Systhesis and characterization of some chromium (III) Schiff base complexes

Article abstract of DOI:10.13005/ojc/310168

Chromium (III) Schiff base complexes have been synthesized using Schiff base formed by the condensing by the respective aldehyde with diamene in ethanol (rectified). All the complexes were characterized on the basis of their micro analytical data, element

Full text of DOI:10.13005/ojc/310168

ISSN: 0970-020 X
CODEN: OJCHEG
2015, Vol. 31, No. (1):
Pg. 547-551
ORIENTAL JOURNAL OF CHEMISTRY
An International Open Free Access, Peer Reviewed Research Journal
www.orientjchem.org
Systhesis and Characterization of Some
Chromium (III) Schiff Base Complexes
KALPANARAIKWAR1 and D.D. AGARWAL2
1Department of Chemistry, Government P.G. College, Guna - 473001, India.
2SOS, Department of Chemistry, Jiwaji University, Gwalior - 474011, India.
*Corresponding author E-mail: kalpanaraikwar45@gmail.com
http://dx.doi.org/10.13005/ojc/310168
(Received: November 30, 2014; Accepted: January 10, 2015)
ABSTRACT
Chromium (III) Schiff base complexes have been synthesized using Schiff base formed
by the condensing by the respective aldehyde with diamene in ethanol (rectified). All the complexes
were characterized on the basis of their micro analytical data, elemental analysis, melting points,
IR, UV- vis spectra and magnetic moment properties. The magnetic moment suggest that all the
complexes are in the range 3.6-4.1 indicating the three unpaired electron. The infrared spectrum
of the complexes under investigation confirmed the site of chelation, hence the complexes showed
stretching due to n(C=N) and n(C-O) which suggest the involvement of phenolic group in the
coordination. The UV-Vis spectral data shows the p®p* transition which suggest to involves
molecular orbital p localized at the azomethane linkage.
Key word- Schiff bases, Salicylaldehyde, Characterization,
IR, Magnetic moment, Dimethyl formamide.
INTRODUCTION
ability to selectively attach oxygen atom to olefins
and other organic substrates. Recently metal
catalyst of various organic oxidations effectively
promoted chromium complexes acting via. their
oxidation states, presumably chromium(III) has
been reported9-13. Schiff base ligands14 are able to
coordinate with metal through imine nitrogen and
another group usually linked to the aldehyde. Infect
Schiff bases are able to stabilize many different
Schiff base complexes find important
position in coordination chemistry and schiff base
complexes with transition as well with heavy metals
are used in organic synthesis, analytical reagents,
and catalysts and in medicine1. Certain oxo metal
complexes of U2,3, OS4, 5,W6 and Cr7,8 play an
important role in organic synthesis because of their

548
RAIKWAR & AGARWAL, Orient. J. Chem., Vol. 31(1), 547-551 (2015)
metals in various oxidation states, controlling the separated out, which were filtered washed with
performance of metal and a large variety of useful water and recrystallized from ethanol. The
catalytic transformations15,16. Chromium(III) characteristics of all synthesized Schiff bases are
complexes containing schiff bases and substituted given in TABLE-1.
benzimidazole / benzoxazole have attracted many
workers17-19 due to their biological, pharmacological, Synthesis of Cr(III)Schiff Base Complexes
clinical and analytical importance. The biologically
Schiff base complexes were synthesized
important form of chromium is the trivalent ion, Cr3+, by taking chromium tri chloride + ligand (SALEN) +
which is required for carbohydrate and lipid sodium carbonate 1:1:3/4 molar ratio using solvent
metabolism in mammals20.
system ethylene glycol + water + methanol in (1:1:3
w/w ratio) and the contents were refluxed for about
The coordination chemistry of Schiff bases 5hours and color was checked. After the completion
derived from the reaction of salicylaldehyde and of reaction the contents were concentrated which
o-diamines has been the subject of many studies results in a solid which was filtered off and dissolved
and a number of them are used as oxygen carriers in sodium hydroxide solution, yellow needle like
to mimic complicated biological systems21, 22. They crystals of [Cr (SALEN) (H2O)2(Cl)] was obtained
are also efficient reagents in trace analysis of some after nutralization using dil. hydrochloric acid. Similar
metal cations23. Most of the Schiff bases are procedure was adopted for the preparation of other
chemically unstable and show tendency to be Chromium(III) Schiff bases complexes.
involved in various equilibrium, like tautomeric inter
conversions, hydrolysis or formation of ionized Measurements
species24.
The Schiff base ligand and its complexes
under investigation were subjected to (C, H and N)
elemental analysis which performed at analytic unit
of the D.R.D.E. Gwalior using CARLO-ERBA and
EXPERIMENTAL
The material and reagents used in this Haereus C, H, N, O–rapid elemental analyser.
study were laboratory pure chemical. The chemical Melting points were measured in “TEMPO”
components needed for the synthesis of desired electrically operated melting point apparatus. For
schiff base complexes were chromium trioxide, conductance measurement solutions (10-3M) of
thionyl chloride, salicylaldehyde, 1,3-diamino metal complexes were prepared in dimethyl
ethaane, ethylene diamine, p-cresol, 2-isopropyl formamide. The conductivity of the solution was
phenol, 2-tert, butyl phenol, glycerol, boric acid, measured using a digital conductivity meter.
hexamine, ethanol, dichloro methane chloroform,
methanol, dichloromethane, dimethyl formamide
(DMF).
The magnetic moment measurements
were carried out at room temperature using a Gouy
balance on a Brucker magnet B-E15.The electronic
spectra of complexes has been recorded in dimethyl
Synthesis of Schiff base Ligands
All the Schiff base ligands viz; formamide using SHIMADZU UV- 160A UV visible
bis(salicylaldehyde)1,2- diaminoethane(H2SALEN), spectrophotometer in the range 200-800nm.
bis (2-hydroxy-5-methyl benzaldehyde) 1,2-
diaminoethane(H2HMBEN),
3.Isopropyl benzaldehyde) 1,2-diaminoethane
(H2HPBEN), bis(3-tert,butyl-2-hydroxy benzaldehyde) Elemental Analysis
bis(2-hydroxy-
RESULTSAND DISCUSSION
1,2-diaminoethane (H2BHBEN),were synthesized by
the procedure as given below.
The complexes were subjected to
chemical analysis and results fall within the range
expected for the proposed structures. It is seen that
All the Schiff bases were synthesized by experimentally observed analytical values for C, H
condensing the respective aldehyde with diamine and N are in close agreement with the values
(in 2:1 ratio) in ethanol (rectified). The mixture was calculated for the molecular formula assigned to
refluxed for 3hours on cooling crystals were these complexes.

RAIKWAR & AGARWAL, Orient. J. Chem., Vol. 31(1), 547-551 (2015)
549
Molar Conductance
The molar conductance of these metal
expected on the basis of molecular formula
assigned to these complexes.
complexes in dimethyl formamide(10-3M) is listed
in TABLE-II. The molar conductivity data for Cr(III)
shows that these complexes behave as 1:1
electrolyte. This behavior for these complexes was
I.R.Spectral Studies
The IR spectra in the range of 4000-400cm-
1
for some of the representative complexes were
Scheme

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RAIKWAR & AGARWAL, Orient. J. Chem., Vol. 31(1), 547-551 (2015)
Table 1: Characteristics of schiff bases and Cr (III) schiff base complexes
S.
Schiff Bases/
Complexes
Colour
M.p./
Analytical Data*
H %
No.
B.p.(0c )
C %
N %
1.
2.
3.
4.
5.
6.
7.
H2(SALEN)
H2(HMBEN)
H2(HPBEN)
H2(BHBEN)
[Cr(SALEN)(H2O)2]Cl
[Cr(HMBEN)(H2O)2]Cl
[Cr(HPBEN)(H2O)2]Cl
Yellow
Yellow
Red
Yellow
Brown
Brown
135
149
-
70.02(71.64)
72.59(72.97)
74.26(75.00)
75.08(75.79)
49.01(49.34)
51.69(51.55)
56.00(55.81)
5.10(5.97)
6.31(6.77)
7.10(7.95)
8.10(8.42)
4.0(4.6)
9.67(10.45)
9.50(9.46)
7.08(7.95)
7.05(7.73)
16.89(16.45)
6.22(6.68)
6.21(5.91)
-
172
181
5.99(5.72)
6.54(6.34)
Yellowish 176
Green
8.
[Cr(BHBEN)(H2O)2]Cl
Whitish
Brown
181
58.22(57.48)
6.94(6.48)
5.01(5.58)
*Calculated values are given in %
Table 2: I.R.Frequency(cm-1)assignments for chromium(III) schiff base complexes
S.
No.
Complexes
C - H
C = N
C - O

Molar
Conductivity
Ohm-1 cm2 mol-1
Magnetic
Moment
µeff / BM
1.
2.
3.
4.
[Cr(SALEN) (H2O)2]Cl
[Cr(HMBEN)(H2O)2]Cl
[Cr(HPBEN)(H2O)2]Cl
[Cr(BHBEN) (H2O)2]Cl
3200-3010 1630
3080-2900 1630
3085-2800 1615
3140-2820 1610
1350
1320
1310
1320
764
762
760
760
51
67
83
86
4.1
3.6
3.8
3.9
recorded. The characteristic bands are given in 1610cm-1 which can be assigned to C=N and
TABLE-II.The IR spectrum of Chromium(III) complex C=C stretching respectively. The C=N stretching
shows no strong band in region 3500-3200cm-1 on coordination was found to shift to lower value on
indicating deprotonation of OH group and its coordination (1630cm-1) and over lapped with C=C
coordination.
of phenyl ring. The C-O stretching was found to
shift to 1320cm-1 suggesting its involvement in
In the IR spectrum of [Cr(SALEN)(H2O)2]Cl coordination. The absorption band at 762cm-1 can
complex shows bands in the region 3200 -3010cm- be assigned to the aromatic vicinal trisubstitution.
1
which can be assigned to deprotonation of OH
group and its coordination with metal.The band due
The IR spectrum of [Cr(HPBEN)(H2O)2]Cl
to C=N is shifted to 1630cm-1 and overlapped with shows that bands in the region 3520-3000cm-1 are
C=C. A band at 1350 cm-1 to C-O stretching which absent which are observed in the IR spectrum of
suggest the involvement of phenolic group in the ligand suggesting deprotonation of OH groups and
coordination.
its participation in coordination. Strong peaks in the
region 3085-2800cm-1 can be assigned for C-H
The IR spectra of [Cr(HMBEN)(H2O)2]Cl stretching vibration. The peak at 1615cm-1 can be
complex shows band in the region 3080-2900cm- assigned to C=N suggesting its participation in
1 which can be assigned to C-H stretching. The coordination. The absorption band at 1320cm-1 can
spectra of the ligand showed bands at 1640 and be attributed to for C-O stretching mode.

RAIKWAR & AGARWAL, Orient. J. Chem., Vol. 31(1), 547-551 (2015)
551
The [Cr(BHBEN)(H2O)2]Cl complex shows
absorption bands in the region 3140-2820cm-1,
which can be assigned to nC-H asymmetric
stretching vibration of -CH3 and -CH2 groups. Strong
bands at 1610cm-1 can be assigned to C=N
suggesting its participation in coordination. The IR
spectra also shows strong peaks at 1410cm-1 and
1460cm-1 respectively which are due to nC-H
stretching of tert.butyl group. The peak at 1320cm-1
can be attributed to C-O group.
recorded in solvent (dimethyl formamide). The
electronic spectra show absorption in the range
550-275nm which can be assigned to n - * and 
- * transitions. The  -* transition are suggested
to involves molecular orbital localized at the
azomethane linkage. The information regarding the
geometry of the complexes could not be ascertained
with the observed data.
Magnetic Moment
The magnetic moment for the Cr(III) Schiff
base complexes is the range 3.6- 4.1 BM indicating
the three unpaired electron.
Electronic Spectra
The UV-visible spectra of some
representative Schiff base complexes of Cr(III) were
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