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Transition Met Chem (2010) 35:159–163
Scheme 1 The deprotonated
form of the Schiff bases
H
N
Cl
N
Br
N
N
_
O
_
O
Br
L1
X-ray crystallography
(20 mL) of N-ethylethane-1,2-diamine (88.2 mg, 1.0 mmol),
with stirring. The mixture was stirred for 30 min at room
temperature to give a yellow solution. Most of the methanol
was evaporated to give a yellow precipitate. Yield: 99%.
Anal. Found (%): C, 58.0; H, 6.9; N, 12.7. Calcd (%) for
C11H15ClN2O: C, 58.3; H, 6.7; N, 12.4.
Diffraction intensities for the two complexes were
collected at 298(2) K using a Bruker SMART 1000 CCD
˚
area-detector with Mo-Ka radiation (k = 0.71073 A). The
collected data were reduced with the SAINT program [8],
and multi-scan absorption corrections were performed
using the SADABS program [9]. Both structures were
solved by direct methods. The complexes were refined
against F2 by full-matrix least-squares methods using the
SHELXTL package [10]. All of the non-hydrogen atoms
were refined anisotropically. H2A attached to N2 in
[Cu(L1)(N3)]ÁMeOH was located from a difference Fourier
Preparation of 2,4-dibromo-6-[(2-
dimethylaminoethylimino)methyl]phenol (HL2)
To a methanol solution (20 mL) of 3,5-dibromosalicylal-
dehyde (280.0 mg, 1.0 mmol) was added a methanol solu-
tion (20 mL) of N,N-dimethylethane-1,2-diamine (88.2 mg,
1.0 mmol), with stirring. The mixture was stirred for
30 min at room temperature to give a yellow solution. Most
of the methanol was evaporated to give a yellow precipitate.
Yield: 98%. Anal. Found (%): C, 37.5; H, 4.1; N, 8.3. Calcd
(%) for C11H14Br2N2O: C, 37.7; H, 4.0; N, 8.0.
map and refined isotropically, with N–H distance restrained
2
˚
˚
to 0.90(1) A, and with Uiso(H) value constrained to 0.08 A .
Other hydrogen atoms were placed in calculated positions
and constrained to ride on their parent atoms. The crystal-
lographic data for both complexes are summarized in
Table 1. Selected bond lengths and angles are given in
Table 2. Crystallographic data for the complexes have been
deposited with the Cambridge Crystallographic Data Center
(CCDC 638042 for [Cu(L1)(N3)]ÁMeOH and 638051 for
[Cu(L2)(l1,1-N3)]n).
Preparation of [Cu(L1)(N3)]ÁMeOH
To a methanol solution (5 mL) of 2-chloro-2-[(2-ethyla-
minoethylimino)methyl]phenol (22.7 mg, 0.1 mmol) and
sodium azide (6.5 mg, 0.1 mmol) was added a methanol
solution (5 mL) of copper(II) acetate (19.9 mg, 0.1 mmol),
with stirring. The mixture was stirred for 10 min at room
temperature and then filtered. Upon keeping the filtrate in
air for 3 days, blue block-shaped crystals of the complex,
suitable for X-ray diffraction, were formed at the bottom of
the vessel on slow evaporation of the solvent. Yield: 63%.
Anal. Found (%): C, 39.3; H, 5.3; N, 19.7. Calcd (%) for
C12H18ClCuN5O2: C, 39.7; H, 5.0; N, 19.3.
XO inhibitory test
The XO inhibition tests were carried out in triplicate.
Xanthine oxidase from cow’s milk was purchased from
Sigma–Aldrich (St. Louis, MO, USA). The XO activities
with xanthine as the substrate were measured spectropho-
tometrically, based on the procedure reported by Kong et al.
[11], with modification. The activity of XO was measured
by uric acid formation monitored at 295 nm. The assay was
performed in a final volume of 1 mL 50 mM K2HPO4 pH
7.8 in a quartz cuvette. The reaction mixture contained
200 lL of 84.8 lg/mL xanthine in 50 mM K2HPO4. The
reaction was started by addition of 66 lL 37.7 mU/mL XO.
The reaction was monitored for 6 min at 295 nm, and the
product is expressed as lmol uric acid per minute. The
kinetics of the reactions were linear during the 6 min of
monitoring. The test compounds dissolved initially in
DMSO were incorporated in the enzyme assay to assess
their inhibitory activity at different concentrations, in
Preparation of [Cu(L2)(l1,1-N3)]n
[Cu(L2)(l1,1-N3)]n was prepared in methanol solution by a
similar procedure as that described for [Cu(L1)(N3)]ÁMeOH
with 2-chloro-2-[(2-ethylaminoethylimino)methyl]phenol
replaced by 2,4-dibromo-6-[(2-dimethylaminoethylimino)
methyl]phenol (35.0 mg, 0.1 mmol). Blue block-shaped
crystals of the complex were obtained after 7 days. Yield:
71%. Anal. Found (%): C, 29.4; H, 3.2; N, 15.0. Calcd (%)
for C11H13Br2CuN5O: C, 29.1; H, 2.9; N, 15.4.
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