Halo-Wittig- and zirconium-promoted synthesis of conjugated metalloporphyrin dimers

Article abstract of DOI:10.1142/S108842461000215X

The synthesis and spectroscopic studies of metalloporphyrin dimers having 1,3-butadiyne linker attached to the beta pyrrolic positions of the linked porphyrins are reported. Bromoethenyl metalloporphyrins were synthesized by zirconocene-promoted bromomethylenation of beta formyl metalloporphyrins. Bromoethenyl metalloporphyrins were dehydrohalogenated by potassium tertbutoxide to give beta ethynyl or 2-ethynyl metalloporphyrins. It is the first documented example of zirconocene-promoted bromomethylenation of beta formyl metalloporphyrins. Bromoethenyl metalloporphyrins were also synthesized by halo-Wittig route. 2-ethynyl metalloporphyrins were self dimerized to give metalloporphyrin dimers having 1,3-butadiyne linking bridge. FTIR, Raman spectroscopy, UV-visible, elemental analysis, ¹H NMR and mass spectrometry were used to characterize the compounds. Copyright

Full text of DOI:10.1142/S108842461000215X

Journal of Porphyrins and Phthalocyanines
J. Porphyrins Phthalocyanines 2010; 14: 298–304
DOI: 10.1142/S108842461000215X
Published at http://www.worldscinet.com/jpp/
Halo-Wittig- and zirconium-promoted synthesis of conjugated
metalloporphyrin dimers
Muhammad Yaseen*a, Mukhtar Alib, Munawar Ali Munawara, Muhammad Salima,
Muhammad NajeebUllaha, Irshad Khokhara and Muhammad H. Sayyadc
a Institute of Chemistry, University of the Punjab, Lahore 54000, Pakistan
b Government College of Science, Wahdat Road, Lahore 54000, Pakistan
c Faculty of Engineering Sciences, GIK Institute of Engineering Sciences and Technology, Topi, District Swabi,
NWFP 23640, Pakistan
Received 15 June 2009
Accepted 11 September 2009
ABSTRACT: The synthesis and spectroscopic studies of metalloporphyrin dimers having 1,3-butadiyne
linker attached to the beta pyrrolic positions of the linked porphyrins are reported. Bromoethenyl
metalloporphyrins were synthesized by zirconocene-promoted bromomethylenation of beta formyl
metalloporphyrins. Bromoethenyl metalloporphyrins were dehydrohalogenated by potassium tert-
butoxide to give beta ethynyl or 2-ethynyl metalloporphyrins. It is the first documented example of
zirconocene-promoted bromomethylenation of beta formyl metalloporphyrins. Bromoethenyl metallo-
porphyrins were also synthesized by halo-Wittig route. 2-ethynyl metalloporphyrins were self dimerized
to give metalloporphyrin dimers having 1,3-butadiyne linking bridge. FTIR, Raman spectroscopy, UV-
visible, elemental analysis, 1H NMR and mass spectrometry were used to characterize the compounds.
KEYWORDS: porphyrin dimer, metalloporphyrin dimer, bromomethylenation, butadiyne linker, formyl
porphyrins, halo-Wittig.
monomer has a small energy gap between the high-
est occupied molecular orbital (HOMO) and the lowest
INTRODUCTION
The electronic properties of linear π-conjugated poly-
unoccupied molecular orbital (LUMO) [5]. Different
mers can be tuned by the introduction of aromatic systems,
molecules or groups may be introduced on porphyrin and
electron donating or withdrawing substituents into its main
the central metal atom may also be changed. Hence, por-
skeleton [1]. Such π-conjugated polymers have been widely
phyrins offer a wide range of possibilities to tune their
investigated as organic conductors, multifunctional sensors,
electronic properties, either by peripheral substitution or
field effect transistors and as photovoltaic devices [2, 3].
by changing the central metal atom.
Porphyrins are cyclic tetrapyrrolic molecules in which
four pyrrole molecules are joined through their α carbon
A single porphyrin molecule has 22 π-electrons but
only 18 of these are included in any conjugated pathway.
atoms by four methine bridges. Recent researches in the
However, there are many examples of expanded porphy-
field of optoelectronics have opened a new horizon for the
use of porphyrins as advanced materials and as molecular
rins having 26, 30, 34, 38, and 54 π-electrons [6]. Electro-
chemical data and the electronic spectra of such expanded
wires [4]. The high polarizability, strong optical oscilla-
porphyrins exhibit a sharp change when compared with
tor strength, and nonlinear optical behavior of porphyrins
are the desired properties required for ultrafast switching
technology. Because of extensive conjugation, porphyrin
porphyrins and metalloporphyrin having 22 π-electrons.
For example, there is a linear red shift in Soret and Q-bands
upon increasing the π-electrons in the conjugation, result-
ing in the reduction of HOMO-LUMO energy gap [7].
Extension of conjugation outside the porphyrin/metal-
loporphyrin ring is another way to create the red shift in
*Correspondenceto:MuhammadYaseen,email:yaseen747pk@
hotmail.com, tel: +92 300-408-4743 and +92 332-498-7180
Copyright © 2010 World Scientific Publishing Company

HALO-WITTIG- AND ZIRCONIUM-PROMOTED SYNTHESIS
299
the electronic spectra of porphyrins and metalloporphyrins.
A single molecule of porphyrin/metalloporphyrin offers
12 peripheral substitution positions on which various
functional groups have been introduced. But in the major-
ity cases, complete electronic communication between the
π-electrons of the porphyrin or metalloporphyrin ring and
the moiety attached to the porphyrin or metalloporphyrin
ring failed because of the steric hindrances. In fact, phe-
nyl or alkyl groups attached to the meso- or beta positions
are twisted due to the steric hindrance at the porphyrin
peripheries, resulting in limited π overlap [8].
During the last 20 years, there has been a consider-
able research directed towards the synthesis of multi-
porphyrin systems having 1,3-butadiyne linker [9, 10].
Because of its cylindrical symmetry 1,3-butadiyne linker
is an efficient bridge to facilitate conjugation between the
linked porphyrin or metalloporphyrin macrocycles in any
plane. Such extended conjugated systems are expected to
have lower HOMO-LUMO energy gaps than their par-
ent monomeric porphyrins or metalloporphyrins. Such
systems could allow direct electronic communication
between the linked porphyrins and therefore be of inter-
est in the field of molecular electronics and for the manu-
facturing of photovoltaic devices.
In this paper we report the synthesis and spectroscopic
studies of metalloporphyrin dimers having 1,3-butadiyne
linker attached to the beta pyrrolic positions of the linked
macrocycles. The target dimers were prepared by two
different synthetic paths. The presented synthesis is the
part of our research project aimed at evaluating the effect
of extended conjugation outside the porphyrin ring in the
terms of their electronic properties and their use as mul-
tifunctional sensors. We selected 5,10,15,20-tetrakis(4′-
isopropylphenyl)porphyrin to be the basis of our dimeric
system.
In 1978, Arnold and co-workers reported the first syn-
thesis and dimerization of a meso-ethynyl porphyrin [17].
Their synthetic paths involved Wittig and Grignard meth-
ylenation of meso-formyloctaethylporphyrin. In 1992,
Arnold and co-workers reported an improved synthesis
of their previously reported bis-porphyrin by four-step
halo-Wittig synthetic path [18]. Gosper and Ali extended
Arnold halo-Wittig reaction methodology for the synthe-
sis of a conformationally constrained conjugated porphy-
rin dimer [11].
Our starting materials 2-formyl-5,10,15,20-tetrakis
(4′-isopropylphenyl)porphyrinatonickel(II) (Porphyrin 1)
and 2-formyl-5,10,15,20-tetrakis(4′-isopropylphenyl)por-
phyrinatocopper(II) (Porphyrin 2), were synthesized
according to the method described in the literature [19]
and were used as precursors for self dimerization.
Initially, we applied the halo-Wittig reaction scheme
described by Arnold [18] to Porphyrins 1 and 2 for the
synthesis of trans and cis bromoethenyl porphyrins.
According to Arnold, halo-Wittig reaction failed for
the copper complex of meso formyl octaethylporphyrin
[18]. However, in our case halo-Wittig scheme worked
well for both the copper and nickel complexes of beta
or 2-formyl porphyrin. In a typical reaction, bromometh-
yltriphenylphosphonium bromide [18] was stirred with
one equivalent of potassium tert-butoxide under nitro-
gen atmosphere to produce bright yellow ylide at -78 °C.
Porphyrin 1 or 2 was made to react with this ylide at -78 °C
for three hours and then at room temperature for the next
four hours under nitrogen atmosphere. This produced
2-{(E)-2′-bromoethenyl)}-5,10,15,20-tetrakis(4′-iso-
propylphenyl)porphyrinatonickel(II) (Porphyrin 3), and
2-{(Z)-(2′-bromoethenyl)}-5,10,15,20-tetrakis(4′-
isopropylphenyl)porphyrinatonickel(II) (Porphyrin 4), or
2-{(E)-2′-bromoethenyl)}-5,10,15,20-tetrakis(4′-
isopropylphenyl)porphyrinatocopper(II) (Porphyrin 5) and
2-{Z)-(2′-bromoethenyl)}-5,10,15,20-tetrakis(4′-
isopropylphenyl)porphyrinatocopper(II) (Porphyrin 6).
The Porphyrins 3 and 4 were obtained in 80% and 16%
yields whereas Porphyrins 5 and 6 were obtained in 72%
and 10% yields, respectively.
Porphyrins 3 and 4 or 5, and 6 were dehydrobrominated
into 2-ethynyl-5,10,15,20-tetrakis(4′-isopropylphenyl)
porphyrinatonickel(II) (Porphyrin 7) or 2-ethynyl-
5,10,15,20-tetrakis(4′-isopropylphenyl)porphyrinato-
copper(II) (Porphyrin 8) on further reacting with excess
of potassium tert-butoxide in THF at room temperature.
The yield of the dehydrohalogenated reaction from the
bromoethenyl Porphyrins 3 and 4 or 5 and 6 was 80%.
One-pot synthesis of Porphyrin 7 or 8 was also achieved
when two equivalents of potassium tert-butoxide was
made to react with bromomethyltriphenylphosphonium
bromide and Porphyrin 1 or 2. The yields of Porphyrins
7 and 8 for one-pot procedure were found to be 77% and
65% respectively (Scheme 1).
RESULTS AND DISCUSSION
Functionalization of porphyrin is one of the hottest
topics in field of porphyrin research. Various methods are
available in the literature to functionalize the porphyrin
macrocycle at both meso and beta positions [12–14]. In
this connection, introduction of formyl group onto the
porphyrin molecule has an advantage over other func-
tional groups as this group can be converted into a num-
ber of other functional groups by reacting it with different
reagents [15, 16].
From the outset of our research, we aimed to inves-
tigate a synthetic path for the synthesis of a multipor-
phyrin system having direct electronic communication
through the beta pyrrolic positions of the linked porphy-
rins or metalloporphyrins. For this purpose, we selected
1,3-butadiyne as a bridge to link two porphyrins. 1,3-
butadiyne linker has an advantage over the other linkers
because it possesses cylindrical symmetry and hence the
problems of steric hindrance and limited π-conjugation
are ruled out.
In 1989, Tour et al. [20] described zirconium-promoted
methylenation of aldehydes, ketones and enones. Tour
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300
M. YASEEN ET AL.
used dibromomethane for the methylenation of alde-
hydes; we replaced it with bromoform. This modified
Tour reaction worked well for the synthesis of bromoethe-
nyl porphyrins. Unlike the halo-Wittig reaction scheme,
zirconocene-promoted halomethylenation reaction gave
the same product yield both for Porphyrins 1 and 2. In a
typical reaction, the mixture of zinc metal, zirconocene
dichloride, THF, Porphyrin 1 or 2 and bromoform were
stirred at room temperature for 12 hours under the dry
N2 atmosphere. This gave a mixture of trans and cis bro-
moethenyl Porphyrins 3 and 4 or 5 and 6 in 70% yield.
The ratio of Porphyrins 3 to 4 or 5 to 6 obtained in this
reaction was 3:1. Porphyrins 3 and 4 or 5 and 6 were
dehydrohalogenated at room temperature by reacting
with an excess of potassium tert-butoxide in THF to give
2-ethynyl Porphyrin 7 or 8 in 80% yield. The dehydro-
halogenation was also achieved in situ by the addition
of potassium tert-butoxide base after the 12 h during the
zirconium-promoted bromomethylenation of Porphyrin 1
or 2. This one-pot procedure gave the Porphyrin 7 or 8 in
56% yield (Scheme 1).
Initially standard Glaser conditions were employed
for the self dimerization of Porphyrin 7 or 8, which failed
to give the required product. Alternatively, Eglinton con-
ditions were employed and a solution of Porphyrin 7 or
8 in dry pyridine was stirred at 60 °C with anhydrous
copper(II) acetate in the presence of air for eight hours. No
reaction was observed even when the reaction temperature
was raised to reflux. It resulted in the slow degradation of
the starting materials. No dimerization was observed even
after bubbling oxygen through the solution.
When the dimerization was carried out at 28 °C in
acetone solvent with the use of N,N,N′,N′-tetramethyl-
enediamine (TMEDA) and copper(I) chloride catalyst,
it again resulted in no reaction. Glaser-Hay coupling of
Porphyrin 7 or 8 with CuCl and TMEDA in CH2Cl2/1%
pyridine produced metalloporphyrin dimer Porphyrin 9 or
10 (Scheme 1). Demetallation of Porphyrin 9 or 10 under
the acidic conditions gave metal-free Porphyrin dimer 11.
FTIR-spectrum of Porphyrin 1 or 2 showed strong
absorption around 1670 cm-1 due to C=O stretching that
disappearedafterbromomethylenation.FTIR-spectrumof
Porphyrin7or8showedweakabsorptionaround2162cm-1
for C≡C stretch and a peak of medium intensity around
3314 cm-1 due to ≡C-H stretch. The Raman spectra of Por-
phyrins 7 and 8 showed strong absorption around 2162
cm-1 for C≡C stretch. As was expecting for symmetrical
alkynes, FTIR of Porphyrins 9 and 10 showed no
absorptions for C≡C stretch but their Raman spectra
showed clear, strong absorptions at 2180 and 2172 cm-1
for C≡C stretch, respectively. The Raman spectrum of
metal-free dimer, Porphyrin 11, showed absorption at
2175 cm-1 for C≡C stretch.
Metalloporphyrin Dimer
Scheme 1
R
R
O
N
M
N
H
N
N
R=4-isopropylphenyl
R
R
Porphyrin 1; M= Ni+2
or
Porphyrin 2; M= Cu+2
Ziconocene or halo-Wittig
path
R
R
R
R
Br
N
M
N
N
Br
+
N
N
N
M
N
N
R
R
R
R
A comparison of UV-visible spectra of Porphyrin 9
with Porphyrin 7 (Fig. 1) shows that the Soret band of
Porphyrin 9 undergoes 3 nm bathochromic shift with sig-
nificant broading. The UV-visible spectrum of Porphyrin
7 shows absorption peaks at 430 and 540 nm. The elec-
tronic absorption spectrum of Porphyrin 9 shows absorp-
tions at 433 and 545 nm along with an extra absorption
Porphyrin 3; M= Ni+2
or
Porphyrin 5; M= Cu+2
Porphyrin 4; M= Ni+2
or
Porphyrin 6; M= Cu+2
Base
R
R
N
M
N
N
N
R
R
Porphyrin 7; M= Ni+2
or
Porphyrin 8 M= Cu+2
Glaser-Hay Coupling
R
R
R
R
N
M
N
N
M
N
N
N
N
N
R
R
R
R
Porphyrin 9; M= Ni+2
or
Porphyrin 10; M= Cu+2
Scheme 1.
Fig. 1. Absorption spectrum of Porphyrins 7 and 9
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HALO-WITTIG- AND ZIRCONIUM-PROMOTED SYNTHESIS
301
sequentially charged with activated zinc powder
(16 mmole, particle size <150 µm), zirconocene dichlo-
ride (2.4 mmole) Porphyrin 1 or 2 (0.46 mmole), dry THF
(60 mL), and bromoform (4.4 mmole). The solution was
stirred at room temperature for 12 h, after which reaction
was stopped by the addition of distilled water (10 mL).
Reaction mixture was stirred for the next 30 min.
Reaction mixture was filtered and the filtrate was
evaporated under vacuum. The residue was first washed
with distilled water (3 × 20 mL) and then with methanol
(3 × 20 mL). The dried crude product was applied onto the
top of a silica column and eluted with cyclohexane. The
first two slow-moving red bands were collected and the
solvent was evaporated to get trans and cis bromoethenyl
porphyrins (3 and 4 or 5 and 6). Red crystals of Porphyrin
3 or 4 were obtained by the slow evaporation of dichlo-
romethane and methanol (4:1) mixture whereas red rose
crystals of Porphyrins 5 or 6 were obtained by the similar
process of crystallization.
Halo-Wittig-promoted bromoethenyl porphyrin
synthesis. A dry N2-flushed round-bottom flask was
filled with dry THF (50 mL). It was cooled at dry ice tem-
perature. Bromomethyltriphenylphosphonium bromide
(1.0 mmole) and potassium tert-butoxide (1.0 mmole)
were added at dry ice temperature with vigorous stirring.
A bright yellow ylide was formed after 30 min. Porphyrin
1 or 2 (0.23 mmole) was then added into the reaction flask.
The reaction mixture was stirred at dry ice temperature
for 3 h and then at room temperature for the next 4 h.
The reaction mixture was filtered and the filtrate was
evaporated under vacuum. The residue was first washed
with distilled water (3 × 25 mL) and then with methanol
(3 × 50 mL). The dried crude product was applied onto the
top of a silica column and eluted with cyclohexane. The
first two slow-moving red bands were collected and the
solvent was evaporated to get trans and cis bromoethenyl
porphyrins (3 and 4 or 5 and 6). Red crystals of Porphyrin
3 or 4 were obtained by the slow evaporation of dichlo-
romethane and methanol (4:1) mixture whereas purple
red crystals of Porphyrins 5 or 6 were obtained by the
similar process of crystallization.
Ethyne-substitutedporphyrinsynthesis. Porphyrins3and
4 or 5 and 6 (1.0 mmole) were stirred with an excess of potas-
sium tert-butoxide (4.0 mmole) in dry THF (100 mL) for
6 h. THF was evaporated and the residue was first washed
with distilled water (3 × 20 mL) and then with methanol
(3 × 20 mL). The dried crude product was applied onto
the top of a silica column and eluted with the mixture
of chloroform and cyclohexane (1:10). The fast-moving
band was collected and the solvent was evaporated under
vacuum to get Porphyrin 7 or 8. Crystallization from
the mixture of chloroform and methanol (3:1) produced
dark red crystals of Porphyrin 7 whereas rose red crystals
of Porphyrin 8 were obtained by the similar process of
crystallization.
Fig. 2. Absorption spectrum of Porphyrins 8 and 10
at 591 nm. These changes indicate that some degree of
electronic perturbation has occurred upon dimerization.
A comparison of UV-visible spectra of Porphyrin 10
with the Porphyrin 8 (Fig. 2) shows that the Soret band
of Porphyrin 10 undergoes 2 nm red shift with signifi-
cant broading. An extra absorption at 596 nm was also
observed for Porphyrin 10. It shows that even though the
Porphyrin 10 has conjugation pathway via beta positions,
only minor electronic interaction is observed between the
Porphyrin macrocycles and the same is true for the Por-
phyrin 9.
1H NMR spectra of Porphyrin 7 showed a singlet at
3.11 δ for ≡C-H that disappeared after the self dimeriza-
tion of Porphyrin 7. Porphyrin 7 showed another singlet
at 8.98 δ for the β-pyrrolic proton at the C3 position due to
the neighboring ethyne substituent. Porphyrin 11 showed
a broad singlet at -2.62 δ because of four imino protons
and a singlet at 9.18 δ for β-pyrrolic protons at C3, 3′
.
EXPERIMENTAL
Melting points were determined on a Kofler micro-
melting point apparatus without correction. IR spectra
were recorded on a Nicolet Impact-410 FTIR spectro-
photometer in KBr. Raman spectra were recorded with a
Spex Model 1401 spectrometer using 488.0 and 514.5 nm
1
wavelength excitation from an argon laser. H NMR
spectra were measured in CDCl3 using TMS as internal
standard with a Bruker 400 MHz spectrometer. Mass
spectra were taken on a Bruker BioApex 47e FTMS
fi tted with an analytical electrospray source. Elemental
analyses were performed on a PE-2400 CHN elemental
analyzer. UV-vis measurements were performed with a
Shimadzu Multispec-1501. Reagents from Merck and
Aldrich Chemical Co. were used.
General procedures
Zirconocene-promoted bromoethenyl porphyrin
synthesis. A dry N2-flushed round-bottom flask was
Dimerization of porphyrin. CuCl (2.3 mmole) and
TMEDA (2.8 mmole) were added to a vigorously stirred
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M. YASEEN ET AL.
solution of Porphyrin 7 or 8 (0.03 mmole) in dichlo-
romethane (100 mL) and pyridine (1.0 mL). Reac-
tion mixture was stirred at room temperature for 6 h
after which the organic phase was washed with water
(3 × 25 mL). Organic phase was evaporated and the resi-
due was purified by column chromatography using petro-
leum ether (bp 60–90 °C) and chloroform (1:3) as mobile
phase. The fast-moving band was collected and the sol-
vent was evaporated to get pure Porphyrin 9 in 73% yield
or pure Porphyrin 10 in 83% yield. Green crystals of Por-
phyrin 9 were obtained from the mixture of chloroform
and methanol (3:1) whereas Porphyrin 10 produced dark
green crystals by the similar process of crystallization.
Demetallation of porphyrin. Porphyrin 9 or 10
(0.03 mmole) was dissolved in dichloromethane (50 mL).
Two drops of concentrated sulfuric acid were added and
the solution was stirred at room temperature for 12 h.
Progress of the reaction was monitored by thin-layer
chromatography. The solution was poured into ice cold
water (20 mL) and stirred for 5 min. The organic layer
was separated and washed first with saturated solution
of sodium bicarbonate (2 × 25 mL) and then with water
(2 × 25 mL). The organic phase was dried over anhy-
drous sodium sulfate. Dichloromethane was evaporated
under vacuum and the residue was purified by column
chromatography using petroleum ether (bp 60–80 °C)
and dichloromethane (1:4.5) as eluent. The fast-moving
red band was collected and the solvent was evaporated
to get Porphyrin 11 in 86% yield. Purple red crystals of
Porphyrin 11 were obtained from the mixture of dichlo-
romethane and methanol (3:1).
UV-vis (CHCl3): λmax, nm (rel. int.) 420 (11.53), 535
(1.0). 1H NMR (400 MHz; CDCl3; Me4Si): δH, ppm 1.52
(24H, d, -CH-(CH3)2, J = 6.5 Hz), 3.20 (4H, sep, -CH-
(CH3)2, J = 6.5 Hz), 6.43 (1H, d, -CH=CHBr, J = 13.8
Hz), 6.71 (1H, d, -CH=CHBr, J = 13.8 Hz), 7.56 (8H,
m, m-PhH), 7.91 (6H, m, o-PhH of C5,10,15), 7.98 (2H, m,
o-PhH of C20), 8.68 (1H, s, β-pyrrolic H on C3), 8.76 (6H,
m, β-pyrrolic H at C7,8,12,13,17,18). MS (ESI): m/z 943.29
(calcd. for [M + H]+).
Porphyrin 4. mp > 350 °C. Anal. calcd. for
C58H53BrN4Ni: C, 73.74; H, 5.65; N, 5.93. Found: C,
73.84; H, 5.63; N, 5.94. IR (KBr): νmax, cm-1 2955, 2920,
2850, 1654, 1609, 1458, 1347, 1292, 1006, 812, 717.UV-
vis (CHCl3): λmax, nm (rel. int.) 420 (11.53), 535 (1.0).
1H NMR (400 MHz; CDCl3; Me4Si): δH, ppm 1.52 (24H,
d, -CH-(CH3)2, J = 6.5 Hz), 3.20 (4H, sep, -CH-(CH3)2,
J = 6.5 Hz), 6.5 (1H, d, -CH=CHBr, J = 7.9 Hz), 6.71
(1H, d, -CH=CHBr, J = 7.9 Hz), 7.56 (8H, m, m-PhH),
7.91 (6H, m, o-PhH of C5,10,15), 7.98 (2H, m, o-C20 PhH),
8.68 (1H, s, β-pyrrolic H on C3), 8.76 (6H, m, β-pyrrolic
H at C7,8,12,13,17,18). MS (ESI): m/z 943.29 (calcd. for [M
+ H]+).
Porphyrin 5. mp > 350 °C. Anal. calcd. for C58H53Br-
CuN4: C, 73.37; H, 5.63; N, 5.90. Found: C, 73.30; H,
5.65; N, 5.86. IR (KBr): νmax, cm-1 2954, 2920, 2850,
1655, 1609, 1458, 1345, 1292, 1000, 815, 720. UV-vis
(CHCl3): λmax, (rel. int.), nm 425 (10.82), 545 (1.0). MS
(ESI): m/z, 948.29 (calcd. for M+ H)+.
Porphyrin 6. mp > 350 °C; Anal. calcd. for C58H53Br-
CuN4: C, 73.37; H, 5.63; N, 5.90. Found: C, 73.22; H,
5.64; N, 5.91. IR (KBr): νmax, cm-1 2954, 2920, 2850,
1655, 1609, 1458, 1345, 1292, 1000, 815, 720. UV-vis
(CHCl3): λmax, nm (rel. int.) 425 (10.82), 545 (1.0). MS
(ESI): m/z 948.29 (calcd. for [M+ + H]+).
Synthesis
Porphyrin 1. mp > 350 °C. Anal. calcd. for
C57H52N4NiO: C, 78.90; H, 6.04; N, 6.46. Found: C,
78.80; H, 6.03; N, 6.48. IR (KBr): νmax, cm-1 2956, 2923,
1669 (C=O), 1545, 1507, 1459, 1351, 1056, 1001, 937,
813, 797, 719. UV-vis (CHCl3): λmax, nm (rel. int.) 435
(16.4), 545 (1.26), 585 (1.0). 1H NMR (400 MHz; CDCl3;
Me4Si): δH, ppm 1.48 (24H, d, -CH-(CH3)2, J = 6.7 Hz),
3.18 (4H, sep, -CH-(CH3), J = 6.7 Hz), 7.52 (8H, d,
m-PhH, J = 6.9 Hz), 7.89 (8H, d, o-PhH, J = 6.9 Hz),
8.72 (6H, m, β-pyrrolic H at C7,8,12,13,17,18), 9.20 (1H, s,
β-pyrrolic H at C3), 9.34 (1H, s, -CHO). MS (ESI): m/z
867 (calcd. for [M]+).
Porphyrin 2. mp > 350 °C. Anal. calcd. for
C57H52CuN4O: C, 78.46; H, 6.01; N, 6.42. Found: C,
78.51; H, 6.03; N, 6.44. IR (KBr): νmax, cm-1 2957,
2923, 1670 (C=O), 1559, 1540, 1507, 1458, 1342, 1055,
1000, 798, 721. UV-vis (CHCl3): λmax, nm (rel. int.) 430
(16.68), 550 (1.31), 595 (1.0). MS (ESI): m/z 872 (calcd.
for [M]+).
Porphyrin 7. mp > 350 °C. Anal. calcd. for C58H52N4Ni:
C, 80.65; H, 6.07; N, 6.49. Found: C, 80.84; H, 6.06; N,
6.50. IR (KBr): νmax, cm-1 3314 (≡C-H), 2956, 2923, 2162
(C≡C), 1507, 1342, 1055, 1001, 798, 719. Raman (solid):
ν
max, cm-1 2162 (C≡C). UV-vis (CHCl3): λmax, nm (rel.
1
int.) 430 (8.5), 540 (1.0). H NMR (400 MHz; CDCl3;
Me4Si): δH, ppm 1.54 (24H, d, -CH-(CH3)2, J = 6.4 Hz),
3.11 (1H, s, ≡C-H), 3.24 (4H, sep, -CH-(CH3)2, J = 6.4
Hz), 7.55 (6H, m, m-PhH of C5,10,15), 7.68 (2H, d, m-PhH
of C20, J = 6.7 Hz), 7.94 (2H, d, o-PhH of C20, J = 6.7 Hz),
8.66 (1H, d, β-pyrrolic H at C17, J = 5 Hz), 8.73–8.78
(4H, m, β-pyrrolic H at C7,8,12,13), 8.88 (1H, d, β-pyrrolic
H at C18, J = 5 Hz), 8.98 (1H, s, β-pyrrolic H on C3). MS
(ESI): m/z 862.30 (calcd. for [M]+).
Porphyrin 8. mp > 350 °C. Anal. calcd. for
C58H52CuN4: C, 80.20; H, 6.03; N, 6.45. Found: C, 80.01;
H, 6.03; N, 6.43. IR (KBr): νmax, cm-1 3318 (≡C-H), 2956,
2924, 2158 (C≡C), 1559, 1459, 1350, 1261, 1055, 1004,
812, 712. Raman (solid): νmax, cm-1 2158 (C≡C). UV-vis
(CHCl3): λmax, nm (rel. int.) 435 (7.69), 550 (1.0). MS
(ESI): m/z 867.30 (calcd. for [M]+).
Porphyrin 3. mp > 350 °C. Anal. calcd. for
C58H53BrN4Ni: C, 73.74; H, 5.65; N, 5.93. Found: C,
73.78; H, 5.62; N, 5.94. IR (KBr): νmax, cm-1 2955, 2920,
2850, 1654, 1609, 1458, 1347, 1292, 1006, 812, 717.
Porphyrin 9. mp > 350 °C. Anal. calcd. for
C116H102N8Ni2: C, 80.74; H, 5.96; N, 6.49. Found: C,
Copyright © 2010 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2010; 14: 302–304

HALO-WITTIG- AND ZIRCONIUM-PROMOTED SYNTHESIS
303
80.9; H, 5.97; N, 6.51. IR (KBr): νmax, cm-1 2958, 2922,
1550, 1510, 1455, 1340, 1051, 1001, 937, 813, 797, 719.
Raman (solid): νmax, cm-1 2180 (C≡C). UV-vis (CHCl3):
2. a) Saleem M, Sayyad MH, Karimov KS, Ahmad Z,
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eem M, Sayyad MH, Karimov KS, Yaseen M and
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and Ali M. J. Phys. D: Appl. Phys. 2009; 42: doi:
10.1088/0022–3727/42/10/105112.
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2003; 2986–2987. b) Saleem M, Sayyad MH, Kari-
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44: 1192–1197.
λ
max, nm (rel. int.) 433 (7.36), 545 (1.69), 591 (1.0).
1H NMR (400 MHz; CDCl3; Me4Si): δH, ppm 1.50 (36H,
m, (CH3)2-CH-), 1.57 (12H, d, (CH3)2-CH-, J = 6.8 Hz),
3.24–3.34 (8H, m, -CH-(CH3)2), 7.73 (12H, m, m-PhH
at C5,5′,10,10′.15,15′), 7.78 (4H, d, m-PhH at C20,20′, J = 7.0
Hz), 7.94 (12H, m, o-PhH, at C5,5′,10,10′,15,15′), 8.0 (4H, d,
o-PhH at C20,20′, J = 7.0 Hz), 8.72 (2H, d, β-pyrrolic H
on C17,17′ or C18,18′, J = 5 Hz), 8.68 (8H, m, β-H), 8.8 (2H,
d, β-pyrrolic H on C17,17′ or C18,18′, J = 5 Hz), 8.99 (2H, s,
β-pyrrolic H on C3,3′). MS (ESI): m/z 1724.2 (calcd. for
[M + 2H]+).
Porphyrin 10. mp > 350 °C. Anal. calcd. for
C116H102Cu2N8: C, 80.29; H, 5.92; N, 6.46. Found: C,
80.08; H, 5.93; N, 6.46. IR (KBr): νmax, cm-1 2960, 2925,
1552, 1538, 1510, 1455, 1340, 1056, 1004, 800, 717.
Raman (solid): νmax, cm-1 2172 (C≡C). UV-vis (CHCl3):
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Electrochem. 2003; 7: 254–258.
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Lawton KB, Wilson GS, Dolney N, Ispasoiu R, III
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λ
max, nm (rel. int.) 437 (7.13), 553 (1.88), 589 (1.0). MS
(ESI) m/z 1733.24 (calcd. for [M + H]+).
Porphyrin 11. mp > 350 °C. Anal. calcd. for
C116H106N8: C, 86.42; H, 6.63; N, 6.95. Found: C, 86.26;
H, 6.64; N, 6.95. IR (KBr): νmax, cm-1 3320 (N-H), 2952,
1560, 1478, 1350, 1190, 1101, 1053, 969, 800, 731.
Raman (solid): νmax, cm-1 2175. UV-vis (CHCl3): λmax,nm
(rel. int.) 425 (5.50), 520 (3.37), 551 (1.95), 600 (1.0),
628 (1.25). 1H NMR (400 MHz; CDCl3; Me4Si): δH, ppm
-2.62 (4H, bs, -NH), 1.56 (36H, m, (CH3)2-CH-), 1.63
(12H, d, (CH3)2-CH-, J = 6.8 Hz), 3.31–3.4 (8H, m, -CH-
(CH3)2), 8.13 (12H, m, m-PhH of C5,5′,10,10′.15,15′), 8.21 (4H,
d, m-PhH at C20,20′, J = 6.9 Hz), 8.16 (12H, m, o-PhH at
C5,5′,10,10′,15,15′), 8.28 (4H, d, o-PhH at C20,20′, J = 7.6 Hz),
8.86 (2H, d, β-pyrrolic H on C17,17′ or C18,18′, J = 4.8 Hz),
8.81 (8H, m, β-H), 8.99 (2H, d, β-pyrrolic H on C17,17′ or
C
18,18′, J = 4.8 Hz), 9.18 (1H, s, β-pyrrolic H on C3,3′). MS
(ESI) m/z 1614.06 (calcd. for [M + 4H]+).
CONCLUSION
Zirconocene-promoted bromomethylenation of beta
formyl metalloporphyrins is a new route for the synthesis
of bromoethenyl metalloporphyrins.
Acknowledgements
We are thankful to the Higher Education Commission
of Pakistan for the financial support to this research work.
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