Synthesis, spectral characterization and biocidal studies of copper(II) complexes of chromen- 2-one-3-carboxy hydrazide and 2-(Chromen-3'-onyl)- 5-(aryl)-1,3,4-oxadiazole derivatives

Article abstract of DOI:10.1155/2011/240196

Copper(II) complexes of chromen-2-one-3-carboxyhydrazide and 2-(chromen-3'-onyl)-5-(aryl)-1,3,4-oxadiazole derivatives have been synthesized. The structural features have been determined from their microanalytical, magnetic susceptibility, molar conductance, IR, UV Vis, ¹H NMR and ESR spectral data. All the Cu(II) complexes exhibit the composition Cu(Ln) ₂X₂; where L1= chromen-2-one-3-carboxy hydrazide, L2 = 2-(chromen-3'-onyl)- 5-(2"-hydroxy phenyl)-1,3,4-oxadiazole, L3 = 2-(chromen-3'-onyl)-5-(4"- nitrophenyl)-1,3,4 -oxadiazole and L4 = 2-(chromen-3'-onyl)-5-(4"- chlorophenyl)-1,3,4-oxadiazole; X = Cl-, Br-, NO3 -, CH₃COO-, ClO₄ - and CNS-. The N, O donor ligands act as a bidentate ligand in all the complexes. Distorted octahedral geometry for all the Cu(II) complexes is proposed. Molecular modeling studies have been made for the rapid structure building, geometry optimization and molecular display. These complexes show the conductance values, supporting their non-electrolytic nature. The monomeric nature of the complexes was confirmed from their magnetic susceptibility values. These complexes have been screened for their antimicrobial activities against some bacterial species like S.aureus, E.coli, Pseudomonas aeruginosa and few fungal strains C.albicans and Cryptococcus neoformans.

Full text of DOI:10.1155/2011/240196

ISSN: 0973-4945; CODEN ECJHAO
E-Journal of Chemistry
2011, 8(3), 1346-1354
http://www.e-journals.net
Synthesis, Spectral Characterization and Biocidal
Studies of Copper(II) Complexes of Chromen-
2-one-3-carboxy Hydrazide and 2-(Chromen-3'-onyl)-
5-(aryl)-1,3,4-oxadiazole Derivatives
GLORY MATHEW*, R KRISHNAN§, MOLLY ANTONY# and M S SUSEELAN
*Department of Chemistry, Christian College
Kattakada, Thiruvananthapuram Dist, Kerala, India
§University College of Engineering, Kariyavattom, Kerala, India
#Microbiology Dept, SCT Institute of Medical Sciences &Technology
Thiruvananthapuram-695011, India
Government College, Attingal, Kerala, India
gloryvellicode@yahoo.com
Received 1 November 2010; Accepted 20 January 2011
Abstract: Copper(II) complexes of chromen-2-one-3-carboxyhydrazide and
2-(chromen-3'-onyl)-5-(aryl)-1,3,4-oxadiazole derivatives have been synthesized.
The structural features have been determined from their microanalytical,
1
magnetic susceptibility, molar conductance, IR, UV Vis, H NMR and ESR
spectral data. All the Cu(II) complexes exhibit the composition Cu(Ln)2X2;
where L1= chromen-2-one-3-carboxy hydrazide, L2 = 2-(chromen-3'-onyl)-
5-(2"-hydroxy phenyl)-1,3,4-oxadiazole, L3 = 2-(chromen-3'-onyl)-5-(4"-
nitrophenyl)-1,3,4 -oxadiazole and L4
=
2-(chromen-3'-onyl)-5-(4"-
-
-
chlorophenyl)-1,3,4-oxadiazole; X = Cl-, Br-, NO3 , CH3COO-, ClO4 and
CNS-. The N, O donor ligands act as a bidentate ligand in all the complexes.
Distorted octahedral geometry for all the Cu(II) complexes is proposed.
Molecular modeling studies have been made for the rapid structure building,
geometry optimization and molecular display. These complexes show the
conductance values, supporting their non-electrolytic nature. The
monomeric nature of the complexes was confirmed from their magnetic
susceptibility values. These complexes have been screened for their
antimicrobial activities against some bacterial species like S.aureus, E.coli,
Pseudomonas aeruginosa and few fungal strains C.albicans and
Cryptococcus neoformans.
Keywords: Chromene, Hydrazide, 1,3,4- Oxadiazole, Octahedral geometry, Antimicrobial

1347
GLORY MATHEW et al.
Introduction
The drugs containing a chromen-2-one nucleus have been reported in therapeutics for a wide
variety of antibiotics1, anticoagulants2 and skin pigmenting agents3. Hydrazides have been
investigated due to their antibacterial, antifungal, antitumour and biocidal activity4.
Hydrazides are highly useful starting materials and intermediates in the synthesis of
heterocyclic molecules5. Metal chelates with hydazide derivatives have been the subject of
several studies due to their structural aspects6. Many 1,3,4-oxadiazole derivatives show
remarkable bactericidal and fungicidal activities7. The development of bacterial or fungal
resistance to existing drugs is a major problem in anti microbial therapy and necessitates
continuing research into new classes of antimicrobials8. The interesting properties of the
metal chelates of chromen-2-one carboxy hydrazide and 1,3,4-oxadiazole derivatives have
stimulated research in these compounds that find a variety of laboratory uses and many
industrial applications9,10. For the study and designing of drug like molecules, the structure -
reactivity correlation is very important11. In order to develop new compounds of high
potency, the biologically important moieties have been coupled and with the resulting
molecules, metal chelates were synthesized and characterized.
Experimental
All chemicals used were of A.R. grade. The metal salts were prepared and analysed
following the standard procedures12. The analyses for metal and anions were carried out by
known methods12. Copper was estimated iodometrically by titration, chloride by Volhard’s
method, perchlorate by Kurz’s method and acetate and nitrate by elemental analysis. C, H, N
analyses were performed by microanalytical unit, CDRI, Lucknow. IR spectra were recorded
on a Perkin-Elmer 783 IR-spectrophotometer. UV-Vis spectra of the complexes were
recorded on Perkin-Elmer Lambda-25 spectrophotometer. The 1H NMR spectra were
recorded on a Bruker DRX-300 spectrometer at SAIF, Lucknow. The X-band ESR spectra
of the complexes were recorded at room temperature in solid state in a Varian E112 X/Q
band ESR- spectrometer at IIT Madras. Magnetic susceptibility was measured by vibrating
sample magnetometer at IIT Madras.
Conductivity measurements were made on a Systronics direct reading conductivity
meter. Molecular modeling studies were carried out in computer, 3D MAX, MAYA
professional version at Bangalore. Antimicrobial studies were also carried out from sree
chithra thirunal institute for medical sciences and technology, thiruvananthapuram.
Synthesis of ligands
Chromen and its derivatives were synthesized by Pechmann reaction method13. All the ligands
(L1, L2, L3 and L4) were prepared using the methods reported earlier14. 3-Ethyl carbethoxy
coumarin ester was prepared by condensation of salicylaldehyde with diethyl malonic ester
using conc. H2SO4 according to Pechmann reaction13. The compound obtained above
(14 mmole) and hydrazine hydrate (16 mmole) were dissolved in a sufficient quantity of
ethanol to give a clear solution and refluxed for 3 h. The contents were concentrated to a small
volume. On cooling, the crystals of chromen-2-one-3-carboxy hydrazide (L1) separated out
which were filtered and recrystallized from ethanol to give TLC pure colourless needles15.
Ligands, 2-(chromen-3'-onyl)-5-(2''-hydroxy phenyl)-1,3,4-oxadiazole [L2], 2-(chromen-3'-
onyl)-5-(4''-nitrophenyl)-1,3,4-oxadiazole [L3] and 2-(chromen-3'-onyl)-5-(4''-chlorophenyl)-
1,3,4-oxadiazole [L4] were synthesized by condensing chromen-2-one-3-carboxy hydrazide with
salicylic acid, p-nitro benzoic acid and p-chloro benzoic acid respectively15.

Synthesis, Spectral Characterization and Biocidal Studies
1348
Chromen-2-one-3-carboxy hydrazide (10 mmole) in phosphorous oxychloride (15 mL)
and the acids [salicylic acid or p-nitro benzoic acid or p-chloro benzoic acid] (10 mmole)
were added into a 100 mL R.B. flask. The reaction mixture was refluxed for 5 h, cooled to
room temperature and poured on to crushed ice. On neutralization with 2% NaHCO3
solution, a solid mass separated out, which was filtered, washed with water and
recrystallized from methanol to give L2 or L3 or L4 which were purified by TLC. The
melting point of the four ligands were L1=136 ºC, L2=310 ºC, L3=203 ºC and L4=138 ºC. All
the ligands were confirmed by m.pts, IR and 1H NMR spectra.
8
O
O
7
6
-
NH NH2
5
4
O
Figure 1. Chromen-2-one-3-carboxy hydrazide (L1); m.p. 136º
Figure 2. 2-(Chromen-3'-onyl)-5-(2"-hydroxy phenyl)-1,3,4-oxadiazole (L2); m.p. 310º
O
O
N
N
NO2
O
Figure 3. 2-(Chromen-3'-onyl)-5-(4"-nitrophenyl)-1,3,4 -oxadiazole (L3); m.p. 203º
O
O
N
N
Cl
O
Figure 4. 2-(Chromen-3'-onyl)-5-(4"-chlorophenyl)-1,3,4-oxadiazole (L4); m.p.138º
Synthesis of complexes
Copper(II) metal salts with different anions were freshly prepared from EMerck grade
CuCO3 and using 1:1 respective acids. The solution of 1 mmole of metal salt
(e.g. Cu(NO3)2.3H2O, 242 mg) in ethanol was mixed with ethanolic solution of 1 mmole of
the ligands (L1= 204 mg, L2=306 mg, L3= 335 mg or L4 = 324 mg) and refluxed for 2-3 h.
Volume of the solution was then reduced by keeping on a hot water bath and after cooling,
pH of the mixture was raised to ~7.2 with one or two drops of alcoholic ammonia solution.
The metal complexes that precipitated were filtered, washed with ethanol and dried in a
desiccator over anhydrous calcium chloride.
Results and Discussion
Analytical data given in Table 1 suggest that the metal-ligand stoichiometry is 1:2 and the
complexes are monomeric in nature. Molar conductivity data obtained in methanol,
acetonitrile and nitrobenzene suggest that all the complexes are of non-electrolyte type16,17
.
All the Cu(II) complexes are greenish brown or greenish grey in colour. These complexes
are stable in air and insoluble in H2O, slightly soluble in ethanol and methanol and very well
soluble in chloroform, nitrobenzene and dimethylformamide.

1349
GLORY MATHEW et al.
Table 1. Analytical, magnetic and electronic spectral data of Cu(II) chromen-2-one-3-
carboxy hydrazides and 1,3,4-oxadiazoles
Analyses Calcd (Found), %
Magnetic
Yield
%
UV-vis bands
in cm-1
Complex
Colour
Cu
C
H
N
susceptibility
µeff in BM
Dark
greenish brown
11.78 41.19 2.94 10.31
(11.79) (41.20) (2.95) (10.32)
15384 d-d,
24390 CT
15672 d-d,
24589 CT
16000 d-d,
25000 CT
16160 d-d,
25547 CT
15583 d-d,
25520 CT
16130 d-d,
23126 CT
16124 d-d,
24780 CT
16142 d-d,
24478 CT
16098 d-d,
24343 CT
16154 d-d,
24876 CT
15779 d-d,
24780 CT
15698 d-d,
24768 CT
15723 d-d,
24457 CT
15684 d-d,
24226 CT
15720 d-d,
24768 CT
16139 d-d,
25160 CT
16152 d-d,
24453 CT
16124 d-d,
24640 CT
16156 d-d,
24682 CT
16157 d-d,
24786 CT
16029 d-d,
24425 CT
15732 d-d,
25321 CT
16000 d-d
24992 CT
Cu(L1)2Cl2
Cu(L1)2Br2
80
1.89
10.12 37.97 2.52
8.86
Greenish brown 85
1.95
1.91
2.01
1.99
1.92
1.94
1.90
1.91
1.98
1.94
1.89
1.92
2.01
1.99
1.97
1.91
1.90
2.01
1.95
1.89
1.95
1.91
(10.13) (37.98) (2.53) (8.86)
10.73 40.26 2.68 14.08
(10.74) (40.27) (2.68) (14.09)
Cu(L1)2(NO3 )2 Yellowish brown 77
Cu(L1)2(Ac)2 Greenish brown 75
Cu(L1)2(ClO4)2 Greenish grey 85
Cu(L1)2(CNS)2 Greenish brown 79
10.84 48.81 3.72
(10.85) (48.80) (3.73) (9.49)
9.53 35.76 2.37 8.34
(9.54) (35.77) (2.38) (8.35)
8.5 54.6 2.67 7.49
(8.45) (54.59) (2.68) (7.50)
7.59 48.8 2.39 6.69
(7.58) (48.79) (2.38) (6.70)
7.93 51.1 2.5 10.5
(7.92) (51.2) (2.49) (10.51)
7.99 57.4 3.27 7.05
(7.97) (57.35) (3.26) (7.10)
7.25 46.62 2.28 6.4
9.49
Cu(L2)2Cl2 Yellowish brown 70
Dark greenish
brown
Cu(L2)2Br2
74
Cu(L2)2(NO3 )2 Greenish brown 82
Dark greenish
brown
Cu(L2)2(Ac)2
80
(7.26) (46.63) (2.29) (6.39)
7.95 50.68 2.23 10.43
(7.96) (50.67) (2.24) (10.42)
Cu(L2)2(ClO4)2 Light brown
75
7.10 45.63 2.01
9.39
Cu(L2)2(CNS)2 Greenish brown 79
Greenish
grey
(7.11) (45.64) (2.01) (9.40)
7.45 47.55 2.09 13.05
(7.46) (47.54) (2.08) (13.11)
Cu(L3)2Cl2
78
7.51
(7.51) (53.52) (2.82) (9.86)
6.85 43.72 1.92 9.01
(6.86) (43.74) (1.93) (9.02)
8.16 52.02 2.29 7.14
(8.15) (52.05) (2.3) (7.15)
7.33 46.73 2.06 6.41
53.5
2.81
9.85
Cu(L3)2Br2
Yellowish grey 81
Cu(L3)2(NO3)2 Greenish brown 75
Dark greenish
brown
Cu(L3)2(ClO4)2
74
Cu(L3)2(Ac)2 Greenish brown 70
Cu(L3)2(CNS)2 Yellowish brown 75
(7.34) (46.72) (2.07) (6.40)
7.64 48.74 2.15 10.03
(7.65) (48.74) (2.16) (10.04)
7.70 54.87 2.94
(7.71) (54.86) (2.95) (6.74)
7.01 44.73 2.52 6.14
6.73
Cu(L4)2Cl2
Cu(L4)2Br2
Greenish brown 80
Greenish grey 70
(7.02) (44.73) (2.53) (6.15)
11.78 41.19 2.68 10.31
(11.79) (41.20) (2.68) (10.32)
Dark greenish
75
Cu(L4)2(NO3)2
brown
10.12 37.97 3.72
8.86
Cu(L4)2(ClO4)2 Greenish brown 79
Cu(L4)2(CNS)2 Yellowish brown 75
(10.13) (37.98) (3.73) (8.86)
10.73 40.26 2.37 14.08
(10.4) (40.27) (2.38) (14.09)

Synthesis, Spectral Characterization and Biocidal Studies
1350
1H NMR spectra
1
The four ligands L1, L2, L3 and L4 were characterized by H NMR spectroscopy, at a
frequency 300 MHz. The 1H NMR spectral data are given in Table 2. The 1H NMR spectral
data confirms the reported ligands14.
Table 2. The 1H NMR spectral data of the ligands
Ligand
L1
δ Values, ppm
6.98
7.40
Nature of signal
m, 2H
m, 1H
m, 1H
s, 1H
Corresponding proton
H-6, H-8
H-7
H-5
7.69
8.14
H-4
CONH
NH2
8.43
8.61
s, 1H
s, 2H
L2
L3
7.13
7.91
m, 4H
m, 4H
s, 1H
H-6',H-8',H-3",H-5"
H-5',H-7',H-4",H- 6"
H-4'
8.10
7.21
m, 2H
d, 2H
m, 1H
m, 1H
s, 1H
H-6',H-8'
H-3",H-5"
H-7'
7.52
7.67
7.83
8.10
H-5'
H-4'
8.15
7.44
d, 2H
m, 3H
d, 1H
H-2",H-6"
H-6',H-7',H-8'
H-5'
L4
7.86
8.05
s, 1H
m, 4H
H-4'
H-2", H-3",H-5", H-6"
8.12
Electronic spectra
The electronic spectra in methanolic solution were taken in the range 11111 to 50000 cm-1
and the absorption bands along with their assignments are given in Table 1. Cu(II) is a
typical case where strong Jahn Teller distortion prevents the formation of regular octahedral
complexes. The electronic spectra of the present copper(II) complexes show a broad band
with a maximum of ~16160 cm-1. This band may be due to the square planar or tetragonally
distorted octahedral geometry around Cu(II)18. The band is likely to be the result of
2
2
2
2
2
combination of B1g→ A1g, B1g → B2g and B1g→2E1g transitions in D4h symmetry19. The
high intensity band observed around ~24000 cm-1 for all the complexes in the u.v. region
may be assigned to a ligand to metal, charge transfer excitation.
Magnetic moment
The effective magnetic moments of the Cu(II) complexes at room temperature are also
shown in Table 1. The magnetic moment measurements indicate that the Cu(II) complexes
are paramagnetic and the magnetic moment values are close to the spin only value of
1.73 BM, expected for one unpaired electron of a d9 configuration20. According to Lewis and
Walton the octahedral complexes of copper(II) have room temperature moments in the range
of 1.9 to 2.0 BM21. Planar complexes have as high a moment as 2.2 BM at room
temperature, although distortion would appreciably reduce it if the low symmetry ligand
fields produced are large, compared to spin-orbit coupling22. The magnetic moments for the
present Cu(II) complexes vary from 1.89 to 2.01 BM suggestive of octahedral coordination.

1351
GLORY MATHEW et al.
IR spectra
The IR spectral bands and their assignments for the important groups of the free ligands and
the complexes are helpful in deciding the stereochemical environment around Cu(II) ion in the
complexes. The IR spectrum of the ligand L1 shows bands at 3458 and 3305 cm-1, which are
assigned to the two >NH stretching vibrations of the carboxy hydrazide group23. The band at
3458 cm-1 due to –NH stretching vibration of the terminal -NH2 group is unaffected in the
complexes, indicating the non-coordination of –NH2 group to the metal atom23. The significant
band in ligand (L1) undergoing change on complexation is that at 3305 cm-1 representing the
stretching mode of hydrazide >NH group. This band is shifted by around 45-60 cm-1 to lower
frequencies in the complexes confirming its involvement in co-ordination. Also, the bands at
1526 cm-1 and 731 cm-1 representing the in-plane and out-of-plane bending modes of >NH
group show pronounced downshift (~30 cm-1) in the complexes24. The ligand spectrum
exhibits two bands occurring at 1700 cm-1 and 1650 cm-1, which may be due to the ring
carbonyl (νC= 0, coumarin) and hydrazide carbonyl stretching frequencies. On chelation, the
ring carbonyl band is red shifted by 30-40 cm-1 and the other carbonyl band is unaffected. The
appearance of bands at 1272, 1156, 1030 and 980 cm-1 in the spectrum of Cu(II) complexes of
chromen-2-one-3-carboxy hydrazide suggests the bidentate nature of the ligand23.
IR spectra of the ligands L2, L3 and L4 exhibit a strong band at 1710 cm-1 representing
the ν(C=O) chromen carbonyl group. On chelation this band is shifted to lower frequencies
(∼ 20-40 cm-1) showing its involvement in complexation25.
The significant band around 3580 cm-1 representing the oxadiazole ring stretching
frequency is highly altered and shifted to about 40-50 cm-1 to lower frequencies in the
oxadiazole containing complexes26. This is further confirmed by the bands at 1600 cm-1 and
840 cm-1 representing the in-plane and out-of-plane bending modes of νC=N group in the
oxadiazole ring showing pronounced downshift ∼30 cm-1 in the complexes26.
The bands around 1480, 1370, 1030 and 970 cm-1 are assigned to the oxadiazole ring
(nucleus) vibrations26. The bands at 1030 cm-1 can be assigned to υ C-O and the bands in the
region 970-945 cm-1 are assigned to ν(N-N) groups. A strong band around 820 cm-1
representing the stretching mode of the disubstituted benzene is also present in all the
oxadiazole ligands and their Cu(II) complexes. These bands are unaffected in the complexes,
showing their non-involvement in complexation27. The bands around 530 and 480 cm-1 are
assigned to ν(M-N) and ν(M-O) modes respectively28. The appearance of bands at 1404, 1313,
1071 and 982 cm-1 in the spectrum of Cu(II) complexes of 2 (chromen-3'-onyl)-5-(aryl)-
1,3,4-oxadiazole suggests the bidentate nature of the ligand28.
The bands at 1422 cm-1 and 1312 cm-1 assigned to ν2 vibration of coordinated nitrate in
the complex29. The spectrum of the perchlorate complex shows strong bands at 1147 (ν3)
and 621 cm-1 (ν4) with pronounced splitting30. In the IR spectra of Cu(II) acetate complex,
strong bands appear at 1570 cm-1 and 1395 cm-1 assignable to coordinated acetate group
vibrations31. The thiocyanate complex of Cu(II) shows a strong band at 2040 cm-1 along with
medium bands at 828 and 460 cm-1 indicating N-coordinated thiocyanate in the complex32.
The univalent nature of the halide ion evidenced by IR spectra of the chloride complexes
and their non-electrolyte nature suggest that the chloride ion is coordinated to the metal33.
ESR spectra
The x-band ESR spectrum of Cu(L3)2Cl2 complex recorded at 300K, at a microwave
frequency 9.33 GHz with a field strength of 4000G, is characteristic of copper(II) in axial
field symmetry, g|| = gz and g┴ = gx = gy. Calculated values of g || and g┴ are 2.215 and 2.08

Synthesis, Spectral Characterization and Biocidal Studies
1352
respectively. The trend g|| > g┴ > ge (free ion value) observed for this complex shows that the
unpaired electron is located in the dx2– y2 orbital of the copper(II) ion and the spectrum obtained
is characteristic of axial symmetry34. A|| value calculated for the complex is 200x104 cm-1 since
the hyperfine component shows no hyperfine split; A┴ = 035. From the observed value, it is
clear that g|| > g┴ >2.00 and A|| > A┴ which suggests that the complex is present in distorted
octahedral geometry. Molecular orbital coefficients, α2 (covalent in - plane σ - bonding) and β2
(covalent in-plane π -bonding) were calculated and it is found that α2 > β2 which shows that the
σ -bonding is more covalent than that of the in-plane π – bonding36.
Molecular modeling studies
Molecular modeling studies are carried out in computer, using 3D MAX software and energy
minimized configurations are shown below. To describe the physical, chemical and biological
properties, the structure is very important. For the study of the binding modes of drug like molecules
and for the designing of molecular systems, the structure - reactivity correlation is important.
Energy minimized configuration for
[Cu(Ll)2Cl2]
Energy minimized configuration for
[Cu(L3)2Cl2]
Energy minimized configuration for
[Cu(L2)2Br2]
Energy minimized configuration for
[Cu(L4)2Br2]
Antimicrobial activity
Carboxy hydrazide of chromen-2-one and 2-(chromen-3'-onyl)-5-(aryl)-1,3,4-oxadiazole
derivatives and their Cu(II) metal complexes were screened for antibacterial activity and
antifungal activity against the bacterial strains S. aureus, E. Coli and Pseudomonas aeruginosa
and the fungal strains C. albicans and Cryptococcus neoformans by disc diffusion technique.
The test solutions were prepared in DMSO and DMF at different concentrations
(50-500 µg/mL). Chloromycetin and Amphotericin B discs were used as standard drugs for
evaluating the antibacterial and antifungal activity. Nutrient agar was used as culture medium.
The zones of inhibition formed were measured in mm. Cu(II) metal complexes were found to
be more active than their ligands. In general, metal complexes are more active than their
ligands because the metal complexes may serve as a vehicle for activation of ligands as the
principal cytotoxic species37. The results of the biological activities show that these complexes
are very active and so they can be used as drugs against the above mentioned bacterial and
fungal diseases. Table 3 below shows the antimicrobial data of few Cu(II) complexes.

1353
GLORY MATHEW et al.
ATCC Staphylococcus aureus
ATCC pseudomonas aeruginosa
Figure 5. Antimicrobial activity
Table 3. Antimicrobial activity of Cu(II) complexes (Zone of inhibition in mm)
Complex
Cu(L1)2Br2
S.aureus
17
21
E.coli
12
16
P.aeruginosa C.albicans
Cryptococcus
16
22
12
25
11
27
21
20
10
21
14
16
17
9
12
20
17
12
19
18
25
16
Cu(L1)2(ClO4)2
Cu(L2)2Cl2
18
36
15
20
Cu(L2)2(CNS)2
Cu(L3)2(NO3)2
Cu(L3)2(Ac)2
Cu(L4)2(ClO4)2
Cu(L4)2Cl2
20
10
18
19
17
18
14
30
22
18
DMF control
[10 micro litres per disc]
Acknowledgment
1
We thank the Head, SAIF, CDRI, Lucknow for C, H, N analysis, IR and H-NMR spectra.
Thanks are also due to the Head, SAIF, IIT-Madras for Magnetic susceptibility and FT-IR
spectra. Thanks are also due to UGC Bangalore for financial support.
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