Synthesis and characterization of novel M(II) (M = Mn(II), Ni(II), Cu(II) or Zn(II)) complexes with tridentate N2, O-donor ligand (E)-2-amino-N'-[1-(pyridin-2-yl)ethylidene]benzohydrazide

Article abstract of DOI:10.4314/bcse.v30i1.9

The coordination chemistry towards the M(II) metal centre (M = Mn, Ni, Cu or Zn) of the hydrazone ligand (E)-2-amino-N'-[1-(pyridin-2-yl)ethylidene]benzohydrazide (H3L) has been explored and complexes having formulae [Mn(H2L)2] (1), {[Ni(H₂L)₂].DMF.0.4H₂O} (2), {[Cu₂(H₂L)2(μ-Cl)₂].DMF} (3) and [Zn(H₂L)₂] (4) have been isolated and characterized by IR, UV-Visible spectroscopy, elemental analysis and Xray crystal diffraction. Structural studies reveal that the mononuclear complexes (1), (2) and (4) adopt highly distorted octahedral geometries while the dinuclear complex (3) adopts a square pyramidal geometry around each copper(II) ion.

Full text of DOI:10.4314/bcse.v30i1.9

Bull. Chem. Soc. Ethiop. 2016, 30(1), 101-110.
Printed in Ethiopia
DOI: http://dx.doi.org/10.4314/bcse.v30i1.9
ISSN 1011-3924
 2016 Chemical Society of Ethiopia
SYNTHESIS AND CHARACTERIZATION OF NOVEL M(II) (M = Mn(II), Ni(II),
Cu(II) OR Zn(II)) COMPLEXES WITH TRIDENTATE N2,O-DONOR LIGAND
(E)-2-AMINO-N’-[1-(PYRIDIN-2-YL)ETHYLIDENE]BENZOHYDRAZIDE
Cheikh Hamidou Kane1, Daniel Tinguiano1, Farba Bouyagui Tamboura1, Ibrahima Elhadj
Thiam1, Aliou Hamady Barry2, Mohamed Gaye1* and Pascal Retailleau3
1Department of Chemistry, University Cheikh Anta Diop, Dakar, Sénégal
2Department of Chemistry, University of Nouakchott, Mauritania, France
3Centre de Recherche de Gif, Institut de Chimie des Substances Naturelles, CNRS-UPR2301, 1
Avenue la Terrasse, 91198 Gif sur Yvette, France
(Received March 23, 2015; revised January 4, 2016)
ABSTRACT. The coordination chemistry towards the M(II) metal centre (M = Mn, Ni, Cu or Zn) of the
hydrazone ligand (E)-2-amino-N’-[1-(pyridin-2-yl)ethylidene]benzohydrazide (H3L) has been explored and
.
.
.
complexes having formulae [Mn(H2L)2] (1), {[Ni(H2L)2] DMF 0.4H2O} (2), {[Cu2(H2L)2(µ-Cl)2] DMF} (3) and
[Zn(H2L)2] (4) have been isolated and characterized by IR, UV-Visible spectroscopy, elemental analysis and X-
ray crystal diffraction. Structural studies reveal that the mononuclear complexes (1), (2) and (4) adopt highly
distorted octahedral geometries while the dinuclear complex (3) adopts a square pyramidal geometry around each
copper(II) ion.
KEY WORDS: Schiff base, Phenolate, Manganese(II), Nickel(II), Copper(II), Zinc(II), Mononuclear
complexes, X-Ray structure
INTRODUCTION
Versatility coordination to metal [1, 2], flexibility in assuming different conformations [3, 4],
possibility of tautomerism forms [5, 6] and possibility of reacting in anionic or neutral forms [7,
8], make the study of hydrazones chemistry extremely interesting. The chelating properties of
this kind of ligands are diversified by their possible presence in neutral, protonated or
deprotonated forms leading of various geometries upon coordination [9-11].
On continuing our work in the field of the synthesis of hydrazide ligand and the studies of
their reactivities with transition metal, we describe
a simple condensation of 2-
aminobenzoylhydrazide and 2-acetylpyridine to yield the title compound (E)-2-amino-N’-[1-
(pyridin-2-yl)ethylidene]benzohydrazide (H3L). The chelating behaviors of this ligand have
been investigated towards several transition metal ions. The synthesis and characterization of
three mononuclear (Mn(II), Ni(II) and Zn(II)) and one dinuclear (Cu(II)) metal complexes with
the potentially pentadentate Schiff base ligand H3L, having amine, hydrazone and pyridine
moieties with potential atoms donor (Scheme 1). The X-ray crystal structure of Mn(II), Ni(II),
Cu(II) and Zn(II) complexes are reported in this present work.
EXPERIMENTAL
Materials and procedures
.
.
Methyl anthranilate, hydrazine hydrate, 2-acetylpyridine, MnCl2 4H2O, NiCl2 6H2O,
.
CuCl2 2H2O as well as ZnCl2 were commercial products (from Alfa and Aldrich) and were used
without further purification. Solvents were of reagent grade and were purified by the usual
methods. Elemental analyses were performed in a Carlo-Erba EA microanalyser. Infra-red
__________
*Corresponding author. E-mail: mohamedl.gaye@ucad.edu.sn

102
Cheikh Hamidou Kane et al.
spectra were recorded as KBr discs on a Bruker IFS-66V spectrophotometer. For the ligand,
LSI-MS were recorded using a Micromass Autospec spectrometer with 3-nitrobenzyl alcohol as
the matrix. The 1H and 13C NMR spectra of the Schiff base were recorded in CDCl3 on a Bruker
500 MHz spectrometer at room temperature using TMS as an internal reference. The UV-Vis
spectra were run on a Jenway 6505 UV- Spectrophotometer (1100-200 nm) on 10-3 M DMF
solutions of the complexes. The molar conductance of 10-3 M solutions of the metal complexes
in DMF was measured at 25 oC using a WTW LF-330 conductivity meter with a WTW
conductivity cell. Room temperature magnetic susceptibilities of the powdered samples
{calibrant Hg[Co(SCN)4]} were measured using a Johnson Mattey scientific magnetic
susceptibility balance. Melting points were recorded on a Büchi apparatus and are uncorrected.
X-ray data collection, structure determination, and refinement
The details of the X-ray crystal data, and the structure solution and refinement are given in
Table 1. Diffraction data were collected using an ENRAF NONIUS Kappa CCD diffractometer
with graphite monochromatized Mo K radiation ( = 0.71073 Å). All data were corrected for
Lorentz and polarization effects and for absorption by semi empirical methods based on
symmetry-equivalent and repeated reflections. Complex scattering factors were taken from the
program package SHELXTL [12]. The structures were solved by direct methods which revealed
the position of all non-hydrogen atoms. All the structures were refined on F2 by a full-matrix
least-squares procedure using anisotropic displacement parameters for all non hydrogen atoms
[13]. The hydrogen atoms were located in their calculated positions and refined using a riding
model. Molecular graphics were generated using ORTEP-3 [14].
Synthesis of the (E)-2-amino-N’-[1-(pyridine-2-yl)ethylidene]benzohydrazide ligand
Methylanthranilate (3 g, 20 mmol) and excess of hydrazine hydrate (8 mL, 160 mmol) were
refluxed during 24 hours and stored overnight in a refrigerator. A white solid was separated,
filtered off and recrystallized from ethanol to yield 2-aminobenzohydrazide (2.37 g, 15.69
mmol). The whole solid was dissolved in 40 mL of ethanol and 2-acetylpyridine (1.90 g, 15.69
mmol) was added. The resulting mixture was refluxed during 3 hours to yield a yellow solution.
The solution was evaporated to dryness to give yellow solid which was washed with ether and
dried in the air. Yield: 53.5% (2.13 g). Anal. calcd (found) for C14H14N4O (H3L): C, 66.13
(66.15); H, 5.55 (5.54); N, 22.03 (22.01) %. M.p. 170 oC. MS (FAB, m/z): 254 [H3L]+. IR (KBr,
cm-1): 3434m (asym(NH )) and 3317m (sym(NH )); 3284m (N-H); 1651s (C=O); 1615s (C=N); 1583s
2
2

((C=N) ); 1567s, 1512m, 1465m ((C=C) ). RCDCl 2.40 (s, 3H, -CH3), 5.54 (s, 2H,
py
Ar
NH2), 6.73-7.27 (m, 4H, HAr, 7.77-8.60 (m, 4H, HPy, 9.09 (s (broad), 1H, -NH) ppm.
CRCDCl 154.98 (-C=O), 149.40 (-C=N-), 148.68, 136.86, 136.36, 133.14, 124.02,
121.23, 119.31, 117.70, 116.70, 114.39 (CAr), 10.95 (-CH3) ppm.
H3L
Scheme 1
Bull. Chem. Soc. Ethiop. 2016, 30(1)

Synthesis and characterization of novel M(II) complexes with tridentate N2,O-donor ligand 103
Table 1. Crystallographic data and refinement parameters for (1), (2), (3) and (4).
Identification code
(1)
(2)
(3)
(4)
Empirical formula C28H26MnN8O2
C28H26NiN8O2·C3H7 C28H26Cl2Cu2N8O2· C28H26ZnN8O2
NO·0.4H2O
642.70
293 (2)
C3H7NO
777.64
293 (2)
Formula weight
T (K)
561.51
293 (2)
571.94
293 (2)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
 (°)
 (°)
Monoclinic
C2/c
21.970 (5)
10.440 (5)
12.736 (5)
Triclinic
Pī
Monoclinic
C2/c
16.076 (2)
8.3040 (11)
25.892 (3)
Monoclinic
P21/c
11.0150(10)
25.405(2)
10.3030 (10)
11.0987 (3)
11.32842 (5)
13.7624 (5)
102.3972 (16)
110.589 (2)
94.30 (2)
1560.9 (5)
2
1.374
0.67
0.71073
676
117.137 (5)
101.887 (2)
117.494 (2)
 (°)
V (Å3)
2599.6 (17)
4
1.435
0.55
0.71073
1164
3382.4 (8)
4
1.527
1.46
0.71073
1592
2557.5 (4)
4
1.485
1.00
0.7173
1184
Z
Dcalc (g cm-3)
 (mm-1)
(Å)
F(000)
Crystal size
2
Index ranges
0.20 x 0.10 x 0.05 0.2 x 0.10 x 0.05
2.21 to 27.50 1.6 to 26.4
-2828 ; -1213 ; -1313 ; -1413 ; - -1919 ; -99 ; - -1313 ; -3029 ; -
0.09 x 0.07 x 0.05 0.10 x 0.07 x 0.05
1.61 to 25.02 4.17 to 25.03
-1616
5158
1617
9694
3030
12431
1212
7673
Reflections
collected
Independant
2980 [0.021]
2980/0/177
6279 [0.019]
6279/17/456
2981 [0.031]
2981/6/223
4305 [0.048]
4305/0/349
refls [Rint
]
Data/restraints/
parameters
Goodness-of-fit
R Indices [I>2(I)]:
R1, wR2
1.11
0.043, 0.121
1.04
0.049, 0.133
1.04
0.033, 0.084
1.14
0.070, 0.185
R Indices (all data) 0.064, 0.147
R1, wR2
0.064, 0.144
0.046, 0.094
0.082, 0.193
Peak and hole
0.44 and -0.62
(e Å-3)
0.23 and -0.38
0.66 and -0.66
0.43 and -0.42
Synthesis of metal complexes
Ligand H3L (1.0 mmol, 254.3 mg) was dissolved under reflux in ethanol (10 mL) to give a clear
yellow solution. A solution of metal(II) chlorides (1 mmol) in ethanol (10 mL) was slowly
added with stirring. The colored resulting mixture was refluxed for about two hours and the
suspension was allowed to cool to room temperature and then filtered off. The precipitate was
washed with cold ethanol and acetone and dried in air. The resulting solid was dissolved in
dimethylformamide (DMF) solvent and the solution was allowed to concentrate in air.
.
.
.
Appropriate crystals of [Mn(H2L)2], {[Ni(H2L)2] DMF 0.4H2O}, {[Cu2(H2L)2(µ-Cl)2] (DMF)}
and {[Zn(H2L)2] suitable to be studied by X-ray diffraction were obtained by slow
recrystallization of the solids from DMF.
[Mn(H2L)2](1). Yield: 86% (0.4823 g). Anal. calc for C28H26N8MnO2: C, 59.89; H, 4.67; N,
19.96. Found: C, 59.87; H, 4.65; N, 19.93%. IR (KBr, cm-1): 3342 [NH ]; 1626 [C=O]; 1595,
2
Bull. Chem. Soc. Ethiop. 2016, 30(1)

104
Cheikh Hamidou Kane et al.
1463 [(C=N)py and (C=C)Ar], 1248 [(C-O)]. eff (B) 5.88. M (DMF, -1 cm2 mol-1) = 32. UV-Vis
(, nm) (, M-1 cm-1) 345(0.77), 415(0.016). Colour: yellow.
.
.
{[Ni(H2L)2] DMF 0.4H2O} (2). Yield: 52% (0.3359 g). Anal. calc for C31H33.8N9NiO3.4: C,
57.68; H, 5.28; N, 19.53. Found: C, 57.72; H, 5.25; N, 19.49%. IR (KBr, cm-1): 3296 [NH ];
2
1622 [C=O]; 1595, 1467 [(C=N)py and (C=C)ar], 1256 [(C-O)]. eff (B) 2.81. M (DMF, -1 cm2
mol-1) = 27. UV-Vis (, nm) (, M-1 cm-1) 401(3), 555(0.301), 729(0.554), 935(0.745). UV-Vis
(, nm). Colour: red.
.
{[CuCl(H2L)]2 (DMF)} (3). Yield: 92% (0.7154 g). Anal. calc for C31H33N9Cu2Cl2O3: C, 47.88;
H, 4.28; N, 16.21. Found: C, 47.72; H, 4.37; N, 16.33%. IR (KBr, cm-1): 3284 [NH ]; 1620
2
[C=O]; 1592, 1461 [(C=N)py and (C=C)ar], 1244 [(C-O)]. eff (B) 1.74. M (DMF, -1 cm2 mol-1) =
30. UV-Vis (, nm) (, M-1 cm-1) 293(3), 358(3), 461(3), 615(0.19). Colour: green.
[Zn(H2L)2](4). Yield : 83% (0.4747 g). Anal. calc for C28H26N8ZnO2: C, 58.80; H, 4.58; N,
19.59. Found: C, 58.78; H, 4.57; N, 19.54%. IR (KBr, cm-1): 3342 [NH ]; 1620 [C=O]; 1591,
2
1460 [(C=N)py and (C=C)Ar], 1248 [(C-O)]. M (DMF, -1 cm2 mol-1) = 36. Colour: yellow.
RESULTS AND DISCUSSION
General characterization
One-pot synthesis of 1:1 molar ratio of the Schiff base (H3L) and M(II) metal salts in refluxing
ethanol (M = Mn, Ni, Cu or Zn) afforded mononuclear or dinuclear complexes. The complexes
gave analytically pure products and were characterized by elemental analysis, IR, UV-Vis
spectroscopy and constant temperature magnetic measurements. Colors, magnetic moment,
molar conductivity and spectral data of all the prepared Schiff base complexes are given in the
experimental section. All complexes are paramagnetic in nature except the Zn(II) complex
which is diamagnetic. The observed value of effective magnetic moment of the Mn(II) complex
is 5.88 µB. This value is close to the spin-only value (5.92 at room temperature and typical for
high-spin Mn(II) complex with d5 configuration (S = 5/2) and shows an octahedral environment
.
.
in the vicinity of the manganese atom [15, 16]. For the {[Ni(H2L)2] DMF 0.4H2O} complex, the
value of the magnetic moment of 2.81 µB is above the expected value of 2.83 µB for nickel(II)
.
mononuclear complex in octahedral environment [17]. {[CuCl(H2L)]2 (DMF)} complex shows
µeff value of 1.74 µB. which is closer to the spin only value of 1.73 µB. expected for copper
2
2
complexes [18] with single unpaired electron located in an d
orbital. In fact no coupling
x -y
phenomen exists in this complex at room temperature.
The IR spectrum of the H3L ligand display two sharp bands around 3450-3310 cm-1
assignable to sym and asym vibrations of the NH2 group and a band around 3285 cm-1 due to
(N–H) of the amide moiety. Strong bands at 1651 and 1615 cm-1 assignable to (C=O) and
(C=N) respectively, and bands of medium intensity at 1583, 1567, 1512 and 1461 cm-1
attributable to (C=C) are also pointed. On complexation the values of (C=O) and (C=N)
stretching vibrations are found to be lower (1626-1620 cm-1 and 1569-1467 cm-1, respectively)
than the values observed in spectrum of the ligand. This lower values of (C=O) and (C=N)
stretching may be explained by the involvement of the carbonyl oxygen atom and the
azomethine nitrogen atom in the coordination to the metal ions [19, 20]. The bands due to
(NH2) and (N–H) remain in the spectra of the complexes 1-4. All the complexes are soluble in
DMF. The measurement of molar conductance gives M values of 32, 30 and 36 S cm2 mol-1 for
Bull. Chem. Soc. Ethiop. 2016, 30(1)

Synthesis and characterization of novel M(II) complexes with tridentate N2,O-donor ligand 105
complex 1, 3 and 4 respectively and 27 for complex 2 confirming that the three mononuclear (1,
2 and 4) complexes and the dinuclear complex 3 are neutral and non-electrolyte [21]. The
electronic spectra in DMF are recorded in the range 200-1000 nm. The intense absorption bands
at short wavelengths, between 290 and 405 nm, may be assigned to ligand-metal ion charge
transfer bands (LMCT). The octahedral geometry of the manganese(II) complex cannot be
supported by the electronic spectrum of the complex. As expected, spin-forbidden d–d bands
were not observed in the spectra of the high-spin d5 Mn(II) complex studied in this work. The
absorptions in the range 550-1000 nm may be assigned to d–d transitions of the nickel(II)
complex. The octahedral geometry can be supported by the d–d transition bands revealed in
electronic spectrum of the nickel(II) complex at 935, 729 and 401 nm. These three bands are
3
3
3
assigned to 1 T2g(F)←3A2g(F), 2 T1g(F)←3A2g(F) and 3 T1g(P)←3A2g(F), in octahedral
geometry of nickel(II) [22] complex. Electronic spectrum of Cu(II) complexes gave transitions,
A1g←B1g, B2g←B1g and Eg←B1g [22-25], but it is very difficult to resolve them into separate
bands due to the very low energy difference between these bands. The observed band at 615 nm
can be assigned to d-d transition [26].
.
.
.
Crystal structures of [Mn(H2L)2], {[Ni(H2L)2] DMF 0.4H2O}, {[CuCl(H2L)]2 (DMF)} and
[Zn(H2L)2] complexes, have been also determined by X-ray diffraction.
Crystal structures of complexes
Crystals of 1-4 suitable for X-ray diffraction were obtained by slow recrystallization of the
compound from dimethylformamide. The crystals structures of 1-4 are respectively shown in
Figures 1-4 together with the atomic numbering scheme adopted and selected bond lengths and
angles. Crystal data and structure refinement are given in Table 1.
(a)
(b)
Figure 1. (a) Molecular structure of [Mn(H2L)2] and selected bond lengths /Å and angles /o:
Mn1–O1 2.1351(16), Mn1–O1 2.1350(16), Mn1–N2 2.2054(18), Mn1–N2 2.2054(18),
Mn1–N3 2.332(2), Mn1–N3 2.332(2), O1–Mn1–O1 99.30(10), O1–Mn1–N2
114.68(6), O1–Mn1–N2 71.48(6), O1–Mn1–N2 71.48(6), O1–Mn1–N2 114.68(6),
N2–Mn1–N2 171.16(9), O1–Mn1–N3 141.24(6), O1–Mn1–N3 98.53(7), N2–Mn1–N3
103.55(7), N2–Mn1–N3 69.83(7), O1–Mn1–N3 98.53(7), O1–Mn1–N3 141.24(6),
N2–Mn1–N3 69.83(7), N2–Mn1–N3 103.55(7), N3–Mn1–N3 88.42(11). Symmetry
transformations used to generate equivalent atoms: (i) −x+1, y, −z+2. (b) A view of the
coordination environment around the Mn(II) ion in complex 1.
Bull. Chem. Soc. Ethiop. 2016, 30(1)

106
Cheikh Hamidou Kane et al.
a)
(b)
.
.
Figure 2. (a) Molecular structure of {[Ni(H2L)2] DMF 0.4H2O} and selected bond lengths /Å
and angles /°: Ni1–N6 1.985(2), Ni1–N2 1.989(2), Ni1–O2 2.093(2), Ni1–N5
2.104(3), Ni1–O1 2.113(2), Ni1–N1 2.119(2), N6–Ni1–N2 175.91(9), N6–Ni1–O2
76.20(9), N2–Ni1–O2 105.34(9), N6–Ni1–N5 78.31(10), N2–Ni1–N5 100.17(10),
O2–Ni1–N5 154.49(9), N6–Ni1–O1 107.31(9), N2–Ni1–O1 76.49(9), O2–Ni1–O1
93.30(9), N5–Ni1–O1 93.06(10), N6–Ni1–N1 98.22(10), N2–Ni1–N1 78.02(10), O2–
Ni1–N1 91.77(9), N5–Ni1–N1 93.05(10), O1–Ni1–N1 154.45(9). (b) Complex
molecules linked by the hydrogen bonds through the water molecule yielding dimmers
units. and selected bond lengths /Å and angles /o: N4—H4NA···O2i 2.996(2), 153.3;
N4—H4NB···N3 2.682(3), 130.6; N8—H8NA···O1ii 3.107(3), 175; N8—H8NB···N7
2.708(3), 126.6. Symmetry codes: (i) −x+2, −y+2, −z+2; (ii) −x+2, −y+2, −z+1.
Compound 1, [Mn(H2L)2] crystallizes in the centrosymmetric space group C2/c. The
geometry around the manganese ion can be described as slightly distorted octahedral, with a
N4O2 core comprised by six donor atoms of two ligand molecules. Each ligand acts with two
nitrogen and one oxygen atoms. The equatorial plane of the octahedron is formed by one
hydrazone and two pyridine N atoms and one O atom from the carbonyl moiety, (rms mean
deviation 0.043) with the Mn center 0.079 Å out of this plane. The axial positions are occupied
by one oxygen atom and one hydrazino N atom, 141.24(6) [O1–Mn–N3]. The Mn-O1, 2.135(2)
Å and Mn-N3, 2.332(2) Å distances correspond to the shortest and the longest bond distance to
the manganese center respectively. The hydrazone N distances, Mn1–N2, 2.205(2) Å is smaller
than those found in a similar complex [27]. The coordination of each hydrazone to Mn results in
the formation of two five membered chelating rings (MnNNCO and MnNCCN). The Mn–O is,
thus, stronger than the Mn–N bond and correlates with the slightly less strained five-member
ring defined by the MnN2N1C7O1 atoms, which has the N2–Mn–O1 angle of 71.48(6)o. The
ring formed by MnN3C9C8N2 is slightly more rigid and has a N2–Mn–N3 angle of 69.83(7)o.
.
.
The complex 2, {[Ni(H2L)2] DMF 0.4H2O} crystallizes in the triclinic space group Pī. The
structure is of a mononuclear nickel complex with the metal ion bound to two nitrogen and one
oxygen atoms from each of the two molecules ligand in an octahedral environment. The
arrangement around the nickel ion can be described as distorted octahedral, being the main
distortion due to the tense five members ring [O1–Ni1–N2 76.44(7)o; N1–Ni1–N2 77.94(7)o;
O2–Ni1–N6 76.25(7)o; N6–Ni1–N5 78.20(7)o]. The axial positions of the distorted octahedral
environment can be considered that occupied by one hydrazone nitrogen atom and one oxygen
of the carbonyl, [O1-Ni-N1 154.32(6)o] and the equatorial plane is thus formed by one oxygen
atom, two pyridyl nitrogen atoms and one nitrogen atom of the hydrazonic moiety. Interestingly,
Bull. Chem. Soc. Ethiop. 2016, 30(1)

Synthesis and characterization of novel M(II) complexes with tridentate N2,O-donor ligand 107
the distorted octahedral polyhedron can be viewed in two ways: firstly, the plane with axial
position O1-Ni-N1 154.42(6)o and equatorial plane N2N5N6O2 (rms mean deviation of 0.034
and Ni1 0.025 away from that plane), secondly, the plane with axial position O2-Ni-N5
154.42(6)o and equatorial plane N2N1N6O1 (rms mean deviation of 0.023 and Ni1 0.002 away
from that plane). These equatorial planes are roughly perpendicular (89.67(6)o). The asymmetric
unit of 2 contains one molecule of the complex with two lattice disordered solvent molecules:
one dimethylformamide molecule disordered over two positions and two water molecules,
which occupies each partially it site (16 and 26% respectively). Thus, the title complex is 0.4
water solvated. Intramolecular hydrogen bond involving the free amino group, and the
uncoordinated nitrogen atom of the hydrazone moieties lead to the formation of six membered
rings. No intermolecular hydrogen bonds were observed.
(a)
(b)
.
Figure 3. (a) : Molecular structure of {[CuCl(H2L)]2 (DMF)} and selected bond lengths /Å and
angles /°: Cu1–N2 1.928(3), Cu1–O1 1.945(3), Cu1–N1 2.004(3), Cu1–Cl1
2.2315(10), N2–Cu1–O1 79.71(13), N2–Cu1–N1 80.78(14), O1–Cu1–N1 160.36(13),
N2–Cu1–Cl1 168.47(10), O1–Cu1–Cl1 99.29(9), N1–Cu1–Cl1 99.39(10). N4—
H4NA···N3 2.697(4), 131.8; N4—H4NB···O2i 3.035(4), 176.3 . Symmetry codes: (i)
−x+1, −y+1, −z+1. (b) : Representation showing the disordered DMF solvent molecule
around the twofold axis.
.
The structure of {[CuCl(H2L)]2 DMF} 3 is centrosymmetric with space group C2/c and
is consistent with dinuclear neutral units in which the two metal centers are linked by two ligand
molecules and two chloride. The two copper atoms are pentacoordinated with a {N2OCl2} core
formed by one monoanionic tridentated ligand molecule coordinated through the pyridine and
the hydrazino nitrogen atoms and the oxygen of the carbonyl group. Two chloride ions shared
by the two copper atoms complete the coordination sphere around each metal ion. The two
chloride anions acts as bidentate bridging mode. The coordination of the hydrazone to Cu results
in the formation of two five membered chelating rings (CuOCNN and two CuNCCN). The
distortion of the coordination polyhedron from the square pyramid to the trigonal bipyramid is
calculated by the Addison parameter  where  and  are the two largest donor–
metal–donor angles [28]. A value of = 0 indicates an ideal square pyramid and when  = 1, the
geometry around the metal center is a perfect trigonal bipyramid.
The geometry around each copper(II) ion can be best described as a square pyramidal
arrangement as indicated by the Addison’s parameter: τ = 0.135 [28] [O1−Cu−N1, 160.35(9);
N2−Cu−Cl1, 168.50(7); O1−Cu−Cl1, 99.28(6); N1−Cu−Cl1, 99.42(7); N2−Cu−O1, 79.74(10);
N2−Cu−N1, 80.72(10)°]. The equatorial plane of the distorted square pyramidal environment
around each Cu can be defined by one of the bridging chloride atom, the oxygen atom from one
molecule ligand and the two nitrogen atoms (equatorial plane: Cl1, N1, N2, O1; rms mean
deviation of 0.082 and Cu 0.1121(8) away from that plane). The apical position is occupied by
Bull. Chem. Soc. Ethiop. 2016, 30(1)

108
Cheikh Hamidou Kane et al.
the other Cl with Cu–Cl distance of 2.775 Å. The longer bond length in the equatorial plane
correspond to the chloride and the nitrogen pyridine atoms respectively, Cu–Cl1 2.2314(8) Å
and Cu–N1 2.003(2) Å. The shorter bond length corresponds to the hydrazino nitrogen atom of
the Schiff base, Cu–N2 1.927(2) Å. The Cu···Cu separation is 3.415 Å, not showing interaction
between the metal ions. This distance is similar to those found for the chloride dinuclear
complexes prepared by Mukherjee et al. [29] (3.523 Å) and (4.499 Å) [30]. The DMF solvent
molecule was found to be disordered around the twofold axis, in two positions with equal site
occupancy (Figure 3b).
Intramolecular hydrogen bond involving the free amino group, and the uncoordinated
nitrogen atom of the hydrazone moieties lead to the formation of six membered ring. In the
crystal structure, a weak intermolecular H bond (N4 ….O2) is also observed, involving the free
amino group, and the O atom of the DMF solvent molecule.
Compound 4, [Zn(H2L)2] crystallizes in the centrosymmetric space group P21/c. The
geometry around the zinc ion can be described as slightly distorted octahedral, with a N4O2 core
comprised by six donor atoms of two ligand molecules. Each ligand acts with two nitrogen and
one oxygen atom. The axial positions of the distorted octahedral environment can be considered
that formed by one hydrazone nitrogen atom and one oxygen atom and the equatorial plane
formed by one oxygen atom, one nitrogen atom from the hydrazone moiety and two pyridyl
nitrogen atoms. Interestingly, the distorted octahedral polyhedron can be viewed in two ways:
firstly, the plane with axial position O1-Ni-N7 148.84(16)o and equatorial plane N3N6N8O2
(rms mean deviation of 0.054 and Zn -0.047 away from that plane), secondly, the plane with
axial position O2-Ni-N6 147.93(15)o and equatorial plane N8N7N3O1 (rms mean deviation of
0.035 and Zn -0.052 away from that plane). Two intramolecular hydrogen bond involving the
free amino group and the uncoordinated nitrogen atom of the hydrazone moieties and one weak
intermolecular H bond (N4 ….O2) are observed.
Figure 4. Molecular structure of {[Zn(H2L)2]} and selected bond lengths /Å and angles /o: Zn1-
N8 = 2.069(4), Zn1-N3 = 2.070(4), Zn1- O1 = 2.103(4), Zn1-O2 = 2.142(3), Zn1-N7 =
2.187(5), Zn1-N6 = 2.235(4), N8-Zn1-N3 = 177.76(17), N8-Zn1-O1 = 74.17(15), N3-
Zn1-O1 = 106.12(15), N8-Zn1-O2 = 107.67(15), N3-Zn1-O2 = 74.53(15), O1-Zn1-O2
= 98.26(16), N8-Zn1-N7 = 75.00(17), N3-Zn1-N7 = 104.52(17), O1-Zn1-N7 =
148.84(16), O2-Zn1-N7 = 95.21(16), N8-Zn1-N6 = 103.76(16), N3-Zn1-N6 =
74.01(16), O1-Zn1-N6 = 96.22(16), O2-Zn1-N6 = 147.93(15)N7-Zn1-N6 = 86.76(16).
N4 H4NB… N5 0.86 2.06 2.707(6) 131.0, N4 H4NA…. O2i 0.86 2.28 3.057(6) 151.0,
N1 H1NB N2 0.86 2.03 2.668(7) 130.5. Symmetry codes: (i) −x+1, −y, −z+1.
Bull. Chem. Soc. Ethiop. 2016, 30(1)

Synthesis and characterization of novel M(II) complexes with tridentate N2,O-donor ligand 109
CONCLUSION
The potentially pentadentate hydrazone ligands reported here, obtained by condensation of 2-
acetyl pyridine with 2-aminobenzohydrazide, form mononuclear octahedral manganese(II) and
nickel(II) complexes or dichloro bridged binuclear copper(II) complex with square pyramidal
geometry. Though the ligand is potentially pentadentate, it acts as tridentate donors with the
metal ions used in this work. The oxygen atom and the imino nitrogen atom of the hydrazone
moiety and the pyridine nitrogen of the ligand are involved in coordination, while the amino
moiety remains uncoordinated. According to the data of elemental analysis, molar conductivity,
FT-IR and UV-Vis spectra, and X-ray crystallographic structure determination, these complexes
have a metal to hydrazone stoichiometry of 1:2 in mononuclear species and 1:1 in dinuclear
complex.
Supplementary data. CCDC 988200, 988201, 988202 and 998022 contain the supplementary
.
.
crystallographic
.
data
for
{[Cu2(H2L)2(µ-Cl)2] ((CH3)2CO) (H2O)},
[Mn(H2L)2],
.
{[Ni(H2L)2] DMF 0.4H2O} and [Zn(H2L)2], respectively. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB21EZ, UK; fax: (+44) 1223-336-
033; or e-mail: deposit@ccdc.cam.ac.uk.
REFERENCES
1. Pal, S. J. Chem. Crystallogr. 2000, 30, 329.
2. Saghatforoush, L.A.; Chalabian,F.; Aminkhani,A.; Karimnezhad,G.; Ershad, S. Eur. J. Med.
Chem. 2009, 44, 4490.
3. Maiti, A.; Ghosh, S. J. Inorg. Biochem. 1989,36, 131.
4. Gudasi, K.B.; Shenoy, R.V.; Vadavi, R.S.; Patil, S.A.; Nethaji, M. J. Mol. Struc. 2006, 788,
22.
5. Knoeppel, D.W.; Liu, J.; Meyers, E.A.; Shore, S.G. Inorg. Chem. 1998, 37, 4828.
6. Sy, A.; Dieng, M.; Thiam, I.E.; Gaye, M.; Retailleau, P. Acta Cryst. 2013, E69m, 108.
7. Iskander, M.F.; El-Sayed, L.; Salem,N.M.H.; Haase, W.; Linder, H.J.; Foro, S. Polyhedron
23, 2004, 23.
8. Gudasi, K.B. ; Patil, S.A. ; Vadavi, R.S. ; Shenoy, R.V. ; Patil, M.S. Trans. Met. Chem.
2005, 30, 726.
9. Ainscough, E.W.; Brodie, A.M.; Dobbs, A.J.; Ranford, J.D.; Waters, J.M. Inorg. Chim. Acta
1998, 267, 27.
10. Gudasi, K.B.; Patil, S.A.; Vadavi, R.S.; Shenoy, R.V.; Patil, M.S. Trans. Met. Chem. 2005,
30, 1014.
11. Gudasi, K.B.; Patil, S.A.; Bakale, R.P.; Nethaji, M. J. Mol. Struc. 2014, 1065-1066, 179.
12. SHELXTL version An Integrated System for Solving and Refining Crystal Structures from
Diffraction Data (Revision 5.1), Bruker AXS Ltd.: WI, USA; 1997.
13. Sheldrick, G.M. SHELXTL-97 Program for the Refinement of Crystal Structures, University
of Gottingen: Germany; 1997.
14. Farrugia, L.J. J. Appl. Crystallogr. 1997, 30, 565.
15. Mandal, S.; Karmakar, T.K.; Ghosh, A.; Fleck, M.; Bandyopadhyay, D. Polyhedron 2011,
30, 790.
16. Shelke, V.A.; Jadhav, S.M.; Shankarwar, S.G.; Munde, A.S.; Chondhekar, T.K. Bull. Chem.
Soc. Ethiop. 2011, 25, 381.
17. Sahoo, S.C.; Dubey, M.; Alam, Md.A.; Ray, M. Inorg. Chim. Acta 2010, 363, 3055.
18. Bhowmik, P.; Chattopadhyay, S.; Drew, M.G.B.; Ghosh, A. Inorg. Chim. Acta 2013, 395,
24.
Bull. Chem. Soc. Ethiop. 2016, 30(1)

110
Cheikh Hamidou Kane et al.
19. Lodeiro, C.; Basitida, R.; Bertolo, E.; Macias, A.R. Trans. Metal Chem. 2003, 28, 388.
20. Alhadi, A.A.; Shaker, S.A.; Yehye, W.A.; Ali, H.M.; Abdullah, M.A. Bull. Chem. Soc.
Ethiop. 2012, 26, 95. Chandra, S.; Sharma, A.K. Spectrochim. Acta A 2009, 72, 851.
21. Geary, W.J. Coord. Chem. Rev. 1971, 7, 81.
22. Kala, U.L.; Suma, S.; Kurup, M.R.P.; Krishnan, S.; John, R.P. Polyhedron 2007, 26, 1427.
23. Bhaumik, P.K.; Harms, K.; Chattopadhyay, S. Polyhedron 2013, 62, 179.
24. John, R.P.; Sreekanth, A.; Rajakannan, V.; Ajith, T.A.; Kurup, M.R.P. Polyhedron 2004, 23,
2549.
25. Siji, V.L.; Sudarsanakumar, M.R.; Suma, S.; Kurup, M.R.P. Spectrochim. Acta A 2010, 76,
22.
26. Kurup, M.R.P.; Varghese, B.; Sithambaresan, M.; Krishnan, S.; Sheeja, S.R.; Suresh, E.
Polyhedron 2011, 30, 70.
27. Pouralimardan, O.; Chamayou, A.-C.; Janiak, C.; Hosseini-Monfared, H. Inorg. Chim. Acta
2007, 360, 1599.
28. Addison, A.W.; Rao, T.N.; Reedijk, J.; van Rijn, J.; Verschoor, G.C. J. Chem. Soc. Dalton
Trans. 1984, 1349.
29. Mukherjee, S.; Basu, C.; Chowdhury, S.; Chattopadhyay, A.P.; Ghorai, A.; Ghosh, U.;
Stoeckli-Evans, H. Inorg. Chim. Acta 2010, 363, 2752.
30. Song, Y.; Massera, C.; Roubeau, O.; Lanfredi, A.M.M.; Reedijk, J. Polyhedron 2005, 24,
1599.
Bull. Chem. Soc. Ethiop. 2016, 30(1)