Mass, EPR, IR and electronic spectroscopic studies on newly synthesized macrocyclic ligand and its transition metal complexes

Article abstract of DOI:10.1016/j.saa.2005.03.029

Manganese(II), cobalt(II), nickel(II) and copper(II) complexes have been synthesized with a new tetradentate ligand viz. 1,3,7,9-tetraaza-2,4,8,10- tetraketo-6,12-diphenyl-cyclododecane (L) and characterized by the elemental analysis, molar conductance measurements, magnetic susceptibility measurements, mass, ¹H NMR, IR, electronic and EPR spectral studies. The molar conductance measurements of the complexes in DMF correspond to be nonelectrolytic nature for Mn(II), Co(II) and Cu(II) while 1:2 electrolytes for Ni(II) complexes. Thus, these complexes may be formulated as [M(L)X₂] and [Ni(L)]X₂ (where M = Mn(II), Co(II) and Cu(II) and X = Cl ^- and NO₃^-). On the basis of IR, electronic and EPR spectral studies an octahedral geometry has been assigned for Mn(II) and Co(II) complexes, square-planar for Ni(II) whereas tetragonal for Cu(II) complexes. The ligand and its complexes were also evaluated against the growth of bacteria and pathogenic fungi in vitro.

Full text of DOI:10.1016/j.saa.2005.03.029

Spectrochimica Acta Part A 62 (2005) 1125–1130
Mass, EPR, IR and electronic spectroscopic studies on newly
synthesized macrocyclic ligand and its transition metal complexes
Sulekh Chandra∗, Lokesh Kumar Gupta
Department of Chemistry, Zakir Husain College, University of Delhi, JLN-Marg, New Delhi 110002, India
Received 24 January 2005; accepted 16 March 2005
Abstract
Manganese(II), cobalt(II), nickel(II) and copper(II) complexes have been synthesized with a new tetradentate ligand viz. 1,3,7,9-tetraaza-
2,4,8,10-tetraketo-6,12-diphenyl-cyclododecane (L) and characterized by the elemental analysis, molar conductance measurements, magnetic
susceptibility measurements, mass, 1H NMR, IR, electronic and EPR spectral studies. The molar conductance measurements of the complexes
in DMF correspond to be nonelectrolytic nature for Mn(II), Co(II) and Cu(II) while 1:2 electrolytes for Ni(II) complexes. Thus, these complexes
may be formulated as [M(L)X2] and [Ni(L)]X2 (where M = Mn(II), Co(II) and Cu(II) and X = Cl− and NO3−).
On the basis of IR, electronic and EPR spectral studies an octahedral geometry has been assigned for Mn(II) and Co(II) complexes, square-
planar for Ni(II) whereas tetragonal for Cu(II) complexes. The ligand and its complexes were also evaluated against the growth of bacteria
and pathogenic fungi in vitro.
© 2005 Elsevier B.V. All rights reserved.
Keywords: Spectroscopic; Macrocyclic; Physicochemical; Antibacterial; Antifungal
1. Introduction
2. Experimental
All the chemicals used were of AnalaR grade, and pro-
cured from Fluka. Metal salts were purchased from E. Merck
and were used as received.
Synthetic macrocycles are a growing class of compounds
with varying chemistry a wide range of different molecular
topologies and sets of donor atoms [1–5]. The chemical
properties of macrocyclic complexes can be tuned to
force metal ions to adopt unusual coordination geometry.
Transition metal macrocyclic complexes have received
much attention as a active part of metalloenzymes [6] as
biomimic model compounds [7] due to its resemblance with
natural proteins like hemerythrin and enzymes. In view
of the above in the present paper, we report the synthesis
and characterization of macrocyclic complexes by the
urea containing nitrogen donor macrocyclic ligand (L)
(Fig. 1).
2.1. Synthesis of ligand
The hot ethanolic solution (20 mL), of ethylcinnamate
(3.52 g, 0.02 mol), and a hot ethanolic solution (20 mL), of
urea (1.20 g, 0.02 mol) were mixed slowly with constant stir-
ring. This mixture was refluxed at ∼75 ◦C for 9 h in the
presence of few drops of concentrated hydrochloric acid (pH
∼4–5). Cooling give a cream precipitate, which was filtered,
washed with cold EtOH, and dried under vacuum over P4O10.
Yield 69%, mp 274 ◦C. Elemental analysis found %(found
381 u), C63.03;H5.33;N14.82. CalculatedforC20H20N4O4
(calculated 380 u), C 63.16; H 5.26 and N 14.74%.
2.2. Synthesis of complexes
∗
Corresponding author. Tel.: +91 11 229 112 67; fax: +91 11 232 159 06.
The hot ethanolic (20 mL) solution of ligand (0.76 g,
0.002 mol) and hot ethanolic (20 mL) solution of
E-mail addresses: schandra 00@yahoo.com (S. Chandra),
lokesh kg@rediffmail.com (L.K. Gupta).
1386-1425/$ – see front matter © 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2005.03.029

1126
S. Chandra, L.K. Gupta / Spectrochimica Acta Part A 62 (2005) 1125–1130
Fig. 2. Electron-impact mass spectra of the ligand (L).
Fig. 1. Preparation and structure of the ligand.
corresponding metal salts (0.002 mol) were mixed together
with constant stirring. The mixture was refluxed for 6–14 h at
60–85 ◦C. Cooling gives a colored complex. It was filtered,
washed with cold EtOH and dried under vacuum over P4O10.
to the macrocyclic moiety (C20H20N4O4). It also shows a
series of peaks, i.e. 58, 77, 104, 132, 175, 190, 248, 303 and
381, etc., corresponding to various fragments. Their inten-
1
sity gives an idea of stability of fragments Fig. 2. The H
NMR spectrum of the ligand (L) does not gives any sig-
nal corresponding to primary amine and alcoholic protons.
It gives a doublet in the region 8.56 ppm, which is due
to the amide group ( NH CO , 2H) protons [8]. Signals
appear in the region 1.54, 2.41 and 7.25 ppm, correspond to
methyne ( CH CH2 ), methylene ( CH2 CO ) and ben-
zenoid protons, respectively. The presence of another signal
at δ 5.16 ppm is due to the protons of NH group [9]. IR spec-
trumoftheliganddoesnotexhibitanybandcorrespondingfor
the free primary diamine and hydroxyl group [5]. The absorp-
tion in IR spectrum of (L) in the range of 715–756 cm−1
and 1432–1633 cm−1 [10,11] is due to the presence of
phenyl group. Four new bands appear in the spectrum of the
free ligand in the regions 1628, 1592, 1239 and 771 cm−1
assignabletoamideI[ν(C O)], amideII[ν(C N) + δ(N H)],
amide III [δ(N H)] and amide IV [φ(C O)] bands respec-
tively [11–13]. A sharp band observed ∼3276 cm−1, may be
assigned to ν(N H) of he secondary amino group [14–15].
2.3. Physical measurements
The C, H and N were analysed on a Carlo-Erba 1106
elemental analyzer. Molar conductance was measure on
the ELICO (CM82T) conductivity bridge. Magnetic sus-
ceptibility was measured at room temperature on a Gouy
balance using CuSO4·H2O as a callibrant. Electron-impact
mass spectra were recorded on JEOL, JMS, DX-303
mass spectrometer. 1H NMR spectra were recorded on
Hitachi FT-NMR, model R-600 spectrometer using CDCl3
as solvent, chemical shifts are given in ppm relative to
tetramethylsilane. IR spectra (KBr) were recorded on a
FTIR Spectrum BX-II spectrophotometer. The electronic
spectra were recorded in DMF on Shimadzu UV mini-1240
spectrophotometer. EPR spectra of the complexes were
recorded as polycrystalline sample and in the DMF solution,
at liquid nitrogen temperature for Co(II) and at room
temperature for Mn(II) and Cu(II) complexes on E4-EPR
spectrometer using the DPPH as the g-marker.
3.2. Complexes
3. Results and discussion
On the basis of elemental analysis, the complexes were
assigned to possess the composition shown in Table 1. The
molar conductance measurements of the complexes in DMF
correspond to be nonelectrolytic nature for Mn(II), Co(II)
and Cu(II) while 1:2 electrolytes for Ni(II) complexes.
Thus, these complexes may be formulated as [M(L)X2]
3.1. Ligand
The EI Mass spectrum of free ligand confirm the pro-
posed formula by showing a peak at 381 u corresponding
Table 1
Molar conductance and elemental analysis data of the complexes
Complex
MW Molar conductance Color
mp (◦C) Yield Elemental analysis data found (calculated)%
(%)
(ꢀ−1 cm2 mol−1
)
Metal
C
H
N
[Mn(L)Cl2] C20H20MnN4O2S2Cl2 506
[Mn(L)(NO3)2] C20H20MnN6O8S2 559
[Co(L)Cl2] C20H20CoN4O2S2Cl2 510
[Co(L)(NO3)2] C20H20CoN6O8S2 563
10.03
12.09
10.06
6.92
Brown
Light brown 285
Lotus pink
Rose pink
Purple red
Shiny orange 286
Blue
Shiny blue
295
66
71
67
73
60
62
59
63
10.93 (10.87) 47.52 (47.43) 4.02 (3.95) 11.01 (11.07)
9.96 (9.84) 43.04 (42.93) 3.50 (3.58) 14.97 (15.03)
290
288
280
11.64 (11.57) 47.00 (47.06) 3.98 (3.92) 11.09 (10.98)
10.36 (10.48) 42.69 (42.63) 3.49 (3.55) 15.01 (14.92)
11.50 (11.57) 46.98 (47.06) 3.84 (3.92) 10.89 (10.98)
10.59 (10.48) 42.55 (42.63) 3.61 (3.55) 14.80 (14.92)
12.58 (12.43) 46.71 (46.60) 3.96 (3.88) 11.00 (10.87)
11.15 (11.27) 42.16 (42.25) 3.60 (3.52) 14.92 (14.79)
[Ni(L)]Cl2 C20H20NiN4O2S2Cl2
[Ni(L)] (NO3)2 C20H20NiN6O8S2 563 218
510 225
[Cu (L)Cl2] C20H20CuN4O2S2Cl2 515
[Cu (L)(NO3)2] C20H20CuN6O8S2 568
8.18
10.11
>300
290

S. Chandra, L.K. Gupta / Spectrochimica Acta Part A 62 (2005) 1125–1130
1127
(ε = 66–71 mol−1 cm−1), and 37581–38127 cm−1 (ε = 129–
and [Ni(L)]X2 (where M = Mn(II), Co(II), and Cu(II) and
X = Cl− and NO3−). In the IR spectra of complexes, the
shifting in lower side of the band [ν(N H)] and the band of
amides II and III, suggest the coordination through nitrogen
of NH group (N4).
133 L mol−1 cm−1) (Table 2). These bands may be assigned
4
4
to the transitions: 6A1g → T1g (4G), 6A1g → Eg, 4A1g (4G)
6
4
6
4
(10B + 5C), A1g → Eg (4D) (17B + 5C) and A1g → T1g
(4P) (7B + 7C), respectively.
EPR spectra were recorded at room temperature as
polycrystalline sample and in solution of DMF. The poly-
crystalline spectra were isotropic and exhibit the ‘g’ value
in the range 2.0054–2.0099 (Table 3). In DMF solution,
Mn(II) complexes give EPR spectra containing the six lines
arising due to the hyperfine interaction between the unpaired
electron with the 55Mn nuclear (l = 5/2). The nuclear mag-
netic quantum number M1, corresponding to these lines are
−5/2, −3/2, −1/2, +1/2, +3/2 and +5/2 from low to the high
field.
The parameters B and C were calculated from the second
and third transitions because these transitions are free from
the crystal field splitting and depend on B and C parameters
[11,12]. The calculated values of the ligand field parameters
are given in Table 4.
3.3. IR bands due to anions
IR spectra of nitrato complexes display three (N O)
stretching bands at ∼1415–1431 cm−1 (ν5), 1306–1317
cm−1 (ν1) and 1006–1019 cm−1 (ν2). The separation of two
highestfrequencybands(ν5 − ν1)is109–114 cm−1. Suggest-
ing that both the nitrate groups are coordinated to the central
metal ion [14].
However, the IR spectrum of Ni(II) nitrate complex dis-
plays a sharp and strong band at 1391 cm−1 which suggests
that the nitrate group is uncoordinated.
3.4. Manganese(II) complexes
Manganese(II) complexes show magnetic moment at
room temperature in the range 5.84–5.96 B.M. corresponding
to five unpaired electrons. Electronic spectra of Mn(II) com-
plexes, Fig. 3(a–b), exhibit four weak intensity absorption
bands in the range 18509–18919 (ε = 37–39 L mol−1 cm−1),
22550–23100 (ε = 41–43 L mol−1 cm−1), 29344–29731
3.5. Cobalt(II) complexes
At room temperature the magnetic moment measurements
of cobalt(II) complexes lie in the range 4.86–4.93 B.M. cor-
responding to three unpaired electrons (Table 2).
Fig. 3. Electronic spectra of the complexes. (a) [Mn(L)Cl2], (b) [Mn(L)4O3]2, (c) [Ni(L)Cl2], (d) [Ni(L)(NO3)2].

1128
S. Chandra, L.K. Gupta / Spectrochimica Acta Part A 62 (2005) 1125–1130
Table 2
Magnetic moment and electronic spectral data of the complexes
Complex
µeff (B.M.)
λmax (cm−1
)
ε (L mol−1 cm−1
)
[Mn(L)Cl2]
[Mn(L)(NO3)2]
[Co(L)Cl2]
[Co(L)(NO3)2]
[Ni(L)]Cl2
[Ni(L)](NO3)2
[Cu(L)Cl2]
5.84
5.96
4.86
4.93
Diamagnetic
Diamagnetic
1.95
18509, 22550, 29344, 37581
18919, 23100, 29731, 38127
10173, 14620, 18692, 26596
11198, 14793, 18657, 32680
16178, 22090, 29543
16548, 21307, 29825
10905, 11249, 16447, 27933
10183, 11223, 16260
37, 41, 66, 129
39, 43, 71, 133
73, 81, 90, 141
72, 81, 92, 139
57, 93, 134
57, 94, 132
59, 63, 155
57, 61, 153
[Cu(L)(NO3)2]
2.06
Table 3
EPR spectral data of the complexes
Complexes
Data as polycrystalline sample
Data in DMF solution
Temperature
g
g
giso
G
g
g
giso
G
||
⊥
||
⊥
[Mn(L)Cl2]
[Mn(L)(NO3)2]
[Co(L)Cl2]
[Co(L)(NO3)2]
[Cu(L)Cl2]
[Cu(L)(NO3)2]
RT
RT
LNT
LNT
RT
–
–
–
–
2.0054
2.0099
2.1155
2.1245
2.0682
2.0840
–
–
–
–
–
–
–
–
2.0017
2.0020
2.1205
2.1135
2.0910
2.0737
–
–
–
–
2.3268
2.3387
2.0853
2.1182
2.0098
2.0174
2.0597
2.0669
2.3256
2.3298
2.1329
2.0831
2.0179
2.0053
2.0701
2.0690
1.4288
1.7668
1.8959
1.2043
RT
94 L mol−1 cm−1
)
and 29543–29825 cm−1 (ε = 132–
The electronic spectra of all the cobalt(II) com-
plexes exhibit absorption in the region 10173–11198
(ε = 72–73 mol−1 cm−1), 14620–14793 (ε = 81 L mol−1
134 L mol−1 cm−1). An examination of these bands indi-
cates that the complexes have square planar geometry. These
bands may be assigned to the three spin allowed transitions:
cm−1), 18657–18692 (ε = 90–92 L mol−1 cm−1
)
and
These
26596–32680 cm−1(ε = 139–141 L mol−1 cm−1).
1A1g (D) → A2g (G) (ν1), A1g (D) → B2g (G) (ν2) and
1
1
1
4
4
1
1A1g (D) → Eg (G) (ν3), respectively.
bands may be assigned to the transitions: T1g (F) → T2g
4
4
4
4
(F) (ν1), T1g → A2g (ν2) and T1g (F) → T1g (P) (ν3),
respectively, and the fourth band may be due to charge
transfer. The position of bands indicates that these complexes
have distorted octahedral geometry [15–18].
3.7. Copper(II) complexes
The magnetic moment of the Cu(II) complexes at room
temperature lie in the range 1.95–2.06 B.M. corresponding
to one unpaired electron.
EPR spectra of cobalt(II) complexes were recorded as
polycrystalline sample and in DMF solution at LNT. ‘g’
Values are found to be almost same in both cases in poly-
crystalline sample as well as in the solution (Table 3).
Electronic spectra of copper(II) complexes display three
2
bands (Table 2), corresponding to the transitions B1g → A1g
(dx2−y2 → dz2 ) ν1, 2B1g → B2g (dx2−y2 → dzy) ν2 and
2
2
2B1g → Eg (dx2−y2 → dzy, dyz) ν3, respectively [19,20].
3.6. Nickel(II) complexes
Room temperature EPR spectra of Cu(II) complexes were
recorded as polycrystalline sample and in the solution of the
DMF, on X-band at frequency 9.5 GHz under the magnetic
field strength 3400 G. Polycrystalline spectra exhibit a single
At room temperature these complexes show the diamag-
netic behavior, indicating the square planar environment
around the Ni(II) ion (Fig. 4).
The electronic spectra of the Ni(II) complexes,
Fig. 3(c–d) exhibit three absorption bands in the range
16178–16548 (ε = 57 L mol−1 cm−1), 21307–22090 (ε = 93–
Table 4
Ligand field parameters of the complexes
Complex
Dq (cm−1
)
B (cm−1
)
C (cm−1
)
β
LFSE
(kJ mol−1
)
[Mn(L)Cl2]
1851.90
613.71
518.29
644.55
574.06
735.36
752.18
3060.44
3581.01
–
–
–
–
0.78
0.66
0.58 121.54
0.52 133.79
0.71 231.94
0.72 237.25
00
00
[Mn(L)(NO3)2] 1891.10
[Co(L)Cl2] 1271.62
[Co(L)(NO3)2] 1399.75
[Ni(L)]Cl2
[Ni(L)](NO3)2
1617.80
1654.80
Fig. 4. Suggested structures of the complexes where M = Mn(II), Co(II), and
Cu(II) and X = Cl− and NO3−).

S. Chandra, L.K. Gupta / Spectrochimica Acta Part A 62 (2005) 1125–1130
1129
broadsignal. NobandcorrespondingtoꢁMs = 2transitions
was observed in the spectrum suggesting Cu–Cu interaction
[21,22]. The absence of above transition can be explained by
proposing interaction between two paramagnetic centers is
negligible [23]. The analysis of spectra gives the values for
g = 2.0831–2.1329 and g = 2.0597–2.0701. The observed
||
⊥
g values for the complexes are less than 2.3 in agreement
||
with the covalent character of the metal ligand bond. The
trend g > g > 2.0023 observed for the complexes indicate
||
⊥
that the unpaired electron is localized in dx2−y2 orbital of the
Cu(II) ion and the spectral figures are characteristic of axial
symmetry. Tetragonaly elongated structure are confirmed for
the Cu(II) complexes (Fig. 4).
Fig. 5. Biological screening of the ligand and complexes: (a) antibacterial
and (b) antifungal activity.
G = (g − 2)/(g − 2), which measure the exchange inter-
||
⊥
action between the metal centers in a polycrystalline solid has
been calculated. According to Hathaway [24,25] if G > 4, the
exchange interaction is negligible but G < 4 indicates con-
siderable exchange interaction in the solid complexes. In the
complexes, reported in this paper the ‘G’ value are <4 indi-
cating the exchange interaction in solid complex.
Hundred percent growth of bacteria which is repre-
sented as +, 50% growth by ++, less then 50% growth
by +++ and noble inhibition by ++++. The bacterial
growth inhibition capacity of the complexes follow the
order Cu(II) > Ni(II) > Mn(II) > Co(II), given in Fig. 5(a) and
Table 5.
3.8. Ligand field parameters
3.11. Antifungal screening
Various ligand field parameters were calculated for the
complexesandarelistedinTable4. ThevaluesofDqinCo(II)
complexes were calculated from transition energy ratio dia-
gram using the ν3/ν2 ratio [17]. Our results are in agreement
with the complexes reported earlier [18,21]. The Nephelaux-
etic parameter β was readily obtained by using the relation:
The antifungal activity of the ligand and its complexes
was checked, by the agar plate technique for the Aspergillus
niger and Aspergillus glaucus fungi. The compounds were
directly mixed to the medium in different concentrations.
The fungus was placed on the medium with the help of the
inoculum needle. The pettridishes were wrapped in polythene
sheets, containing some drops of EtOH and put in incubator
at 31 1 ◦C for 75–100 h. The growth of fungus was mea-
sured by the recording the diameter of fungal colony. The
following relation calculated the fungal growth inhibition:
B(complex)
β =
B(free ion)
where B(free ion) for Mn(II) is 786 cm−1, for Ni(II) is
1041 cm−1 and for Co(II) is 1120 cm−1 [11,12]. The val-
ues of β lie in the range of 0.54–0.81. These values indicate
the appreciable covalent character of metal ligand ‘␴’ bond.
(A − B) × 100
fungal growth inhibition% =
A
where A is the diameter of fungal colony in control plate and
B is the diameter of fungal colony in test plate.
Hundred percent growth of fungus which is represented
as *, 50% growth by **, less then 50% growth by *** and
noble inhibition by ****.
The results of antifungal activity are shown in Table 5.
The complexes show fungal inhibition in the following order:
Co < Mn < Ni < Cu.
3.9. Antimicrobial screening
The ligand (L) and its transition metal complexes were
evaluated against different species of bacteria and fungi
[26,27].
3.10. Antibacterial screening
Table 5
The antibacterial action of the ligand and the complexes
of Mn(II), Co(II), Ni(II) and Cu(II) was checked by the
disc diffusion technique. This was done on Sarcina lutea
(gram-positive) and Escherchia coli (gram-negative) bacte-
ria at 35 ◦C. The disc of Whatmann no. 4 filter paper having
the diameter 6.00 mm were soaked in the solution of com-
pounds in DMF (1.0 mg cm−1). After drying, it was placed
on nutrient agar plates. The inhibition areas were observed
after 48 h. DMF was used as a control and Gentamycin as a
standard drug.
Antimicrobial activity data of the ligand and complexes
Compound
Bacterial inhibition (%)
Fungal inhibition (%)
Sarcina
lutea
Escherichia
coli
Aspergillus
niger
Aspergillus
glaucus
Ligand
++
+++
++
++
++
+
**
**
**
**
[Mn(L)Cl2]
[Co(L)Cl2]
[Ni(L)]Cl2
*
**
+++
++++
++++
**
****
***
****
[Cu (L)Cl2] ++++

1130
S. Chandra, L.K. Gupta / Spectrochimica Acta Part A 62 (2005) 1125–1130
[11] S. Chandra, K. Gupta, Transition Met. Chem. 27 (2002) 329;
Copper(II) complexes exhibits noble antifungal activity
against both the species Fig. 5(b).
L.T. Kist, M.J. Fernadej, B. Scpoganicsz, M.A. Manez, M.G. Basal-
lote, Polyhedron 16 (1997) 3827.
[12] S. Chandra, Sangeetika, Indian J. Chem. 41A (2002) 1629;
E.Q. Gao, H.Y. Sun, D.Z. Liao, Z.H. Jiang, S.P. Yan, Polyhedron 21
(2002) 359.
Acknowledgements
[13] S. Chandra, L.K. Gupta, D. Shukla, J. Saudi Chem. Soc. 7 (2003)
331.
We are thankful to the Principal, Zakir Husain College for
providing research facilities, RSIC, IIT Mumbai for record-
ing EPR spectra and University Grant Commission, New
Delhi, for financial assistance.
[14] S. Chandra, L.K. Gupta, Spectrochim. Acta 60A (2004) 1563;
M. Shakir, S.P. Varkey, P.S. Hameed, Polyhedron 12 (1993) 2775;
S. Chandra, S.D. Sharma, Trans. Met. Chem. 27 (2002) 732;
S. Chandra, L.K. Gupta, Spectrochim. Acta 60A (2004) 3079.
[15] S. Chandra, L.K. Gupta, Spectrochim. Acta 60A (2004) 1751;
M. Shakir, O.S.M. Nasman, A.K. Mohamed, S.P. Varkey, Indian J.
Chem. 35A (1996) 710.
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