Infrared spectrum of nitro(5,10,15,20-tetraphenylporphyrinato)(4- methylpyridine)cobait(III)

Article abstract of DOI:10.1246/cl.2009.92

IR spectrum of the title compound is measured in the 500 to 300 cm ^-1 region. The band at 346 cm^-1 is shifted depending on the fifth ligand (L) and assigned to the skeletal deformation vibration band coupled with the Co-NO₂

Full text of DOI:10.1246/cl.2009.92

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Chemistry Letters Vol.38, No.1 (2009)
Infrared Spectrum of Nitro(5,10,15,20-tetraphenylporphyrinato)(4-methylpyridine)cobalt(III)
y
Kenichi Yamamoto
(Received October 20, 2008; CL-081005; E-mail: yama 8ky@wine.plala.or.jp)
IR spectrum of the title compound is measured in the 500 to
ꢀ ꢀ1
1
3
00 cm region. The band at 346 cm is shifted depending on
the fifth ligand (L) and assigned to the skeletal deformation vi-
bration band coupled with the Co–NO2 stretching and Co–L
stretching vibration bands.
1
2
Nitrosyl(5,10,15,20-tetraphenylporphyrinato)cobalt(II)
II
6
00 500 400
1
([Co (tpp)(NO)]) reacts with molecular oxygen in the presence
of 4-methylpyridine (4-Mepy) to give nitro(5,10,15,20-tetra-
-1
Wavenumber / cm
Figure 2. IR spectrum of 4-methylpyridine: 1, 510; 2, 481 cm 1.7
ꢀ
III
phenylporphyrinato)(4-methylpyridine)-cobalt(III) ([Co (tpp)-
2
(
of [Co (tpp)(pip)(NO2)] (pip: piperidine) and band assignments
4-Mepy)(NO2)], (1)). Previously we reported the IR spectrum
III
ꢀ1 3
of the nitro group in the range of 2000 to 500 cm . There, the
asymmetric stretching, symmetric stretching, and deformation
ꢀ1
vibrations of the nitro group [ꢀas, ꢀs, and ꢁ (cm )] were
4
assigned. These bands for (C2H5OH)Co(TPP)(NO2) and
5
(a)
(b)
Fe(TPP)(NO2)(1-MeIm) are shown mainly in the 1800–
ꢀ
1
ꢀ1
800 cm region, and the spectra under 800 cm are not shown.
In this paper the IR spectra in the lower frequency region (500–
Figure 3. Out of plane skeletal deformation modes.
ꢀ
1
ꢀ
1
481 cm . As the average value of the two frequencies is
300 cm ) and the band assignments of the nitro group in 1 are
presented. The purpose of this work is to assign the Co–NO2
stretching band.
ꢀ1
6
496 cm , band 1 is attributable to the absorptions due to the
fifth ligand (L), 4-Mepy. The IR absorptions by L were scarcely
observed when L were piperidine (pip) and pyridine (py). But
when L is 4-Mepy the absorptions around 496 cm are very
strong and the absorptions of L may appear.
II
Compound 1 is obtained from [Co (tpp)(NO)], 4-Mepy, and
ꢀ
1
O2 gas at a pressure of 1 atm in 1,2-dichloroethane. After the
evaporation of solvent the crude 1 is recrystallized from a mix-
ture of dichloromethane and methyl alcohol. The IR spectra were
recorded on a JASCO DS-701G spectrometer in the range of
2þ
The IR spectrum of the analogous [Co(NO2)(NH3)5] ion
2) has already been reported, and the band appearing at
(
361 cm was assigned to the skeletal deformation bands as
ꢀ1
ꢀ
1
5
00–300 cm at room temperature using KBr pellets.
II
8
ꢀ1
shown in Figures 3a and 3b. Band 2 at 360 cm in 1 also seems
to be due to the same skeletal deformation bands as shown in 2.
But the absorption frequencies of band 2 were scarcely affected
by L and the rocking mode vibration of the nitro group also
The IR spectra of [Co (tpp)(NO)] and 1 are shown in
Figure 1. The band at 506 cm due to the nitrosyl group in
ꢀ1
II
[
new bands appeared at 496, 360, 346, 332, and 316 cm for
Co (tpp)(NO)] (Figure 1a) disappeared completely, and five
ꢀ
1
ꢀ
1
ꢀ1
appeared at 361 cm in 2; the possibility is not denied that
band 2 is also due to the rocking mode vibration in 1. If band 2
is attributed to the skeletal deformations as shown in Figure 3,
the absorption frequencies may change depending on L. Thus
it cannot be denied that band 2 is the overlapped bands of the
rocking and skeletal deformation mode vibrations as in the case
of 2.
1
under 500 cm . The assignments of these five bands are
described below.
The IR spectrum of free (noncoordinated) 4-Mepy is shown
in Figure 2.7 There are two strong absorptions at 510 and
(a)
ꢀ
1
Band 3 at 346 cm is shifted to higher frequencies when L
is py as is shown in Figure 4. In the case of 2 it was described that
some vibrations may be coupled together and reveal several
6
ꢀ1 8
bands in the region 400–250 cm . Similarly it may be often
difficult to assign one band to a pure vibration mode in the region
400–250 cm in 1. The absorption position (346 cm ) and the
shift by L indicate that band 3 may be assigned to the skeletal
deformation mode vibration (ꢀ12 ) as is shown in Figure 5b cor-
responding to the band at 335 cm in 2 and probably coupled
with other vibrations, ꢀ10 and ꢀ13 which are shown in
Figures 5a and 5c.
4
5
(b)
ꢀ1
ꢀ1
3
2
1
8
ꢀ
1
8
5
00
400-
300
1
Wavenumber / cm
ꢀ1
Bands 4 and 5 shift from 332 and 316 to 337 and 324 cm
as is shown in Figure 4 and Table 1 when L is changed from 4-
Mepy to py. These higher frequency shifts are the same as that of
Figure 1. IR spectra: (a) [Co(tpp)(NO)], 6: 506 cm 1; (b) 1, 1: 496; 2:
ꢀ
ꢀ
1
3
60; 3: 346; 4: 332; 5: 316 cm .
Copyright Ó 2009 The Chemical Society of Japan

Chemistry Letters Vol.38, No.1 (2009)
93
(
(
a)
b)
(
(
(
a)
b)
c)
(
c)
4
5
3
2
1
400
300
-1200
Wavenumber / cm
Figure 6. IR spectra of [Co(tpp)(L)(NO2)]: (a) L = py, (b) L = 4-Mepy,
8
(
c) 2.
500
400
Wavenumber / cm
300
-
1
Figure 4. IR spectra of [Co(tpp)(L)(NO2)]: (a) L = pip, (b) L = py,
c) L = 4-Mepy.
(
(
(
a)
b)
(
a)
(b)
(c)
2000
1500
1000 -1
500 300
Wavenumber / cm
Figure 5. Out of plane skeletal deformation modes.
Figure 7. IR spectra of nitrosyl and nitro complexes of porphyrinatoco-
balt (KBr pellets), (a) [Co(tpp)(NO)]; (b) 1.
Table 1. Some IR bands concern with metal–NO2 stretching vibrations
Band 3 Band 4 Band 5
the lower frequencies are very weak compared to that at the high
frequencies, and it seems more difficult to assign the spectra pre-
cisely in the lower frequencies region. Some metal–NO2 stretch-
ing IR bands are reported for various complexes, for example,
Complex
ref
cm 1
ꢀ
/cm
344
337
332
ꢀ1
/cm
335
324
316
482
ꢀ1
/
[
[
[
[
Co(tpp)(pip)(NO2)]
360
355
346
335
t. w.a
t. w.
t. w.
8
Co(tpp)(py)(NO2)]
Co(tpp)(4-Mepy)(NO2)]
Co(NO2)(NH3)5]2
ꢀ1
K3[Co(NO2)6] (418 cm ), Na3[Co(NO2)6] (451 and 373
þ
cm ),9 and recently for (iPr-TIC)Cu(NO2) (393 cm ), but
the absorption positions are considerably different for each
complex. The apparent couplings among the three bands in
[Co(tpp)(L)(NO2)] complexes as described above seem to be
characteristic for [Co(tpp)(L)(NO2)] complexes.
ꢀ1
ꢀ1 10
(290)
at. w. represents this work.
band 3. Thus bands 3, 4, and 5 may appear to be coupling with
each other. As band 3 is assigned to ꢀ12 (the skeletal deforma-
tion vibration) as described above, bands 4 and 5 can be assigned
to ꢀ13 and ꢀ10 (approximately the Co–NO2 stretching and Co–L
stretching vibrations), respectively. But it is difficult to decide
which one of the bands 4 or 5 corresponds to ꢀ13 or ꢀ10. Some
speculation is shown below that band 4 and band 5 are assigned
References and Notes
y
The experiments of this work were carried out at Faculty of Pharmaceutical
Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033
(between Jan., 1981-July, 1985); Present address: 1-15-2 Fujimoto,
Kokubunji, Tokyo 185-0031
ꢀ1
to ꢀ13 and ꢀ10. Band 4 shifts by 12 cm and band 5 shifts by
1
2
3
4
W. R. Scheidt, J. L. Hoard, J. Am. Chem. Soc. 1973, 95, 8281.
S. G. Clarkson, F. Basolo, Inorg. Chem. 1973, 12, 1528.
K. Yamamoto, Chem. Lett. 1991, 1509.
ꢀ1
1
9 cm when L is changed from 4-Mepy to pip. The shift of
band 4 is smaller than that of band 5. The vibration modes of
13 and ꢀ10 (Figure 5) show that though ꢀ10 is affected by L di-
rectly, ꢀ13 is not affected by L directly. So the effect of L may be
smaller in band 4 than in band 5. Thus band 4 is assigned to ꢀ13
and band 5 is assigned to ꢀ10 for the time being.
ꢀ
J. Goodwin, T. Kurtykian, J. Standard, R. Walsh, B. Zheng, D. Parmley,
J. Howard, S. Green, A. Mardyukov, D. E. Przybyla, Inorg. Chem. 2005,
4
4, 2215.
5
6
7
T. S. Kurtikyan, A. A. Hovhannisyan, G. M. Gulyan, P. C. Ford, Inorg.
Chem. 2007, 46, 7024.
The IR spectra of [Co(tpp)(L)(NO2)] complexes are shown
together with that of 2 to compare the spectra in Figure 6. It
shows that the couplings of the three bands (bands 3, 4, and 5)
are characteristically remarkable for [Co(tpp)(L)(NO2)] com-
plexes.
K. Yamamoto, Presented at the 88th Annual Meeting of the Chemical
Society of Japan, Tokyo, March 26–30, 2008, Abstr., No. 2A5-40.
Collection of Infrared spectra: Infrared Spectra and Characteristic Fre-
quencies 700–300 cm 1, ed. by F. F. Bentley, L. D. Smithson, A. L. Rozek,
ꢀ
Interscience Publishers, New York, 1968, Part III, S1175.
ꢀ27 (B1), ꢀ44 (B2), ꢀ10 (A1), ꢀ12 (A1), and ꢀ13 (A1), see: I. Nakagawa, T.
8
The IR spectra in the range of 2000–300 cm 1 are also
ꢀ
Shimanouchi, Spectrochim. Acta, Part A 1967, 23, 2099.
I. Nakagawa, T. Shimanouchi, K. Yamasaki, Inorg. Chem. 1964, 3, 772.
M. Kujime, C. Izumi, M. Tomura, M. Hada, H. Fujii, J. Am. Chem. Soc.
2008, 130, 6088.
shown to view the wide range of spectra for some representative
[Co(tpp)(NO)] and [Co(tpp)(4-Mepy)(NO2)] complexes in
Figure 7. It should be noted that the intensities of the bands in
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Published on the web (Advance View) December 20, 2008; doi:10.1246/cl.2009.92