Synthesis, characterization and spectral investigation of Salen-type cobalt(III) schiff base complexes. X-ray crystal structure of trans-[Co(Me-Salen)(3-acetylpyridine)2]ClO41

Article abstract of DOI:10.1134/S1070328412070093

Two new cobalt(III) complexes of the Schiff base N,N'- bis(methylsalicylidene)-1,2-ethylenedi-imine dianion (Me-Salen), trans-[Co(Me-Salen)(L)₂]ClO₄ (L = 3-acetylpyridine) (I) and (L = 4-acetylpy-ridine) (II), have been synthesized a

Full text of DOI:10.1134/S1070328412070093

ISSN 1070ꢀ3284, Russian Journal of Coordination Chemistry, 2012, Vol. 38, No. 8, pp. 573–578. © Pleiades Publishing, Ltd., 2012.
Synthesis, Characterization and Spectral Investigation
of SalenꢀType Cobalt(III) Schiff Base Complexes. Xꢀray Crystal
1
Structure of transꢀ[Co(MeꢀSalen)(3ꢀAcetylpyridine)2]ClO4
M. Salehia, *, K. Mereiterb, and M. Amirnasrc
a Department of Chemistry, Faculty of Science, Semnan University, Semnan, Iran
b Faculty of Chemistry, Vienna University of Technology, Vienna, Aꢀ1060 Austria
c Department of Chemistry, Isfahan University of Technology, Isfahan, 84156ꢀ83111 Iran
*eꢀmail: msalehi@sun.semnan.ac.ir; amf_salehi@yahoo.com
Received May 6, 2011
Abstract
imine dianion (MeꢀSalen), transꢀ[Co(MeꢀSalen)(L)2]ClO4 (L = 3ꢀacetylpyridine) (
ridine) (II), have been synthesized and characterized by elemental analyses, FTꢀIR, UVꢀVis, and 1H NMR
spectroscopy. The Xꢀray diffraction analysis reveals that I crystallizes in the monoclinic space group 21/ and
—
Two new cobalt(III) complexes of the Schiff base N,N'ꢀbis(methylsalicylidene)ꢀ1,2ꢀethylenediꢀ
I
) and (L = 4ꢀacetylpyꢀ
P
c
displays a distorted octahedral coordination geometry about Co with the equatorial plane formed by the N2O2
donors of the tetradentate Schiff base dianion, the two phenolate O atoms and the two imine N atoms of which
are each mutually in cisꢀposition. Two 3ꢀacetylpyridine molecules are attached to the metal atom to fill its axial
positions.
DOI: 10.1134/S1070328412070093
INTRODUCTION
lective reduction [9]. Cobalt(III) Schiff base comꢀ
plexes with two amines in axial positions have also
been used as antibacterial agents [10]. This study
aims to obtain new coordinative compounds with
similar properties. Therefore, the present paper
describes the synthesis, characterization and the
spectroscopic study of two new cobalt(III) comꢀ
plexes with the general formula presented in the folꢀ
The condensation of primary amines with carboꢀ
nyl compounds yields Schiff bases [1, 2]. In the
recent years, there has been considerable interest in
the chemistry of transition metal complexes of tetꢀ
radentate Schiff bases [2–4]. The cobalt complexes
of such ligands have been extensively used to mimic
cobalamin (B12) coenzymes [5, 6], as oxygen carriꢀ
ers and oxygen activators [7, 8], and for enantioseꢀ lowing scheme:
+
b
L
H
a
H
H3C
CH3
H3C
CH3
N
O
N
N
N
d
II
Co
L
Co (CH COO)
⋅ 4H O
2 2
3
methanol
ClO4–
e
OH HO
O
g
f
N
N
i
j
h
h
i
h
c
L =
L =
i
CH3
k
O
O
CH3
(I)
(II
)
1
The article is published in the original.
573

574
SALEHI et al.
The Xꢀray crystal structure of the complex trans
ꢀ
and a green solid product was obtained after four days.
[Co(MeꢀSalen)(3ꢀacetylpyridine)2] ClO4 (
studied.
I)
was also The yield was 55%.
For C32H32ClN4O8Co
anal. calcd., %:
Found, %:
C, 55.30;
H, 4.64;
H, 4.64;
N, 8.06.
N, 7.95.
EXPERIMENTAL
C, 54.62;
Materials and methods. All solvents and chemicals
were used as received, except for the amines which
were distilled under reduced pressure prior to use. Elꢀ
emental analyses were performed by using a Perkinꢀ
Elmer 2400II CHNSꢀO elemental analyzer. Infrared
spectra (KBr pellets) were obtained on a FTꢀIR
JASCO 680 plus spectrophotometer. UVꢀVis spectra
were recorded on a JASCO Vꢀ570 spectrophotometer.
1H NMR spectra of the complexes were obtained on a
Bruker Avance DR X500 (500 MHz) spectrometer.
Proton chemical shift are reported in part per million
(ppm) relative to an internal standard of Me4Si.
FTꢀIR (KBr,
ν
, cm–1): 1598
ν
(C=N), 1091 ν(Cl–O)
, l mol–1 cm–1)): 254
UVꢀVis (CHCl3; λmax, nm (
(45624), 377 (7593), 526 (400). 1H NMR (500 MHz;
CDCl3; , ppm): 2.50 (s., 6Ha), 2.88 (s., 6Hc), 4.30
ε
δ
(m., 4Hb), 6.50 (t., 2He), 7.16 (d., 4Hg), 7.30 (t., 2Hf),
7.38(m., 2Hd) 7.64 (d., 2Hi), 8.38 (d., 4Hh).
Xꢀray structure determination. Brown crystals suitꢀ
able for Xꢀray crystallography were obtained by slow
evaporation of methanol solution of the complex
room temperature. Xꢀray data were collected on a
Bruker Kappa APEXꢀ2 CCD diffractometer with
graphite monochromated Mo = 0.71073 ) radiꢀ
ꢀscan frames covering a comꢀ
I at
Synthesis of H2MeꢀSalen. H2MeꢀSalen, N,N'ꢀ
bis(methylsalicylidene)ꢀ1,2ꢀethylenediamine,
prepared as reported in the literature [11] by the conꢀ
densation of 1,2ꢀethylenediamine with 2ꢀhydroxyaceꢀ
tophenone (2 : 1 mol stoichiometric ratio) in methaꢀ
nol at room temperature, and was recrystallized from
hot methanol. The yield was 80%.
was
K
(λ
Å
α
ation and 0.5° ωꢀ and
ϕ
plete sphere of the reciprocal space. Cell refinement
and data reduction were performed with the help of
the SAINT program [12]. Corrections for absorption
were carried out with the multiꢀscan method and proꢀ
gram SADABS [12]. The structure was solved using diꢀ
FTꢀIR (KBr;
(C=N). UVꢀVis (CH3CN; λmax, nm (
380 (960), 318 (7248), 252 (16600).
Synthesis of complex I. To a stirring solution of
Co(CH3COO)2 4H2O (0.125 g, 0.5 mmol) in methaꢀ
ν
, cm–1): 3383–3483 m, br
ν
(OH), 1610 s
, l mol–1 cm–1)):
rect methods (SHELXSꢀ97) and refined against F
2 usꢀ
ν
ε
ing SHELXLꢀ97 [13]. All nonꢀhydrogen atoms were
refined anisotropically. Hydrogen atoms were inserted
in idealized positions and refined riding with the atꢀ
oms to which they were bonded. A significant differꢀ
ence Fourier peak between two symmetry equivalent
⋅
nol (25 mL) was added an equimolar amount of
H2MeꢀSalen (0.148 g, 0.5 mmol). The pink solution
turned red brown immediately upon the formation of
[CoII(MeꢀSalen)] complex. To this solution was added
4 mmol of 3ꢀacetylpyridine, and air was bubbled
through the reaction mixture for about 3 h. The resultꢀ
ing brown solution was filtered off and 0.5 mmol
NaClO4 in 5 mL methanol was added to the filtrate and
ClO4 groups (Ci related) was attributed to a substoichiꢀ
ometric water molecule of crystallization and was reꢀ
fined in population parameter, pp = 0.256(12), as an oxꢀ
ygen atom without hydrogen atoms. The crystalloꢀ
graphic and refinement data are summarized in Table 1.
The atomic coordinates and other parameters of strucꢀ
ture I have been deposited with the Cambridge Crystalꢀ
lographic Data Centre (no. 813875; deposit@ccdc.
cam.ac.uk or http://www.ccdc.cam.ac.uk).
stirred for 5 min. Brown crystals of complex I suitable
for Xꢀray crystallography were obtained after three days
by slow evaporation of the solvent. The yield was 60%.
For C32H32ClN4O8Co
RESULTS AND DISCUSSION
anal. calcd., %:
Found, %:
C, 55.30;
C, 54.85;
H, 4.64;
H, 4.67;
N, 8.06.
N, 7.96.
The Schiff base and two complexes were readily
synthesized in methanol solutions. The complexes are
stable in air at room temperature, soluble in methanol,
ethanol, acetonitrile, DMF, a n d D M S O . T h e s t r u c ꢀ
ture of the H2MeꢀSalen was confirmed by the FTꢀIR
and UVꢀVis spectra. The FTꢀIR spectrum of the
H2MeꢀSalen shows a broad absorption band of the
FTꢀIR (KBr;
ν
, cm–1): 1598
ν
(C=N), 1091 ν(Cl–O)
, l mol–1 cm–1)): 259
UVꢀVis (CHCl3; λmax, nm (
(55625), 376 (8728), 529 (390). 1H NMR. (500 MHz;
CDCl3; , ppm): 2.46 (s., 6Ha), 2.92 (s., 6Hc), 4.35
ε
δ
(m., 4Hb), 6.53 (t., 2He), 7.17 (d., 4Hg), 7.32 (t., 2Hf),
7.44 (m., 4Hd,j) 8.15 (d., 2Hk), 8.29 (d., 4Hi), 8.80 (s.,
2Hh).
OH group in the 3383–3483 cm–1 region. The
ν
(C=N) band appearing at 1610 cm–1 is shifted to
lower energies (1601 cm–1) in the spectra of the comꢀ
Synthesis of complex II. This complex was preꢀ plexes, indicating that the ligands are coordinated to
pared by the same method as for except that the metal ions through the nitrogen atoms of the
4ꢀacetylpyridine was used instead of 3ꢀacetylpyridine azomethine groups [14].
I
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 38
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2012

SYNTHESIS, CHARACTERIZATION AND SPECTRAL INVESTIGATION
575
Table 1. Crystal data, data collection and structure refineꢀ
ment for complex
The electronic absorption spectrum of H2MeꢀSalen
in acetonitrile consists of two relatively intense bands
I*
centered at 252 and 318 nm, assigned to the π → π
transitions of the benzene ring of salicylaldehyde and
the azomethine group, respectively, and a third band at
380 nm, corresponding to → π* which, upon coorꢀ
*
Parameter
Chemical formula
Value
n
C32H32ClCoN4O8
695.00
dination of the ligand, disappears from the UVꢀVis
spectra of the cobalt complexes. The first d–d transiꢀ
tion in the two cobalt complexes is observed as a disꢀ
Formula weight
Color; habit
tinct shoulder at about 529 nm (
~ 390 L mol–1 cm–1)
ε
Brown; prism
Monoclinic
for
I
and 526 nm ( .
~ 400 L mol–1 cm–1) for II
ε
Crystal system
Crystal size, mm
Space group
1
The H NMR spectroscopic data of cobalt comꢀ
plexes
The 1H NMR spectrum of
(assignment as in Scheme). Two signals appearing as a
singlet at 2.46 and 2.92 ppm for and at 2.50 and
I
and II are given in the experimental section.
0.20
×
0.25
21/
×
0.46
I
in CDCl3 is shown in Fig. 1
P
c
I
a
, Å
, Å
, Å
6.8528(5)
26.1942(19)
17.2923(15)
98.255(4)
3071.9(4)
4
2.88 ppm for II assigned to two sets of CH3 protons,
Ha and Hc, respectively. The signal due to the aliphatic
protons of the ethylene chelate ring, Hb, is observed as
b
a multiplet at 4.35 ppm for I and at 4.30 ppm for II.
c
The presence of the aromatic protons of the
phenyl rings and those of the axial (3ꢀacetylpyridine)
and (4ꢀacetylpyridine) amines as complex multiplets
located between 6.53 and 8.80ppm (Hd, He, Hf, Hg,
β
V
Z
, deg
, Å3
Hh, Hi, Hj, Hk) in
I and between 6.50 and 8.38 ppm
(Hd, He, Hf, Hg, Hh, Hi) in II
.
ρcalcd, g cm–3
1.512
Figure 2 gives perspective view of the asymmetric
unit of complex I. The solid state form of complex is
a disordered solvate Solv, where Solv is most likely a
partially occupied water molecule (O9 , occupancy
only about 25% at the time of the Xꢀray experiment)
that appears to be hydrogen bonded to two neighborꢀ
ing ClO4 groups at O⋅⋅⋅O distances of 2.56 and 2.90
Fig. 3 shows a packing diagram of the compound inꢀ
cluding the solvent peaks O9s. Selected bond lengths
and angles of the Co complex in are given in Table 2.
The MeꢀSalen ligand in shows a cisoid conformation
and chelates the Co atom by two imine nitrogen atoms
and two phenolate oxygen atoms in a squareꢀlike fashꢀ
ion. Two 3ꢀacetylpyridine molecules attached to the
metal atom via their nitrogens fill its axial sites and
adopt a mutually perpendicular disposition with a diꢀ
I
I
·
F
(000)
1448
s
μ
, mm–1
0.705
Å
.
Crystal sise, mm
Range for data collection, deg
0.20
×
0.25
×
0.46
θ
2.5–27.0
I
Index range (hkl)
–8
≤
h
≤
8, –33
≤
k ≤ 33,
I
–22 22
≤
l
≤
Measured refflections
36894
Unique refflections (Rint
)
6662 (0.058)
4883
hedral angle of 79.5
ments the MeꢀSalen ligand is strongly curved with its two
phenyl rings directed to the first 3ꢀacetylpyridine. The inꢀ
terplanar angle of the two MeꢀSalen phenyl rings is 48.7
The coordination geometry about the Co(III) atom is
distorted octahedral with the trans and cis angles lying in
the ranges 177.40(11) –179.93(13) and 86.41(10)
93.65(10) , respectively. Two related structures with
°. Due likely to packing requireꢀ
Observed refflections with
> 2 ))
(I
σ(I
°.
Parameters
429
Goodness of fit on F2
1.03
°
°
°–
°
Final
R
indices (
I
> 2σ(
I))
R
1 = 0.0532, wR2 = 0.1170
amine ligands, trans[CoIII(MeꢀSalpn)(Py)2]PF6 [15]
and transꢀ[Co(Tmsalen)(Py)2]ClO4 [16], have been
reported and the bond angles around the metal comꢀ
pare well with the values determined for I. For examꢀ
ple, all angles around the Co center deviate signifiꢀ
R
indices (all data)
Å–3
R1 = 0.0808, wR2 = 0.1345
Δρmax/Δρmin, e
cantly from 90
86.6(3)°–93.9(3)°) [16]. The two phenolic oxygen atꢀ
°
(83.57(8)
°
–96.25(8)
°
[15] and * Chemical formula and derived quantities for
I (= I ⋅ Solv) disreꢀ
gard the solvent content, see text for details.
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576
SALEHI et al.
Ha
O
CH3
Hc
N
Hb
H
a
H3C
CH3
N
O
N
d
Co
N
c
O
Hb
g
f
i
j
h
c
CH3
k
O
Hh
Hf
Hd, j
Hi
Hg
Hk
He
δ
, ppm
9
8
7
6
5
4
3
2
1
1
Fig. 1. H NMR spectrum of complex
I
in CDCl .
3
O(8)
O(6)
C(32)
Cl(1)
O(8S)
C(31)
O(5)
O(7)
C(29)
C(28)
O(4)
C(27)
C(26)
C(30)
C(10)
C(11)
C(9)
N(1)
N(4)
N(2)
C(12)
O(2)
C(13)
C(14)
C(17)
C(8)
C(7)
C(15)
Co(1)
N(3)
C(18)
C(1)
O(1)
C(23)
C(6)
C(16)
C(5)
C(2)
C(19)
C(20)
C(3)
C(4)
C(22)
C(21)
O(3)
C(24)
C(25)
Fig. 2. The asymmetric unit of complex
I with two C–H⋅⋅⋅O hydrogen bonds (dashed lines).
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 38
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SYNTHESIS, CHARACTERIZATION AND SPECTRAL INVESTIGATION
577
x
0
z
y
Fig. 3. The crystal packing of complex
I
as seen along [100] direction. The dashed lines denote hydrogen bonds.
Table 3. Geometric parameters of hydrogen bonds for comꢀ
plex
Table 2. Selected bond distances and bond angles for comꢀ
plex
I*
I
Distance, Å
D–H H⋅⋅⋅
Bond
d
, Å
Bond
d, Å
Angle
DHA,
deg
Contact D–H⋅⋅⋅
A
A
D⋅⋅⋅A
Co(1)–O(1)
Co–O(2)
1.877(2) Co(1)–N(2)
1.881(2) Co(1)–N(3)
1.889(3) Co(1)–N(4)
1.908(3)
1.961(3)
1.970(3)
C(8)–H(8
C)
⋅⋅⋅(O)3i
0.98 2.59 3.426(4) 144
0.99 2.46 3.236(4) 135
0.95 2.32 3.202(4) 153
0.95 2.48 3.187(4) 131
0.95 2.58 3.465(4) 156
Co(1)–N(1)
C(9)–H(9B)⋅⋅⋅(O)7
C(14)–H(14)⋅⋅⋅(O)4ii
C(22)–H(22)⋅⋅⋅(O)3iii
C(21)–H(21)⋅⋅⋅(O)6iv
Angle
ω
, deg
Angle
ω
, deg
O(1)Co(1)N(2) 179.93(13) O(2)Co(1)N(3) 91.70(11)
O(2)Co(1)N(1) 177.40(11) O(2)Co(1)N(4) 88.17(10)
N(3)Co(1)N(4) 177.42(11) N(1)Co(1)N(2) 87.20(11)
O(1)Co(1)O(2) 86.41(10) N(1)Co(1)N(3) 90.74(11)
O(1)Co(1)N(1) 92.74(10) N(1)Co(1)N(4) 89.35(11)
O(1)Co(1)N(3) 89.31(10) N(2)Co(1)N(3) 90.68(11)
O(1)Co(1)N(4) 88.11(10) N(2)Co(1)N(4) 91.90(11)
O(2)Co(1)N(2) 93.65(10)
C(25)–H(25
C)
⋅⋅⋅(O)6iv 0.98 2.52 3.325(5) 140
C(28)–H(28)⋅⋅⋅(O)6v
0.95
2.5 3.380(5) 154
C(32)–H(32
A)
⋅⋅⋅(O)6v
0.98 2.43 3.384(5) 164
0.98 2.37 3.335(7) 168
C(32)–H(32C)⋅⋅⋅(O)8
* Symmetry transformation used to generate equivalent atoms:
i
ii
iii
–1 +
x
, 1/2 –
y
, –1/2 +
z
; 1 –
x, 1 –
y, 1 –
z;
–1 + x, y, z;
iv
v
–x, –1/2 +
y
, 1/2 –
z; 1 + x, y, z.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 38
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578
SALEHI et al.
2. Nakajima, K., Ando, Y., Mano, H., and Kojima, M.,
Inorg. Chim. Acta, 1998, vol. 274, p. 184.
3. G lc , A., Tumer, M., Demirelli, H., and Wheatley, R.A.,
Inorg. Chim. Acta, 2005, vol. 358, p. 1785.
4. Chaviara, A.T., Christidis, P.C., Papageorgiou, A.,
et al., J. Inorg. Biochem. 2005, vol. 99, p. 2102.
5. Aly, M.M., J. Coord. Chem., 1998, vol. 43, p. 89.
6. Cini, R., Moore, S.J., and Marzilli, L.G., Inorg. Chem.,
1998, vol. 37, p. 6890.
7. Henson, N.J., Hay, P.J., and Redono, A., Inorg. Chem.,
1999, vol. 38, p. 1618.
8. Bianchini, C. and Zoellner, R., Adv. Inorg. Chem.,
1997, vol. 44, p. 263.
9. Nagata, T., Yorozu, K., Yamada, T., and Mukaiyama, T.,
Angew. Chem. Int. Ed., 1995, vol. 34, p. 2145.
oms and the two imine nitrogen atoms are located in
cis positions. The average Co–Neq distance (1.898 ) is
slightly longer than that of [16] (1.884 ) and distinctly
shorter than that of [15] (1.963 ). The Co–O distances
(Co(1)–O(1) 1.877(2) and Co(1)–O(2) 1.881(2)
compare well with those reported for[15] (Co(1)–O(1)
1.884(2) and Co(1)–O(2) 1.887(2) ) and for [16]
(Co(1)–O(1) 1.867(6) and Co(1)–O(2) 1.863(7) ).
In the crystal structure the Co complexes are arranged
in undulating infinite layers parallel to (100) with the
ClO4 anions and the disordered substoichiometric solꢀ
vent located between the layers (Fig. 3). A larger numꢀ
Å
ö
ü
Å
Å
Å
Å)
Å
Å
Å
Å
ber of C⎯H⋅⋅⋅O hydrogen bonds to the 3ꢀacetylpyriꢀ
dine and ClO4 oxygen atoms contributes to the coherꢀ
ence of the structure and is listed in Table 3.
10. Bottche, A. Takeuchi, T., Hardcastle, K.I., et al., Inorg.
Chem., 1997 vol. 36, p. 2498.
11. Hariharan, M. and Urbach, F.L., Inorg. Chem., 1969,
Significant arene
sent.
π–πꢀstacking interactions are abꢀ
vol. 8, p. 556.
12. APEX2 (version 2008), SAINT (version 7.53A), SADꢀ
ABS (version 2008/3), SHELXTL (version 2008/4),
Madison (WI, USA): Bruker AXS Inc., 2009.
13. Sheldrick, G.M., Acta Crystallogr., A, 2008, vol. 64, p. 112.
14. Amirnasr, M., Vafazadeh, R., and Mahmoudkhani, A.,
ACKNOWLEDGMENTS
M. Salehi thanks Semnan University for supportꢀ
ing this study.
Can. J. Chem., 2002, vol. 80, p. 1196.
15. Schenk, K.J., Meghdadi, S., Amirnasr, M., et al., Polyꢀ
hedron, 2007, vol. 26, p. 5448.
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RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 38
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2012