Synthesis, spectral characterization and crystal structure of N-2-hydroxy-4-methoxybenzaldehyde-N′-4-nitrobenzoyl hydrazone and its square planar Cu(II) complex

Article abstract of DOI:10.1016/j.saa.2008.03.025

A new aroyl hydrazone, N-2-hydroxy-4-methoxybenzaldehyde-N′-4-nitrobenzoyl hydrazone (H₂L) and its mixed ligand Cu(II) complex [CuLpy] [py, pyridine] have been prepared. The ligand is characterized by elemental analysis, electronic, infrared an

Full text of DOI:10.1016/j.saa.2008.03.025

Spectrochimica Acta Part A 71 (2008) 1253–1260
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, spectral characterization and crystal structure of
N-2-hydroxy-4-methoxybenzaldehyde-Nꢀ-4-nitrobenzoyl
hydrazone and its square planar Cu(II) complex
B.N. Bessy Raja, M.R. Prathapachandra Kurupa,∗, E. Sureshb
a Department of Applied Chemistry, Cochin University of Science and Technology, Kochi 682022, Kerala, India
b Analytical Science Division, Central Salt and Marine Chemicals Research Institute, Bhavnagar 364002, Gujarat, India
a r t i c l e i n f o
a b s t r a c t
A new aroyl hydrazone, N-2-hydroxy-4-methoxybenzaldehyde-Nꢀ-4-nitrobenzoyl hydrazone (H2L) and
its mixed ligand Cu(II) complex [CuLpy] [py, pyridine] have been prepared. The ligand is characterized by
elemental analysis, electronic, infrared and NMR spectral studies and the complex by electronic, infrared,
EPR spectral studies and the magnetic susceptibility data. The structures of the compounds were deter-
mined by single crystal X-ray diffraction studies. Both the ligand and the Cu complex crystallize into a
Article history:
Received 7 September 2007
Accepted 19 March 2008
Keywords:
Aroyl hydrazone
Cu complex
Crystal structure
NMR
¯
triclinic lattice with a space group of PI. From the crystal studies, it is concluded that the ligand molecule
exits in the keto form in the solid state, while at the time of complexation, it tautomerises into the enol
form. The complex is formed by the double deprotonation of the ligand molecule—both the phenolic and
the enolic protons.
COSY
HSQC
© 2008 Elsevier B.V. All rights reserved.
EPR
1. Introduction
Aroyl hydrazones are potential multidentate ligands in coor-
dination chemistry. As the part of our work for the search of
Schiff bases derived from the condensation of salicylaldehyde
and its derivatives with alkyl and aroyl hydrazones play a very
important role in coordination chemistry [1–5]. They display bio-
logical activity, play an important role in biological systems [6–10]
and are considered to be suitable models for pyridoxal, and in gen-
eral B6, vitamins. Adducts of nontransition, early transition, and
f metals with o-hydroxy Schiff bases have been widely studied
[11–13]. Furthermore, abilities of aroyl hydrazones to coordinate
to metals either in keto or enol tautomeric form make them attrac-
tive as ligands. As the salicylaldehyde aroyl hydrazone Schiff base is
concerned, it can act as a tridentate ligand both in the monoanionic
and dianionic forms and hence can form very stable chelates with
metal ions. Salen-based metal complexes also play an important
role in the SHG efficiency [14]. Thompson et al. in 1991 reported
the first salen based NLO metal complex of the tetradentate salen
[N,Nꢀ-bis(salicylaldeminato) ethylene] ligand. Compared to organic
molecules, they can offer a large variety of molecular structures,
the possibility of high thermal and environmental stability and a
diversity of electronic properties by the virtue of coordinated metal
atom.
new ligands which can form nonlinear optical active coordina-
tion complexes [15,16], we herein report the synthesis, spectral
characterization and crystal structure of a new aroyl hydrazone, N-
2-hydroxy-4-methoxybenzaldehyde-Nꢀ-4-nitrobenzoyl hydrazone
(Scheme 1) and one of its square planar Cu(II) complex.
2. Experimental
2.1. Reagents
The solvents used for synthesis were purchased from
Merck and used without further purification. 2-Hydroxy-4-
methoxybenzaldehyde, 4-nitrobenzoyl hydrazine and copper(II)
acetate were purchased from Sigma–Aldrich. Spectrograde solvents
were used for spectral recording.
2.2. Physical measurements
Analysis of C, H and N were done on Elementar Vario EL
III CHNOS Elemental Analyzer. IR spectra were recorded as
KBr discs on SHIMADZU IR Spectrophotometer. Electronic spec-
tra were carried out in UVWIN 5.0 Spectro UV–vis double
beam UVD 3500 Spectrophotometer in the region 250–900 nm
by using DMF as solvent. The 1H NMR, 13C NMR, COSY and
∗
Corresponding author. Tel.: +91 484 2575804; fax: +91 484 2577595.
E-mail addresses: mrp@cusat.ac.in, mrp k@yahoo.com
(M.R. Prathapachandra Kurup).
1386-1425/$ – see front matter © 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2008.03.025

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B.N. Bessy Raj et al. / Spectrochimica Acta Part A 71 (2008) 1253–1260
Table 2
Selected bond lengths and bond angles of the ligand and the complex
Ligand
Complex
N1–C8 1.278(2)
N1–N2 1.384(1)
N2–C9 1.338(2)
C12–C11 1.376(2)
C12–C13 1.379(2)
O3–C9 1.232(2)
N1–C8 1.287(3)
N1–N2 1.413(3)
N2–C9 1.312(3)
C11–C12 1.367(4)
C12–C13 1.369(4)
O3–C9 1.300(3)
Scheme 1. Structure of compound H2L.
O2–C6 1.350(2)
O2–C6 1.318(3)
Cu1–O2 1.892(1)
Cu1–N1 1.921(2)
Cu1–O3 1.932(1)
Cu1–N4 2.000(2)
HSQC spectra were recorded on
a Brucker DRX500 using
DMSO-d6 as solvent and TMS as standard. EPR spectral mea-
surements were carried out on a Varian E-112 X-band spec-
trometer using TCNE as standard at the Sophisticated Analytical
Instruments Facility, Indian Institute of Technology, Mumbai,
India.
C8–N1–N2 114.95(15)
C9–N2–N1 120.59(15)
C11–C12–C13 118.43(16)
O4–N3–C13 117.62(15)
O3–C9–N2 124.66(15)
O3 – C9 – C10 120.47(15)
N2–C9–C10 114.87(15)
C8–N1–N2 116.9(2)
C9–N2–N1 108.0(2)
C11–C12–C13 119.8(3)
O4–N3–C13 118.6(2)
O3–C9–N2 124.6(2)
O3–C9–C10 117.7(2)
N2–C9–C10 117.7(2)
2.3. Crystallography
Single crystal X-ray diffraction experiments were performed
on a ‘Bruker Smart Apex CCD Diffractometer’ using graphite-
monochromated MoK␣ radiation (ꢀ = 0.71073 A) (all crys-
C14–C15–C10 120.53(15)
C14–C15–C10 120.8(2)
O2–Cu1–N1 93.55(9)
O2–Cu1–O3 174.32(7)
N1–Cu1–O3 80.96(9)
O2–Cu1–N4 92.46(9)
N1–Cu1–N4 172.65(8)
O3–Cu1–N4 93.13(9)
˚
tallographic data are deposited with the Cambridge
Crystallographic data centre). Ligand crystal with dimensions
0.16 mm × 0.10 mm × 0.07 mm and complex crystal with dimen-
sions 0.22 mm × 0.14 mm × 0.10 mm were used and the data
collected at 293(2) K is shown in Table 1. The structure was solved
by direct and refined by full matrix least squares on F2 with
SHELXL-97 program [17]. The graphical tool used was DIAMOND
version 3.1d [18]. All non-hydrogen atoms were refined anisotrop-
ically. Selected bond lengths and bond angles of the compounds
are listed in Table 2.
(0.905 g, 5 mmol) to 10 mL of DMF (Scheme 2). The solution was
heated to boiling for 5 min, cooled to room temperature and then
poured into 40 mL of water containing crushed ice and 1 mL of con-
centrated sulphuric acid. The product formed was filtered, washed
repeatedly with water, finally with a little ether and recrystallized
from DMF (m.p. 228–230 ◦C, yield 85%). Yellow plate-like crystals
suitable for single crystal X-ray diffraction studies were obtained
by the slow evaporation of its solution in DMF. Anal. Calcd. for
2.4. Synthesis
The ligand was prepared by adding 2-hydroxy-4-methoxy-
benzaldehyde (0.761 g, 5 mmol) and 4-nitrobenzoyl hydrazine
C
15H13N3O5·½H2O (%): C, 55.56; H, 4.35; N, 12.96. Found: C, 55.12;
H, 4.52; N, 12.76.
Table 1
Crystal data and structure refinement for the ligand and the complex
Ligand
Complex
Empirical formula
Formula weight
Temperature
Wavelength
Crystal system
Space group
C15 H15 N3O6
333.30
C20H16 CuN4O5
455.91
293(2) K
0.71073 A
Triclinic
¯
PI
293(2) K
0.71073 A
Triclinic
¯
PI
˚
˚
Unit cell dimensions
a = 6.721(6) A
a = 6.400(4) A
˚
˚
b = 7.009(6) A
b = 10.082(6) A
˚
˚
c = 16.839(14) A
˛ = 78.103(13)◦
ˇ = 80.585(13)◦
ꢁ = 78.125(13)◦
c = 15.206(9) A
˛ = 97.936(9)◦
ˇ = 91.940(9)◦
ꢁ = 107.864(9)◦
3
3
˚
˚
Volume, Z
753.5(11) A , 2
921.9(10) A , 2
Calculated density
Absorption coefficient
F (0 0 0)
1.469 mg/m3
0.116 mm−1
348
1.642 mg/m3
1.228 mm−1
466
Crystal size
ꢂ Range for data collection
Index ranges
Reflections collected/unique
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2ꢃ(I)]
R indices (all data)
Largest difference peak and hole
0.16 mm × 0.10 mm × 0.07 mm
0.22 mm × 0.14 mm × 0.10 mm
1.25–28.48◦
2.15–28.33◦
−8 ≤ h ≤ 8, −9 ≤ k ≤ 9, −22 ≤ l ≤ 22
6316/3357 [R(int) = 0.0174]
Full-matrix least-squares on F2
3357/0/277
−8 ≤ h ≤ 8, −13 ≤ k ≤ 13, −19 ≤ l ≤ 19
7468/4015 [R(int) = 0.0239]
Full-matrix least-squares on F2
4015/0/335
1.025
1.065
R1 = 0.0483, wR2 = 0.1279
R1 = 0.0582, wR2 = 0.1386
R1 = 0.0423, wR2 = 0.1022
R1 = 0.0520, wR2 = 0.1068
−3
−3
˚
˚
0.269 and −0.181 eA
0.664 and −0.252 eA

B.N. Bessy Raj et al. / Spectrochimica Acta Part A 71 (2008) 1253–1260
1255
Scheme 2.
Scheme 3.
For the preparation of the Cu(II) complex, a method was adapted
to prepare the binuclear precursor according to the reported proce-
dures [19] for the synthesis of similar complexes and then convert
it to the mononuclear analogue. To a boiling solution of the lig-
and (0.1575 g, 0.5 mmol) in a 1:1 mixture of ethanol and DMF, an
ethanolic solution of copper(II) acetate (0.0998 g, 0.5 mmol) was
added and refluxed continuously for about four hours (Scheme 3)
The brown colored product obtained was filtered and washed with
a 1:1 mixture of ethanol/DMF and recrystallized from DMF (yield
78%). Anal. Calcd. for Cu2C30H22N6O10 (%): C, 46.16; H, 3.23; N, 10.77.
Found: C, 45.98; H, 2.75; N, 10.81.
About 200 mg of the dimeric Cu(II) complex was dissolved in
about 10 mL of boiling pyridine and refluxed for about 5 min. A
dark red colored product was obtained by the addition of water
to this solution (Scheme 4). It was filtered, washed several times
with water, finally with a little diethyl ether and dried (yield 86%).
Dark yellow plate-like crystals of Cu(II) complex suitable for single
crystal X-ray diffraction studies were obtained by the slow evapo-
ration of its solution in pyridine. Anal. Calcd. for CuC20H16 N4O5 (%):
C, 52.69; H, 3.54; N, 12.29. Found: C, 52.70; H, 3.28; N, 12.19.
two well-defined bands in the UV region and weak absorption
in the visible region. The strong bands are at 270–319 nm and
320–380 nm. The former is assigned to the ꢄ → ꢄ* electronic tran-
sitions of the p-substituted benzene and the azomethine bonds.
The latter one is due to n → ꢄ* transitions of carbonyl and nitro
chromophores. A weak absorption is also observed in the vis-
ible region at 440–580 nm range due to the much extended
electron delocalization from one to other end of the overall
molecule.
In the case of square planar copper complexes, three allowed
transitions are expected in the visible region, but often these the-
oretical expectations are overlooked in practice, and these bands
usually appear overlapped due to the very small energy difference
between the d levels [20]. The molecule reveals ꢄ → ꢄ* and n → ꢄ*
transitions of the pyridyl and principal ligand functions as a very
broad band in the region 268–343 nm. The charge transfer tran-
sitions are observed as two bands in the region 424–448 nm and
440–517 nm. The broad band appeared at 588–722 nm, when the
spectrum was recorded high concentrations in the visible region
as a continuation to the charge transfer band is due to the d–d
transitions.
3. Results and discussion
3.2. IR spectra
3.1. Electronic spectrum
The IR spectra of the compounds were recorded as KBr discs
in the range 4000–400 cm−1. Hydrazones can exist in the keto or
in the enol tautomeric form in the solid state. In the present lig-
The electronic spectra of the compounds were recorded in
solution state by dissolving in DMF. The ligand spectrum shows
Scheme 4.

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B.N. Bessy Raj et al. / Spectrochimica Acta Part A 71 (2008) 1253–1260
and, the absorption due to ꢅ(C O) observed at 1655 cm−1 confirms
that the compound is in the keto form in the solid state. There
are two well-defined infrared absorptions at 1655 and 1599 cm−1
,
which were assigned to the amide I and amide II bands, respec-
tively. These bands are shifted to the low frequency region than
the theoretical values due to the conjugation of the amide groups
with the aromatic group. Because of conjugation, the double bond
nature of C O decreases and hence the bond order decreases,
which causes a shift to the lower frequency region. Amide II band
seen at 1599 cm−1 points out to the secondary amide exists in
the trans conformation, which is confirmed by the crystal struc-
ture. A very broad band observed in the region 3000–3500 cm−1
comprising of both the –OH and –NH– stretching absorptions. Two
bands at 1512 and 1472 cm−1 are due to the aromatic C C stretch-
ing absorptions. It is very difficult to differentiate the bands in the
fingerprint region, but a well-defined band at 1221 cm−1 may be
due to phenolic C–O stretching vibration. The characteristic ꢅ(C N)
absorptions of Schiff bases come in the region 1689–1471 cm−1. In
the present case, it appears as a shoulder to the amide II band nearly
at 1550 cm−1
.
The IR spectrum of the complex was compared with that of the
ligand and remarkable differences are noticed between them. The
ꢅ(O–H) broad band at 3000–3500 cm−1 for the ligand disappears in
the complex, suggesting coordination through deprotonated phe-
nolic oxygen. It also substantiates the enolization of the ligand at
the time of complexation. The absence of strong band at 1655 cm−1
due to ꢅ(C O) (amide I), which was present in the ligand spectrum,
in the complex spectrum bears out the deprotonation of the eno-
lised hydrazone tautomer. The band due to ꢅ(C N) (amide II) at
1599 cm−1 is shifted to 1512 cm−1 in the complex indicates coordi-
nation of the azomethine nitrogen to the metal atom. In the far
IR region, the band at 272 nm confirms the coordination of the
pyridine nitrogen to copper [21].
Fig. 1. 1H NMR spectrum of the ligand.
to OH and NH protons, respectively. These hydrogen resonances are
seen in the high ı values because they are attached to highly elec-
tronegative atoms oxygen and nitrogen, respectively, and hence in
a low electron density environment. This assignment can be con-
firmed by the deuteriated proton spectra in which the intensity of
these bands is considerably decreased. Position of these peaks in the
downfield region suggests the possibility of considerable extent of
hydrogen bonding involved by them. Hydrogen bonding decreases
the electron density around the proton and thus moves the pro-
ton absorption to lower field. The doublets observed at 8.15 and
8.37 ppm are assigned to the equivalent protons at C11 and C15
and C12 and C14, respectively. Protons at C12 and C14 resonate at
more downfield compared to those at C11 and C15 because of the
presence of electron withdrawing nitro group at its ortho position.
The singlet with an area integral of one at ı 8.57 ppm is due to the
3.3. 1H NMR and 1H–1H COSY data of the ligand
The 1H NMR spectrum of the compound H2L and its assignments
are shown in Fig. 1. There are two sharp singlets at the very down-
field region of the spectrum i.e., at 12.24 and 11.43 ppm are assigned
Fig. 2. 1H–1H COSY spectrum of the ligand.

B.N. Bessy Raj et al. / Spectrochimica Acta Part A 71 (2008) 1253–1260
1257
Fig. 3. 13 C–1H HSQC spectrum of the ligand.
resonance of the proton at C8. The peak at ı 7.47 ppm is the C4
proton resonance, is a doublet due to the presence of a neighbor-
ing proton at C3. Peaks generated by C3 and C7 are very close to
each other because of their nearly same electron environment. C7
gives a singlet at 6.49 ppm and C3 gives a doublet due to the pres-
ence of neighboring proton C4 at 6.53 ppm. The singlet at 3.77 ppm,
having an area integral of three is assigned to the methoxy pro-
tons.
to locate due to the poor solubility of the compound. Secondly, the
common spin-lattice relaxation mechanism for 13C results from
dipole–dipole interaction with directly attached protons. Thus,
nonprotonated carbon atoms often have longer relaxation times
The above assignments of the proton NMR spectrum are also
confirmed by 1H–1H correlation spectroscopy. The COSY spectrum
is shown in Fig. 2. There is no correlation for the peaks at ı 3.77,
8.57, 11.43 and 12.24 in the COSY spectrum, which confirms the
above assignments. Correlation patterns are observed in the aro-
matic region only. Peaks at ı 8.15, 8.37, 6.53 and 7.47 ppm make good
contours in the COSY spectrum and peak at ı 6.49 ppm makes only
a small correlation. Horizontal and vertical straight lines drawn
from ı 8.15 ppm in the diagonal of COSY spectrum will meet the
contours at ı 8.37 ppm, confirms the correlation between C11 and
C15 protons with C12 and C14 protons. Similarly lines from ı 6.53
meet at ı 7.47, confirming the aforesaid assignments of the peaks.
Small contour made by ı 6.49 peak with ı 6.53 peak suggests
the small extent of correlation with the proton at the meta posi-
tion.
3.4. 13 C NMR and 13 C–1H HSQC spectra of the ligand
The 13C spectrum and 13C–1H correlation HSQC spectrum of the
compound were also recorded in DMSO-d6 and the HSQC spectrum
is shown in Fig. 3. The correct assignment of the 13C peaks can
be done with the help of HSQC. The 13C peaks at ı 162.6,111.88,
159.2, 169.8, 138.8 and 149.82 do not make any correlation pattern
in HSQC suggesting that these peaks are made by nonprotonated
carbons and are assigned as C2 (162.2), C5 (111.88), C6 (159.2),
C9 (169.8) C10 (138.8) and C13 (149.82). The peak due to the
carbonyl carbon C9 at ı 169.8 ppm is very weak and is difficult
to distinguish from the noise. This may be due to the following
reasons. Firstly, in the solution state, there may be considerable
extent of keto–enol tautomerism so that the resonance frequency
of carbonyl carbon changes continuously and the peaks are difficult
Fig. 4. The EPR spectra of the copper complex in polycrystalline state at 298 K and
in DMF at 77 K.

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B.N. Bessy Raj et al. / Spectrochimica Acta Part A 71 (2008) 1253–1260
Fig. 5. Molecular structure of H2L. Intramolecular hydrogen bonds are shown as
dotted lines. Ellipsoids are drawn with 50% probability.
and give small peaks. Hence carbonyl carbon will give only small
peaks and at low concentrated solutions, it may not be detected.
Peaks at ı 55.58, 106.87, 131.32, 101.31, 149.54, 129.24 and 123.91
make contours at 1H ı values corresponding to 3.77, 6.53, 7.47,
6.49, 8.57, 8.15 and 8.37 ppm, respectively, and are assigned as C1
(55.58), C3 (106.87), C4 (131.32), C7 (101.31), C8 (149.54), C11 and
C15 (129.24), C12 and C14 (123.91).
Fig. 7. Molecular structure of CuLpy. Ellipsoids are drawn with 50% probability.
The molecule exists in the keto tautomeric form and the con-
figuration of C8–N1 bond is E. The molecule exists mainly in two
planes. One plane corresponding to the phenyl ring of the nitro-
phenyl moiety and the other to the remaining part of the molecule.
This twisting may be to relieve the steric interactions between the
hydrogen atoms N2–H and C11–H. The three bond angles around C9
atom are not equal to 120◦ each. It is seen that the N2–C9–O3 bond
angle is considerably greater than N2–C9–C10 angle. This obser-
vation is similar to the structures of hydrazones reported earlier,
which is explained in order to decrease the repulsion between the
lone pairs present in N2 and O3 atoms. The central part of the
molecule adopts a completely extended double bonded conforma-
3.5. EPR specrum of the copper complex
The EPR spectra of the complex in the polycrystalline state at
298 K and in DMF at 77 K are shown in Fig. 4. Both the spectra
are axial. The first one has g values g = 2.2041 and g = 2.0536
||
⊥
and the later one with g values of g = 2.195 and g = 2.0937. Since
||
⊥
the lowest g value is less than 2.04, the complex may have an
axial symmetry with all the principal axes aligned parallel, which
supports the square planar nature of the complex. The f value
˚
tion. It can be confirmed by the C9–O3 bond length (1.2324(23) A),
which is considerably longer than the standard C O bond length
(f = g /A ), which reveals the extent of tetragonal distortion, is equal
|| ||
´
˚
˚
to 107.07 for the complex. The f values are reported to be in
the range of 105–135 cm for square planar complexes [22]. Also,
the trend ge < g < g observed for the complex shows that the
1.21 A and N2–C9 bond length (1.3380(25) A), which is shorter than
˚
standard N–C single bond length (1.47 A). Similar observation was
reported in the case of early published crystal structures of hydra-
zone molecules.
⊥
||
unpaired electron is localized in the dx
orbital of the copper(II)
2
2
−y
ions and the spectral features are characteristics of axial symme-
try.
The packing of the molecules (Fig. 6) in the crystal is effected by
a wide network of intermolecular hydrogen bonds involving water.
In the crystal lattice, the molecules are arranged parallel to each
other, but in a zigzag fashion such that the nitrobenzoyl fragment of
one molecule is just above the methoxy phenyl fragment of second
one. The molecules are thus stalked together by a wide network of
hydrogen bonds, Cg–Cg interactions and C–H· · ·ꢄ interactions. Each
water molecule forms three intermolecular hydrogen bonds in the
packing pattern. They are O6· · ·H(2A)–O2 and O6–H(62)· · ·O3 with
3.6. Crystal structure of the ligand
The molecule crystallizes in the triclinic crystal system with a
¯
space group of PI. The crystal structure of the compound with atom
numbering scheme showing 50% displacement ellipsoids is shown
in Fig. 5.
Fig. 6. Packing diagram of the compound H2L. Intra and intermolecular hydrogen bonds are shown as dotted lines.

B.N. Bessy Raj et al. / Spectrochimica Acta Part A 71 (2008) 1253–1260
1259
Fig. 8. Packing diagram of the compound CuLpy.
a molecule in the same plane and O6–H(61)· · ·O1 with a molecule
of adjacent plane arranged in an opposite fashion with it. In addi-
tion to this, there are two intramolecular H-bonding present viz.,
O2–H(2A)· · ·N1 and N2–H1· · ·O6. Cg–Cg interactions also have con-
siderable influence in the packing pattern. There is a C–H· · · ꢄ is also
present between C8–H8 and Cg1 comprising of C2, C3, C4, C5, C6
can be obtained free of charge at www.ccdc.cam.ac.uk/conts/
retrieving.html [or from Cambridge Crystallographic Data Centre
(CCDC), 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223
336033; e-mail: deposit@ccdc.cam.ac.uk].
Acknowledgments
˚
and C7 with an H· · ·Cg distance 3.357(21) A.
This work is supported by Department of Science and Tech-
nology, Ministry of Science and Technology, Government of India
(No. SR/S1/IC-31/2002. The authors thank the Sophisticated Ana-
lytical Instrumentation Facility (SAIF), Cochin University of Science
and Technology, Kochi-22, Kerala, India for elemental analyses and
Indian Institute of Science, Bangalore for NMR data.
3.7. Crystal structure of the complex
The structure of the Cu(II) complex together with the atom num-
bering scheme is shown in Fig. 7. In this complex the dinegative
N-2-hydroxy-4-methoxy benzaldehyde-Nꢀ-4-nitrobenzoyl hydra-
zone is coordinated to Cu(II) through the deprotonated phenolic
oxygen O2, azomethine nitrogen N1 and deprotonated enolate oxy-
gen O3 forming five and six membered chelate rings. The fourth
site is occupied by the pyridyl nitrogen N4. The C8–N1 and N1–N2
bonds of the ligand are found to be slightly increased and N2–C9
bond is found to be slightly decreased after coordination confirm-
ing the proposed mode of coordination. The complex is almost
planar with a slight distortion. The distortion from the regular
square planar structure is determined from the departure of the
bong angles around Cu(II) [O2–Cu1–N1 (93.55(9)), N1–Cu1–O3
(80.96(9)), O2–Cu1–N4 (92.46(9)), O3–Cu1–N4 (93.13(9))] from
90◦. The found distortion may be due to the rigidity of the chelate
rings formed. The structures reported here are more or less similar
to the compounds reported earlier [23,24]. The C9–O3 bond length
References
[1] P.B. Sreeja, M.R.P. Kurup, A. Kishore, C. Jasmin, Polyhedron 23 (2004)
575.
[2] P.B. Sreeja, M.R.P. Kurup, Spectrochim. Acta 61 (2005) 331.
[3] C. Pelizzi, G. Pelizzi, J. Chem. Soc., Dalton Trans. (1980) 1970.
[4] S. Abram, C. Maichle-Mo¨ssmer, U. Abram, Polyhedron 17 (1998) 131.
[5] P.B. Sreeja, A. Sreekanth, C.R. Nayar, M.R.P. Kurup, A. Usman, I.A. Razak, S.
Chantrapromma, H.K. Fun, J. Mol. Struct. 645 (2003) 221.
[6] D.K. Johnson, M.J. Pippard, T.B. Murphy, N.J. Rose, J. Pharmacol. Exp. Ther. 221
(1982) 399.
[7] P. Ponka, J. Barova, J. Neuwirt, O. Fuchs, E. Necas, Biochim. Biophys. Acta 586
(1979) 278.
[8] J.R. Dimmock, G.B. Baker, W.G. Taylor, Can. J. Pharm. Sci. 7 (1972) 100.
[9] J. Patole, U. Sandbhor, S. Padhye, D.N. Deobagkar, C.E. Anson, A. Powell, Bioorg.
Med. Chem. Lett. 13 (2003) 51.
[10] W. Xiao, Z.-L. Lu, C.-Y. Su, K.-B. Yu, L.-R. Deng, H.-Q. Liu, B.-S. Kang, J. Mol. Struct.
553 (2000) 91.
˚
is 1.300(3) A is considerably greater than the C O bond length,
which confirms the enolization of the ligand at the time of coor-
dination. In the crystal lattice (Fig. 8), the packing is effected by
a wide network of ꢄ–ꢄ staking interactions. No classic hydrogen
bonds are found in the lattice, but a weak C–H· · ·ꢄ interactions are
found between the hydrogen in the aromatic rings with the oxygen
atoms of the neighboring molecules. Additional Y–X· · ·ꢄ ring inter-
actions are found between N3–O4 and Cg1, where the centroid Cg1
[11] C.M. Armstrong, P.V. Bernhardt, P. Chin, D.R. Richardson, Eur. J. Inorg. Chem.
(2003) 1145.
[12] J.M. Fernandez-G, F.A. Lopez-Duran, S.H. Ortega, V.G. Vidales, N.M. Ruvalcaba,
M.A. Martinez, J. Mol. Struct. 612 (2002) 69.
[13] B.D. Wang, Z.Y. Yang, D.W. Zhang, Y. Wang, Spectrochim. Acta A 63 (2006)
213.
[14] P.G. Lacroix, Eur. J. Inorg. Chem. (2001) 339.
[15] B.N. Bessy Raj, M.R.P. Kurup, E. Suresh, Struct. Chem. 17 (2006) 201.
[16] B.N. Bessy Raj, M.R.P. Kurup, unpublished data.
[17] G.M. Sheldrick, SHELXS-97 Program for the Solution of Crystal Structures, Uni-
versity of Go¨ttingen, Go¨ttingen, Germany, 1997.
˚
consists of Cu1, O3, C9, N2, N1 having the Y· · ·Cg distance 3.585 A.
[18] K. Brandenburg, Diamond Version 3.0, 1997–2004 Crystal Impact GbR, Bonn,
Germany.
[19] F. Carati, U. Caruso, R. Centore, W. Marcolli, A. De Maria, B. Panunzi, A. Roviello,
A. Tuzi, Inorg. Chem. 41 (2002) 6597.
[20] A.B.P. Lever, Inorganic Electronic Spectroscopy, 2nd ed., Elsevier Science Pub-
lishers B.V., Netherlands, 1984.
4. Supplementary data
CCDC 654105 and 654106 contain the supplementary crys-
tallographic data for [CuLpy] and H2L of this paper. These data

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[21] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Com-
pounds, 4th ed., John Wiley & Sons, Inc., 1986.
[23] M.F. Iskander, T.E. Khalil, R. Werner, W. Haase, I. Svoboda, H. Fuess, Polyhedron
19 (2000) 1181.
[22] R. Pogni, M.C. Baratto, A. Diaz, R. Basosi, J. Inorg. Biochem. 79 (2000)
333.
[24] S. Das, G.P. Muthukumaragopal, S. Pal, S. Pal, New J. Chem. 27 (2003)
1102.