Full text of DOI:10.14233/ajchem.2014.17398

Asian Journal of Chemistry; Vol. 26, No. 20 (2014), 6915-6917
ASIAN JOURNAL OF CHEMISTRY
http://dx.doi.org/10.14233/ajchem.2014.17398
Synthesis and Characterization of Bromo-Substituted
Salamo-Type Bisoxime Compounds Series
*
LI XU, NA LI, YANG ZHANG, NA WEN, LI-CHUN ZHU and XIU-YAN DONG
School of Chemical and Biological Engineering, Lanzhou Jiaotong University, Lanzhou 730070, P.R. China
*Corresponding author: E-mail: dxy568@163.com
Received: 14 February 2014;
Accepted: 5 May 2014;
Published online: 25 September 2014;
AJC-16038
Four novel bromo-substituted Salamo-type bisoxime compounds H2L1-H2L4 have been synthesized from 5-bromo-2-hydroxybenzaldehyde
and 1,3-bis(aminooxy)propane, 1,4-bis(aminooxy)butane, 1,5-bis(aminooxy)pentane or 1,6-bis(aminooxy)henane in hot ethanolic medium,
respectively and characterized by elemental analyses, IR, UV-visible spectra and 1H NMR spectroscopy.
Keywords: Salamo-type compound, Synthesis, Characterization.
without further purification. The other reagents and solvents
were analytical grade reagents from Tianjin Chemical Reagent
INTRODUCTION
Factory. The others are the same as literature8-10
.
Salamo-type bisoxime compounds have long been used
as organic chelating ligands in the synthesis of transition metal
complexes, because this compound could be prepared easily
from salicylaldehyde and various amines1-4. In recent years,
these complexes have been found to possess multifarious
interesting property. Thus, we have recently studied three novel
Salamo-type bisoxime chelating compounds on the basis of
O-alkyloxime moiety [-CH=N-O-(CH2)n-O-N=CH-] group5-7.
Herein, we report the synthesis and characterization of
four Salamo-type bisoximes compounds, 4,4'-bibromo-2,2'-
[(propylene-1,3-diyldioxy)bis(nitrilomethylidyne)]-diphenol,
4,4'-bibromo-2,2'-[(butylene-1,4-diyldioxy)bis-(nitrilo-
methylidyne)]diphenol, 4,4'-bibromo-2,2'-[(propane-1,5-
diyldioxy)bis(nitrilomethylidyne)]diphenol and 4,4'-dibromo-
2,2'-[(hexane-1,6-diyldioxy)bis(nitrilomethylidyne)]-
diphenol.
General procedure: Synthetic route to Salamo-type
bisoxime compounds H2L1-H2L4 are shown in Fig. 1. 1,3-bis-
(aminooxy)propane, 1,4-bis(aminooxy)butane, 1,5-bis(amin-
ooxy)pentane and 1,6-bis(aminooxy)henane were synthesized
according to an analogous method reported earlier8-10
.
Preparation of 4,4'-dibromo-2,2'[(propylene-1,3-
diyldioxy)bis(nitrilomethylidyne)]diphenol (H2L1): To an
ethanolic solution (10 mL) of 5-bromo-2-hydroxybenzal-
dehyde (603.1 mg, 3 mmol) was added an ethanolic solution
(10 mL) of 1,3-bis(aminooxy)propane (159.2 mg, 1.50 mmol).
After the solution had been stirred at 55 °C for 2 h, the mixture
was filtered, washed successively with ethanol and n-hexane,
respectively. The product was dried under reduced pressure
and purified with recrystallization from ethanol to yield white
crystalline solid H2L1.
Preparation of 4,4'-dibromo-2,2'-[(butylene-1,4-
diyldioxy)bis(nitrilomethylidyne)]diphenol (H2L2): To a hot
ethanol solution (10 mL) of 5-bromo-2-hydroxybenzaldehyde
(603.1 mg, 3 mmol) was added a hot ethanolic solution (5 mL)
of 1,5-bis(aminooxy)pentane (201.6 mg, 1.50 mmol). After
EXPERIMENTAL
5-Bromo-2-hydroxy-benzaldehyde (≥ 98 %), 1,3-dibro-
mopropane, 1,4-dibromobutane, 1,5-dibromopentane and 1,6-
dibromohexane were purchased from Alfa Aesar and used
n
O
O
N
CHO
OH
N
n
O NH2
ethanol, 60°C
Br
H2L1: n=2; H2L2: n=3; H2L3: n=4; H2L4: n=5
2
O
H2N
+
OH
HO
Br
Br
Fig. 1. Synthetic route to salamo-type bisoxime compounds H2L1-H2L4

6916 Xu et al.
Asian J. Chem.
the solution had been stirred at 55 °C for 3 h, then cooled to
room temperature. The white precipitate was formed, filtered
and washed successively with ethanol and n-hexane, respec-
tively. The product was purified with recrystallization from
ethanol/n-hexane (1/4) and dried under vacuum to obtain white
needle-like compound H2L2.
water. In addition, H2L1 and H2L2 are soluble in hot methanol,
ethanol and acetonitrile, but H2L3 and H2L4 are insoluble in
hot methanol, ethanol and acetonitrile.
IR spectra: The most important IR spectra data for H2L1-
H2L4 are given in Table-2. In the IR spectra of the compounds
H2L1-H2L4, the characteristic C=N stretching bands of the
compound H2L1-H2L4 appear at 1614-1611 cm-1, respec-
tively11. The Ar-O stretching bands occur at 1265-1255 cm-1
as reported for similar bisoxime compounds12. Meanwhile, the
O-H stretching bands of phenolic alcohol in the title com-
pounds H2L1-H2L4 appear at 3441-3424 cm-1 region, but this
frequency is generally displaced to ca. 3424 cm-1 because of
the internal hydrogen bond OH···N=C10. In addition, in the
1481-1479 cm-1 region, the observed bands were attributed to
aromatic C=C vibrations.
UV-visible and 1H NMR spectra: The UV-visible spectra
of the compounds H2L1-H2L4 in 5 × 10-5 mol L-1 dichloro-
methane solution are presented inTable-3.The compounds H2L1-
H2L4 exhibit two intense peaks at around 277 and 315 nm. The
former absorption peaks at about 277 nm can be assigned to the
π-π* transition of the benzene rings, while the latters can be
attributed to the intra-ligand π-π* transition of the C=N bonds13.
It is of note that there was no absorption around 400 nm, which
is seen in the corresponding Salen derivatives. The absorption is
Preparation of 4,4'-dibromo-2,2'-[(propane-1,5-
diyldioxy)bis(nitrilome-thylidyne)]diphenol (H2L3): To a hot
ethanolic solution (15 mL) of 5-bromo-2-hydroxy-benzal-
dehyde (201.3 mg, 1 mmol) was added a hot ethanolic solution
(10 mL) of 1,5-bis(aminooxy)pentane (67.1 mg, 0.50 mmol).
After the solution had been stirred at 60 °C for 6 h, then cooled
to room temperature. The white precipitate which was filtered
and washed successively with ethanol and n-hexane, respec-
tively. The product was purified with recrystallization from
ethanol/n-hexane (1/4) and dried under vacuum to obtain white
cotton-like compound H2L3.
Preparation of 4,4'-bibromo-2,2'-[(hexane-1,6-
diyldioxy)bis(nitrilomethylidyne)]diphenol (H2L4): To a hot
ethanolic solution (15 mL) of 5-bromo-2-hydroxy-benzal-
dehyde (201.3 mg, 1 mmol) was added a hot ethanolic solution
(10 mL) of 1,6-bis(aminooxy)henane (74.1 mg, 0.50 mmol).
After the solution had been stirred at 60 °C for 6 h, then cooled
to room temperature. The white precipitate which was filtered
and washed successively with ethanol and n-hexane, respec-
tively. The product was purified with recrystallization from
ethanol/n-hexane (1/4) and dried under vacuum to obtain white
cotton-like compound H2L4.
ascribed to the quinoid form of H2 salen14,15
.
The 1H NMR spectra of the title compounds H2L1-H2L4
1
in DMSO-d6 are shown in Table-3. The H NMR spectra
showed a singlet at about 8.25-8.45 ppm indicating the
existence of oxime bonds14.
RESULTS AND DISCUSSION
Conclusion
Four Salamo-type bisoxime compounds H2L1-H2L4 have
been synthesized with good yields and the composition are
confirmed by elemental analyses, IR, UV-visible spectra and
1H NMR spectroscopy.
Four novel Salamo-type compounds H2L1-H2L4 that have
two oxime bonds instead of imine bonds have been designed
and synthesized by the reaction of 2 equivalents of 5-bromo-
2-hydroxy-benzaldehyde with 1,3-bis(aminooxy)propane, 1,4-
bis(aminooxy)butane, 1,5-bis(aminooxy)pentane or 1,6-
bis(aminooxy)henane in hot ethanol medium, respectively.And
the structures of the title compounds H2L1-H2L4 have been
analyzed by elemental analysis, IR, UV-visible spectra and
1H NMR spectroscopy. The Salamo-type compounds may be
promising units for the construction of supramolecular metal
complexes.
Physico-chemical properties: The colour, yields, melting
points and elemental analytical results of the synthesized
Salamo-type bisoxime compounds H2L1-H2L4 are presented
in Table-1. Their compositions agree with the proposed mole-
cular formula. All the compounds are stable in air and soluble
in chloroform, dichloromethane, tetrahydrofuran, benzene,
acetone, DMF and DMSO, insoluble in n-hexane, ether and
TABLE-1
COLOUR, YIELDS, MELTING POINTS AND ANALYTICAL
DATA OF SYNTHESIZED SALAMO-TYPE BISOXIME COMPOUNDS H2L1-H2L4
Elemental analysis (%): Found (Calcd.)
Compound
Colour
m.p. (°C)
Yield (%)
m.f. (m.w.)
C
H
N
H2L1
H2L2
H2L3
H2L4
White
White
White
White
163-164
143-144
121-122
134-135
59.0
60.1
76.3
63.2
C17H16N2O4Br2 (472.13)
C18H18N2O4Br2 (486.15)
C19H20N2O4Br2 (500.18)
C20H22N2O4Br2 (514.21)
43.85 (43.25)
44.56 (44.47)
45.62 (45.31)
46.72 (46.65)
3.44 (3.42)
3.96 (3.73)
4.03 (4.10)
4.31 (4.36)
5.69 (5.93)
5.68 (5.76)
5.60 (5.62)
5.45 (5.51)
TABLE-2
KEY IR BANDS FOR THE SALAMO-TYPE BISOXIME COMPOUNDS H2L1-H2L4 (cm-1)
Compound
ν(O-H)
3424
3427
3441
3433
ν(CHarom
3042
)
ν(CH2)
ν(C=N)
1612
ν(C-C)benzene ring
1481
ν(Ar-O)
1255
H2L1
H2L2
H2L3
H2L4
2946, 2889
2937, 2883
2941, 2880
2941, 2882
3045
1613
1480
1264
3057
1611
1481
1261
3053
1614
1479
1265

Vol. 26, No. 20 (2014)
Synthesis of Bromo-Substituted Salamo-Type Bisoxime Compounds Series 6917
TABLE-3
THE UV-VISIBLE SPECTRA AND 1H NMR DATA FOR THE SALAMO-TYPE BISOXIME COMPOUNDS H2L1-H2L4
π- π* (nm)
1H NMR (400 MHz, DMSO-d6, δ/ppm)
Compound
2.14 (t, J = 6.0 Hz, 2H, CH2), 4.31 (t, J = 6.0 Hz, 4H, CH2-O), 6.85 (d, J = 8.0 Hz, 2H, PhH), 7.25 (s, 2H, PhH),
7.33 (d, J = 8.0 Hz, 2H, PhH), 8.09 (s, 2H, N=CH), 9.80 (s, 2H, OH)
H2L1
270, 324
2.04 (t, J = 4.0 Hz, 4H, CH2), 4.23 (t, J = 4.0 Hz, 4H, CH2-O), 6.85 (d, J = 4.0 Hz, 2H, PhH), 7.24 (s, 2H, PhH),
7.34 (d, J = 4.0 Hz, 2H, PhH), 8.08 (s, 2H, N=CH), 9.89 (s, 2H, OH)
H2L2
H2L3
H2L4
269, 323
277, 315
276,322
2.34 (s, 2H, CH2), 2.37 (d, J = 8.7 Hz, 4H, CH2), 4.46 (s, 4H, CH2-O), 7.40 (d, J = 2.0 Hz, 2H, PhH), 7.55 (d, J =
2.0 Hz, 2H, PhH), 7.72 (d, J = 2.2 Hz, 2H), 8.25 (s, 2H, N=CH), 10.14 (s, 2H, OH)
2.33 (s, 4H, CH2), 2.36 (d, J = 8.0 Hz, 4H, CH2), 4.45 (s, 4H, CH2-O), 7.41 (d, J = 2.0 Hz, 2H, PhH), 7.55 (d, J =
2.0 Hz, 2H, PhH), 7.71 (d, J = 2.2 Hz, 2H), 8.25 (s, 2H, N=CH), 10.05 (s, 2H, OH)
and T. Nabeshima, J. Org. Chem., 70, 1704 (2005); (c) W.K. Dong,
C.Y. Zhao, Y.X. Sun, X.L. Tang and X.N. He, Inorg. Chem. Commun.,
12, 234 (2009); (d) W.K. Dong, L. Wang, Y.X. Sun, J.F. Tong and J.C.
Wu, Chinese J. Inorg. Chem., 27, 372 (2011); (e) W.K. Dong and Y.J.
Ding, Cryst. Res. Technol., 43, 321 (2008); (f) W.K. Dong, Y.X. Sun,
S.J. Xing, Y. Wang and X.H. Gao, Z. Naturforsch., 67, 197 (2012); (g)
W.K. Dong, S.J. Xing, Y.X. Sun, L. Zhao, L.Q. Chai and X.H. Gao, J.
Coord. Chem., 65, 1212 (2012); (h) W.K. Dong, Y.X. Sun, G.H. Liu,
L. Li, X.Y. Dong and X.H. Gao, Z. Anorg. Allg. Chem., 638, 1370
(2012); (i) W.K. Dong, Y.X. Sun, X.N. He, J.F. Tong and J.C. Wu,
Spectrochim. Acta A, 76, 476 (2010).
REFERENCES
1. T.K. Saha, V. Ramkumar and D. Chakraborty, Inorg. Chem., 50, 2720
(2011).
2. R.M. Haak, A. Decortes, E.C. Escudero-Adán, M.M. Belmonte, E. Mar-
tin, J. Benet-Buchholz and A.W. Kleij, Inorg. Chem., 50, 7934 (2011).
3. C. Meermann, K.W. Törnroos and R. Anwander, Inorg. Chem., 48,
2561 (2009).
4. P.A. Vigato and S. Tamburini, Coord. Chem. Rev., 252, 1871 (2008).
5. Y. Sui, D.P. Li, C.H. Li, X.H. Zhou, T. Wu and X.Z. You, Inorg. Chem.,
49, 1286 (2010).
6. S. Akine, S. Hotate and T. Nabeshima, J. Am. Chem. Soc., 133, 13868
(2011).
11. W.K. Dong,Y.X. Sun,Y.P. Zhang, L. Li, X.N. He and X.L. Tang, Inorg.
Chim. Acta, 362, 117 (2009).
7. S. Akine, W.K. Dong and T. Nabeshima, Inorg. Chem., 45, 4677 (2006).
8. S. Akine, T. Tadokoro and T. Nabeshima, Inorg. Chem., 51, 11478
(2012).
12. J.A. Faniran, K.S. Patel and J.C. Bailar Jr., J. Inorg. Nucl. Chem., 36,
1547 (1974).
13. T. Ghosh, B. Mondal, T. Ghosh, M. Sutradhar, G. Mukherjee and M.
Drew, Inorg. Chim. Acta, 360, 1753 (2007).
14. H.E. Smith, Chem. Rev., 83, 359 (1983).
9. W.K. Dong, X.N. He, H.B.Yan, Z.W. Lv, X. Chen, C.Y. Zhao and X.L.
Tang, Polyhedron, 28, 1419 (2009).
10. (a) W.K. Dong,Y.X. Sun, C.Y. Zhao, X.Y. Dong and L. Xu, Polyhedron,
29, 2087 (2010); (b) S. Akine, T. Taniguchi, W. Dong, S. Masubuchi
15. S. Akine, T. Taniguchi and T. Nabeshima, Chem. Lett., 30, 682 (2001).