plants and bacteria is based on chemical reactions induced by the
electron-transfer phenomena between natural tetrapyrrolic pig-
ments, such as chlorophyls and related molecules, and quinones,
both embedded in a protein matrix [2]. The entire process is not yet
well understood and more information can be obtained by the use
of synthetic models [3]. In this area, the difficulties of obtaining
new useful models were slowly overcome applying methods based
on the catalytic activity of palladium complexes [4]. The Suzuki and
Sonogashira reactions have been used for building new porphyrin
derivatives able to give charge separation (CS) processes under
irradiation with high efficiency and long lifetime [5].
The discovery of fullerenes, new allotropic forms of carbon, has
disclosed the possibility to explore the electron-transfer processes
using, for example, C60 as the final destination of the negative
charge in the synthetic models [6]. During our studies on the
possibility to use molecular wires to connect to the beta-pyrrole
positions of the porphyrins one C60 unit through the assembling
between the donor and the acceptor moieties of the models [7].
Anderson and coworkers reported similar models but with the
ferrocene and
C60 connected to the meso-positions of the
porphyrin obtaining long-range charge separated states when
photoexcited. The rates of long-range charge recombination in
such compounds, are remarkably fast and not depending from the
distance [6c].
Results and discussion
2
Recently we have reported the beta functionalization of H TPP
by one or two ferrocene molecules in the 2 and 3 positions through
ethynyl or phenylethynyl groups, applying a new approach of the
Sonogashira reaction, never used before in the case of porphyrins
[8].
Some other groups have recently reported on the synthesis and
characterization of different tetraphenylporphyrins bearing ferro-
cene at beta, meso or 4-phenyl positions [9].
In this paper we report on the synthesis of four new triads,
useful as a model for investigating the electron-transfer processes,
connecting ferrocene and C60 to the 2,12 pyrrole positions of H
through ethynyl bonds.
2
TPP
In Figs. 1 and 2 the structures of compound 1 and 8 and their
zinc complexes 2 and 9 are reported.
*
Corresponding authors. Tel.: þ39 6 72594759; fax: þ39 6 72594328.
E-mail address: pietro.tagliatesta@uniroma2.it (P. Tagliatesta).
http://dx.doi.org/10.1016/j.jorganchem.2015.04.006
022-328X/© 2015 Elsevier B.V. All rights reserved.
0

28
P. Tagliatesta, R. Pizzoferrato / Journal of Organometallic Chemistry 787 (2015) 27e32
Ph
N
Fe
N
Ph
M
Ph
N
N
Ph
Compound 1: M=2H
Compound 2: M=Zn
N
CH3
Fig. 1. The structure of compounds 1 and 2.
The synthetic pathways for obtaining the new porphyrin free
bases are reported in Scheme 1.
The starting compound 3, for the synthesis of the triads, the 2,
2-dibromo-tetraphenylporphyrin, was obtained as reported in the
spectra of triad 8 shows a different pattern, with the signals of the
ferrocene splitted into three singlets at 4.70, 4.38 and 4.08 ppm (see
ESI). This situation has been previously reported for similar com-
pounds bearing an ethynylferrocene or an ethynylphenylferrocene
1
literature [10]. The correct stereochemistry of compound 3 was
recently elucidated by another group [11]. Ethynylferrocene was
commercially available while phenylethynylferrocene was synthe-
sized as reported in the literature [8].
on the beta-position of H
of the triads 1 compared with the partial related reference com-
pounds (i.e. H TPP-C60, H TPP-Fc) in THF solutions [7,8].
The emission spectra of the reference compounds, i.e. H
2
TPP [8]. Fig. 3 shows the emission spectra
2
2
2
TPP is
The first step of the synthetic pathway involved the Sonogashira
coupling of compound 3 with the 1.5 equivalent of the ethylene
acetal derivative of 4-ethynylbenzaldehyde, 4 in 40% of yield after
chromatographic purification. We found that the protection of the
aldehyde function gives a better result in the coupling reaction,
comparing with the simple 4-ethynylbenzaldehyde.
The following step was again a Sonogashira coupling between
compound 5 and 2 equivalent of ethynylferrocene or phenyl-
ethynylferrocene giving, after hydrolysis of the dioxolane protective
group, the intermediates 6 or 7 in 70% of yield. Finally these last
compounds were used in the Prato and Maggini reaction [12]
affording the final compounds 1 and 8 in 60e65 % of yield.
Looking at the positions of the Soret bands of compound 1 and
also reported. In Fig. 4 the structures of the related reference
compounds free bases are also reported.
The excitation wavelength was
l
ex ¼ 430 nm for all the com-
pounds. The spectra are normalized by the optical density at exci-
tation wavelength, so that they can be compared to each other and
the PL intensity is an estimate of the relative quantum efficiency. As
the most striking feature of the emission spectra, we note that the
functionalization with either C60 or ferrocene, or with both groups,
strongly decreases the emission intensity of the reference com-
pounds. In our opinion, this fact can be due to a complete charge
delocalization along the carbonecarbon bond that links the ethy-
nylenephenylene subunit and the tetrapyrrole ring [6c].
In fact, the magnitude of the optical quantum efficiency is of the
ꢀ
3
ꢀ4
H
2
TPP, a red shift of 18 nm can be found. In a previous paper [8] we
2
order of F y 10 for H TPP derivatives and F y 10 for ZnTPP
reported for the 2,3-diethynylferrocene-tetraphenylporphyrin, a
Soret band red-shifted by 20 nm, a value close to that for compound
derivatives (see ESI). However, the singlet excited-state nature and
the spectral distribution of the emitted energy is not significantly
altered. Specifically, the fluorescence spectra of both the related
partial compounds and the triads greatly resemble those of the
relative reference compounds, with two main bands in the range
between 600 and 750 nm. The relative intensities of the two peaks
are also substantially retained. On the other hand, a small red shift
is observed as a result of the progressive degree of functionaliza-
tion, mainly with the addition of ferrocene, up to 10 nm for the triad
1 and to 20 nm for the triad 2. This behaviour is in agreement with
the typical trend found for the polycyclic compounds when a
1
which shows the presence of two triple bonds connected on the 2
and 12 beta-positions of the macrocycle.
Compounds 1 and 8 were also converted to the zinc derivatives
2
and 9 by standard procedures. In Table 1 the UVevisible data of all
the compounds are reported.
1
The H NMR spectrum of triad 1, (see ESI) shows a pattern with
the typical signals at 2.74, 3.99, 4.77 and 4.65 ppm of the full-
eropyrrolidine ring and two singlets centered at 4.25 and 4.36 ppm
1
which can be assigned to the ferrocene residue [6]. The H NMR
Fig. 2. The structure of compounds 8 and 9.

P. Tagliatesta, R. Pizzoferrato / Journal of Organometallic Chemistry 787 (2015) 27e32
29
Scheme 1. Synthetic pathways for obtaining compounds 1 and 8.
functionalization is performed with either electron-withdrawing
and electron-donating groups [13].
porphyrin macrocycle and the lower effect of the additional phenyl
ring as a conjugated spacer.
Such spectral characteristics are also found in the emission
spectra of the triads 8 and 9 (see ESI) but some small differences,
yet meaningful, can be observed. A small red shift (i.e. z10 nm) can
be observed in both the emission bands of all the compounds with
an additional phenyl ring spacer. This fact can be reasonably
attributed to their greater conjugation effect. The PL quenching
effect produced by the addition of the ferrocene subunit is much
weaker in this case than that observed in triads 1 and 2. This
observation is consistent with the greater distance from the
Finally, as a common characteristic of the two series of com-
pounds, it should be noted that the same spectral profile was
obtained at concentration from 10
ꢀ
6
ꢀ3
to 10 M in THF, which
Table 1
UVevisible spectral data of all the new compounds in dichloromethane.
Porphyrin
Soret
Visible
abs bands
l
, nm(ε ꢁ 10ꢀ4)
1
2
3
5
6
7
8
9
434(14.10)
449(22.90)
424(28.85)
430(17.09)
431(19.15)
433(15.40)
435(16.85)
438(15.82)
527(3.90)
580(0.65)
574(2.34)
554(0.40)
561(0.43)
567(0.83)
573(1.06)
574(1.61)
570(0.57)
616(0.41)
613(2.21)
596(0.48)
601(0.40)
603(0.77)
608(0.78)
609(1.01)
612(0.41)
670(0.51)
520(1.78)
526(1.58)
526(1.86)
530(1.88)
532(2.35)
651(0.45)
659(0.37)
659(0.44)
664(0.39)
666(0.48)
Fig. 3. Emission spectra of Triad 1 and the partial reference compounds in THF.

30
P. Tagliatesta, R. Pizzoferrato / Journal of Organometallic Chemistry 787 (2015) 27e32
Fig. 4. The structures of the partial reference compounds.
suggests that the concentration-dependent aggregation phenom-
ena are not present in this solvent. In the case of the data reported
by Anderson [6], the steady state fluorescence measurements gave
a very high degree of quenching of the porphyrin emission (>99%)
of the triad. However, when the reference system containing only
the ferrocene and porphyrin was examined, it was found that the
porphyrin fluorescence was also quenched very efficiently by
l
ex ¼ 430 nm was used. The curves were fully corrected for the
spectral response of the apparatus that was calibrated over the
spectral range from 300 nm to 800 nm with a reference black-body
lamp and standard-fluorophore solutions. A spectral band-pass of
2.5 nm was used for both the excitations and emission
monochromators.
ferrocene as we report for our similar compound H
Fc(see SI).
2
TPP-Ph-
Chemicals
Silica gel 60 (70e230 and 230e400 mesh, Merck) was used for
column chromatography. High-purity-grade nitrogen gas was
purchased from Rivoira. C60 was purchased from Term-USA. All the
reagents and solvents were from Fluka Chem. Co., Aldrich Chem. Co.
or Carlo Erba and were used as received. All the compounds gave
satisfactory elemental analysis.
Conclusions
In summary we have reported on the synthesis and character-
ization of four new porphyrin-ferrocene-fullerene triads connected
each other by ethynyl bonds. The reported procedures for obtaining
the compounds are very promising for extending them to other
similar molecules and the work in this field is presently in progress.
Synthesis
Experimental section
4-trimethylsylyethynylbenzaldehyde ethylene acetal. 5 g of 4-
trimethylsylylethynyl benzaldehyde, (0.9 mmol) were dissolved in
200 ml of dry toluene. 5 ml of ethylene glycol and 0.1 g of 4-
toluenesulfonic acid were added and the solution was refluxed
under nitrogen, eliminating the water by-product using a Dean-
eStark apparatus. The final organic solution was washed with a sat.
General methods
1H NMR spectra were recorded as CDCl
AM-300 instrument using residual solvent signal as an internal
standard (7.27 ppm). Chemical shifts are given as values. FAB mass
solutions on a Bruker
3
d
3 2 4
NaHCO and dried on anhydrous Na SO . The residue was recrys-
spectra were measured on a VG-4 spectrometer using m-nitro-
benzyl alcohol (NBA) as a matrix. UV/vis spectra were recorded on a
Varian Cary 50 Scan spectrophotometer in dichloromethane
solution.
tallized from hexane at low temperature giving 5.78 g of the final
þ
1
compound. Yield 95%. Mass (EI): 246(M) ; H NMR (300 MHz,
CDCl ):
(ppm) 7.49 (d, 2H, J ¼ 9 Hz), 7.43 (d, 2H, J ¼ 9 Hz), 5.81 (s,
1H), 4.12 (d, 2H, J ¼ 2 Hz), 4.05 (d, 2H, J ¼ 2 Hz), 0.27 (s, 9H). Anal.
Calcd. for C14 18SiO : C, 68.24; H, 7.36; Found: C, 68.42; H, 7.21.
3
d
Photoluminescence (PL) emission spectra were recorded on a
standard laboratory set-up equipped with a 200-W continuous
Hg(Xe) discharge lamp (Oriel Corp.), an excitation 25-cm mono-
chromator (PMI), an emission 25-cm monochromator (Oriel
Cornerstone 260) and a Hamamatsu R3896 photomultiplier. The
spectra of diluted solutions were recorded using spectroscopic THF
as solvent, with an absorbance <0.1 in the range 250e400 nm, by
H
2
4-ethynylbenzaldehyde ethylene acetal 4. 5.78 g (0.023 mmol)
of 4-trimethylsylyethynylbenzaldehyde ethylene acetal were dis-
solved in 250 ml of methanol and 1 g of anhydrous K CO was
2 3
added with stirring under nitrogen. After 12 h the solution was
diluted with water and extracted three times with diethyl ether.
2 4
The organic solution was dried with anhydrous Na SO and evap-
orated under vacuum. The residue was recrystallyzed from pentane
ꢂ
using conventional 90 geometry on fused-silica cuvettes with an
optical length of 10 mm. The typical excitation wavelength of
at low temperature giving 4.75 g of the final compound. Yield 100%.

P. Tagliatesta, R. Pizzoferrato / Journal of Organometallic Chemistry 787 (2015) 27e32
31
þ
1
Mass(EI): 173 (M ꢀ H) ; H NMR (300 MHz, CDCl
3
):
d
(ppm) 7.53 (d,
Triad 1. 100 mg of 6, (0.1 mmol), were dissolved in 50 ml of dry
toluene under nitrogen and 180 mg, (0.25 mmol) of C60 and 26 mg,
(0.30 mmol) of N-methylglycine were added. The solution was
refluxed for 48 h and then evaporated under vacuum. The residue
was chromatographed on a silica gel column eluting with toluene.
The second fraction containing the desired compound was evapo-
rated under vacuum and recrystallized from toluene/hexane
affording 70 mg, (0.041 mmol). Yield 41%. MS(MALDI-TOF): 1699.32
2
4
H, J ¼ 9 Hz), 7.45 (d, 2H, J ¼ 9 Hz), 5.82 (s, 1H), 4.13 (d, 2H, J ¼ 4 Hz),
.03 (d, 2H, J ¼ 4 Hz), 3.13 (s, 1H). Anal. Calcd. for C11
H
10
O
2
: C, 75.84;
H, 5.78; Found: C, 75.62; H, 5.71.
0
2
-bromo-12-(ethynyl-4 -benzaldehyde
ethylene acetal)-
5
,10,15,20-tetraphenylporphyrin 5. 2,12-dibromo-5,10,15,20-
tetraphenylporphyrin, 3, 200 mg, (0.26 mmol), was dissolved in
50 ml of 5:1 mixture of dry toluene/triethylamine under nitro-
gen and 56 mg of 4 (0.31 mmol) were added. 110 mg, (0.36 mmol)
of AsPh were added and the solution was deareated by argon
bubbling for 10 min 30 mg (0.052 mmol) of bis(dibenzylidenea-
cetone)palladium were added and after 20 min of argon
bubbling, the solution was kept at 60 C for 12 h under nitrogen.
1
þ
1
(M þ H) ; H NMR (300 MHz, CDCl
3
): d(ppm) 9.04 (s, 1H), 8.99 (s,
3
1H), 8.91 (t, 1H, J ¼ 2.9 Hz), 8.87 (t, 1H, 2.9 Hz), 8.84 (s, 1H), 8.78 (t,
1H, J ¼ 5.9 Hz), 8.13 (m, 8H), 7.85 (m, 10H), 7.81 (m, 2H), 7.78 (m,
2H), 4.77 (d, 1H, J ¼ 8.3 Hz), 4.65 (s, 1H), 4.36 (s, 3H), 4.24 (s, 6H),
3.99 (d,1H, J ¼ 8.3 Hz) 2.74 (s, 3H), -2.65 (s,1H), -2.69 (s, 1H); UV/vis
ꢂ
The resulting mixture was evaporated under vacuum and the
residue chromatographed on a silica gel column, eluting with
toluene, affording 175.3 mg (0.091 mmol) of the desired com-
(CH
2
Cl
2
):
N
lmax (nm): 434, 527, 580, 616, 670. Anal. Calcd. for
C
127
H
47
5
Fe: C, 89.80; H, 2.78; N, 4.12. Found: C, 90.08; H, 2.65;
N, 4.26.
þ
1
pound in 60% of yield. MS(FAB): 867(M þ H) ; H NMR
300 MHz, CDCl ):
(ppm) 9.09 (d, 1H, J ¼ 2 Hz), 8.79 (m, 5H),
.10 (m, 8H), 7.80 (d, 2H, J ¼ 4 Hz), 7.71 (m, 10H), 7.43 (d, 2H,
Triad 8. 100 mg of 7, (0.097 mmol), were dissolved in 50 ml of
dry toluene under nitrogen and 180 mg, (0.25 mmol) of C60 and
26 mg, (0.30 mmol) of N-methylglycine were added. The solution
was refluxed for 48 h and then evaporated under vacuum. The
residue was chromatographed on a silica gel column eluting with
toluene. The second fraction containing the desired compound was
evaporated under vacuum and recrystallized from toluene/hexane
affording 60 mg, (0.033 mmol). Yield 35%. MS(MALDI-TOF):
(
3
d
8
J ¼ 9 Hz), 7.39 (d, 2H, J ¼ 9 Hz), 5.85 (s, 1H), 4.19 (s, 2H), 4.15 (s,
2
6
H), -2.78 (s, 2H); UV/vis (CH ):
2
Cl
2
lmax (nm): 430, 526, 561, 601,
59. Anal. Calcd. for C55H N O Br: C, 76.29; H, 4.30; N, 6.47.
Found: C, 75.92; H, 4.21; N, 6.32.
37 4 2
0
2
-ferrocenylethynyl-12-(4 -formylphenylethynyl)-5,10,15,20-
þ
1
tetraphenylporphyrin 6. Compound 5 (108 mg, 0.124 mmol) was
dissolved in 50 ml of dry THF under nitrogen and 0.35 ml of tet-
rabutylammonium fluoride (TBAF), 10% THF solution, were added.
The solution was deareated by argon bubbling for 10 min after that
ethynylferrocene, (46 mg, 0.220 mmol) were added with further
1775.35, (M þ H) ; H NMR (300 MHz, CDCl
3
): d(ppm) 9.02 (s,
1H), 8.92 (d, 1H, J ¼ 1.9 Hz)), 8.77 (m, 4H), 8.21 (m, 8H), 7.78 (m,
12H), 7.59 (m, 2H), 7.47 (m, 6H), 4.90 (d, 1H, J ¼ 1.3 Hz), 4.81 (s, 1H),
4.70 (s, 2H), 4.38 (s, 2H), 4.14 (d, 1H, J ¼ 1.2 Hz) 4.08 (s, 5H), 2.81 (s,
3H), -2.65 (s, 2H); UV/vis (CH
666. Anal. Calcd. for C133
C, 90.08; H, 2.75; N, 3.76.
2 2
Cl ): lmax (nm): 435, 532, 574, 609,
H N Fe: C, 90.01; H, 2.89; N, 3.94. Found:
51 5
argon bubbling of 10 min 40 mg of Pd(PPh
after 20 min of argon bubbling, the solution was kept at 80 C for
3
)
2
Cl
2
were added and
ꢂ
1
2 h under nitrogen. The resulting mixture was evaporated under
vacuum and redissolved in 100 ml of THF/H O under nitrogen.
.1 ml of conc. HCl was added and after 4 h the mixture was diluted
2
General procedure for zinc insertion
0
3
with water and extracted with CHCl . The solvent was evaporated
To a solution of starting compound in chloroform, a saturated
solution of Zn(AcO) in methanol was added and the mixture was
2
and the residue chromatographed on a silica gel column, eluting
with toluene, affording 55 mg (0.055 mmol) of the desired com-
left to react at room temperature under nitrogen for 2 h. The sol-
vent was evaporated and the product was purified using a plug of
silica gel, eluting with toluene.
þ
1
pound in 45% of yield. MS(FAB): 952(M þ H) ; H NMR (300 MHz,
CDCl ):
3
d
(ppm) 10.04 (s, 1H), 9.09 (d, 1H, J ¼ 2.9 Hz), 8.87 (d, 1H,
J ¼ 2.9 Hz), 8.87 (s, 1H), 8.84 (t, 1H, J ¼ 5.9 Hz), 8.78 (t, 1H,
J ¼ 5.9 Hz), 8.76 (s, 1H), 7.83 (m, 8H), 7.68 (m, 12H), 7.67 (m, 2H),
þ
Zn-Triad 2. Yield: 97%. MS(MALDI-TOF), m/z: 1041.41, [M-C60] ;
1
3
H NMR (300 MHz, CDCl ): d(ppm) 9.18 (s, 1H), 9.12 (s,1H), 8.90 (m,
H), 8.82 (m, 1H), 8.67 (s, 1H), 8.18 (m, 8H), 7.82 (m, 12H), 7.57 (m,
7
.50 (d, 2H, J ¼ 9 Hz), 4.37 (s, 3H), 4.26 (s, 6H), -2.65 (s, 1H), -2.68
2
4
(
(
(
s, 1H); UV/vis (CH
Calcd. for C65
H, 4.65; N, 5.56.
2 2
Cl ): lmax (nm): 431, 526, 567, 603, 659. Anal.
H), 7.41 (d, 2H, J ¼ 9.2 Hz), 4.80 (d, 1H, J ¼ 9 Hz), 4.66 (s, 1H), 4.39
42
H N
4
FeO: C, 82.10; H, 4.45; N, 5.89. Found: C, 81.98;
s, 3H), 4.26 (s, 6H), 4.03 (d, 1H, J ¼ 9.2 Hz), 2.80 (s, 3H); UV/vis
CH
2
Cl
2
):
lmax (nm): 449, 574, 613. Anal. Calcd. for C127
H
45
N
5
FeZn:
0
2
-phenylethynylferrocenyl-12-(4 -formylphenylethynyl)-5,10,15,
C, 86.57; H, 2.57; N, 3.97. Found: C, 85.99; H, 2.25; N, 3.80.
2
0-tetraphenylporphyrin 7. Compound 5 (108 mg, 0.124 mmol) was
þ
Zn-Triad 9. Yield: 98%. MS(MALDI-TOF), m/z: 1117.05, [M-C60] ;
dissolved in 50 ml of dry THF under nitrogen and 0.35 ml of tetra-
butylammonium fluoride (TBAF),10% THF solution, were added. The
solution was deareated by argon bubbling for 10 min after that
phenylethynylferrocene, (63 mg, 0.220 mmol) were added with
1
H NMR (300 MHz, CDCl
3
):
H), 8.82 (m, 1H), 8.67 (s, 1H), 8.21 (m, 8H), 7.78 (m, 12H), 7.57 (m,
H), 7.39 (m, 2H), 7.03 (d, 2H, J ¼ 6.2 Hz); 4.84 (d, 1H, J ¼ 9 Hz), 4.73
d(ppm) 9.06 (s,1H), 9.01 (s,1H), 8.90 (m,
2
4
(
s, 1H), 4.40 (s, 3H), 4.10 (s, 6H), 4.03 (d, 1H, J ¼ 9.2 Hz), 2.77 (s, 3H);
UV/vis (CH Cl ): max (nm): 438, 572, 612. Anal. Calcd. for
FeZn: C, 86.90; H, 2.68; N, 3.81. Found: C, 86.99; H, 2.75;
further argon bubbling of 10 min 40 mg of Pd(PPh
and after 20 min of argon bubbling, the solutionwas kept at 80 C for
3
)
2
Cl
2
were added
2
2
l
ꢂ
C
133 49 5
H N
1
2 h under nitrogen. The resulting mixture was evaporated under
vacuum and redissolved in 100 ml of THF/H O under nitrogen. 0.1 ml
of conc. HCl was added and after 4 h the mixture was diluted with
water and extracted with CHCl . The solvent was evaporated and the
N, 3.90.
2
References
3
residue chromatographed on a silica gel column, eluting with
toluene, affording 62 mg (0.06 mmol) of the desired compound in
[1] (a) R.A. Marcus, J. Phys. Chem. 72 (1968) 891;
(b) D. Gust, T.A. Moore, A.L. Moore, Acc. Chem. Res. 42 (2009) 1890.
[2] R.L. Gregory, Biochemistry of Photosynthesis, Wiley-Interscience, , New York,
þ
1
4
8% of yield. MS(MALDI-TOF):1028.51(M þ H) ; H NMR (300 MHz,
CDCl ):
(ppm) 10.05 (s, 1H), 9.07 (d, 2H, J ¼ 1.5 Hz), 8.87 (m, 4H),
.23 (m, 8H), 7.87 (m, 12H), 7.51 (m, 6H), 7.26 (d, 2H, J ¼ 2.1 Hz), 4.73
s, 2H), 4.40 (s, 2H), 4.10 (s, 5H), -2.61 (s, 2H); UV/vis (CH Cl ):
nm): 433, 530, 573, 608, 664. Anal. Calcd. for C71 FeO: C, 83.03;
1971. New York.
3
d
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8
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(
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(
(
2
2
l
max
46 4
H N
(
H, 4.51; N, 5.45. Found: C, 82.98; H, 4.60; N, 5.59.

32
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(