Synthesis and spectroscopic properties of meso-substituted quinoxalinoporphyrins

Article abstract of DOI:10.1039/c1nj20248k

A simple and efficient synthetic protocol for the construction of novel meso-substituted quinoxalinoporphyrins has been developed. The reaction of 5-(3,4-diaminophenyl)-10,15,20-triphenylporphyrin with aromatic or aliphatic α-diones afforded the correspon

Full text of DOI:10.1039/c1nj20248k

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PAPER
Synthesis and spectroscopic properties of meso-substituted
quinoxalinoporphyrinsw
Satyasheel Sharma and Mahendra Nath*
Received (in Montpellier, France) 17th March 2011, Accepted 12th May 2011
DOI: 10.1039/c1nj20248k
A simple and efficient synthetic protocol for the construction of novel meso-substituted
quinoxalinoporphyrins has been developed. The reaction of 5-(3,4-diaminophenyl)-10,15,
20-triphenylporphyrin with aromatic or aliphatic a-diones afforded the corresponding new
quinoxalinoporphyrins in 78–92% yields. Further, this methodology was found to be applicable
to obtain b,b0-meso-phenyl-fused quinoxalinodiporphyrins for the first time from porphyrin-
2,3-diones in 65–70% yields. All the prepared products were characterized on the basis of spectral
and analytical data. The preliminary photophysical studies showed a significant intramolecular
energy transfer in the case of newly synthesized quinoxalinoporphyrin dyads.
meso-substituted quinoxalinoporphyrin dyads. As such, this
Introduction
study leads the way for various p-conjugated porphyrin constructs
to devise novel functional materials for molecular electronics
and photosensitizers for photodynamic therapy applications.
Naturally occurring porphyrin-based pigments such as chloro-
phylls and bacteriochlorophylls are known to capture solar
energy very efficiently, which is ultimately funneled into the
photosynthetic reaction center to initiate photosynthesis in the
plants and bacteria.1 For mimicking the properties of these
macromolecules, many attempts have been made to design
similar macrocyclic donor–acceptor arrays, with the expectation
to develop suitable synthetic systems that can efficiently convert
solar energy into chemical energy.2 To this end, a large number
of porphyrin chromophores were employed in the past due to
their efficient light-harvesting and electron transfer properties.3
Among these, b,b0-fused quinoxalinoporphyrins, primarily
synthesized as a model for the photosynthetic reaction centres
by Crossley and co-workers,4 have been extensively studied in
various contexts such as for molecular electronics,5 molecular
wires6 and dye sensitized solar cells7 because they exhibit the
broadening and red shift in their Soret and Q bands due to the
extension of porphyrin p-systems.
These results prompted us to develop an alternate approach
towards the construction of p-conjugated porphyrin-quinoxaline
systems which have never been synthesized and evaluated for
their optical properties. We report herein an efficient synthesis,
spectroscopic characterization and photophysical properties
of a novel series of meso-substituted quinoxalinoporphyrins
and b,b0-meso-phenyl-fused quinoxalinodiporphyrin analogues.
On photophysical investigation, these molecules revealed the
occurrence of an efficient intramolecular energy transfer in
Results and discussion
Synthesis and characterization
5-(3,4-Diaminophenyl)-10,15,20-triphenylporphyrin (1) was
synthesized8 from meso-tetraphenylporphyrin according to a
series of reactions and used as a starting material for the
synthesis of target porphyrin analogues. Zinc(II) 5-(3,4-diamino-
phenyl)-10,15,20-triphenylporphyrin (Zn-1) was prepared for
photophysical studies via the insertion of zinc in the cavity of
free-base porphyrin 1 using zinc acetate in a chloroform–methanol
mixture at room temperature.
The synthesis of novel meso-substituted quinoxalino-
porphyrins (3a–g) began with a simple condensation cyclization
reaction between 5-(3,4-diaminophenyl)-10,15,20-triphenyl-
porphyrin (1) and various aromatic and aliphatic a-diones
such as benzil, 4,40-dimethoxybenzil, 4,40-dibromobenzil,
2,20-furil, 2,20-pyridil, 1,4-dibromobutan-2,3-dione and butan-
2,3-dione in 1,2-dichlorobenzene at 100 1C for 8 hours
(Scheme 1). The desired products were obtained in 80–92%
yields by column chromatography over silica.
To incorporate the conjugated chromophores at the porphyrin
periphery, the reactions were carried out successfully with p-electron
rich a-diones such as acenaphthenequinone, aceanthrene-
quinone, 9,10-phenanthrenequinone and 5-(3,4-diaminophenyl)-
10,15,20-triphenylporphyrin (1) under standardized reaction
conditions to afford porphyrin dyads (4, 5 and 6) in 78–85%
yields. These free-base porphyrin dyads were converted to the
corresponding zinc(II) porphyrins (Zn-4, Zn-5 and Zn-6), respec-
tively, in quantitative yields after the treatment with
Department of Chemistry, University of Delhi, Delhi 110 007,
India. E-mail: mnath@chemistry.du.ac.in; Fax: +91-11-27666605;
Tel: +91-11-27667794 Extn.186
w Electronic supplementary information (ESI) available. See DOI:
10.1039/c1nj20248k
c
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was carried out in 1,2-dichlorobenzene at 100 1C to afford
bisporphyrins 10a and 10b in 65 and 70% yields, respectively.
The metallo-diporphyrins 10c (M, M1 = Zn) and 10d
(M, M1 = Cu) were prepared by inserting the Zn or Cu ions
to the cavity of free-base diporphyrin (10b) using corresponding
metal(II) acetates in a chloroform–methanol mixture at 25 1C.
The newly synthesized porphyrins were characterized by
1H NMR, IR, electronic absorption and fluorescence spectro-
scopies in addition to mass and elemental analysis. The free-base
meso-substituted quinoxalinoporphyrins (3a–g, 4, 5 and 6)
showed a characteristic singlet around d ꢁ2.7 ppm for two
pyrrolic N–H protons of the porphyrin ring. The b-pyrrolic
protons appeared as a multiplet between d 8.7 to 8.9 ppm. A
characteristic singlet or doublet appeared at the downfield region
between d 8.8–9.0 ppm for C-2 proton of the meso-phenyl ring
fused with the 1,4-diazine moiety, whereas the protons at C-5
and C-6 of the meso-phenyl group appeared as a doublet and
double–doublet at d 8.4 and d 8.6 ppm, respectively, in the case
of porphyrins 3a–g. For the porphyrin-dyads (4, 5 and 6), the
meso-phenyl protons at C-2, C-5 and C-6 were slightly shifted to
downfield as compared to the simple quinoxalinoporphyrins
3a–g and showed signals at d 9.3 ppm for the C-2 proton, d
8.6 ppm for C-5 and d 8.8 ppm C-6 protons.
In proton NMR of the mixture of regioisomers 7 and 8,
some of the characteristic peaks can be assigned (Fig. 1). The
proton on the C-80 of the naphthalene ring in isomer 7 which is
in the concave side with respect to the C-2 of the meso-phenyl
ring appeared downfield as a doublet at d 9.52 ppm with
J = 7.32 Hz whereas the C-80 proton of the naphthalene ring
in isomer 8 which is on the convex side of the C-2 of the meso-
phenyl ring appeared as a multiplet between d 9.32–9.35 ppm.
Similarly, the C-2 proton of the meso-phenyl ring appeared
downfield in isomer 7 as a doublet at d 9.17 ppm with
J = 1.46 Hz, whereas in regioisomer 8 the C-2 proton
appeared slightly upfield as a doublet at d 9.07 ppm with
J = 1.46 Hz. One double doublet appeared at d 8.71 ppm
(J1, J2 = 8.43, 1.45 Hz) for 2 protons, which corresponds
to the C-6 proton of each regioisomer 7 and 8. The C-5 proton
of isomer 8 at d 8.62 ppm (J = 8.79 Hz) was slightly shifted to
the downfield region as compared to the C-5 proton of isomer
7 at d 8.54 ppm (J = 8.79 Hz). This assignment was found to
be consistent with the proton NMR data reported in the
literature for the regioisomeric mixtures in the case of other
quinoxalines.9 The 16 b-pyrrolic protons comprising of both
regioisomers appeared as a multiplet between d 8.87–8.82 ppm.
The remaining meso-phenyl protons and the protons of the
naphthalene ring of both the regioisomers (7 and 8) appeared
as multiplets in the region d 8.17 to 7.68 ppm. The pyrrolic
N–H protons of both the regioisomers appeared as a singlet
for 4 protons at d ꢁ2.22 ppm.
Scheme 1 Synthesis of 5-(2,3-disubstituted quinoxalin-6-yl)-10,15,20-
triphenylporphyrins.
Zn(OAc)2ꢀ2H2O in a dichloromethane–methanol mixture for
30 minutes at room temperature (Scheme 2). In contrast, the
reaction of porphyrin 1 with 1,2-naphthaquinone under same
reaction conditions produced a mixture of two regioisomers 7
and 8 similarly as reported in the case of simple quinoxalines,
obtained from substituted ortho-phenylenediamine derivatives.9
The 1H NMR spectrum of the mixture showed the presence of
two regioisomers, 7 and 8, in 1 : 1 ratio (Fig. 1). The attempts
have been unsuccessful to separate these regioisomers in pure
form by column chromatography due to their close Rf and
always a mixture of porphyrins 7 and 8 was obtained. Similarly,
there was a possibility to obtain another set of regioisomers from
the reaction of porphyrin 1 with aceanthrenequinone, but
surprisingly a single product 5 has been isolated in 78% yield.
This could be attributed due to the difference in the reactivity
of two carbonyl groups, present in aceanthrenequinone as
reported in the literature.10
For the b,b0-meso-phenyl-fused quinoxalinoporphyrin
systems (10a–c), the b-pyrrolic protons appeared as doublets
or multiplets between d 8.8–9.0 ppm. Bis-porphyrins (10a–c)
showed the proton of the C-2 of the meso-phenyl ring fused to
the 1,4-diazinoporphyrin moiety as a doublet at d 8.7 ppm.
Porphyrin 10b displayed two singlets for the four pyrrolic
N–H protons corresponding to both free-base porphyrin rings
at d ꢁ2.47 and d ꢁ2.66 ppm, whereas bis-porphyrin 10a
exhibited only one singlet at d ꢁ2.66 ppm attributing to only
In addition, this synthetic procedure was successfully applied
to obtain b,b0-meso-phenyl-fused quinoxalinodiporphyrins as
shown in Scheme 3. For synthesizing these molecules, firstly
porphyrin-a-diones (9a and 9b) were synthesized by oxidizing
the 2-amino-5,10,15,20-tetraphenylporphyrin with the Dess–
Martin periodinane reagent.11 The condensation cyclization
reaction of porphyrin 1 with porphyrin-a-dione 9a or 9b
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Scheme 2 Synthesis of meso-substituted quinoxalinoporphyrin dyads.
two pyrrolic N–H protons of one free-base porphyrin present
in the dyad.
and porphyrin–phenanthrene dyads (6 and Zn-6) in CHCl3
are shown in Fig. 2. Fig. 2a shows the electronic absorption
spectra of the free-base porphyrin dyads 4, 5 and 6 and
precursor porphyrin (1). These molecules absorb the whole
visible spectral region and display characteristic Soret bands at
422 nm, which are slightly broader as compared to porphyrin 1.
Whereas in Fig. 2b, the electronic absorption spectra of
zinc porphyrin dyads (Zn-4, Zn-5 and Zn-6) showed a Soret
band at 427 nm and two Q bands at 556 and 598 nm similar
to the spectrum of zinc(II) 5-(3,4-diaminophenyl)-10,15,20-
triphenylporphyrin (Zn-1). In addition to the porphyrinic
Soret and Q bands, other absorption bands at around 330,
280 and 270 nm originate due to the presence of acenaphthene,
aceanthrene and phenanthrene moieties in the porphyrin
dyads (4; Zn-4), (5; Zn-5) and (6; Zn-6) respectively. Thus,
Photophysical properties
The UV-Vis absorption spectra for meso-substituted quinoxalino-
porphyrins (3a–g) in chloroform exhibited a typical intense
Soret band at B422 nm and four weak Q bands at B518, 553,
592 and 649 nm. The fluorescence band of meso-substituted
quinoxalinoporphyrins (3a–g) appeared at 655 and 718 nm
similar to the 5-(3,4-diaminophenyl)-10,15,20-triphenyl-
porphyrin (1). The UV and emission data of these porphyrin
analogues are shown in Experimental section. The electronic
absorption spectra of the porphyrin–acenaphthene dyads
(4 and Zn-4), porphyrin–aceanthrene dyads (5 and Zn-5)
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Fig. 1 1H NMR spectrum (400 MHz) of the mixture of porphyrin regioisomers 7 and 8.
Scheme 3 Synthesis of b,b0-meso-phenyl-fused quinoxalinodiporphyrins.
the electronic absorption spectra of the porphyrin dyads in
Fig. 2 are equivalent to the combination of the individual
chromophore attached and the porphyrin ring. These results
imply that there is no significant interaction between the
attached chromophore and the porphyrin nucleus in the
ground state.
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Fig. 2 (a) UV-Vis absorption spectra of free-base meso-substituted
quinoxalinoporphyrins (4, 5 and 6) and porphyrin (1) in CHCl3. (b)
UV-Vis absorption spectra of zinc(II) meso-substituted quinoxalino-
porphyrins (Zn-4, Zn-5 and Zn-6) and porphyrin (Zn-1) in CHCl3.
The insets in both figures show the Q bands.
Fig. 3 (a) Emission spectra of free-base meso-substituted quinoxalino-
porphyrins (4, 5 and 6) and porphyrin 1 in CHCl3; excited at 420 nm.
(b) Emission spectra of zinc(II) meso-substituted quinoxalino-
porphyrins (Zn-4, Zn-5 and Zn-6) and porphyrin (Zn-1) in CHCl3;
excited at 420 nm.
The fluorescence spectra of porphyrin 1 and the porphyrin–
acenaphthene dyad (4), porphyrin–aceanthrene dyad (5) and
porphyrin–phenanthrene dyad (6) are shown in Fig. 3. Fig. 3a
shows an intense emission band and a weak shoulder at B655
and 720 nm, respectively, for the free-base porphyrin dyads
(4–6), which are slightly intense when compared to precursor
porphyrin 1. Similarly in Fig. 3b, the zinc(II) porphyrin dyads
(Zn-4, Zn-5 and Zn-6) show two fluorescence bands at around
611 and 655 nm, which are slightly intense and red shifted by
around 4–9 nm when compared to zinc(II) 5-(3,4-diaminophenyl)-
10,15,20-triphenylporphyrin (Zn-1; lem 607 and 655 nm).
Further, energy transfer behaviour of the porphyrin dyads 5
and 6 has been studied by the absorption and fluorescence
spectra as shown in Fig. 4. The fluorescence spectrum in
Fig. 4a shows the emission spectra of aceanthrenequinone,
porphyrin 1 and the porphyrin–aceanthrene dyad (5) in CHCl3
at the excitation wavelength of 330 nm. It has been observed
that the fluorescence of the aceanthrenequinone is almost
quenched and the intensity of the emission band of the
porphyrin dyad 5 is increased to a large extent as compared
to the emission band of the starting porphyrin compound 1 at
the same excitation wavelength (330 nm). Also, it can be seen
from Fig. 4a, the significant overlapping of the emission band
of aceanthrenequinone and the Soret band of the porphyrin
dyad 5, which fulfills the first condition of energy transfer.12
Thus, it can be concluded that there is an efficient intramolecular
energy transfer from the aceanthrene unit to the porphyrin
unit in the porphyrin–aceanthrene dyad (5). Similarly, Fig. 4b
shows the fluorescence spectrum of phenanthrenequinone,
porphyrin–phenanthrene dyad (6) and porphyrin 1 in CHCl3
at an excitation wavelength of 290 nm and an overlapping
absorption spectrum of porphyrin 6 with the phenanthrene-
quinone emission band. Hence, there is also an efficient energy
transfer from the phenanthrene moiety to the porphyrin
macrocycle.
The electronic absorption spectra of b,b0-meso-phenyl-fused
quinoxalinodiporphyrins (10a–d) are shown in Fig. 5. All the
bis-porphyrins (10a–d) show splitting and broadening of
the Soret bands due to the exciton coupling13 and also exhibit
the superposition of the Q bands of the corresponding free-
base porphyrins and the metalloporphyrins.
The fluorescence spectra of b,b0-meso-phenyl-fused quin-
oxalinodiporphyrins (10a–d) are shown in Fig. 6. The emission
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Fig. 6 Emission spectra of b,b0-meso-phenyl-fused quinoxalino-
diporphyrins (10a–d), porphyrin (1) and Zn-1 in CHCl3; excited at 420 nm.
the free-base porphyrin moiety at 655 and 717 nm having trace
emission from the zinc(II) porphyrin component at 625 nm.
These results indicate the intramolecular energy transfer from
the zinc(II) porphyrin to the free-base porphyrin within the
dyad (10a). The emission spectrum of 10b shows the emission
bands at 656 and 725 nm, which are also quenched in
comparison to the porphyrin 1. Similarly, the fluorescence
spectrum of the dizinc bisporphyrin (10c) exhibits the charac-
teristic emission bands at 632 and 682 nm which were found to
be significantly quenched and red shifted by 25 nm as compared
to the porphyrin (Zn-1). Thus, these results show the occurrence
of efficient intramolecular energy transfer between the two
porphyrin units. However, dicopper diporphyrin (10d) shows
no emission band due to the paramagnetism of the Cu2+ ion.14
Fig. 4 (a) Emission spectra of aceanthrenequinone (acean), porphyrin
dyad (5) and porphyrin (1) in CHCl3; excited at 330 nm and absorption
spectrum of 5; (b) emission spectra of phenanthrenequinone (phen),
porphyrin dyad (6) and porphyrin (1) in CHCl3; excited at 290 nm and
absorption spectrum of 6 in CHCl3.
Conclusions
Novel meso-substituted quinoxalinoporphyrins and b,b0-meso-
phenyl-fused quinoxalinodiporphyrins have been synthesized
and characterized successfully. The photophysical studies
of these quinoxalinoporphyrin dyads have shown possible
efficient energy transfer from the aceanthrene or phenanthrene
unit to the porphyrin core. In addition, the efficient intra-
molecular energy transfer between the two porphyrin macro-
cycles has also been observed within the porphyrin dyad.
These findings may prove useful for the development of
various p-conjugated porphyrin dyads which can modulate
the photophysical properties of the porphyrin core and thereby
applicable as functional materials for the molecular electronics
and photosensitizers for photodynamic therapy.
Experimental
All the chemicals and solvents required for the synthesis were
purchased from Sigma-Aldrich and Merck. The progress of
reactions was monitored by thin layer chromatography (TLC)
Fig. 5 UV-Vis absorption spectra of b,b0-meso-phenyl-fused quinoxalino-
diporphyrins (10a–d) in CHCl3.
1
on silica gel 60 F254 (pre-coated aluminium sheets). H NMR
spectra were obtained in CDCl3, using a Bruker 300 MHz
NMR spectrometer or Jeol ECX 400P (400 MHz) NMR
spectrometer. Chemical shifts are expressed in parts per
spectrum of zinc(II)-free-base diporphyrin (10a) clearly
demonstrated that the fluorescence occurs exclusively from
c
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million (ppm) relative to tetramethylsilane (TMS; 0 ppm) as an
internal standard. Coupling constants J are reported in Hertz
(Hz). Elemental analyses for all the compounds were per-
formed on an Elementar Analysensysteme GmbH VarioEL
elemental analyzer. Infrared spectra were recorded on a Perkin
Elmer IR spectrometer and absorption maxima (umax) are
given in cmꢁ1. Mass spectra were recorded on an ESI–MS
(micromass LCT, waters) mass spectrometer. UV-Vis and
fluorescence spectra were recorded on an Analytik Jena’s
Specord 250 UV-Vis spectrophotometer and Varian Cary
Eclipse fluorescence spectrophotometer, respectively, by using
CHCl3 as a solvent. Melting points of all the newly synthesized
quinoxalinoporphyrins were determined in open capillaries
and were found to be over 300 1C.
5-[2,3-Bis-(4-bromophenyl)quinoxalin-6-yl]-10,15,20-triphenyl-
porphyrin (3c). Yield: 90%; found: C, 71.56; H, 3.84; N,
8.56%. C58H36Br2N6 requires C, 71.32; H, 3.71; N, 8.60%;
l
max(CHCl3)/nm 423 (e/dm3 molꢁ1 cmꢁ1 5 81 900), 518
(34 200), 553 (18 400), 592 (9600) and 649 (5700); lEm
(CHCl3)/nm 655, 719 (lEx 420 nm); nmax(Film)/cmꢁ1 3316,
1596, 1560, 1472, 1441, 1400, 1347, 1219, 1187, 1073, 1002,
969, 801, 753, 701; dH (400 MHz, CDCl3) 9.02 (1H, d, J = 2.01 Hz,
meso-ArH), 8.87–8.84 (8H, m, b-pyrrolic H), 8.68 (1H, dd,
J1 = 8.73, J2 = 2.01 Hz, meso-ArH), 8.48 (1H, d, J = 8.06 Hz,
meso-ArH), 8.22 (6H, d, J = 6.72 Hz, meso-ArH), 7.76–7.75
(9H, m, meso-ArH), 7.55–7.43 (8H, m, ArH), ꢁ2.72 (2H, s,
internal NH); m/z (ESI) 975.4 ([M+H]+ requires 975.1).
5-(2,3-Difuran-2-yl-quinoxalin-6-yl)-10,15,20-triphenylporphyrin
(3d). Yield: 80%; found: C, 79.94; H, 4.24; N, 10.21%.
C56H34N6O2 + 0.5H2O requires C, 80.28; H, 4.37; N, 10.40%;
Syntheses
General procedure for the synthesis of meso-substituted
quinoxalinoporphyrins (3a–g, 4–6, 7 and 8). To a solution of
5-(3,4-diaminophenyl)-10,15,20-triphenylporphyrin (30 mg,
0.046 mmol) in 1,2-dichlorobenzene (10 mL), the corresponding
a-dione (0.065 mmol) was added. The reaction mixture was
heated under stirring at 100 1C for 8 h. After the completion
of the reaction, the mixture was cooled to room temperature
and loaded on a silica gel column. 1,2-Dichlorobenzene was
removed by eluting the column with hexane. The desired
product was obtained by using chloroform as eluent.
l
max(CHCl3)/nm 422 (e/dm3 molꢁ1 cmꢁ1 4 08 600), 518 (31 400),
553 (17 300), 592 (8400) and 651 (4000); lEm (CHCl3)/nm 655, 718
(lEx 420 nm); nmax(Film)/cmꢁ1 3318, 1597, 1560, 1473, 1440,
1354, 1214, 1187, 1073, 1001, 969, 801, 752, 702; dH (400 MHz,
CDCl3) 8.99 (1H, d, J = 2.01 Hz, meso-ArH), 8.91–8.85 (8H, m,
b-pyrrolic H), 8.63 (1H, dd, J1 = 8.4, J2 = 2.01 Hz, meso-ArH),
8.46 (1H, d, J = 8.73 Hz, meso-ArH), 8.22–8.21 (6H, m,
meso-ArH), 7.79–7.77 (11H, m, meso-ArH and ArH), 6.81 (2H,
dd, J1 = 12.76, J2 = 3.36 Hz, ArH), 6.66–6.59 (2H, m, ArH),
ꢁ2.71 (2H, s, internal NH); m/z 799.5 ([M+H]+ requires 799.2).
5-(2,3-Diphenylquinoxalin-6-yl)-10,15,20-triphenylporphyrin
(3a). Yield: 90%; found: C, 83.49; H, 4.76; N, 9.92%.
C58H38N6 + H2O requires C, 83.23; H, 4.82; N, 10.04%;
5-(2,3-Dipyridin-2-yl-quinoxalin-6-yl)-10,15,20-triphenyl-
porphyrin (3e). Yield: 82%; found: C, 81.77; H, 4.65; N,
13.41%. C56H36N8 requires C, 81.93; H, 4.42; N, 13.65%;
l
max(CHCl3)/nm 422 (e/dm3 molꢁ1 cmꢁ1 4 74 900), 518
l
max(CHCl3)/nm 422 (e/dm3 molꢁ1 cmꢁ1 4 83 700), 518
(30 200), 553 (18 500), 592 (8400) and 650 (5000); lEm
(CHCl3)/nm 655, 719 (lEx 420 nm); nmax(Film)/cmꢁ1 3318,
1597, 1560, 1473, 1442, 1399, 1343, 1220, 1058, 1001, 969, 937,
800, 754, 698; dH (300 MHz, CDCl3) 9.04 (1H, s, meso-ArH),
8.88–8.86 (8H, m, b-pyrrolic H), 8.66 (1H, d, J = 8.1 Hz,
meso-ArH), 8.51 (1H, d, J = 8.1 Hz, meso-ArH), 8.22 (6H, d,
J = 6.0 Hz, meso-ArH), 7.77–7.75 (9H, m, meso-ArH),
7.71–7.76 (4H, m, ArH), 7.44 (3H, s, ArH), 7.37 (3H, s,
ArH), ꢁ2.71 (2H, s, internal NH); m/z (ESI) 819.2
([M+H]+ requires 819.3).
(30 100), 553 (18 000), 592 (8000) and 649 (3600); lEm
(CHCl3)/nm 654, 718 (lEx 420 nm); nmax(Film)/cmꢁ1 3316,
1595, 1357, 1220, 968, 937, 799, 756, 723, 701; dH (400 MHz,
CDCl3) 9.08 (1H, d, J = 2.0 Hz, meso-ArH), 8.88–8.63 (8H, d,
b-pyrrolic H), 8.71 (1H, dd, J1 = 6.72, J2 = 2.01 Hz, meso-
ArH), 8.56 (1H, d, J = 8.73 Hz, meso-ArH), 8.48–8.43 (2H, m,
ArH), 8.23–8.21 (6H, m, meso-ArH), 8.14 (1H, d, J = 7.39 Hz,
meso-ArH), 8.07 (1H, d, J = 8.06 Hz, meso-ArH), 7.91 (1H, t,
J = 7.72 Hz, meso-ArH), 7.83 (1H, t, J = 7.72 Hz, meso-
ArH), 7.78–7.73 (9H, m, meso-ArH), 7.33–7.26 (2H, m, ArH),
ꢁ2.71 (2H, s, internal NH); m/z (ESI) 821.3 ([M+H]+
requires 821.3).
5-[2,3-Bis-(4-methoxyphenyl)quinoxalin-6-yl]-10,15,20-triphenyl-
porphyrin (3b). Yield: 85%; found: C, 80.65; H, 5.08; N,
9.14%. C60H42N6O2 + H2O requires C, 80.34; H, 4.94; N,
9.37%; lmax(CHCl3)/nm 420 (e/dm3 molꢁ1 cmꢁ1 4 63 600),
518 (26 800), 553 (11 500), 592 (7800) and 648 (3700); lEm
(CHCl3)/nm 653, 718 (lEx 420 nm); nmax(Film)/cmꢁ1 3318,
1597, 1560, 1473, 1442, 1399, 1343, 1220, 1058, 1001, 969, 937,
800, 754, 698; dH (400 MHz, CDCl3) 8.98 (1H, d, J = 2.2 Hz,
meso-ArH), 8.90–8.85 (8H, m, b-pyrrolic H), 8.59 (1H, dd,
J1 = 8.42, J2 = 2.2 Hz, meso-ArH), 8.45 (1H, d, J = 8.05 Hz,
meso-ArH), 8.22 (6H, d, J = 7.32 Hz, meso-ArH), 7.76–7.73
(9H, m, meso-ArH), 7.67 (2H, d, J = 8.79 Hz, ArH), 7.61
(2H, d, J = 8.79 Hz, ArH), 6.97 (2H, d, J = 8.79 Hz, ArH),
6.89 (2H, d, J = 8.79 Hz, ArH), 3.89 (3H, s, OCH3), 3.82
(3H, s, OCH3), ꢁ2.71 (2H, s, internal NH); m/z (ESI) 879.0
([M+H]+ requires 879.3).
5-(2,3-Dibromomethylquinoxalin-6-yl)-10,15,20-triphenyl-
porphyrin (3f). Yield: 92%; found: C, 66.03; H, 4.37; N,
9.74%. C48H32Br2N6 + 1.2H2O requires C, 65.94; H, 3.97;
N, 9.61%; lmax(CHCl3)/nm 422 (e/dm3 molꢁ1 cmꢁ1 4 41 300),
518 (30 300), 553 (16 400), 592 (8700) and 649 (9800); lEm
(CHCl3)/nm 654, 720 (lEx 420 nm); nmax(Film)/cmꢁ1 3318,
1597, 1560, 1473, 1440, 1354, 1214, 1187, 1073, 1001, 969, 801,
752, 702; dH (300 MHz, CDCl3) 8.91 (1H, s, meso-ArH),
8.86–8.80 (8H, m, b-Pyrrolic H), 8.69 (1H, d, J = 8.7 Hz,
meso-ArH), 8.40 (1H, d, J = 8.7 Hz, meso-ArH), 8.23–8.21
(6H, m, meso-ArH), 7.77 (9H, s, meso-ArH), 5.11 (2H, s,
CH2), 5.05 (2H, s, CH2), ꢁ2.73 (2H, s, internal NH); m/z
(ESI) 851.0 ([M+H]+ requires 851.1).
c
1636 New J. Chem., 2011, 35, 1630–1639
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2011

View Article Online
5-(2,3-Dimethylquinoxalin-6-yl)-10,15,20-triphenylporphyrin
(3g). Yield: 90%; found: C, 82.65; H, 5.11; N, 11.81%.
C48H34N6 requires C, 82.97; H, 4.93; N, 12.10%;
5-(Benzo[a]phenazin-10-yl)-10,15,20-triphenylporphyrin (7)
and 5-(benzo[a]phenazin-9-yl)-10,15,20-triphenylporphyrin (8).
Yield: 80%; found: C, 84.28; H, 4.55; N, 10.67%. C54H34N6
requires C, 84.57; H, 4.47; N, 10.96%; nmax(Film)/cmꢁ1 3316,
1597, 1473, 1440, 1354, 1261, 1095, 1021, 799, 754, 701; dH
(400 MHz, CDCl3) 9.52 (1H, d, J = 7.32, ArH (isomer 7)),
9.35 (1H, m, ArH (isomer 8)), 9.17 (1H, d, J = 1.46 Hz, meso-
ArH (isomer 7)), 9.07 (1H, d, J = 1.46 Hz, meso-ArH (isomer
8)), 8.82–8.87 (16H, m, b-pyrrolic H (isomers 7 and 8)), 8.71
(2H, dd, J1 = 8.43, J2 = 1.45 Hz, meso-ArH (isomers 7 and
8)), 8.62 (1H, d, J = 8.79, meso-ArH (isomer 8)), 8.54 (1H, d,
J = 8.79, meso-ArH (isomer 7)), 8.17–8.15 (12H, m, meso-
ArH (isomers 7 and 8)), 8.04–7.96 (4H, m, ArH (isomers 7 and
8)), 7.90–7.77 (4H, m, ArH (isomers 7 and 8)), 7.70–7–76
(20H, m, meso-ArH and ArH (isomers 7 and 8)), ꢁ2.77 (4H, s,
internal NH (isomers 7 and 8)); m/z (ESI) 767.1 ([M+H]+
requires 767.2).
l
max(CHCl3)/nm 421 (e/dm3 molꢁ1 cmꢁ1 5 30 400), 518
(25 900), 553 (12 800), 592 (7100) and 650 (4600); lEm
(CHCl3)/nm 653, 717 (lEx 420 nm); nmax(Film)/cmꢁ1 3319,
1597, 1560, 1473, 1441, 1400, 1347, 1219, 1157, 1072, 969, 801,
753, 701; dH (400 MHz, CDCl3) 8.85–8.82 (9H, m, b-pyrrolic
H and meso-ArH), 8.55 (1H, dd, J1 = 8.73, J2 = 2.01 Hz,
meso-ArH), 8.32 (1H, d, J = 8.73, meso-ArH), 8.22 (6H, d,
J = 7.4 Hz, meso-ArH), 7.76–7.73 (9H, m, meso-ArH), 2.92
(3H, s, CH3), 2.87 (3H, s, CH3), ꢁ2.73 (2H, s, internal NH); m/
z (ESI) 695.1 ([M+H]+ requires 695.2).
5-(Acenaphtho[1,2-b]quinoxalin-9-yl)-10,15,20-triphenyl-
porphyrin (4). Yield: 80%; found: C, 84.87; H, 4.23; N,
10.72%. C56H34N6 requires C, 85.04; H, 4.33; N, 10.63%;
l
max(CHCl3)/nm 423 (e/dm3 molꢁ1 cmꢁ1 4 14 600), 518
General procedure for the synthesis of zinc(II) meso-substituted
(30 500), 553 (18 200), 592 (8700) and 648 (3500); lEm
(CHCl3)/nm 654, 719 (lEx 420 nm); nmax(Film)/cmꢁ1 3316,
1596, 1439, 1350, 1301, 1218, 1182, 1101, 963, 825, 799, 753,
726; dH (300 MHz, CDCl3) 9.29 (1H, s, meso-ArH), 8.86–8.84
(8H, m, b-pyrrolic H), 8.66–8.52 (2H, m, meso-ArH),
8.36–8.20 (6H, m, meso-ArH), 8.14 (1H, d, J = 8.4 Hz,
ArH), 8.00 (1H, t, J = 6.0 Hz, ArH), 7.77–7.74 (10H, m,
meso-ArH and ArH), 7.65–7.57 (2H, m, ArH), 7.38 (1H, t,
J = 7.2 Hz, ArH), ꢁ3.09 (2H, s, internal NH); m/z (ESI) 791.3
([M+H]+ requires 791.2).
quinoxalinoporphyrins (Zn-4, Zn-5 and Zn-6)
To a solution of meso-substituted quinoxalinoporphyrins
(0.025 mmol) in dichloromethane (10 mL), a solution of
Zn(OAc)2ꢀ2H2O (0.05 mmol) in methanol (0.5 mL) was added.
The reaction mixture was stirred at room temperature for
20–30 min. After completion of the reaction, the reaction
mixture was washed thoroughly with water. The organic layer
was dried over anhydrous sodium sulfate and evaporated to
dryness. The crude product was purified by column chromato-
graphy over silica gel by eluting with chloroform.
5-(Aceanthryleno[1,2-b]quinoxalin-12-yl)-10,15,20-triphenyl-
porphyrin (5). Yield: 78%; found: C, 83.64; H, 4.23; N, 9.69%.
C60H36N6 + H2O requires C, 83.89; H, 4.46; N, 9.78%;
Zinc(II) 5-(acenaphtho[1,2-b]quinoxalin-9-yl)-10,15,20-triphenyl-
porphyrin (Zn-4). Yield: 90%; found: C, 76.94; H, 4.27; N,
9.58%. C56H32N6Zn + H2O requires C, 77.10; H, 3.93; N,
9.63%; lmax(CHCl3)/nm 427 (e/dm3 molꢁ1 cmꢁ1 3 28 200), 555
(26 600), and 598 (9600); lEm (CHCl3)/nm 610, 652 (lEx 420 nm);
l
max(CHCl3)/nm 423 (e/dm3 molꢁ1 cmꢁ1 3 43 800), 518
(30 700), 553 (19 100), 592 (12 700) and 650 (7200); lEm
(CHCl3)/nm 655, 720 (lEx 420 nm); nmax(Film)/cmꢁ1 3317,
1597, 1435, 1350, 1224, 968, 936, 825, 799, 753, 700; dH
(400 MHz, CDCl3) 9.83 (1H, d, J = 8.05 Hz, ArH), 9.18
(1H, s, meso-ArH), 8.95 (2H, d, J = 5.13 Hz, b-pyrrolic H),
8.78–8.85 (6H, m, b-pyrrolic H), 8.69 (1H, s, ArH), 8.67 (2H, s,
meso-ArH), 8.40 (1H, d, J = 6.59 Hz, meso-ArH), 8.26–8.15
(7H, m, meso-ArH and ArH), 8.16 (1H, d, J = 8.05 Hz, ArH),
7.93 (1H, t, ArH), 7.76–7.17 (11H, m, meso-ArH and ArH),
ꢁ2.77 (2H, s, internal NH); m/z (ESI) 841.5 ([M+H]+
requires 841.3).
n
max(Film)/cmꢁ1 1597, 1526, 1483, 1441, 1340, 1204, 1178,
995, 797, 754, 700; dH (400 MHz, CDCl3) 9.72 (1H, s, meso-
ArH), 8.96–8.93 (4H, m, b-pyrrolic H), 8.79 (4H, s, b-pyrrolic H),
8.55–8.52 (3H, m, meso-ArH), 8.43–8.41 (2H, m, ArH),
8.24–8.13 (4H, m, meso-ArH), 7.88–7.64 (10H, m, meso-
ArH), 7.55–7.46 (4H, m, ArH); m/z (ESI) 853.0 ([M+H]+
requires 853.2).
Zinc(II) 5-(aceanthryleno[1,2-b]quinoxalin-12-yl)-10,15,20-
triphenylporphyrin (Zn-5). Yield: 90%; found: C, 78.44; H,
4.13; N, 8.94%. C60H34N6Zn + H2O requires C, 78.13; H,
3.93; N, 9.11%; lmax(CHCl3)/nm 427 (e/dm3 molꢁ1 cmꢁ1
3 97 000), 556 (27 800), and 597 (8600); lEm (CHCl3)/nm 611,
652 (lEx 420 nm); nmax(Film)/cmꢁ1 1597, 1525, 1480, 1440,
1341, 1202, 1176, 995, 796, 753, 701; dH (400 MHz, CDCl3)
9.86 (1H, s, ArH), 9.50 (1H, d, J = 8.05 Hz, ArH), 8.91 (2H, d,
J = 5.13 Hz, b-pyrrolic H), 8.60 (2H, d, J = 4.39 Hz,
b-pyrrolic H), 8.80 (2H, d, J = 4.39 Hz, b-pyrrolic H), 8.76
(3H, d, J = 4.39 Hz, b-pyrrolic H and meso-ArH), 8.62 (2H, s,
meso-ArH), 8.52 (3H, d, J = 7.32 Hz, meso-ArH), 8.17 (1H, d,
J = 7.32 Hz, meso-ArH), 8.06 (2H, d, J = 8.05, meso-ArH),
7.91–7.66 (13H, m, meso-ArH and ArH), 7.55–7.51 (2H, m,
ArH); m/z (ESI) 903.5 ([M+H]+ requires 902.2).
5-(Dibenzo[a,c]phenazin-11-yl)-10,15,20-triphenylporphyrin (6).
Yield: 85%; found: C, 84.21; H, 4.76; N, 9.86%. C58H36N6 +
0.5H2O requires 84.34; H, 4.52; N, 10.17%; lmax(CHCl3)/nm
423 (e/dm3 molꢁ1 cmꢁ1 5 46 500), 518 (44 200), 553 (25 800),
592 (12 700) and 650 (7200); lEm (CHCl3)/nm 655, 719
(lEx 420 nm); nmax(Film)/cmꢁ1 3316, 1595, 1357, 1220, 968,
937, 799, 756, 723, 701; dH (300 MHz, CDCl3) 9.44 (1H, br s,
ArH), 9.35 (1H, s, meso-ArH), 9.18 (1H, br s, ArH), 8.86 (8H,
s, b-pyrrolic H), 8.72 (1H, d, J = 8.7 Hz, meso-ArH), 8.63
(1H, d, J = 8.4 Hz, meso-ArH), 8.33–8.19 (6H, m, meso-ArH),
8.05 (1H, br s, ArH), 7.78–7.76 (12H, m, meso-ArH and ArH),
7.45 (2H, br s, ArH), ꢁ2.87 (2H, s, internal NH); m/z (ESI)
817.5 ([M+H]+ requires 817.3).
c
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2011
New J. Chem., 2011, 35, 1630–1639 1637

View Article Online
Zinc(II)
5-(dibenzo[a,c]phenazin-11-yl)-10,15,20-triphenyl-
8.95–8.91 (2H, m, b-pyrrolic H), 8.88–8.86 (6H, m,
b-pyrrolic H), 8.11 (2H, d, J = 4.7 Hz, b-pyrrolic H), 8.74
(2H, s, b-pyrrolic H), 8.69 (1H, d, J = 2.01 Hz, meso-ArH),
8.65 (1H, dd, J1 = 8.40, J2 = 2.01 Hz, meso-ArH), 8.33 (15H,
m, meso-ArH), 7.98 (1H, t, J = 7.39 Hz, meso-ArH), 7.91 (2H,
t, J = 7.39 Hz, meso-ArH), 7.80–7.75 (15H, m, meso-ArH),
7.57 (2H, t, J = 7.39 Hz, meso-ArH), 7.44 (1H, t, J = 7.39 Hz,
meso-ArH), ꢁ2.47 (2H, s, internal NH), ꢁ2.66 (2H, s, internal
NH). m/z (ESI) 1253.3 ([M+H]+ requires 1253.4).
porphyrin (Zn-6). Yield: 92%; found: C, 76.64; H, 4.43; N,
9.17%. C58H34N6Zn + 1.5H2O requires C, 76.77; H, 4.11; N,
9.26%; lmax(CHCl3)/nm 425 (e/dm3 molꢁ1 cmꢁ1 3 70 600), 556
(32 900), and 598 (13 800); lEm (CHCl3)/nm 616, 650 (lEx 420 nm);
n
max(Film)/cmꢁ1 1596, 1524, 1482, 1441, 1343, 1198, 1170,
990, 796, 750, 700; dH (400 MHz, CDCl3) 9.79 (1H, s, meso-
ArH), 9.18 (1H, d, J = 8.05, meso-ArH), 8.94 (2H, d, J =
4.39 Hz, b-pyrrolic H), 8.89 (2H, d, J = 5.13 Hz, b-pyrrolic
H), 8.83 (2H, d, J = 5.13 Hz, b-pyrrolic H), 8.77 (2H, d, J =
4.39 Hz, b-pyrrolic H), 8.70 (1H, dd, J1 = 8.8, J2=2.2 Hz,
meso-ArH), 8.61 (1H, d, J = 8.05 Hz, meso-ArH), 8.50 (2H, d,
J = 8.05 Hz, meso-ArH), 8.46–8.41 (2H, m, meso-ArH), 8.26
(1H, d, J = 6.59 Hz, meso-ArH), 8.07 (2H, d, J = 8.05 Hz,
ArH), 7.87–7.67 (9H, m, meso-ArH), 7.49 (1H, t, ArH), 7.36
(1H, t, ArH), 7.19 (1H, d, J = 7.32 Hz, ArH), 6.63–6.57 (2H, m,
ArH), 6.47–6.44 (1H, m, ArH); m/z (ESI) 879.1 ([M+H]+
requires 879.2).
Zinc(II) 5-(zinc(II) 5,10,15,20-tetraphenylporphyrin[2,3-b]-
quinoxalin-6-yl)-10,15,20-triphenylporphyrin (10c)
To a solution of free-base-free-base diporphyrin 10b (15 mg,
0.011 mmol) in chloroform (10 mL), a solution of Zn(OAc)2ꢀ
2H2O (10 mg, 0.05 mmol) in methanol (0.5 mL) was added.
The reaction mixture was stirred at room temperature for 40 min
and then washed thoroughly with water. The organic layer was
dried over anhydrous sodium sulfate and evaporated to dryness.
The crude product was purified by column chromatography
over silica gel using chloroform as eluent.
General procedure for the synthesis of b,b0-meso-phenyl-fused
quinoxalinodiporphyrins (10a and 10b)
Yield: 88%; found: C, 75.48; H, 4.01; N, 9.86%.
C88H52N10Zn2 + H2O requires C, 75.59; H, 3.89; N,
10.02%; lmax(CHCl3)/nm 426 (e/dm3 molꢁ1 cmꢁ1 3 35 400),
452 (1 76 100), 558 (45 300), 572 (43 200) and 618 (32 600); lEm
(CHCl3)/nm 632, 681 (lEx 420 nm); nmax(Film)/cmꢁ1 1597,
1524, 1482, 1441, 1343, 1198, 1170, 990, 796, 750, 700; dH
(400 MHz, CDCl3) 9.02 (1H, d, J = 4.39 Hz, b-pyrrolic H),
8.99–8.96 (7H, m, b-pyrrolic H), 8.92–8.88 (4H, m, b-pyrrolic H),
8.86 (2H, s, b-pyrrolic H), 8.79 (1H, d, J = 2.01 Hz, meso-
ArH), 8.71 (1H, dd, J1 = 8.79, J2 = 2.2 Hz, meso-ArH),
8.31–8.15 (15H, m, meso-ArH), 7.99–7.88 (3H, m, meso-ArH),
7.89–7.73 (15H, m, meso-ArH), 7.55 (2H, t, J = 7.69 Hz,
meso-ArH), 7.42 (1H, t, J = 8.05 Hz, meso-ArH); m/z (ESI)
1377.6 ([M+H]+ requires 1377.3).
To a solution of 5-(3,4-diaminophenyl)-10,15,20-triphenyl-
porphyrin (30 mg, 0.046 mmol) in 1,2-dichlorobenzene (10 mL),
2,3-dioxo-5,10,15,20-tetraphenylchlorin 9a or 9b (0.046 mmol)
was added. The reaction mixture was stirred at 100 1C for 3 h
and then cooled to room temperature. The reaction mixture
was directly loaded on a silica gel column and 1,2-dichloro-
benzene was removed by using hexane as solvent. The desired
product (10a or 10b) was obtained by eluting the column with
60% chloroform in hexane.
5-(Zinc(II) 5,10,15,20-tetraphenylporphyrin[2,3-b]quinoxalin-
6-yl)-10,15,20-triphenylporphyrin (10a). Yield: 65%; found: C,
78.58; H, 4.34; N, 10.37%. C88H54N10Zn + 1.5H2O requires
C, 78.65; H, 4.28; N, 10.42%; lmax(CHCl3)/nm 420 (e/dm3
molꢁ1 cmꢁ1 3 44 300), 456 (1 49 500), 517 (39 400), 553
(28 300), 577 (30 300), 619 (15 600) and 649 (7200); lEm
(CHCl3)/nm 625, 655, 717 (lEx 420 nm); nmax(Film)/cmꢁ1
3320, 1596, 1524, 1482, 1441, 1343, 1198, 1170, 990, 796,
750, 700; dH (400 MHz, CDCl3) 9.02 (1H, d, J = 5.13 Hz,
b-pyrrolic H), 8.99 (1H, d, J = 4.39 Hz, b-pyrrolic H),
8.93–8.86 (10H, m, b-pyrrolic H), 8.80 (2H, d, J = 4.39 Hz,
b-pyrrolic H), 8.77 (1H, d, J = 1.46 Hz, meso-ArH), 8.71 (1H,
dd, J1 = 8.42, J2 = 1.46 Hz, meso-ArH), 8.32–8.21 (13H, m,
meso-ArH), 8.16 (2H, d, J = 7.32 Hz, meso-ArH), 7.97 (1H, t,
J = 7.32 Hz, meso-ArH), 7.90 (2H, t, J = 7.32 Hz, meso-
ArH), 7.79–7.74 (15H, m, meso-ArH), 7.56 (2H, t, J = 7.32 Hz,
meso-ArH), 7.42 (1H, t, J = 7.32 Hz, meso-ArH), ꢁ2.66 (2H, s,
internal NH); m/z (ESI) 1315.6 ([M+H]+ requires 1315.3).
Copper(II) 5-(copper(II) 5,10,15,20-tetraphenylporphyrin[2,3-b]-
quinoxalin-6-yl)-10,15,20-triphenylporphyrin (10d)
To a solution of free-base-free-base diporphyrin 10b (15 mg,
0.011 mmol) in chloroform (10 mL), a solution of Cu(OAc)2ꢀ
2H2O (10 mg, 0.05 mmol) in methanol (0.5 mL) was added.
The reaction mixture was stirred at room temperature for 10 h
and the progress of the reaction was monitored by TLC. After
completion of the reaction, the mixture was washed with
water, the organic layer was dried over anhydrous sodium
sulfate and evaporated to dryness. The crude product was
purified over a silica-gel column by using 50% CHCl3 in
hexane as solvent.
Yield: 90%; found: C, 75.72; H, 4.12; N, 9.74%.
C88H52N10Cu2 + H2O requires C, 75.79; H, 3.90; N,
10.04%; lmax(CHCl3)/nm 416 (e/dm3 molꢁ1 cmꢁ1 5 62 900),
444 (2 44 100), 542 (66 200), 572 (42 800) and 609 (27 700);
5-(5,10,15,20-Tetraphenylporphyrin[2,3-b]quinoxalin-6-yl)-
10,15,20-triphenylporphyrin (10b). Yield: 70%; found: C, 81.62;
H, 4.76; N, 10.61%. C88H56N10 + 2H2O requires C, 81.97; H,
4.69; N, 10.86%; lmax(CHCl3)/nm 422 (e/dm3 molꢁ1 cmꢁ1
3 47 900), 438 (3 25 500), 524 (44 900), 550 (24 300), 598 (17 400)
and 649 (4900); lEm (CHCl3)/nm 655, 725 (lEx 420 nm);
n
max(Film)/cmꢁ1 1600, 1459, 1345, 1273, 1072, 1004, 799, 751,
699; m/z (ESI) 1375.1 ([M+H]+ requires 1375.3).
Acknowledgements
n
max(Film)/cmꢁ1 3320, 1596, 1524, 1482, 1441, 1343, 1198,
We thank the University of Delhi, India for providing financial
support to complete this work. Satyasheel is grateful to Council
of Scientific and Industrial Research, New Delhi, India for Senior
1170, 990, 796, 750, 700; dH (400 MHz, CDCl3) 9.06 (1H, d,
J = 4.7 Hz, b-pyrrolic H), 8.99 (1H, d, J = 5.3 Hz, b-pyrrolic H),
c
1638 New J. Chem., 2011, 35, 1630–1639
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2011

View Article Online
Research Fellowship. The JEOL ECX (400 MHz) NMR facility
at USIC, University of Delhi and SAIF, CDRI, Lucknow are
1
acknowledged for H NMR and mass spectra, respectively.
5 K. M. Kadish, W. E. P. J. Sintic, Z. Ou, J. Shao, K. Ohkubo,
S. Fukuzumi, L. J. Govenlock, J. A. McDonald, A. C. Try,
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2007, 111, 8762–8764.
6 (a) M. J. Crossley and P. L. Burn, J. Chem. Soc., Chem. Commun.,
1991, 1569–1571; (b) R. Azumi, M. Matsumoto, S. Kuroda,
L. G. King and M. J. Crossley, Langmuir, 1995, 11, 4056–4060;
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