Synthesis and structural characterization of supramolecular mn(II)-Li(I) complex with salen-type bisoxime

Article abstract of DOI:10.14233/ajchem.2013.13942

Supramolecular manganese(II)-Li(I) complex, [MnL(OH)(H₂O)Li]n, has been prepared and characterized by elemental analyses, FTIR, UV-visible spectra, molar conductance measurement and X-ray crystallography (where H ₂L = 4,4′,6,6'-tetra

Full text of DOI:10.14233/ajchem.2013.13942

Asian Journal of Chemistry; Vol. 25, No. 8 (2013), 4289-4292
http://dx.doi.org/10.14233/ajchem.2013.13942
Synthesis and Structural Characterization of Supramolecular
Mn(II)-Li(I) Complex with Salen-Type Bisoxime
*
XIU-YAN DONG , LI WANG, YU-HUA YANG, FA WANG and YUAN LI
School of Chemical and Biological Engineering, Lanzhou Jiaotong University, Lanzhou 730070, P.R. China
*Corresponding author: E-mail: dxy568@163.com
(Received: 23 April 2012;
Accepted: 9 February 2013)
AJC-12946
Supramolecular manganese(II)-Li(I) complex, [MnL(OH)(H2O)Li]n, has been prepared and characterized by elemental analyses, FT-
IR, UV-visible spectra, molar conductance measurement and X-ray crystallography (where H2L = 4,4',6,6'-tetrachloro-2,2'-
[ethylenedioxybis(nitrilomethylidyne)]diphenol). The complex is self-assembled using various non-covalent interactions including
hydrogen bonding interactions and π-π stacking to form chain supramolecular structure.
Key Words: Salen-type bisoxime, Complex, Synthesis, Crystal structure.
ER/S·WP-1 ICP atomic emission spectrometer. IR spectra were
recorded on a VERTEX70 FT-IR spectrophotometer, with
samples prepared as KBr (4000-500 cm-1) and CsI (500-100
INTRODUCTION
In the past decades, the complexes containing transition
metal ions and various Schiff-base ligands have been exten-
sively investigated due to their novel structures and potential
applications in many fields1. Particularly, a large number of
transition metal complexes of Salen-type ligands derived from
the condensation of salicylaldehyde and its derivatives with
various primary amines become the hot topics of contemporary
research2. The Salen-type bisoxime ligands have been reported
by using an O-alkyloxime unit (-CH=N-O-(CH)2-O-N=CH-)
instead of the (-CH=N-(CH)2-N=CH-) group, which can lead
to different and novel properties and structures of the resulted
complexes3-5. but the Mn(II) complexes with salen-type
bisoxime ligands have been reported rarely. In this paper, we
report the synthesis, characterization and X-ray crystal
structure of the µ-oxo bridged [MnL2(OH)(H2O)Li]n complex
with tetradentate Salen-type bisoxime ligand. The complex is
self-assembled using various non-covalent interactions including
hydrogen bonding interaction6 and π-π stacking7 to form chain
supramolecular structure.
1
cm-1) pellets. H NMR spectra were determined by German
BrukerAVANCE DRX-400 spectroscopy. X-Ray single crystal
structure determination was carried out on a Bruker Smart
1000 CCD diffractometer. Molar conductance value measure-
ment was carried out on a model DDS-11D type conductivity
bridge using 1.0 × 10-3 mol × dm-3 solution in DMF at 18 ºC.
Melting points were obtained by use of a microscopic melting
point apparatus made in Beijing Taike Instrument Limited
Company and were uncorrected.
General procedure
4,4',6,6'-Tetrachloro-2,2'-[ethylenedioxybis(nitrilo-
methylidyne)]diphenol (H2L): H2L was prepared according
to an analogous method reported earlier5,10,11. By mixing of
3,5-dichloro-2-hydroxybenzaldehyde (399.0 mg, 2.10 mmol)
and 1,2-bis(aminooxy)ethane (180.1 mg, 1.05 mmol) in ethanol
solution (8 mL), a pale-yellow solution was obtained. After
the solution had been stirred at 55 ºC for 3 h, the mixture was
filtered, washed successively with ethanol and hexane, respec-
tively. The product was dried under reduced pressure and
purified with recrystallization from ethanol to yield 318.95
mg of colourless crystalline solid. Yield 72.8 %. m.p. 204-
205 ºC. Anal. calcd. (%) for C16H12N2O4Cl4: C, 43.87; H, 2.76;
N, 6.39. Found (%): C, 43.95; H, 2.68; N, 6.28. 1H NMR (400
MHz, DMSO-d6, δ, ppm) 4.48 (s, 4H, CH2), 7.53 (t, J = 2.6
Hz, 2H, Ar-H), 7.61 (t, J = 2.6 Hz, 2H, Ar-H), 8.47 (d, J = 2.0
Hz, 2H, =C-H), 10.38 (s, 2H, OH).
EXPERIMENTAL
3,5-Dichlorosalicylaldehyde was purchased from Alfa
Aesar and used without further purification. 1,2-Bis(aminooxy)-
ethane was synthesized according to an analogous method
reported earlier8,9. The other reagents and solvents were of
analytical reagent grade and were used without further purifi-
cation. C, H and N analyses were obtained using a GmbH
VarioEL V3.00 automatic elemental analysis instrument.
Elemental analyses for Mn and Li were detected by an IRIS

4290 Dong et al.
Asian J. Chem.
[MnL(OH)(H2O)Li]n: A solution of Mn(II) acetate
in Fig. 1. Selected bond distances and angles of the complex
are listed in Table-2.
tetrahydrate (12.3 mg, 0.05 mmol) in methanol (15 mL) was
added dropwise to a solution of H2L (21.9 mg, 0.05 mmol) in
THF (45 mL) at room temperature. The colour of the mixing
solution turned to yellow immediately.After 10 min, LiCl (4.2
mg, 0.1 mmol) dissolved in the minimum amount of water,
was poured into the solution. After continuing stirring for 5
days at room temperature, the mixture was filtered and the
filtrate was allowed to stand at room temperature for several
weeks. Then the solvent partially evaporated and yellow
needle-like single crystals suitable for X-ray crystallographic
analysis were obtained. Yield: 35.7 %. Anal. calcd. (%) for
C16H13Cl4LiMnN2O6 ([MnL(OH)(H2O)Li]n): C, 36.12; H, 2.39;
Li, 1.30; Mn, 10.33; N, 5.22. Found (%): C, 36.11; H, 2.43;
Li, 1.31; Mn, 10.29; N, 5.24.
X-Ray structure determination: The crystal data and
structure refinement for [MnL(OH)(H2O)Li]n is given in Table-1.
The single crystal of [MnL(OH)(H2O)Li]n with approximate
dimension of 0.40 mm × 0.13 mm × 0.02 mm were placed on
a Bruker Smart 1000 CCD area detector. The diffraction were
collected using a graphite monochromated MoKα radition (λ
= 0.71073 Å) at 298(2) K. The structure was solved by using
the program SHELXL-97 and Fourier difference technique
and refined by full-matrix least-square method on F2. All
hydrogen atoms were added theoretically.
Fig. 1. Molecule structure of the title complex with atom numbering
scheme. Displacement ellipsoids for non-hydrogen atoms are drawn
at the 30 % probability level
The complex has been synthesized from the reaction of
the ligand (H2L), Mn(II) acetate tetrahydrate and LiCl in
mixing solution and revealed by X-ray crystallography. The
complex is crystallized in the monoclinic system, space group
C2/c. The structural of [MnL2(OH)(H2O)Li]n adopts a slightly
distorted octahedral geometry with a hexa-coordinated Mn(II)
center. L2- unit behaves as a tetradentate agent via two phenolic
oxygen and two oxime nitrogen atoms, which are in the
equatorial positions. The Mn-O (phenolic) bond of 2.122(2)
Å and Mn-N(oxime) bond of 2.307(3) Å are in agreement
with the average bond lengths seen for the corresponding bonds
in the Mn(II) complexes bearing tetradentate salen-type ligands
in a planar fashion12. The four N2O2 donor atoms of L2- unit
are approximately coplanar and the dihedral angle of O2-Mn1-
N1 and O2i-Mn1-N1i is 2.08º. The axial sites of Mn(II) atom
is occupied by two oxygen atoms of one coordinated water
molecule and one hydroxy group in a considerably large angle
of O3-Mn1-O3i (167.63(14)º). It is noticeably that the bond
distance Mn1-O3 (2.152(3) Å) is the same with Mn1-O3i,
which indicate the same coordination abilities of the two µ-oxo
bridges.
In addition, every monomer of the complex contains a
Li(I) atom. The coordination geometry around the Li(I) (Li1)
atom can be best described as slightly distorted square pyra-
midal geometry with unexpected penta-coordinated. Two
phenolic oxygen atoms (O2ii and O2iv) and two chlorine (Cl1ii
and Cl1iv atoms of L2- unit constitute the basal plane and one
oxygen atoms from the bridging hydroxy group in the axial
position. The distance of Mn1···Li1ii (2.800(15) Å) is signifi-
cantly longer than all the Mn-O and Mn-N bonds in the com-
plex, indicating a weaker intermetal interaction. The complex
has four intermolecular hydrogen bonds (O3-H3A···O2, O3-
H3B···O2, O3-H3A···Cl1 and O3-H3B···Cl1) which help to
connect the individual monomer to form and stabilize the three-
dimensional structure (Table-3). The special interest of the
complex is its self-assembling Mn(II)-O-Li(I) chain array
stacked by hydrogen bonding interactions and π-π stacking of
TABLE-1
CRYSTAL DATA AND STRUCTURE
REFINEMENT FOR THE TITLE COMPLEX
Empirical formula
Formula weight
Temperature
C16H13Cl4LiMnN2O6
532.96
298(2) K
Wavelength
0.71073 Å
Crystal system
Space group
Monoclinic
C2/c
Cell dimensions
a = 17.2609(18) Å, b = 15.1325(16)
Å, c = 7.7642(9) Å, β = 97.1480(10)
Volume
2012.3(4) Å3
Z
4
Density (calculated)
Absorption coefficient
F(000)
1.759 mg/m3
1.225 mm-1
1068
Index ranges
-20 ≤ h ≤ 19, -14 ≤ k ≤18, -9 ≤ l ≤ 9
5052/1762 [R(int) = 0.0314]
2092
1762/0/137
0.981
R1 = 0.0441, wR2 = 0.1153
0.694 and -0.367 e. Å
Reflections collected/unique
Independent reflections
Data/restraints/parameters
Goodness of fit indicator
R [I > 2σ(I)]
Largest diff. peak and hole
RESULTS AND DISCUSSION
Crystal structure of [MnL(OH)(H2O)Li]n: Interaction
of Mn(II) acetate tetrahydrate with the appropriate Salen-type
ligand in a basic medium yields [MnL(OH)(H2O)Li]n depending
on the time of reaction. Suitable single crystals of the complex
was obtained by natural evaporation method. X-Ray single
crystal determination shows that the complex forms a self-
assembling continual supramolecular structure by hydrogen
bonding interactions and π-π stacking. The atom numbering
and the chain supramolecular structure of the complex is given

Vol. 25, No. 8 (2013)
Synthesis of Supramolecular Mn(II)-Li(I) Complex with Salen-Type Bisoxime 4291
TABLE-2
SELECTED BOND DISTANCES (Å) AND ANGLES (º) FOR THE TITLE COMPLEX
Bond
Mn1-O2
Lengths
2.122(2)
2.122(2)
2.152(3)
2.152(3)
Angles
Bond
Mn1-N1i
Lengths
2.307(3)
2.307(3)
2.800(15)
1.761(3)
Angles
Bond
Li1-O2iv
Lengths
2.058(10)
2.058(10)
3.003(7)
3.003(7)
Angles
Mn1-O2i
Mn1-N1
Li1-O2ii
Mn1-O3i
Mn1-O3
Bond
Mn1-Li1ii
Li1-Cl1iv
Li1-O3iii
Li1-Cl1ii
Bond
Bond
C(10)-N(1)-O(1)
O2-Mn1-O2i
O2-Mn1-O3
O3i-Mn1-O3
O2-Mn1-N1
113.3(5)
93.96(13)
94.07(10)
167.63(14)
79.61(10)
C(11)-C(12)-C(13)
N1i-Mn1-N1
O2-Mn1-Li1ii
N1-Mn1-Li1ii
O3-Mn1-N1
116.9(6)
106.84(16)
46.98(6)
126.58(8)
84.78(11)
O(4)-C(23)-C(24)
O3-Mn1-Li1ii
Li1-O3-Mn1
O2ii-Li1-Cl1ii
Cl1iv-Li1-Cl1ii
121.9(6)
96.18(7)
165.4(5)
68.11(9)
126.4(5)
Symmetry transformations used to generate equivalent atoms: (i) -x+1,y,-z+1/2 (ii) -x+1,-y+1,-z (iii) -x+1,y,-z-1/2 (iv) x,-y+1,z-1/2.
TABLE-3
HYDROGEN BONDS [Å, º] FOR THE TITLE COMPLEX
D–H···A
d(D–H)
d(H···A)
d(D···A)
Symmetry
∠DHA
144
129
153
120
O3-H3A···O2
O3-H3A···Cl1
O3-H3B···O2
O3-H3B···Cl1
0.85
0.85
0.85
0.85
2.18
2.79
1.93
2.89
2.913(3)
3.393(3)
2.714(3)
3.398(3)
-x+1, -y+1, -z
-x+1, -y+1, -z
x, -y+1, z-1/2
x, -y+1, z-1/2
TABLE-4
neighboring benzene rings (Fig. 2). Two neighboring monomers
have the anti-conformation, the angle of the two neighboring
benzene rings is 0.87(3)º and the mean distance between the
two neighboring benzene rings is 3.638 Å, indicating weak
π-π stacking interaction.
KEY IR BANDS FOR THE LIGAND
AND THE TITLE COMPLEX (cm-1)
Compound
ν(O-H) ν(CHarom
)
ν(CH2)
ν(C=N ) ν(C-O)
H2L
Complex
3427
3414
3078
3079
2963, 2899
2955, 2891
1609
1603
1277
1304
to lower frequency by ca. 6 cm-1 upon complexation. At the
same time, C-Ophenol stretching frequency appears as a strong
band in the compound. This band occurs at 1277 cm-1 for H2L
and at 1304 cm-1 for the complex. The C-Ophenol stretching band
is shifted to higher frequency by 27 cm-1 upon complexation.
These data suggest the coordination of the ligand in their
dianionic form to the Mn(II) atom through the phenol oxygen and
the oxime nitrogen atoms and show the tetradentate character
of the ligand in the complex13-15. Additionally, strong and broad
bands at 3414 cm-1 indicates that O-H is existent in the complex.
The far-infrared spectrum of the complex is also obtained
in the region 500-100 cm-1 in order to identify frequencies
due to the ν(Mn-O) and ν(Mn-N) bonds. IR spectrum of the
complex shows ν(Mn-N) and ν(Mn-O) vibrational absorption
frequencies at 473 and 448 cm-1, respectively, which are consis-
tent with the literature frequency values16. These bands are
observed as new peaks for the complex are not present in the
spectrum of the free ligand.
UV-visible absorption spectra: The UV-visible absorp-
tion spectra of the ligand H2L and its corresponding complex
in diluted DMF solution are shown in Fig. 3. It can be seen
that the absorption peaks of the complex are obviously different
from those of the free ligand upon complexation. Compared
with the complex, an important feature of the absorption
spectrum of H2L is shown that one absorption peak is observed
at 324 nm, which is absent in the spectrum of the complex.
The other feature is that the absorption peak at 268 nm in H2L
is shifted to 266 nm in the complex and a new absorption
peak at 377 nm was observed in the complex, indicating that
the coordination of Mn(II) atom with H2L.
Fig. 2. View of the 1D chain supramolecular structure of Mn(II)-Li complex
along the a axis (hydrogen atoms, except those forming hydrogen
bonds, are omitted for clarity)
Molar conductance: Molar conductance values of the
complex at 18 ºC of 10-3 mol × dm-3 DMF solution is 7.6 S ×
cm2 × mol-1, indicating that the complex is non-electrolyte.
This implies that all the Mn(II) and Li(I) atoms in the complex
are firmly held in the coordination sphere in solution.
IR spectra: The main characteristic infrared spectral
bands of the free ligand and its Mn(II)-Li(II) complex are
shown in Table-4. IR spectrum of H2L exhibits characteristic
C=Noxime stretching band at 1609 cm-1, while the C=Noxime of the
complex was observed at 1603 cm-1. The C=Noxime band is shifted

4292 Dong et al.
Asian J. Chem.
4
deposit@ccdc.cam.ac.uk, on quoting the depository number
CCDC 712160.
H L
2
ACKNOWLEDGEMENTS
3
2
1
0
[MnL(OH)(H O)Li)
2
n
The authors acknowledged the finanical support from 'Jing
Lan' Talent Engineering Funds of Lanzhou Jiaotong University.
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According to the data and discussion above, the new
complex, [MnL(OH)(H2O)Li]n, has been synthesized and
structurally characterized. In FT-IR spectra of the complex,
the ν(M-O) and ν(M-N) vibrational absorption frequencies
have been observed. The structure of the complex has been
determined by X-ray diffraction technique, The complex forms
a one-dimensional infinite self-assembling chain supramole-
cular structure by hydrogen bonding interactions and π-π
stacking of neighbouring benzene rings.
Supplement data: Further details of the crystal structure
investigation(s) may be obtained from the Cambridge
Crystallographic Data Centre, Postal Address: CCDC, 12
Union Road, CAMBRIDGE CB2 1EZ, UK. Telephone: (44)
01223 762910; Facsimile: (44) 01223 336033; E-mail:
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