Synthesis of Complexes
of Copper Electrolytically
Sneha Kumari
Agarwal, M. Alam*
Department of Chemistry, Ranchi University, Ranchi-834008
*Corresponding Author
E-mail: malamgold@gmail.com
ABSTRACT:
The
interaction of elemental copper with ligands, Dimethyl glyoxime and
salicylaldehyde leads to the formation of chelates MLn or MLn.mH20
through electrochemical synthesis. On the basis of elemental analysis, IR
spectroscopy and TGA, the structures are discussed.
KEYWORDS: Cu, Pt, sal, dmg, LiClO4
Over the past 25-30 years
the use of electrochemistry as a synthetic tool in organic chemistry has
increased remarkably in lab scale synthesis, solving R&D objectives for a
multi-step targeted synthesis, or one-step synthesis of intermediates or
starting materials(1). Electrosynthesis has wide application to
synthesis of molecular complexes and metal chelates. Various metals (almost of
all groups of the periodic table) and ligands, including both inorganic and
organic compounds have been used. Electrosynthesis of coordination compounds is
carried out by using a sacrificial anode or cathode (sources of metal ions to
form complexes).(2-5)
The essence of
electrosynthesis of complex compounds is described
simply
as (6)
In
the present work, we have used Cu
electrode as anode to form complexes with salicyldehyde and dimethyl glyoxime.
Pt electrode was used as cathode. Acetone was used as solvent and lithium
perchlorate as electrolyte with 3v DC supply under atmospheric condition. The
solids formed were isolated in the pure form and characterized on the basis of
elemental analysis, FTIR spectra studies and thermal analysis.
Chemical used:
LiClO4,
KClO4, SAL, DMG, acetone. (The chemicals used were of A.R. grade).
EXPERIMENTAL
PROCEDURES:
(a) Ligand: Salicylaldehyde:
0.5g
KClO4 was dissolved in 30ml of DMF in a 100ml beaker. 2ml of
salicyldehyde was added .The solution was subjected to electrolysis using Pt
electrode as cathode and Cu electrode as sacrificial anode under 3v DC supply.
The electrolytic process going on can be confirmed through the bubbles emerging
out of Pt electrode. After 7 hr, green powder was deposited at the bottom of
the cell. It was filtered, dried and bottled as sample SSC1.
(b) Ligand: Dimethylglyoxime:
Solution
was prepared dissolving 0.5g KClO4 in 30ml of DMF.1.16g of dmg was
mixed in the solution. It was electrolyzed using Pt electrode as cathode and Cu
electrode as sacrificial anode under 3v DC supply .The electrolytic process
going on can be confirmed through the bubbles emerging out of Pt electrode.
After 8 hr, black solids was filtered, dried and bottled as SDC.
Elemental
analysis and related data
|
No. |
Colour |
C% |
H% |
O% |
N% |
M% |
Empirical formula |
|
SSC1 |
green |
f:
53.9 c:54.9 |
f:2.9 c:3.2
|
c:20.95 |
|
c:20.88 |
C14H10O4Cu |
|
SDC |
black |
f:32.47 c:32.71 |
f:4.86 c:4.77 |
c:21.80 |
c:19.08 |
c:21.64 |
C8H14
N4O4Cu |
Table-1 FTIR Results (sample SSC1)
|
Peaks |
Nature of peaks |
Group assignment |
|
3051.39 |
strong |
=C-H stretching |
|
3012.81 |
Strong |
Aromatic C-H stretch |
|
2920.23 |
weak |
C-H stretch |
|
2819.93 |
Weak |
Aldehydic C-H stretch |
|
2696.48 |
Sharp |
Aldehydic C-H stretch |
|
2387.87 |
Sharp |
C-C stretch |
|
2048.40 |
Sharp |
C=O stretch second overtone |
|
1948.10 |
Sharp |
C=O stretch second overtone |
|
1801.51 |
medium |
O-H combination |
|
1604.7 |
Sharp |
-C=O stretch |
|
1523.76 |
Sharp |
C=C stretch |
|
1435.04 |
Sharp |
O-H combination andC=C |
|
1338.60 |
Medium |
C-OH bending
phenolic group |
|
1192.01 |
Sharp |
C-OH stretching phenolic
group |
|
1149.57 |
Sharp |
C-H-C aromatic bending |
|
1022.27 |
Sharp |
O-H stretching |
|
852.54 |
Sharp |
O-H rocking phenyl group |
|
667.67 |
Sharp |
O-substituted phenyl group |
|
547.78 |
Sharp |
M-O,OH wagging |
|
428.20 |
Sharp |
M-O,OH stretching |
Thermogravimetric
results:Table-2
|
Temperature |
Formulation sequence |
Experimental loss |
Theoretical loss |
|
267.55
0C residue |
Cu.(C6H4O.CHO)2 ↓
- C6H4O.CHO -C6H4
. CHO CuO |
72% 27.95% |
73.98% 26.02% |
Thermogravimetric
results:
PROPOSED FORMULATION:
SSC1
Table-2 FTIR Results (sample SDC)
|
Peaks |
Nature of peaks |
Group assignment |
|
2627.05 |
broad |
O-H stretching H-bonded |
|
1585.49 |
sharp |
C=N stretching |
|
1539.20 |
sharp |
v(C=N) |
|
1431.18 |
sharp |
v(C=C) |
|
1377.17 |
sharp |
(-C-H)bending |
|
1323.17 |
sharp |
v(C-N) |
|
1211.30 |
sharp |
v(N-O) |
|
1068.56 |
sharp |
v(N-O) |
|
964.41 |
sharp |
C-CH3 |
|
864.11 |
sharp |
O-H |
|
729.09 |
sharp |
v(C=N-O) |
|
489.92 |
sharp |
v(M-N) |
RESULTS AND DISCUSSION:
The FTIR curves (Table-1)
of sample SSC1 contain almost all the peaks which are expected for the
formulation. The experimental data suggest that salicylaldehyde is on deprotonated mode
acting as a bidentate ligand coordinated to the metal ion through the phenolato
and one aldehydo oxygen atoms . The spectra of these complexes do not contain a broad band around 3530–3545cm−1 attributed to ν(OH). The disappearance of phenolic v(O-H) band at 3300cm-1 in
the complex suggest the coordination by the phenolic oxygen after deprotonation
to the metal ion(7). This is further supported by the shifting of
v(C-O) phenolic to lower wave number at 1435cm-1 in the metal
complex. The appearance of band at 617cm-1 and 547cm-1 in the complex due to
v(M-O) further substantiates it. The band at 1192cm-1 is assigned to stretching of phenolic C-O which has undergone a positive
shift in the complex. This positive shift
which indicates coordination of the phenolic oxygen may be attributed to the
drift of electron density from oxygen to the metal ion resulting in a greater
ionic character of v(C–O) bond and a consequent increase in v(C–O) vibrational
frequency.(8)The band at 1149 cm-1 is due to the bending
in the C-C-H plane in the substituted aromatic ring. The band at 902 cm-1
corresponds to scissoring vibrations in the carbonyl groups. The peak at 852cm-1
corresponds to out of plane bending of hydrogen atoms in the benzene rings. The
bands at 2819 cm-1 and2696 cm-1 are
due to C-H stretching of aldehyde group.(9-15)
Also
in the TGA-DTA curves, complete loss of ligand occurs at 267.55 0C
leaving behind Cu oxide as ultimate product. The proposed
formulation is supported by FTIR peaks and Thermogravimetric loss pattern. In SDC, the infrared spectra of the dimethylglyoxime
exhibited absorption bands at 3400, 2931,1570, 1141 and 756 cm-1 which are
attributed to v(OH), v(C-H) aliphatic, v(C=N), v(N-O) and v(C=N-O)
respectively. In addition, on the complex the bands of v(C=N) and v(C=N-O) were
shifted to the lower frequencies at 1539 and 729 cm-1. This type of
coordination is usual in the complexes, as the ligand forms six-member chelate
ring by coordinating with metal ions through the N and O atoms (16,17).Thus,
the spectra of the complex appear as weak band at 489cm-1 which is
due to the v(M-N). This indicates that the dimethylglyoxime as a bidentate and
are coordinated with the metal ions through the N and O atoms.(18,19)
The free uncoordinated dimethylglyoxime has no band at 1240 cm−1. In the
Cu(DH)2 complex, a band appears at 1211 cm−1 due to
v(N—O) of the ionized (N—OH) group of dimethylglyoxime and additional band v(N—O) appears at ν =1068 cm-1. From this it is
evident that the N—O bonds of coordinated dimethylglyoxime are not entirely
equivalent.(20).The weak broad band appearing at around 3410 cm−1 belongs
to the intramolecular hydrogen bonding . The oxime part (C=N) takes part in the
chelate ring formation in copper complexes. The normal stretching vibration
v(C=N) of free DH2 is at ν = 1620 cm−1. In the
present case this band shifted to 1585 cm−1. The
characteristic band of v(Cu—N) appears
at 489 cm−1. (21-24) the broad band at 2600 cm-1shows intramolecular
hydrogen bonding. The changes in stretching frequencies concerned with v(NH)
and v(OH) cannot be identified as that region is merged with v(OH) of water and
appear as a broad band in the complex. Also, in the TGA, before 190°C, TG curves of complex show that the
thermogram does not display any inflexion point, which
indicates that complex has excellent
thermal reliability , and it
does not contain
any kind of
small ligands (water or acetic
acid). Upon heating
above 190°C, a rapid collapse took place, indicating the decomposition
of the complex. At 1970C,in course of burning, sublimation also occurs whereby
some sample(including copper content) is lost as gas. After burning
,the residue left is made up of oxide of metal. The residue consists 11% of the
complex. The residual amount cannot be correlated with the initial amount of
sample, since there has been uncertain loss of sample in course of sublimation
at 197oC.(25)
ACKNOWLEDGEMENT:
The author is grateful to
Dr. M. Alam for improvement of paper. The author is thankful to the CIF, BIT
Mesra, for providing useful data of elemental analysis. This work was supported
by Chemistry laboratory, Department of Chemistry, Faculty of Science, Ranchi
University.
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Received
on 19.08.2015 Modified on 11.09.2015
Accepted
on 20.09.2015 © AJRC All right
reserved
Asian J. Research Chem. 8(10): October 2015; Page 625-629
DOI: 10.5958/0974-4150.2015.00099.1