Vibrational properties of new corrole-fullerene dyad and its components

Article abstract of DOI:10.1016/j.dyepig.2012.07.024

We present first systematic spectral studies of a new corrole-fullerene dyad and its components: modified corrole and suitable spacer. The infrared absorption and Raman scattering spectra were measured in polycrystalline samples, at room temperature. Quantum chemical calculation results were compared with the experimental IR and Raman spectra. An attribution of the strongest IR and Raman bands was proposed. It was found that the strongest excitations in the dyad are mainly related to the excitations of the modified corrole part with some influence from the spacer and fullerene parts.

Full text of DOI:10.1016/j.dyepig.2012.07.024

Dyes and Pigments 96 (2013) 249e255
Contents lists available at SciVerse ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Vibrational properties of new corroleefullerene dyad and its components
,
a
a
b
Kornelia Lewandowska a, Boles1aw Barszcz a , Jacek Wolak , Andrzej Graja , Marek Grzybowski ,
*
Daniel T. Gryko b
a
ꢀ
Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznan, Poland
b Institute of Organic Chemistry, Polish Academy of Sciences, 01-224 Warsaw, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
We present first systematic spectral studies of a new corroleefullerene dyad and its components:
modified corrole and suitable spacer. The infrared absorption and Raman scattering spectra were
measured in polycrystalline samples, at room temperature. Quantum chemical calculation results were
compared with the experimental IR and Raman spectra. An attribution of the strongest IR and Raman
bands was proposed. It was found that the strongest excitations in the dyad are mainly related to the
excitations of the modified corrole part with some influence from the spacer and fullerene parts.
Ó 2012 Published by Elsevier Ltd.
Received 15 May 2012
Received in revised form
20 July 2012
Accepted 31 July 2012
Available online 7 August 2012
Keywords:
Corrole
Fullerene
Dyad
Infrared absorption
Raman scattering
Density Functional Theory
1. Introduction
four pyrrole rings [9]. When compared with porphyrins, these
tribasic aromatic macrocycles exhibit lower oxidation potentials,
Design and characterization of electronic components with
molecular dimensions is an area of extensively active studies. The
reason of these investigations is to enquire about new artificial
molecular systems mimicking the primary phenomena of natural
photosynthesis. Photosynthesis has been widely investigated not
only for understanding all aspects of this fascinating process [1] but
also by reason of its potential applications e for construction of
organic solar cells [2e6]. Organic cells are the most promising
devices taking advantages of the artificial photosynthesis effect.
Dyads containing an organic chromophore (working as an
electron donor) bonded to an electron acceptor (e.g. fullerene) are
active materials in the simplest solar cells. The excellent electron-
accepting capability of fullerenes renders them attractive building
blocks for organic solar cells [7]. On the other hand, porphyrinoids
[8] are perfect and commonly used chromophores in these solar
cells. Meso-substituted corroles are recently among the most
widely investigated compounds, in this regard [9e12].
higher fluorescence quantum yields, larger Stokes shifts, and more
intense absorption of red light [13,14]. Free-base corroles reveal the
Soret-type absorption in the 400e440 nm region and Q band
transitions between 500 and 700 nm. The absorption spectra of
corroles exhibit two important differences versus porphyrins.
Firstly, there is more pronounced change in the optical absorption
of the corroles upon variation of the substitution on the phenyl
group than in the corresponding porphyrins and secondly, corroles
exhibit very significant solvent-dependent absorptions in contrast
to the small shifts typically detected in porphyrins [15]. It is
necessary to notice, that the effect of substitution on the optical
properties of corroles is significantly larger than in porphyrins.
Finally, corroles can be highly emissive, with high quantum yields
of fluorescence [9,13e15]. The corroles are, in general, less stable
than porphyrins but the stability of their dyads is better than that of
the corresponding component corroles [10].
The comprehensive spectral investigations of corroles and their
dyads with the fullerene are very important because the knowledge
of vibrational and electronic properties of these materials facilitate
appropriate selection of molecular systems for designing solar cells.
Besides, there are only a few papers describing selected aspects of
the IR or Raman spectra of some corroles [16e19]. Vibrational
spectral studies of a few corroles were recently reviewed in [20].
Corroles are one C atom fewer analogues of porphyrins pos-
sessing the skeleton of corrin with three meso-carbons between the
* Corresponding author.
E-mail address: barszcz@ifmpan.poznan.pl (B. Barszcz).
0143-7208/$ e see front matter Ó 2012 Published by Elsevier Ltd.
http://dx.doi.org/10.1016/j.dyepig.2012.07.024

250
K. Lewandowska et al. / Dyes and Pigments 96 (2013) 249e255
In this paper we present unique investigations of the vibrational
(d, J ¼ 4.6 Hz, 2H), 8.58 (d, J ¼ 4.0 Hz, 2H), 8.17 (d, J ¼ 8.6 Hz, 2H),
properties of the new fullerene-corrole dyad (6) and its compo-
nents (3, 4). Spectral investigations of IR absorption and Raman
scattering were compared with quantum chemical calculations.
According to our knowledge there are first complex spectral
investigations of the dyad and its components.
7.42 (d, J ¼ 8.6 Hz, 2H). 19F NMR (470 MHz, CDCl3):
d
ꢂ137.9 (d,
J ¼ 17.6 Hz, 2F), ꢂ144.6 (dt, J ¼ 13.1, 4.5 Hz, 1F), ꢂ152.5 (dt, J ¼ 13.1,
4.5 Hz, 1F), ꢂ152.7 (t, J ¼ 19.1 Hz, 1F), ꢂ161.7 (t, J ¼ 18.5, 2F). HRMS
(ESI) calcd for C44H17F14N4O2 (M þ Hþ): 899.1122, found: 899.1150.
Corrole 5: 0.202 mg (11%). Mp: >400 ꢀC. 1H NMR (500 MHz, CDCl3):
d
10.04 (s, 1H), 9.08 (s, 2H), 8.82 (d, J ¼ 4.2 Hz, 2H), 8.69 (d,
2. Experimental section
J ¼ 4.2 Hz, 2H), 8.54 (s, 2H), 8.06 (d, J ¼ 8.7 Hz, 2H), 7.42 (d,
J ¼ 8.7 Hz, 2H). HRMS (FD-TOF) calcd for C44H16F14N4O2 (Mþ):
898.1050, found: 898.1082.
2.1. General experimental
All chemicals were used as received unless otherwise noted.
Reagent grade solvents (CH2Cl2, hexanes, cyclohexane) were
distilled prior to use. All reported 1H NMR and 13C NMR spectra
were recorded on Bruker AM 500 MHz or Varian 400 MHz spec-
F
OH
F
F
F
F
+
trometer. Chemical shifts (d ppm) were determined with TMS as
the internal reference; J values are given in Hz. UVeVis spectra
were recorded in CH3CN. Chromatography was performed on silica
(Kieselgel 60, 200e400 mesh) or size-exclusion chromatography
(SEC) was performed using BioRad Bio-Beads SX-1 with toluene as
eluent. Mass spectra were obtained via electrospray MS (ESI-MS).
Pentafluorophenyldipyrrane was synthesized according to the
literature procedure [21].
CHO
1
CHO
2
CsF, DMF
RT, 1h, 59%
F
F
2.2. 2,3,5,6-Tetrafluoro-4-(4-formylphenyloxy)benzaldehyde (3)
F
CHO
OHC
Pentafluorobenzaldehyde (1, 1.59 mL, 10 mmol) was slowly
added to a mixture of 4-hydroxybenzaldehyde (2, 1.22 g, 10 mmol),
cesium fluoride (3.04 g, 20 mmol) and anhydrous DMF (20 mL)
under an argon atmosphere. The reaction mixture was stirred for
1 h at RT and then diluted with water and ethyl acetate. Subse-
quently the aqueous layer was washed three times with ethyl
acetate. Combined organic layers were washed with water and
brine, dried with anhydrous Na2SO4 and concentrated. The product
was purified by the column chromatography using methylene
chloride as an eluent. After the solvent evaporation, 1.76 g of white
solid was obtained (59%). Mp: 85e86 ꢀC. 1H NMR (500 MHz, CDCl3):
F
O
3
C6F5
1.
NH NH
HCl, H2O, MeOH
d
10.32 (t, 1H e 19F coupling, 4J1H,19F ¼ 2.1 Hz, 1H), 9.98 (s, 1H), 7.93,
7.14 (AA0XX0, 2 ꢁ 2H), 13C NMR (125 MHz, CDCl3):
d 190.3, 181.7,
2. DDQ
160.5,148.6,146.5,142.2,140.2,137.7,133.0,132.1,116.2,112.1. HRMS
(EI 70 eV) calcd for C14H6F4O3 (Mþ): 298.0253, found: 298.0256.
Elemental analysis calcd (%) for C14H6F4O3: C 56.39, H 2.03; found:
C 56.07, H 2.30.
CHO
F
C6F5
F
F
NH
N
NH
NH
2.3. Corroles 4 and 5
O
F
A mixture of water (200 mL) and c.HCl (10 mL) was added to
a
stirred solution of 3 (0.596 g, 2.0 mmol) and penta-
(28%)
4
fluorophenyldipyrrane (1.250 g, 4.0 mmol) in methanol (200 mL).
After 30 min of stirring at RT, the reaction mixture was diluted with
chloroform. The aqueous layer was extracted with chloroform,
combined organic layers were washed twice with water, dried over
sodium sulphate, concentrated to a volume of 40 mL and placed
into 40 mL syringe. 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone
(DDQ, 1.180 g, 5.2 mmol) was dissolved in a minimum volume of
toluene, diluted to 40 mL with methylene chloride and placed into
second syringe. The contents of each syringes were simultaneously
added dropwise to vigorously stirred methylene chloride (50 mL)
for 10 min at room temperature (the same rate of addition from
both syringes is crucial). After complete addition the reaction was
continued for 15 min. Solvents were then evaporated and products
were separated by the column chromatography (hexanes:-
methylene chloride 1:1). Two regioisomers were obtained: Corrole
4: 0.493 mg (27%). Mp: 237e239 ꢀC. 1H NMR (500 MHz, CDCl3):
C6F5
C6F5
+
CHO
F
F
F
NH
N
NH
NH
O
F
(11%)
5
C6F5
d
10.36 (s, 1H), 9.12 (d, J ¼ 4.0 Hz, 2H), 8.73 (d, J ¼ 4.6 Hz, 2H), 8.68
Scheme 1. The synthesis of formyl-corroles 4 and 5.

K. Lewandowska et al. / Dyes and Pigments 96 (2013) 249e255
251
chromatography (SEC, toluene as an eluent). After the solvent
evaporation 65 mg of black solid was obtained which was then
recrystallized from toluene/heptane to give 49 mg (15%) of 6 as
F
CHO
C F
6
5
F
F
F
a black powder. Mp: >400 ꢀC. 1H NMR (500 MHz, CDCl3):
d 8.83 (s,
NH
N
NH
NH
2H), 8.53 (d, J ¼ 4.6 Hz, 2H), 8.44 (d, J ¼ 4.6 Hz, 2H), 8.36 (s, 2H), 8.06
(d, J ¼ 8.6 Hz, 2H), 7.33 (d, J ¼ 8.6 Hz, 2H), 5.45 (s, 1H), 4.48 (d,
J ¼ 9.6 Hz, 1H), 3.73 (dd, J ¼ 9.6, 2.6 Hz, 1H), 2.64 (s, 3H). LRMS (FD-
TOF) calcd for C106H21F14N5O (M þ): 1645, found: 1645 as high
purity amorphous powders obtained by chromatography and
characterized by 1H NMR spectroscopy.
O
4
C F
6
5
The vibrational IR absorption spectra of the corrole-based-
fullerene dyad (6) and its main components (3, 4) were investi-
gated at room temperature in polycrystalline powder. The investi-
gations were performed with an FT-IR Bruker Equinox 55
spectrophotometer within the range 400e7000 cmꢂ1. Raman
scattering spectra of the investigated compounds were recorded
with Bruker IFS 66 FRA 106 spectrophotometer at room tempera-
ture, with laser excitation lexc ¼ 1064 nm. Additionally, the Raman
spectra were recorded using LabRAM HR 800 spectrophotometer
(HORIBA Jobin Yvon) with excitation lexc ¼ 488 and 514 nm from
the Stabilite 2017 Ar laser. The power of the laser beam at the
sample in all cases was less than 1 mW with a power density of
about 3 ꢁ 108 mW cmꢂ2. Such a low power density was necessary
to avoid decomposition of the sample.
In order to realize of an optimal structure of the compounds and
to interpret the experimental results of IR absorption and Raman
scattering investigations quantum chemical calculations were
performed. The molecular geometries were optimized using the
Density Functional Theory (DFT) method with B3LYP hybrid func-
tional and 6-31G and 6-31G(d) basis sets. The calculations of
normal mode frequencies and intensities were also performed. All
calculations were made using Gaussian 03 package [22]. The
GaussView program was used to propose an initial geometry of
investigated molecules and for visual inspection of the normal
modes.
C6 , sarcosine
0
PhMe, 120°C, 20h
15%
N
F
F
F
F
O
NH
N
C F
6
H
N
H
N
F C
5
5
6
3. Results and discussion
6
Scheme 2. The synthesis of corroleefullerene dyad 6.
We designed the fullerene-corrole dyad
6 based on the
following principles: (a) two C6F5 units should be present at posi-
tions 5 and 15 of corrole core to ensure high stability; (b) the semi-
rigid spacer should link both chromophores. Diaryl ether linker
appeared to fullfill these conditions. The key intermediate (dia-
ldehyde 3) was prepared by the nucleophilic aromatic substitution
2.4. Corroleefullerene dyad (6)
Aldehyde 4 (180 mg, 0.2 mmol), C60 (144 mg, 0.2 mmol) and
sarcosine (89 mg, 1 mmol) were placed in 100 mL Schlenk flask and
argonated (purge-and-refill technique). Dry, air-free toluene (25 mL)
was added and obtained mixture was stirred for 20 h at 120 ꢀC.
Then, toluene was evaporated and the residue was passed through
a silica gel pre-column (heptane:toluene, 1:1). Finally, the product
was separated by the preparative size exclusion column
between
pentafluorobenzaldehyde
(1)
and
p-hydrox-
ybenzaldehyde (2) in the presence of cesium fluoride as a base
(Scheme 1). In agreement with previously published methodology
[23] only the product of fluorine atom substitution at position 4
was obtained. In the next step, dialdehyde 3 was converted into
trans-A2B-corrole using the modified H2O/MeOH/HCl [24] method,
Scheme 3. Optimized geometry of the investigated newly synthesized fullereneecorrole dyad (6) and its components (3, 4). Theory level B3LYP/6-31G. Note: grey e carbon, red e
oxygen, blue e nitrogen, white e hydrogen, cyan e fluorine.

252
K. Lewandowska et al. / Dyes and Pigments 96 (2013) 249e255
in which dipyrrane reacts with an aldehyde and subsequently crude
tetrapyrrane is oxidized with DDQ. Due to the fact, that aldehyde 3
has two different formyl groups, the reaction with penta-
fluorophenyldipyrrane leads to the formation of two regioisomeric
corroles 4 and 5 (Scheme 1). Quite surprisingly, the yield of corrole
4 (28%) was significantly higher than the yield of corrole 5 (11%).
Apparently steric hindrance imparted by fluorine atoms had more
pronounced effect on the reactivity of the carbonyl group than
electron density. Structures of these products were assigned after
the comparision of their formyl protons shifts on 1H NMR spectra
with shifts of starting aldehyde 3, whose formyl groups signals can
be easily distinguished due to the 1He19F coupling.
Corroleefullerene dyad 6 was synthesized in 15% yield, by the
Prato reaction of corrole 4 with formaldehyde and sarcosine
(Scheme 2). The product was purified by size exclusion chroma-
tography (SEC). In analogy to another corroleefullerene dyad [9]
compound 6 is unstable when both light and oxygen are present.
The optimal configurations of the investigated molecules 3, 4, and 6
are shown in Scheme 3.
The quantum chemical calculations of the normal modes of
vibrations permit us to assign the bands observed in the experi-
mental spectra to specific vibrations of various functional groups of
the molecule. The experimental results were compared with
calculations obtained using two different basis sets (6-31G and 6-
31G(d)). The comparison shows that the results of calculations with
the base 6-31G are more consistent with the experimental spectra
(Fig. 1). Therefore, the interpretation of the spectra and assignment
of vibrational bands were based on the results obtained with 6-31G
base. In general, conformity between the calculated and experi-
mental spectra is quite good. The wavenumber shifts between them
are typical and arise from approximations used in the computa-
tional procedure. Mainly the anharmonicity of vibrations and
environment of the molecules which are neglected in our calcula-
tions cause those shifts.
In Fig. 1 the experimental and calculated infrared spectra of the
samples 3, 4, 6 in the spectral ranges 400e1900 and 3200e
3500 cmꢂ1 are presented. The most significant is the region 600e
1800 cmꢂ1 where intense and characteristic bands related to
intramolecular vibrations of the molecules are observed, including
the deformation of benzene and pentafluorobenzene C6F5 rings as
well as stretching of various CeC bonds. Some information follows
from an analysis of the bands located at about 3000 cmꢂ1, where
the stretching vibrations of CeH bonds and the stretching of NeH
bonds at corrole ring are observed.
In the calculated infrared spectrum of the dialdehyde 3 (Fig. 1a)
a strong band at 1238, related to the in plane bending of CeCeH
bonds in benzene ring is observed. Its counterpart in the experi-
mental spectrum is located at 1230 cmꢂ1. The bands related to the
out of plane bending of CeCeH bonds in the benzene ring are ex-
pected at 852 and 875 cmꢂ1 but in the experimental spectrum they
are seen at 825 and 854 cmꢂ1. The most intense band in the
experimental spectrum is the doublet at 1597/1646 cmꢂ1; this is
mainly due to the in-plane stretching vibrations of the C]C bonds
in the benzene ring with some influences of the C]C stretching in
C6F4 ring and CeCeH bending vibrations (calculated wavenumbers
1629 and 1657 cmꢂ1). The medium band at 955 cmꢂ1 in the
calculated spectrum related to the stretching of CeC bonds in C6F5
ring is stronger in the experimental spectrum and observed at
948 cmꢂ1. The calculated bands in the spectra of dialdehyde 3 at
about 1007 and 1420 cmꢂ1 correspond to the experimental bands
at 1006 and 1393 cmꢂ1 and they are related to the stretching of CeF
and CeC bonds in the C6F4 ring. The weak band related to the
bending mode of C¼OeH bond is observed at 1457 cmꢂ1
(1425 cmꢂ1 in experiment). The characteristic strong bands at 1705
and 1713 cmꢂ1 are related to the C]O stretching vibrations in the
Fig. 1. IR absorption spectra of the fullereneecorrole dyad components (3 (a), and 4
(b)) and the dyad (6 (c)) at room temperature in polycrystalline powder. The appro-
priate calculated IR absorption spectra (B3LYP/6-31G) are also added in each panel.

K. Lewandowska et al. / Dyes and Pigments 96 (2013) 249e255
253
aldehyde eCHO group. In the experimental spectrum they form
a doublet with the maxima at 1695 and 1705 cmꢂ1. Besides, we
observed a medium strength band at 1121 cmꢂ1 and strong one at
1488 cmꢂ1 related to the stretching of the CeO bonds between the
benzene and C6F5 rings, which are located in the calculated spec-
trum at 1149 and 1508 cmꢂ1. The weak bands at about 2879 and
3370 cmꢂ1 are related to the stretching of the CeH bond in alde-
hyde eCHO group.
856 and 847 cmꢂ1 in experimental spectra of 4 and 6, respectively.
For 4 and 6 the in-plane stretching vibrations of the C]C bonds in
the benzene ring with some influences of the C]C stretching in
C6F4 ring and CeCeH bending vibrations are located at 1627 cmꢂ1
(1600 cmꢂ1 in the experiment), 1655 cmꢂ1 (1645 cmꢂ1 in the
experiment), 1634 cmꢂ1 (experimental 1602 cmꢂ1) and 1658 cmꢂ1
(experimental 1648 cmꢂ1), respectively. The band related to the
stretching of CeC bonds in C6F4 ring for 4 is shifted by 5 cmꢂ1 in
relation to 3 and is located in the experimental spectrum at
953 cmꢂ1 (in the calculated spectrum we see this band at
955 cmꢂ1). The bands related to the stretching mode of CeO bond
are located at 1488 and 1492 cmꢂ1 for 4 and 6, respectively. The first
band attributed to the stretching of CeF bonds in the C6F4 ring
observed for 3 at 1006 cmꢂ1 is shifted to 1016 cmꢂ1 for 4 and
1019 cmꢂ1 for 6. The second band of this vibration mode located at
1393 cmꢂ1 for 3, is observed only for 4 at 1398 cmꢂ1. The absence of
this band in the IR spectrum of 6 is attributable to stiffening of the
CeF bonds in the pyrrole ring by linking to the fullerene. For 4 and 6
we observe strong band located at about 3260e3300 cmꢂ1 and
attributed to stretching of CeH bonds in pyrrole ring in corrole; this
band is stronger than that observed in calculated spectra. In the
experiment for both 4 and 6 dyads we observe the strong band at
3363 cmꢂ1 related to the stretching of NeH bond in corrole ring. For
these molecules the bands related to the bending of CeNeH bonds
in the corrole ring are located at about 1600 cmꢂ1. The stretching of
CeF bonds in the pentafluorobenzene C6F5 rings is the origin of
band located in calculated spectra of 4 and 6 at 1536 cmꢂ1. For the
dyad 6 we also observed the bands related to the deformations of
the fullerene C60. According to our calculations these bands should
be observed at 550e570, 945, 1214, 1464 cmꢂ1 and in the range
1619e1627 cmꢂ1. Of course, these vibrations are complex and
involve not only the fullerene cage but also other parts of molecule
IR absorption spectra of the 4 and 6 are presented in Fig. 1b and
c, respectively. The specific differences in the positions of calculated
and experimental bands are gathered in Table 1. Bonding of the
modified corrole 4 with the fullerene C60 by the diarylether spacer
causes some changes in positions and intensities of the bands of the
spacer. For example the stretching mode of C]O observed for 3 at
1705 cmꢂ1 is shifted to 1707 cmꢂ1 for 4; this mode is not observed
in the dyad 6, because the aldehyde eCHO group has been replaced
by a modified fullerene connected with C6F4 tetrafluorobenzene
ring by pyrrol ring. The bands associated with the stretching of the
CeH bonds in the CH2 groups are observed at 2779 and 2848 cmꢂ1
,
but the stretching of the CeH bonds in the methyl group e at 2793
and 2871 cmꢂ1. A strong band related to the scissoring mode of e
CH2 and eCH3 groups is located at 1517 cmꢂ1. Weak bands corre-
sponding to the stretching of CeN bond in the pyrrol ring are
observed at about 1550 cmꢂ1. In the calculated spectrum the
adequate bands are registered at 2988, 3078, 3031, 3123, 1532, and
1583 cmꢂ1, respectively. In the spectrum of 6 we observe the bands
related to the bending mode of CeCeN bond in pyrrole ring at
1247 cmꢂ1 (according to calculations at 1299 cmꢂ1). The calculated
band related to in-plane bending of CeCeH bonds in the benzene
ring is observed at 1240 cmꢂ1 and 1243 cmꢂ1 (experimental at
1202 cmꢂ1 and 1208 cmꢂ1), for 4 and 6. The bands due to out of
plane bending of the CeCeH in the benzene ring are observed at
Table 1
Selected experimental (bold) and calculated normal vibrational modes of the investigated molecules. Notation: s-stretching, b-bending, sc-scissoring, ip-in plane, op-out of
plane.
3 (cmꢂ1
)
4 (cmꢂ1
)
6 (cmꢂ1
)
Band assignment
IR
Raman
IR
Raman
IR
Raman
exp/calc
exp/calc
399/400
exp/calc
exp/calc
exp/calc
exp/calc
CeF b in C6F4 ring
CeCeH b op benzene ring
CeC s in benzene ring
def. corolle rings
CeC s in C6F4 ring þ CeF s
CeF s in C6F4 ring
CeO s
CeO s þ CeCeH bip benzene ring
CeCeH b ip benzene ring
CeCeN b in pyrrole ring
CeF b in C6F4
854/875
856/844
847/843
927/953
861/865
928/953
953/955
1016/1007
1119/1149
1173/1213
1202/1240
948/955
1006/1007
1121/1149
1209/1211
1230/1238
1019/973
1209/1211
1167/1213
1208/1243
1247/1299
1312/1334
1393/1420
1393/1420
1425/1457
1488/1508
1398/1420
1433/1455
1488/1507
1403/1420
1524/1536
1423/1420
CeF s þ CeC s in C6F4 ring
C¼OeH b
1488/1508
1492/1508
1517/1532
1519/1536
1550/1583
1602/1634
1648/1658
1502/1498
e/1532
1527/1536
1560/1583
CeO s
CH2 sc þ CH3 sc
1521/1536
CeF s in C6F5 ring
CeN s in pyrrole ring
C]C s ip in benzene ring
C]C s ip in benzene ring
C]O s
1597/1629
1646/1657
1695/1707
1705/1713
1597/1629
1646/1657
1695/1707
1705/1713
1600/1627
1645/1655
1597/1627
1646/1655
1648/1658
1707/1711
3363/3651
1708/1711
C]O s
2779/2988
2793/3031
2848/3078
2871/3123
CeH s in eCH2 group
CeH s in eCH3 group
CeH s in eCH2 group
CeH s in eCH3 group
CeH s in eCOH group
CeH s in eCOH group
NeH s in corrole ring
NeH s in corrole ring
2879/2970
2923/3052
2879/2970
2923/3052
2951/3151
3363/3648

254
K. Lewandowska et al. / Dyes and Pigments 96 (2013) 249e255
like eCH3 group. Additional details of assignment can be found in
Table 1.
Concluding the analysis of the infrared vibrational spectra of the
investigated molecules one can see relatively good conformity
between the experimental and calculated spectra. On the other
hand the spectral changes caused by bonding the corrole with the
C60 molecule are distinct and characteristic e the bonds involved in
formation of the fullerene-corrole dyad are usually weakened e it
results in hypsochromic shifts of the adequate bands. Some of
them, e.g. CeF vibration of the C6F4 ring are shifted by 10e15 cmꢂ1
.
The calculated and experimental Raman spectra of 3, 4 and 6 are
presented in the Fig. 2. It is necessary to notice that Raman spectra
of the samples 4 and 6 were very hard to obtain. Our attempts to
measure the spectra with excitation lines 633 nm (from the HeeNe
laser), 488 nm, and 514 nm (from the argon ion laser) were
unsuccessful. The only excitation that allow us to get any result was
the excitation line from the Nd:YAG laser (1064 nm). In general, the
agreement between the experimental and calculated spectra was
better in the case of IR spectra than Raman scattering. However, we
were able to identify and assign the most important bands
observed in the spectra to appropriate normal modes of vibration.
In the Fig. 2a the Raman scattering spectra of 3 obtained with two
excitations (488 and 514 nm) are presented together with the
calculated spectrum. In the calculated Raman spectrum of 3 the
dominant vibrations are the in-plane stretching of C]C bonds in
benzene ring at 1629 and 1657 cmꢂ1, that corresponds very well
with IR bands and that are observed in the experimental spectrum
at 1597 and 1646 cmꢂ1. The other intensive bands observed in the
experimental spectra at 1695 and 1705 cmꢂ1 are related to the
stretching of C]O bonds and they are located in the calculated
spectrum at 1707 and 1713 cmꢂ1, respectively. The band located in
calculated spectrum at 1420 cmꢂ1 is due to the stretching of CeF
and CeC bonds in C6F4 ring. In experimental spectra of 3, 4 and 6
this band is observed at 1393, 1403 and 1423 cmꢂ1, respectively. In
the experimental Raman scattering spectrum of 3 we observe also
distinct bands at 2879 and 2923 cmꢂ1 related to the stretching
vibration of CeH bond in eCOH group (calculated wavenumbers
2970 and 3052 cmꢂ1, respectively). The region 2500e3600 cmꢂ1 is
not shown to preserve the clarity of the picture. The bands
observed at about 1200 cmꢂ1 are related to the stretching of CeC
bonds in benzene ring. The bands observed in the experimental
spectra at Raman Shifts lower than 800 cmꢂ1 are quite distinct but
unfortunately their intensities in the calculated spectra are very
low what makes the interpretation uncertain.
The vibrations characteristic for 3 can also be found in the
spectra of 4 and 6. However their positions are slightly changed and
in many cases the vibrations involve also other parts of the mole-
cule. In experimental Raman scattering spectrum of 4 we observe
a quite strong band at 1646 cmꢂ1 and very weak band at 1597 cmꢂ1
related to the stretching vibration of C]C bonds in the benzene
ring. These bands in 6 are observed at 1648 cmꢂ1 and 1601 cmꢂ1. In
the experimental spectra of 4 and 6 we observe quite strong bands
at 1524 and 1527 cmꢂ1 related to the stretching of CeF bonds in
C6F5 ring. Besides, in calculated Raman scattering spectra of these
two samples at 1583 cmꢂ1 we observe very strong band related to
the vibration involving stretching of CeC bonds and bending of Ce
CeH bonds in corrole ring, but it is not observed or is very weak in
experimental spectra. Quite weak bands observed between 1150
and 1400 cmꢂ1 are related to the stretching of CeC and bending of
CeC¼C bonds in corrole ring. Also, in this region the bands related
to the rocking, wagging, and twisting vibrations of CH2 and CH3
groups and stretching vibration of CeF in C6F4 ring are located. The
band related to the bending vibration of the CeH bonds in CH3
group in 6 is clearly visible in calculated spectrum at 1106 cmꢂ1 and
it corresponds quite well to the band at 1074 cmꢂ1 observed in the
Fig. 2. Raman scattering spectra of the fullereneecorrole dyad components (3 (a), and
4 (b)) and the dyad (6 (c)) recorded at room temperature with excitations lexc ¼ 488,
514, and 1064 nm. The calculated Raman scattering spectra (B3LYP/6-31G) of inves-
tigated molecules are added for comparison.
experimental spectrum. Very strong band related to the various
vibrations of the CeC bonds in fullerene cage in experimental
spectrum is located at 1462 cmꢂ1 and it is observed in calculated
spectrum at 1475 cmꢂ1. This band is characteristic for the many

K. Lewandowska et al. / Dyes and Pigments 96 (2013) 249e255
255
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functionalized fullerenes and it was observed by us in many
different samples at almost the same position [25e28]. Weaker but
also clearly visible band related to the fullerene molecule vibration
is observed at 1172 cmꢂ1 (in calculated spectra at 1170 cmꢂ1).
Summarizing the Raman scattering investigations we can say
that in this case, Raman spectra are rather the addition to the IR
absorption measurements. Of course the spectra are valuable
because they give us some extra information about the vibrational
behaviour of the sample but the IR is the main source of interpre-
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4. Conclusions
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the corrole molecule makes the spectral identification possible.
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