X-ray crystal structure of phenylglycine hydrazide: Synthesis and spectroscopic studies of its transition metal complexes

Article abstract of DOI:10.1016/j.saa.2006.06.041

Phenylglycine hydrazide was synthesized and investigated by X-ray crystallography. It crystallizes in the monoclinic space group P121/c with cell parameters a = 5.9459 (18) A, b = 5.1940 (16) A, c = 26.7793 (83) A and Z = 2. Its conformational changes, on complexation with transition metal ions Cu(II), Co(II), Ni(II), Mn(II) and Zn(II) has been studied on the basis of elemental analysis, magnetic moment and spectral (IR, ¹H NMR, UV-vis) studies. The bidentate nature of the ligand was confirmed on the basis of a comparative IR and NMR spectral studies. The trigonal bipyramidal geometries were observed for Cu(II), Ni(II) and Co(II) complexes, while it is octahedral for the remaining complexes. The conductivity data suggest them to be non-electrolytes.

Full text of DOI:10.1016/j.saa.2006.06.041

Spectrochimica Acta Part A 67 (2007) 172–177
X-ray crystal structure of phenylglycine hydrazide: Synthesis and
spectroscopic studies of its transition metal complexes
Kalagouda B. Gudasia,∗, Manjula S. Patila, Ramesh S. Vadavia,
Rashmi V. Shenoya, Siddappa A. Patila, M. Nethajib
a Department of Chemistry, Karnatak University, Dharwad 580 003, India
b Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012, India
Received 18 February 2006; accepted 28 June 2006
Abstract
Phenylglycine hydrazide was synthesized and investigated by X-ray crystallography. It crystallizes in the monoclinic space group P121/c with
˚
˚
˚
cell parameters a = 5.9459 (18) A, b = 5.1940 (16) A, c = 26.7793 (83) A and Z = 2. Its conformational changes, on complexation with transition
1
metal ions Cu(II), Co(II), Ni(II), Mn(II) and Zn(II) has been studied on the basis of elemental analysis, magnetic moment and spectral (IR, H
NMR, UV–vis) studies. The bidentate nature of the ligand was confirmed on the basis of a comparative IR and NMR spectral studies. The trigonal
bipyramidal geometries were observed for Cu(II), Ni(II) and Co(II) complexes, while it is octahedral for the remaining complexes. The conductivity
data suggest them to be non-electrolytes.
© 2006 Elsevier B.V. All rights reserved.
Keywords: Phenylglycine hydrazide; Amino acid hydrazide; X-ray crystallography; Transition metal complexes
1. Introduction
by hydroxylases such as phenylalanine hydroxylase (PAH) in
the presence of iron or copper and a reduced pterin cofactor
5,6,7,8-tetrahydrobiopterin. This hydroxylation reaction may
be regarded as a functionalization of aromatic amino acids
[9].
Various important properties of carbonic acid hydrazides and
their application in medicine, analytical chemistry have led to
an increased interest in their complexation characteristics with
transition-metal ions [10]. According to Cabezas and Satterth-
wait, relative to simple imines (Schiff bases), hydrazides are
expected to have the advantage of greater stability and the poten-
tial for peptide-like hydrogen bonding [11]. Hydrazides are
reported to exhibit carcinostatic activity against several types of
tumors. As a result of their antibacterial and antifungal proper-
ties [12] acid hydrazides are of great importance. The formation
of metal complexes plays an important role in the enhancement
of their biological activity [13].
Amino acids have proven to play a significant role in
the synthesis of novel drug candidates with the use of non-
proteinogenic and unnatural amino acids [1–8]. Amino acid
side chains of proteins and physiologically active peptides play
essential roles in catalysis, molecular recognition, information
transfer, and other biological functions. They are involved in
binding with target molecules and achieve high efficiency and
specificity by a combination of interacting groups. The prop-
erties of the side groups of aromatic amino acids in metal
complexes are particularly interesting, because they can be
involved in interactions with the central metal ion as well
as other aromatic rings. In addition, these amino acids are
important starting materials for the biosynthesis of neurotrans-
mitters called catecholamines and serotonine, the initial step
for which is the hydroxylation of the aromatic amino acids
To gain an insight into the conformational aspects of the
title compound and in order to study its coordination behav-
ior towards transition metal ions, we have synthesized Cu(II),
Co(II), Ni(II), Mn(II) and Zn(II) complexes of phenylglycine
hydrazide.
∗
Corresponding author. Tel.: +91 836 2460129 (Res)/91 836 2215286 (Off);
fax: +91 836 2771275.
E-mail address: kbgudasi@rediffmail.com (K.B. Gudasi).
1386-1425/$ – see front matter © 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2006.06.041

K.B. Gudasi et al. / Spectrochimica Acta Part A 67 (2007) 172–177
173
Scheme 1.
2. Experimental section
2.3. Synthesis of ligand and complexes
2.1. Measurements
The preparation of phenylglycine ester (pge) and phenyl-
glycine hydrazide (pgh) [16] involves the following steps
(Scheme 1).
The metal content of the complexes was determined by EDTA
titration after decomposition with a mixture of HCl and HClO4.
The chloride content of the complexes was determined as AgCl
gravimetrically [14]. The carbon, hydrogen and nitrogen con-
tents in each sample were determined using a Heraus C H N
rapid analyzer. IR spectra in the 4000–400 cm−1 range were
measured with a Thermo Nicolet 320 FT-IR spectrometer using
KBr discs. 1H NMR spectra were recorded in DMSO-d6 as the
solvent at 400 MHz with a BRUKER AMX 400 spectrometer
using tetramethylsilane (TMS) as an internal reference. UV–vis
spectra of the complexes were recorded on a Varian CARY
50 Bio UV–vis spectrophotometer. The magnetic susceptibil-
ity measurements were carried out on a Faraday balance using
Hg[Co(NCS)4] as the calibrant and diamagnetic corrections
were made by direct weighing of the ligand for diamagnetic pull.
Conductance measurements were recorded in DMSO (10−3 M)
using Elico conductivity bridge type CM-82, provided with a dip
type conductivity cell fitted with platinum electrodes. EPR spec-
tra were recorded on a Varian E-4 X-band spectrometer using
tetracyanoethylene (TCNE) as ‘g’ (g = 2.0027) marker at room
temperature and also at liquid nitrogen temperature. The ther-
mal studies of the complexes were carried with Mettler Toledo
TGA/SDTA851e with stare software, under nitrogen atmosphere
with a heating rate of 10 ◦C/min in the temperature range of
50–1000 ◦C.
2.3.1. Preparation of phenylglycine ester
Equimolar quantities of aniline (0.01 mol), chloroethylac-
etate (0.01 mol) and sodium acetate were mixed with abso-
lute alcohol. The mixture was refluxed on an oil bath for
6 h at 225–230 ◦C. The product was cooled to room temper-
ature and mixed with 100 ml of water. The solid ester was
extracted with ether and dried in vacuo over anhydrous CaCl2.
Excess chloroethylacetate was removed by vacuum distilla-
tion. The product was recrystallised from aqueous alcohol. The
purity of the compound was tested by TLC. Yield: 85%, mp:
85 ◦C.
2.3.2. Preparation of phenylglycine hydrazide
A 0.01 mol of pge and 90% hydrazine hydrate (0.01 mol)
were mixed with 50 ml of absolute alcohol. The mixture was
refluxed on a water bath for 8 h. Alcohol and excess hydrazine
hydrate were removed by rotary evaporation. The remaining por-
tion was cooled to get the pgh, which was recrystallised from
methanol. The colourless crystals were obtained which were
suitable for X-ray diffraction. Yield: 90%.
2.3.3. Cu(II), Co(II), Ni(II), Mn(II) and Zn(II) complexes
An ethanolic solution (10 ml) of 0.001 mol of metal (II) chlo-
ride was added to 10 ml of a clear solution of pgh (0.165 g,
0.001 mol) in 10 ml of ethanol. The resulting mixture was
refluxed for 4 h on a water bath. The volume was reduced to
half by slow evaporation. After cooling, the complex precipi-
tates out, which was filtered, washed with ethanol and dried in
vacuo. Attempts to grow single crystals of the complexes were
unsuccessful.
The crystal data were collected on a BRUKER SMART
APEX CCD DIFFRACTOMETER equipped with a fine-focus
sealed tube employing graphite monochromatised Mo K␣
˚
radiation (λ = 0.71073 A). The structures were solved using
SHELXS-97 and the model was refined using SHELXL-97.
The hydrogen atoms were refined from the ρ map and included
in the refinement. The non-hydrogen atoms were refined
anisotropically while hydrogens were refined isotropically
[15].
3. Results and discussion
2.2. Materials
All the complexes were stable in air and insoluble in
chloroform, dichloromethane and benzene but soluble in
DMF and DMSO. The elemental analyses indicate the
mononuclear complexes (Fig. 1) with the empirical formula
[M(pgh)Cl2(nH2O)]·xH2O [M = Cu(II), Ni(II), Co(II), Mn(II),
Zn(II) and Cd(II), n = 1, 2 and x = 0, 1, 2]. The molar conduc-
All the solvents used were of analytical grade and used
without further purification. Starting materials, aniline and
chloroethylacetate were obtained from s.d. Fine-chem Ltd.,
India.

174
K.B. Gudasi et al. / Spectrochimica Acta Part A 67 (2007) 172–177
Fig. 1. Proposed structure for the complexes of pgh.
Table 1
Analytical, conductance and magnetic moment data of pgh and its complexes
a
Compound
MF
FW
Found (Calcd.) %
ΛM
μeff (B.M.)
C
H
N
M
–
Cl
–
pgh
C8H11N3O
165.0 58.00 (58.18) 6.30 (6.66) 25.25 (25.45)
–
–
[Cu(pgh)Cl2(H2O)]·H2O
CuC8H15N3O3Cl2 335.5 28.15 (28.61) 4.18 (4.47) 12.00 (12.51) 18.50 (18.92) 21.00 (21.16) 11.25 1.70
[Co(pgh)Cl2(H2O)]·2H2O CoC8H17N3O4Cl2 348.9 27.14 (27.51) 4.50 (4.87) 12.01 (12.03) 16.50 (16.88) 20.15 (20.34) 12.50 4.50
[Ni(pgh)Cl2(H2O)]·2H2O NiC8H17N3O4Cl2
348.6 27.00 (27.53) 4.65 (4.87) 12.00 (12.04) 16.25 (16.81) 20.15 (20.36) 8.6Z8 2.32
[Mn(pgh)Cl2(H2O)2] MnC8H15N3O3Cl2 326.9 29.26 (29.36) 4.39 (4.58) 12.35 (12.84) 16.18 (16.79) 21.50 (21.72) 15.60 5.70
The values in the parentheses are calculated; Diamag., diamagnetic; MF, molecular formula; FW, formula weight.
a
ꢀ
−1 cm2 mol−1
.
The carbonyl stretching vibration observed at 1650 cm−1
has shifted to lower frequencies in the spectra of all the com-
plexes suggesting its involvement in coordination. The non-
ligand bands of weak to medium intensity were observed in the
region 503–581 cm−1 and 410–478 cm−1 and ascribed to M–N
and M–O vibrations, respectively.
tivity, magnetic moment and analytical data are presented in
Table 1.
3.1. IR spectra
Conclusions on coordinating sites are drawn by comparing
the infrared spectra of the ligand and the respective complexes.
Important IR spectral bands of pgh and its complexes along with
their tentative assignments are presented in Table 2.
3.2. 1H NMR spectra
The spectrum of pgh exhibits asymmetric –NH2 stretch-
ing frequency at 3339 cm−1 and symmetric –NH2 stretching
frequency at 3302 cm−1. On complexation it is observed that
asymmetric stretching band has been considerably lowered in
frequency compared with that of the uncoordinated ligand while
the symmetric stretching band has disappeared. These changes
indicate the coordination of hydrazinic-nitrogen to the metal ion.
The changes in –NH frequency are a consequence of drainage
of electrons from nitrogen atom resulting in the weakening in
the N–H bond [17]. This indicates that the nitrogen atom of the
amino group serves as a coordinating center in the ligand. The
appearance of a new broad band in the region 3359–3497 cm−1
followed by another band at ∼826–839 cm−1 indicates the pres-
ence of coordinated water molecule [18].
The ligand spectrum shows a sharp singlet for methylene
protons at 3.61 ppm. The peak corresponding to –NH2 was
observed at 4.22 ppm which is D2O exchangeable. Signal for
–NH attached to phenyl ring was observed at 5.81 ppm and for
amide –NH at 9.04 ppm (D2O exchangeable). The aromatic pro-
tons were observed in the region 6.54–7.10 ppm.
In the NMR spectrum of Zn(II) complex of pgh, the methy-
lene group has shifted from 3.61 to 3.82 ppm due to the involve-
ment of adjacent >C O group in coordination. The –NH2
group has shifted to downfield region to 4.50 ppm indicating
its involvement in coordination. The signal due to amide –NH
has shifted from 9.04 to 9.20 ppm, indicating the coordination
of the ligand through >C O.
Table 2
IR spectral data (cm−1) of pgh and its complexes
Compound
ν(OH) (H2O)
ν(NH) (asymm.)
ν(NH) (sym.)
ν(C O)
ν(M–O)
ν(M–N)
δ(OH) (H2O)
pgh
–
3434
3497
3359
3428
3374
3339
3195
3207
3190
3205
3264
3302
1650
1610
1616
1644
1621
1644
–
507
509
513
524
503
–
417
410
423
421
478
–
839
837
830
826
830
[Cu(pgh)Cl2(H2O)]·H2O
[Co(pgh)Cl2(H2O)]·2H2O
[Ni(pgh)Cl2(H2O)]·2H2O
[Mn(pgh)Cl2(H2O)2]
[Zn(pgh)Cl2(H2O)2]
–
–
–
–
–

K.B. Gudasi et al. / Spectrochimica Acta Part A 67 (2007) 172–177
175
due to the tumbling motion of the molecules. The giso values
at 300 and 77 K are 2.07 and 2.08, respectively. Mononuclear
nature of the complex was also evident from the absence of a
half field signal due to the ms = 2 transitions, ruling out any
Cu–Cu interaction [22].
4. Crystallographic studies
The X-ray quality crystals of pgh were obtained by the slow
evaporation of the methanolic solution. The molecule crystal-
lizes in monoclinic system with the space group P121/c 1, with
˚
β = 94.00. The cell dimensions are a = 5.9459 (18) A, b = 5.1940
˚
˚
˚
(16) A and c = 26.7793 (83) A, Z = 2 and volume = 825.01
3
(44) A (CCDC No. 292960).
Crystallographic parameters, selected bond lengths, bond
angles, torsion angles, equations for the mean least square planes
in the structure and hydrogen bonds are compiled in Tables 3–6,
respectively. The ORTEP and molecular packing diagrams of
the title compound are shown in Figs. 3 and 4, respectively.
The molecular packing diagram shows the presence of three
Fig. 2. Electronic spectrum of [Co(pgh)Cl2(H2O)]·2H2O.
˚
intermolecular hydrogen bonds viz. N1–H5· · ·O1 = 3.011 (2) A,
3.3. Electronic spectra
Table 3
The electronic spectrum of Cu(II) complex shows d–d tran-
Crystallographic parameters of pgh
sitionꢀbands at 10917 and 14285 cm−1 and have been attributed
ꢀ
to A1 → Eꢀ and 2A1 → Eꢀꢀ transitions, respectively. The
position and energy of transitions indicates a trigonal bipyra-
midal geometry for Cu(II) complex [19]. The Ni(II) complex
exhibits two bands at 12562 and 24630 cm−1 corresponding
2
2
2
Empirical formula
FW
Crystal system
Space group
C8H11N3O
165.19
Monoclinic
P121/c
5.9459 (18)
5.1940 (16)
26.7793 (83)
90.00 (0.00)
94.00 (0.00)
90.00 (0.00)
825.01 (0.44)
2
293 (2)
0.074
0.71073
278
˚
a (A)
ꢀꢀ
ꢀꢀ
to the transitions Eꢀ(F) → A1 + A2(F) and 3Eꢀ(F) → Eꢀꢀ
(P), respectively. This suggests a trigonal bipyramidal geometry
for Ni(II) complex. The electronic spectrum of Co(II) com-
plex exhibit the bands around 1168ꢀ2 and 15847 cm−1 assignable
3
3
3
3
˚
b (A)
˚
c (A)
α (◦)
β (◦)
γ (◦)
ꢀ
ꢀ
to 4A2 → Eꢀ(F) and 4A2 → A2 (P) transitions, respectively
favoring the trigonal bipyramidal geometry for Co(II) complex.
The Mn(II) and Zn(II) complexes did not show any d–d transi-
tions. The electronic spectrum of Co(II) complex is displayed in
Fig. 2.
4
4
3
˚
V (A )
Z
T (K)
Absorption coefficient (mm−1
)
˚
λ(Mo K␣) (A)
F (0 0 0)
θ range
Limiting indices
3.05–28.00
3.4. Magnetic moments
−7 ≤ h < 7, −5 ≤ k < 6, −34 ≤ l < 35
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2σ(I)]
5378
1941
The magnetic moment values of all the complexes of pgh are
recorded at room temperature. The Cu(II) complex exhibits a
μeff value of 1.70 B.M. The proximity of the observed μeff value
with the spin only value rules out the possibility of metal–metal
interaction. The magnetic moment value of Co(II) complex
is found to be 4.50 B.M., which is well within the reported
range for trigonal bipyramidal geometry [20,21]. Ni(II) complex
shows a μeff value of 2.32 B.M. for trigonal bipyramidal com-
plex [20,21]. The effective magnetic moment of Mn(II) complex
observedis5.70 B.M., whichisindicativeofhigh-spintypecom-
plex and also the non-involvement of orbital contribution. Zn(II)
complex is diamagnetic with d10 configuration.
1941/0/153
0.785
R1 = 0.0523, wR2 = 0.1499
3.5. EPR spectra
The EPR spectra of the Cu(II) complex at both 300 and 77 K
show intense absorption band at high field, which is isotropic
Fig. 3. ORTEP diagram of pgh.

176
K.B. Gudasi et al. / Spectrochimica Acta Part A 67 (2007) 172–177
Table 4
Bond distances (A) in pgh
˚
Bonds
Bond lengths
O1–C8
C1–C6
C1–C2
N1–C7
N1–C4
N2–N3
N2–C8
C7–C8
C6–C5
C4–C5
C4–C3
C2–C3
1.2356 (2)
1.3807 (4)
1.3796 (4)
1.4444 (3)
1.3945 (2)
1.4143 (2)
1.3247 (2)
1.5171 (3)
1.3805 (3)
1.3924 (3)
1.3945 (3)
1.3741 (3)
Bond angle (◦)
118.91
121.41
122.40
113.60
121.24
122.90
118.91
118.12
122.98
121.73
115.29
120.11
120.90
121.23
C6–C1–C2
C7–N1–C4
N3–N2–C8
N1–C7–C8
C1–C6–C5
N1–C4–C5
N1–C4–C3
C5–C4–C3
O1–C8–N2
O1–C8–C7
N2–C8–C7
C6–C5–C4
C1–C2–C3
C4–C3–C2
Table 5
Torsion angles (◦) in pgh
Fig. 4. Molecular packing diagram of pgh.
C4–N1–C7–C8
C7–N1–C4–C5
C7–N1–C4–C3
N3–N2–C8–O1
N3–N2–C8–C7
N1–C7–C8–O1
N1–C7–C8–N2
N1–C4–C5–C6
N1–C4–C3–C2
86.73
−8.19
In the structure of pgh, plane I [C1, C2, C3, C4, C5,
C6] makes a dihedral angle of 86.99◦ with plane II [N1, C7,
C8, N2, N3]. The torsion angles N3–N2–C8–O1 = −3.01◦ and
N1–C7–C8–O1 = −171.61◦ reveal that O1 and N3 are cis to
each other and O1 and N1 are trans to each other. The angles
around C7 [N1–C7–H7 = 112.43◦, N1–C7–H7ꢀ = 107.64◦,
H7–C7–C8 = 107.20◦ and H7ꢀ–C7–C8 = 108.67◦] indicate that
the C7 is in tetrahedral environment.
174.93
−3.01
176.40
−171.61
8.98
−177.68
177.31
Acknowledgements
ꢀ
˚
˚
N3–H3A · · ·O1 = 3.084 (3) A and N2–H2A· · ·N3 = 3.190 (3) A.
The average C–C bond distance among the phenyl ring carbons
is 1.38 A, comparable with the reported value [23]. The Csp –N
[C4–N1 = 1.3945 (25) A] and Csp –N1 [C7–N1 = 1.444 (28) A]
shows the single bond character. The C O [C8–O1 = 1.2356
(24) A] distance shows the double bond character [23].
The authors are thankful to Dr. M. Nethaji, Indian Institute of
Science, Bangalore for the X-ray crystallographic studies. The
authors thank to Sophisticated Instrumentation Facility, Indian
Institute of Science, Bangalore and Indian Institute of Tech-
nology, Bombay for recording 1H NMR and EPR spectra. The
authors also thank Professor S.B. Padhye, University of Pune,
Indiaformagneticmeasurementfacilities. Thanksarealsodueto
the University Sophisticated Instrumentation Center, Karnatak
University, Dharwad for carrying out elemental and electronic
spectral analyses.
2
˚
3
˚
˚
˚
Table 6
Least square planes through the phenyl ring and N1, C7, C8, N2, N3 atoms
Planes
m1
m2
0.67173
m3
D
(1) Phenyl ring C1 C2
C3 C4 C5 C6
(2) Atoms N1, C7,
C8, N2, N3
−0.39735
−0.62522
−3.62564
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