Copper(II) and zinc(II) complexes with 2-benzoylpyridine-methyl hydrazone

Article abstract of DOI:10.1016/j.molstruc.2008.10.025

2-Benzoylpyridine-methyl hydrazone (HBzMe) has been obtained as well as its copper(II) [Cu(HBzMe)Cl₂] (1) and zinc(II) [Zn(HBzMe)Cl₂] (2) complexes. Upon re-crystallization in 1 - 9 DMSO:acetone conversion of 1 into dimeric [Cu(BzMe)

Full text of DOI:10.1016/j.molstruc.2008.10.025

Journal of Molecular Structure 920 (2009) 97–102
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Copper(II) and zinc(II) complexes with 2-benzoylpyridine-methyl hydrazone
Angel A. Recio Despaigne a, Jeferson G. Da Silva a, Ana Cerúlia M. Do Carmo a, Oscar E. Piro b,
Eduardo E. Castellano c, Heloisa Beraldo a,
*
a Departamento de Química, Universidade Federal de Minas Gerais, Av. Antonio Carlos 6627, 31270-901 Belo Horizonte, MG, Brazil
b Departamento de Física, Facultad de Ciencias Exactas, Universidad Nacional de La Plata and Instituto IFLP(CONICET- CCT La Plata), C.C. 67, 1900 La Plata, Argentina
c Instituto de Física de São Carlos, Universidade de São Paulo, C.P. 369, 13560-970 São Carlos, SP, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history:
2-Benzoylpyridine-methyl hydrazone (HBzMe) has been obtained as well as its copper(II) [Cu(HBz-
Me)Cl2] (1) and zinc(II) [Zn(HBzMe)Cl2] (2) complexes. Upon re-crystallization in 1 – 9 DMSO:acetone
conversion of 1 into dimeric [Cu(BzMe)Cl]2 (1a) occurred. The crystal structures of HBzMe, 1, 1a, and 2
were determined. HBzMe adopts the ZE conformation in the solid. In all complexes the hydrazone adopts
the E configuration to attach to the metal through the NpyAN2AO chelating system. In 1 and 2 a neutral
hydrazone coordinates to the metal center while in 1a deprotonation occurs with coordination of an
anionic ligand. 1a presents a dimeric structure, having two copper(II) ions per asymmetric unit. Two chlo-
rides are also present in the copper coordination sphere, which act as bridging ligands and connect the
copper centers to each other.
Received 8 September 2008
Received in revised form 16 October 2008
Accepted 21 October 2008
Available online 26 October 2008
Keywords:
Hydrazones
Crystal structures
Metal complexes
Spectral studies
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
pared. Spectral and structural investigations on the studied com-
pounds were performed.
Hydrazones are a versatile class of compounds with innumerous
chemical as well as pharmacological applications. In fact, hydra-
zones have shown to possess antimicrobial, anticonvulsant, analge-
sic, anti-inflammatory, and antitumoral properties [1–3]. Moreover,
aromatic hydrazone molecules dispersed in a binder polymer are
used as the main constituent of electrophotographic photoreceptors
of laser printers due to their excellent hole-transporting properties
andrelativelysimplesynthesis[4]. Also, di-2-pyridylketonebenzoyl
hydrazone (dpkbh) is widely used as a sensitive analytical reagent
for the determination of trace amounts of metal ions in solutions
[5,6]. Recently hydrazone-based molecular glasses for solid-state
dye-sensitized solar cells have been obtained [7].
Metal complexes of hydrazones proved to have potential appli-
cations as catalysts [8], luminescent probes [9], and molecular sen-
sors [10]. In addition, it has been recently shown that hydrazones
such as pyridoxal isonicotinoyl hydrazone analogues are effective
iron chelators in vivo and in vitro, and may be of value for the treat-
ment of iron overload [11]. Furthermore, some 2-formylpyridine-
derived hydrazones which behave as iron chelators were suggested
as therapeutic agents for the treatment of neurodegenerative dis-
orders [12].
2. Experimental
2.1. Materials and equipment
Partial elemental analyses were performed on a Perkin–Elmer
CHN 2400 analyzer. Infrared spectra were recorded on a Perkin–El-
mer FT-IR Spectrum GX spectrometer using CsI/nujol; an YSI model
31 conductivity bridge was employed for molar conductivity mea-
surements. Electronic spectra were acquired with a Hewlett–Pack-
ard 8453 spectrometer in dimethyl formamide (DMF) solutions
using 1 cm cells. NMR spectra were obtained at room temperature
with a Brucker DPX-200 Avance (200 MHz) spectrometer using
deuterated dimethyl sulfoxide (DMSO-d6) as the solvent and tetra-
methylsilane (TMS) as internal reference. Crystal structures were
investigated using single-crystal X-ray diffraction methods. Data
were collected at room temperature on a Kappa CCD diffractome-
ter working in the u and
x scan mode.
2.2. X-ray cristallography
In the present work 2-benzoylpyridine methyl hydrazone
(HBzMe, Fig. 1) and its copper(II) and zinc(II) complexes were pre-
Crystal data, data collection procedure, structure determination
methods and refinement results are summarized in Table 1 [13–
17]. The ligand hydrogen atoms were included in the molecular
models at stereo-chemical positions and refined with the riding
model. The methyl H-atoms were optimized by treating them as ri-
gid group allowed to rotate around the corresponding CAC bond.
* Corresponding author. Tel.: +55 31 3409 5740; fax: +55 31 3409 5700.
E-mail address: hberaldo@ufmg.br (H. Beraldo).
0022-2860/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2008.10.025

98
A.A. Recio Despaigne et al. / Journal of Molecular Structure 920 (2009) 97–102
The water hydrogen atoms of complex 1 were located in a differ-
ence Fourier map and refined at their found positions with OwAH
and H. . .H distances restrained to target values of 0.86(1) and
1.41(1) Å, respectively.
12
4
12
15
4
13
14
11
10
3
2
5
6
13
11
10
3
2
5
6
14
15
7
N
7
N
1
2.3. Syntheses of 2-benzoylpyridine-methyl hydrazone (HBzMe)
1
N
N
2
2-Benzoylpyridine-methyl hydrazone (HBzMe) was prepared
by mixing equimolar amounts (1.0 mmol) of 2-benzoylpyridine
with methyl hydrazide in methanol with addition of three drops
of acetic acid as catalyst. The reaction mixture was kept under re-
flux for 6 h. After cooling to room temperature the resulting solid
was filtered off, washed with ethanol and ether and dried in vacuo.
2
NH
HN
3
3
8
8
H3C
O
H3C
O
9
9
2.3.1. 2-Benzoylpyridine-methyl-hydrazone (HBzMe)
E configuration
Z configuration
Color: white. Yield: 30% M.P.: 96.8–99.3 °C. Selected IR bands
(cmꢀ1):
m
(C@O) 1663 s,
m(C@N) 1585 m; d(py) 620 m. UV–vis
Fig. 1. Structural representation for 2-benzoylpyridine-methyl hydrazone
(HBzMe).
Table 1
Crystal data and refinement results for HBzMe, [Cu(HBzMe)Cl2]ꢁH2O (1), [Cu(BzMe)Cl]2 (1a) and [Zn(HBzMe)Cl2] (2).
Compound
HBzMe
1
1a
2
Empirical formula
Formula weight
Crystal system
Space group
C14H13N3O
239.27
Orthorhombic
Pna21(#33)
C14H15Cl2CuN3O2
391.73
Monoclinic
P21/a (#14)
C28H24Cl2Cu2N6O2
674.51
Monoclinic
P2/n (#13)
C14H13Cl2N3OZn
375.54
Monoclinic
P21/n (#14)
Unit cell dimensionsa
a (Å)
b (Å)
c (Å)
7.7909(4)
15.285(1)
10.6247(4)
90.00
8.4631(2)
21.6179(8)
9.3480(3)
90.00
7.3876(5)
13.323(1)
13.7890(1)
90.00
11.669(1)
11.483(1)
11.750(1)
90.00
a
(°)
b (°)
90.00
90.00
1265.2(1)
4, 1.256
0.082
104.132(2)
90.00
1658.50(9)
4, 1.569
1.647
796
92.556(5)
90.00
1355.8(2)
2, 1.652
1.805
684
98.13(1)
90.00
1558.6(2)
4, 1.600
1.919
760
c
(°)
Volume (Å3)
Z, density calc. (Mg/m3)
Absorption coefficient (mmꢀ1
F(000)
)
504
Crystal size (mm)
Crystal color, shape
0.20 ꢂ 0.16 ꢂ 0.12
0.31 ꢂ 0.27 ꢂ 0.11
0.28 ꢂ 0.06 ꢂ 0.05
0.22 ꢂ 0.13 ꢂ 0.03
Colorless, prism
Green, prism
Red, prism
Colorless, plate
Diffractometer, scan
Rad., graph. Monoch.
KappaCCD/u and
x
KappaCCD/u and
x
KappaCCD/u and
x
KappaCCD/u and
x
Mo K , k = 0.71073 Å
a
Mo K , k = 0.71073 Å
a
Mo K , k = 0.71073 Å
a
Mo K , k = 0.71073 Å
a
# range for data coll. (°)
Index range (h)
3.51–26.00
3.12–26.00
3.06–25.99
2.91–25.99
ꢀ9 6 h 6 9, ꢀ18 6 k 6 18,
ꢀ13 6 l 6 13
99.4%
2335/1303 [R(int) = 0.0151]
None
ꢀ10 6 h 6 9, ꢀ24 6 k 6 26,
ꢀ9 6 h 6 8, ꢀ14 6 k 6 16,
ꢀ14 6 h 6 10, ꢀ14 6 k 6 10,
ꢀ11 6 l 6 8
ꢀ16 6 l 6 16
ꢀ14 6 l 6 14
Completeness (to # ¼ 26ꢃ)
99.1%
99.7%
99.1%
Reflections collected/unique (Rint
Absorption correction
)
10367/3239 [R(int) = 0.0375]
Numerical [13]
0.840–0.629
6797/2665 [R(int) = 0.0703]
Numerical [13]
0.915–0.632
7946/3043 [R(int) = 0.0791]
Numerical [13]
0.933–0.729
Max. and min. transm.
0.990–0.984
1157
Obs. Refls.[I > 2
r(I)]
2818
1819
2220
Data collection
COLLECT [14]
DENZO and
COLLECT [14]
DENZO and
COLLECT [14]
DENZO and
COLLECT [14]
DENZO and
Data reductionb
SCALEPACK [15]
SHELXS-97 [16]
SHELXL-97 [17]
Full-matrix least-
squares on F2
SCALEPACK [15]
SHELXS-97 [16]
SHELXL-97 [17]
Full-matrix least-
squares on F2
SCALEPACK [15]
SHELXS-97 [16]
SHELXL-97 [17]
Full-matrix least-
squares on F2
2
SCALEPACK [15]
SHELXS-97 [16]
SHELXL-97 [17]
Full-matrix least-
squares on F2
c
Structure solution
Structure refinementd
Refinement method
2
2
2
Weights, w
r2ðF20Þ þ ð0:076PÞ þ 0:04Pꢄꢀ1
;
r2ðF20Þ þ ð0:044PÞ þ 0:79Pꢄꢀ1
;
r2ðF20Þ þ ð0:039PÞ ꢄꢀ1
;
r2ðF20Þ þ ð0:048PÞ þ 0:50Pꢄꢀ1
;
P ¼ ½MaxðF20; 0Þ þ 2F2c ꢄ=3
1.045
P ¼ ½MaxðF20; 0Þ þ 2F2c ꢄ=3
1.034
P ¼ ½MaxðF20; 0Þ þ 2F2c ꢄ=3
P ¼ ½MaxðF20; 0Þ þ 2F2c ꢄ=3
1.020
Goodness-of-fit on F2
Data/restraints/parameters
R1(obs), R(all)e
0.986
1303/1/165
3239/3/208
2665/0/182
3043/0/191
0.0369, 0.1009
0.0424, 0.1067
0.07(1)
0.137 and ꢀ0.121
0.0311, 0.0381
0.0820, 0.0867
–
0.268 and ꢀ0.381
0.0391, 0.0715
0.0843, 0.0959
–
0.351 and ꢀ0.585
0.0398, 0.0618
0.0942, 0.1056
–
0.294 and ꢀ0.504
wR2(obs), wR2(all)e
Extinction coefficient
Largest peak and hole (e Åꢀ3
)
a
Least-squares refinement of the angular settings for 2335 reflections in the 3:51 < # < 26:00ꢃ range for HBzMe, 10367 reflections in the 3:12 < # < 26:00ꢃ range for 1,
6797 reflections in the 3:06 < # < 25:99ꢃ range for 1a and 7946 reflections in the 2:91 < # < 25:99ꢃ range for 2.
b
Corrections: Lorentz, polarization, extinction (HBzMe) and absorption (1, 1a and 2).
Neutral scattering factors and anomalous dispersion corrections. Because this later correction was too small for HBzMe, its molecular chirality could not be determined
c
reliably.
d
Structure solved by direct and Fourier methods. The final molecular model obtained by anisotropic full-matrix least-squares refinement of the non-hydrogen atoms.
P
P
2
2 1=2
R indices defined as: R1
=
R
||F0| ꢀ |Fc||/
R
|F0|, wR2 ¼ ½ wðF20 ꢀ Fc2Þ = wðF02Þ ꢄ
.
e

A.A. Recio Despaigne et al. / Journal of Molecular Structure 920 (2009) 97–102
99
Table 2
Selected bond distances (Å) and angles (°) in the molecular structures of HBzMe,
[Cu(HBzMe)Cl2]ꢁH2O (1), [Cu(BzMe)Cl]2 (1a) and [Zn(HBzMe)Cl2] (2).
Attribution
HBzMe
1
1a
2
Bond lengths
N1AC2
C2AC7
N2AC7
N2AN3
N3AC8
OAC8
MAN1
MAN2
MAO1
CuACl
1.351(3)
1.488(3)
1.286(3)
1.369(3)
1.361(3)
1.217(3)
–
–
–
–
–
–
–
–
1.356(3)
1.481(3)
1.279(3)
1.361(2)
1.347(3)
1.243(3)
2.028(2)
1.962(2)
2.062(2)
–
1.356(4)
1.488(4)
1.287(4)
1.377(3)
1.322(4)
1.271(4)
2.006(3)
1.951(3)
1.958(2)
2.260(1)
–
1.346(4)
1.479(4)
1.294(4)
1.367(4)
1.357(4)
1.225(4)
2.159(3)
2.123(3)
2.313(2)
–
MACl1
MACl2
CuACl#1
M#1ACl
2.4628(7)
2.2098(6)
–
2.2258(9)
2.234(1)
–
–
2.723(1)
2.723(1)
–
–
Bond angles
N1AC2AC7
C2AC7AN2
C7AN2AN3
N2AN3AC8
N3AC8AO
117.8(2)
126.7(2)
120.2(2)
120.4(2)
114.8(2)
112.0(2)
124.9(2)
113.9(2)
120.4(2)
127.7(2)
113.4(2)
120.6(2)
114.5(1)
112.4(1)
78.65(7)
78.02(7)
153.45(7)
97.46(6)
99.92(6)
93.33(6)
161.39(6)
96.36(6)
98.15(5)
105.23(3)
–
114.7(3)
112.0(3)
124.2(3)
107.8(3)
125.3(3)
127.8(2)
113.3(2)
119.4(2)
116.4(2)
111.2(2)
79.8(1)
79.23(9)
158.0(1)
–
–
–
–
–
–
–
115.9(3)
113.3(3)
121.8(3)
116.1(3)
120.3(3)
125.8(2)
115.9(2)
120.7(2)
117.4(2)
114.1(2)
74.1(1)
71.05(9)
144.04(9)
100.77(8)
101.90(8)
131.18(8)
110.62(8)
95.57(7)
98.30(7)
117.81(4)
–
119.0(2)
Fig. 2. Molecular plot of HBzMe showing the labeling scheme of the non-H atoms
and their displacement ellipsoids at the 50% probability level.
C6AN1AM
C2AN1AM
C7AN2AM
N3AN2AM
C8AO1AM
N1AMAN2
N2AMAO1
N1AMAO1
N1AMACl1
N1AMACl2
N2AMACl1
N2AMACl2
O1AMACl1
O1AMACl2
Cl1AMACl2
N2ACuACl
O1ACuACl
N1ACuACl
N2ACuACl#1
O1ACuACl#1
N1ACuACl#1
ClACuACl#1
CuAClACu#1
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
169.39(8)
99.28(7)
100.06(8)
100.24(8)
94.74(8)
95.48(8)
90.34(3)
89.66(3)
–
–
–
–
–
–
–
–
–
–
–
–
–
–
(DMF, cmꢀ1): 32890. 1H NMR (200 MHz, DMSO-d6) [d (ppm)] main
signals: 13.85 (Z), 12.77 (E) [s, 1H, N3H (Z and E isomers)]; 8.77 (Z),
8.57 (E) [d, 1H, H6 (Z and E isomers)]; 7.39 (Z), 8.01 (E) [d, 1H, H3 (E
isomer)]; 7.78 (Z and E) [m, 2H, H4 (Z and E isomers)]; 7.36 (Z), 7.29
(E) [m, H5 (Z and E isomers)]; 2.16 (Z), 2.38 (E) [s, 3H, CH3 (Z and E
isomers)]. 13C NMR (200 MHz, DMSO-d6) [d (ppm)] main signals:
174.3 (Z), 172.9 (E) [C8 (Z and E isomers)]; 152.3 (Z), 154.6 (E)
[C2 (Z and E isomers)]; 148.8 (Z), 148.7 (E) [C6 (Z and E isomers)];
144.3 (Z), 148.0 (E) [C7 (Z and E isomers)]; 137.2 (Z), 137.0 (E) [C4
(Z and E isomers)]; 125.8 (Z), 123.8 (E) [C5 (Z and E isomers)]; 124.0
(Z), 121.6 (E) [C3 (Z and E isomers)]; 20.7 (Z), 20.0 (E) [C9 (Z and E
isomers)].
Fig. 3. Molecular plot of monomeric [Cu(HBzMe)Cl2] (1). Metal–ligand bonds are
indicated by open lines.
2.4.1. Dichloro(2-benzoylpyridine-methyl-hydrazone)copper(II)
[Cu(HBzMe)Cl2] (1)
Green solid. Yield: 71%. Anal. Calc. (C14H13Cl2CuN3O): C, 44.99%;
H, 3.51%; N, 11.24%. Found: C, 44.79%; H, 3.47; N, 11.17%. FW:
373.72 g molꢀ1
.
Selected IR bands (cmꢀ1):
m(C@O) 1630 m;
2.4. Syntheses of the zinc(II) and copper(II) complexes with HBzMe
m
(C@N) 1600 m; d(py) 646 m; m(CuAN) 415 m. UV–vis (DMF,
cmꢀ1): 34010, 26100, 22200 and 11173. Molar conductivity
(1 ꢂ 10ꢀ3 mol Lꢀ1, DMF): 16.28
X .
ꢀ1 cm2 molꢀ1
The zinc(II) and copper(II) complexes (1 and 2) were obtained
by refluxing an ethanol solution of HBzMe with the metal chloride
(ZnCl2 or CuCl2ꢁ2H2O) in 1:1 ligand-to-metal molar ratio
(1.0 mmol). After cooling to room temperature the resulting solids
were filtered off and washed with ethanol followed by diethylether
and then dried in vacuo.
2.4.2. Dichloro(2-benzoylpyridine-methyl-hydrazone)zinc(II)
[Zn(HBzMe)Cl2] (2)
White solid; Yield: 80%. Anal. Calc. (C14H13Cl2N3OZn): C,
44.77%; H, 3.49%; N 11.19%. Found: C, 44.83%; H, 3.53%; N,

100
A.A. Recio Despaigne et al. / Journal of Molecular Structure 920 (2009) 97–102
Fig. 4. Diagram showing dimeric [Cu(BzMe)Cl]2 (1a). The molecular halves are related through a crystallographic inversion center.
nates as a neutral ligand. The molar conductivity data reveal that
the complexes are non-electrolytes, indicating that in both cases
two chlorides are attached to the metal center, in accordance the
proposed formulations.
3.1. Infrared spectra
The m
(C@N) mode at 1585 cmꢀ1 in the spectrum of the free
hydrazone shifts to 1600 cmꢀ1 in the spectrum of complex 1 and
to 1594 cmꢀ1 in that of complex 2, suggesting coordination of
the azomethine nitrogen N2 [18].
The m
(C@O) absorption at 1663 cmꢀ1 in the spectrum of the
uncomplexed hydrazone shifts to 1630 and 1655 cmꢀ1 in the spec-
tra of complexes 1 and 2, respectively, in accordance with coordi-
nation through the carbonyl oxygen [18,19].
The pyridine in-plane deformation mode at 620 cmꢀ1 in the
spectrum of HBzMe shifts to 646 and 640 cmꢀ1 in those of com-
plexes 1 and 2, respectively, indicating coordination of the hetero-
aromatic nitrogen [18]. Therefore, the infrared data for the
complexes indicate coordination of the hydrazones through the
NpyANAO chelating system.
3.2. NMR spectra
Fig. 5. Molecular plot of [Zn(HBzMe)Cl2] (2).
The 1H and 13CNMR assignments for HBzMe and its zinc(II)
complex (2) in DMSO-d6 are reported in Sections 2.2 and 2.3. The
1H resonances were attributed based on chemical shifts, multiplic-
ities and coupling constants. The carbon type (C, CH) was deter-
mined by using DEPT135 experiments. The assignments of the
protonated carbons were made by 2D heteronuclear-correlated
experiments (HMQC) using delay values which correspond to
1J(C, H).
11.25%. FW: 375.57 g molꢀ1. Selected IR bands (cmꢀ1):
1655 s; (C@N) 1594 m; d(py) 640 m; (ZnAN) 412 m. UV–vis
m(C@O)
m
m
(DMF, cmꢀ1): 34250 and 27000. Molar conductivity
(1 ꢂ 10ꢀ3 mol Lꢀ1
,
DMF): 13.67
X
ꢀ1 cm2 molꢀ1
.
1H
NMR
(200 MHz, DMSO-d6) [d (ppm)] main signals: 12.19 (s, 1H, N3H);
8.68 (d, 1H, H6); 7.76 (d, 1H, H3); 7.98 (t, 2H, H4); 7.32 (m, 1H,
H5); 2.16 (s, 3H, CH3). 13C NMR (200 MHz, DMSO-d6) [d (ppm)]
main signals: 173.1 (C8); 151.5 (C2); 149.5 (C7); 149.1 (C6);
138.2 (C4); 124.9 (C5); 125.4 (C3); 20.4 (C9).
In the 1H and 13C NMR spectra of HBzMe the signals of all
hydrogens and carbons are duplicated suggesting the existence of
the E and Z configurations in solution [20–24] (see Fig. 1). In fact,
two signals of N3AH were observed at d 13.85 and 12.77, which
were attributed to the Z and E forms, respectively. In the first
N3AH is hydrogen bonded to the pyridine nitrogen, while in the
latter it is hydrogen bonded to the solvent [20–24]. Similarly, the
signals of C8@O at d 174.3 and 172.9 were attributed to the Z
and E isomers, respectively.
Crystals of HBzMe, 1, [Cu(BzMe)Cl]2, bis[(l-chloro)-2-benzoyl-
pyridine-methyl-hydrazonato)copper(II)] (1a) and 2 were obtained
from a mixture of 1:9 DMSO–acetone and were stable in the air.
Crystals of 1 and 1a co-crystallized from the same DMSO–acetone
solution. We were unable to obtain enough quantity of complex 1a
to perform any experiments other than crystal structure
determinations.
In the 1H and 13C NMR spectra of 2 only one signal was observed
for all hydrogens and carbons. The signals of N3AH and C8@O were
found at d 12.15 and 173.1, respectively, indicating that the hydra-
zone adopts the E configuration in the complex as confirmed by
crystal structure determinations. The signals of C7 and those of
3. Results and discussion
Microanalyses (powder) suggest the formation of [Cu(HBz-
Me)Cl2] (1) and [Zn(HBzMe)Cl2] (2) in which the hydrazone coordi-

A.A. Recio Despaigne et al. / Journal of Molecular Structure 920 (2009) 97–102
101
the pyridine carbons undergo shifts upon coordination. Therefore,
the NMR spectra suggest coordination of HBzMe through the
0.052 Å (2)] with the metal ion laying close onto this plane [at
0.273(1) Å (1), 0.228(2) Å (1a) and 0.209(2) Å (2)]. The phenyl ring
and the coordination plane subtend dihedral angles of 82.53 (7)°
(1), 53.2 (10)° (1a) and 85.5 (1)° (2).
N
pyAN2AO chelating system, forming a complex in which HBzMe
adopts the E configuration.
In HBzMe the C8AO1 bond distance is 1.217(3) Å while in com-
plexes 1 and 2 this distance is 1.243(3) and 1.225(4) Å, respec-
tively, due to the formation of the MAO bond which makes the
CAO bond weaker. In complex 1a the C8AO1 bond distance is
1.271(4) Å due to deprotonation at N3 which leads to a higher sin-
gle bond character for C8AO. In HBzMe the N2AN3 and N3AC8
bond distances are 1.369(3) and 1.361(3) Å. These distances are
1.361(2) and 1.347(3) Å in 1, and 1.367(4) and 1.357(4) Å in 2. In
complexes 1 and 2 CuAL bonds are stronger than ZnAL bonds
(see Table 2). In fact, while complex 1 exhibits ligand field stabil-
ization energy (LFSE), in the case of 2, the d10 configuration of
Zn2+ leads to no LFSE. In 1a N2AN3 and N3AC8 bond distances
are 1.377(3) and 1.322(4) Å and the CuAL distances are
2.006(3) Å (MAN1), 1.951(3) Å (MAN2), 1.958(2) Å (MAO),
2.260(1) Å (MACl), 2.723(1) Å (MACl#1) and 2.723(1) Å (M#1ACl).
In going from HBzMe to 1, 1a and 2 the C2AC7AN2 angle
undergoes a great variation from 126.7(2)° to 112.0(2)°, 112.0(3)°
and 113.3(3)°, respectively, due to the change in configuration of
the hydrazone, from Z when uncomplexed to E in the complexes.
The C7AN2AN3 angle goes from 120.2(2)° in HBzMe to
124.9(2)°, 124.2(3)° and 121.8(3)° in 1, 1a and 2, due to the forma-
tion of the N1AMAN2 chelate ring. Similarly N2AN3AC8 changes
from 120.4(2)° in HBzMe to 113.9(2)°, 107.8(3)° and 116.1(3)° in 1,
1a and 2, respectively, due to the formation of the N2AMAO1 che-
late ring.
3.3. Electronic spectra
*
p transitions asso-
In the electronic spectrum of HBzMe the n–
ciated to the azomethine and carbonyl functions overlap at
32890 cmꢀ1 [18]. In the spectra of complexes 1 and 2 two absorp-
tions attributed to these transitions were observed at 34010 and
26100 cmꢀ1 (1) and at 34250 and 27000 cmꢀ1 (2). In the spectrum
of 1 a shoulder at 22200 cmꢀ1 is associated to a ligand-to-metal
charge transfer transition and a broad new band at 11173 cmꢀ1
to a combination of ligand-field transitions [25,26].
3.4. Structural study of HBzMe, [Cu(HBzMe)Cl2] (1) [Cu(BzMe)Cl]2
(1a) and [Zn(HBzMe)Cl2] (2)
Table 2 shows selected bond distances and angles in the crystal
structures of HBzMe, 1, 1a and 2. Figs. 2–5 are ORTEP [27] draw-
ings of the complexes.
HBzMe crystallizes in the ZE conformation (see Fig. 2). In the
structures of 1 and 2 the copper(II) and zinc(II) ions in a fivefold
environment are attached to a neutral hydrazone molecule acting
as a tridentate ligand which binds the metal center through the
pyridine and imine nitrogens, and the carbonyl oxygen. Two chlo-
ride ions occupy the remaining coordination positions. In complex
1 N1, N2, O and Cl2 occupy the basal plane of a distorted square
pyramid, and Cl1 is located in the apical position. In 2 N2, Cl1
and Cl2 form the equatorial plane of a distorted trigonal bipyramid,
and N1 and O occupy the axial positions. In dimeric [Cu(BzMe)Cl]2
The N2AMACl2 and N2AMACl1 angles are 161.39(6)° and
93.33(6)° in 1 and 110.62(8)° and 131.18(8)° in 2 indicating that
1 adopts a distorted square pyramidal structure whereas 2 adopts
a distorted trigonal bipyramidal arrangement. In fact the MACl1
and MACl2 distances are 2.2098(6) Å and 2.4628(7) Å in 1 and
2.2258(9) and 2.234(1) Å in 2 as a consequence of the presence
of two electrons in the d2z orbital in the first case, which makes
the MACl bond longer as a consequence of repulsion along the z
axis [28].
(1a) each copper(II) center in
arrangement is attached to an anionic hydrazone and to two chlo-
ride ions which act as bridging ligands and connect the two cop-
a distorted square pyramidal
per(II)
ions
to
each
other
[d(CuACl) = 2.260(1) Å,
d(CuACl0) = 2.723(1) Å]. Complex 1a is centrosymmetric.
In all complexes, the hydrazone Pyr(C@N)NA(C@O) skeletal
fragment defines a coordination plane [rms deviation of atoms
from the least-squares plane of 0.045 Å (1), 0.086 Å (1a) and
The [Cu(HBzMe)Cl2]ꢁH2O (1) crystal is further stabilized by a net
of NAH. . .Ow [d(N. . .Ow) = 2.740 Å, \(NAH. . .Ow) = 164.2°] and
Fig. 6. Crystal packing of 1 as seen down the c-axis. The b-axis is along the horizontal. H-bonds are indicated by dashed lines. The largest open disks are Cu(II) ions, the ones of
intermediate size are chloride ions.

102
A.A. Recio Despaigne et al. / Journal of Molecular Structure 920 (2009) 97–102
Acknowledgements
The authors are grateful to Capes, CNPq and FAPESP (Brazil) and
CONICET (Argentina) for financial support. O.E.P. is a research fel-
low of CONICET.
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.molstruc.2008.10.025.
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NpyANAO chelating system. In [Cu(HBzMe)Cl2] (1) the coordina-
tion geometry around the metal is distorted square pyramidal,
with one chloride occupying the apical position. In
[Zn(HBzMe)Cl2] (2) the arrangement around the metal is dis-
torted trigonal, with the pyridine nitrogen and the oxygen occu-
pying the axial positions. Re-crystallization of 1 in 1:9 DMSO–
acetone gives dimeric [Cu(BzMe)Cl]2 (1a) in which a tridentate
NpyANAO anionic ligand is attached to the metal center, along
with two chlorides acting as bridging ligands and connecting
the copper centers to each other.