Unusual metal coordination chemistry from an amino-amide derivative of 4-nitrophenol, a surprising ligand

Article abstract of DOI:10.1039/b905226g

The simple ligand N-(2-aminoethyl)-2-hydroxy-5-nitrobenzamide (1) exhibits several coordination modes depending on the reaction conditions, acting as a zwitterion on its own or being ionic in the presence of acid and depending on the concentration of meta

Full text of DOI:10.1039/b905226g

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/dalton | Dalton Transactions
Unusual metal coordination chemistry from an amino-amide derivative
of 4-nitrophenol, a surprising ligand†
John McGinley,*a Vickie McKee,b Hans Toftlundc and John M. D. Walsha
Received 16th March 2009, Accepted 17th August 2009
First published as an Advance Article on the web 1st September 2009
DOI: 10.1039/b905226g
The simple ligand N-(2-aminoethyl)-2-hydroxy-5-nitrobenzamide (1) exhibits several coordination
modes depending on the reaction conditions, acting as a zwitterion on its own or being ionic in the
presence of acid and depending on the concentration of metal present in a reaction, it can coordinate to
the metal in either a 1:1 or a 1:2 metal:ligand mode. Furthermore, the role of solvent plays an important
role in these complexation reactions with both four and six coordinate copper complexes being obtained
using water as solvent but only six coordinate copper complexes obtained using acetonitrile as solvent.
methylene groups and a broad signal for the amine group. Since
Introduction
the spectrum was obtained in d6-DMSO, it was assumed that the
As part of our research, we have previously reported upper and
hydroxyl signal was hidden by the residual water signal. A slow
lower rim functionalised calix[4]arenes, capable of binding transi-
tion metal salts.1 In extending this theme, we targeted the design of
recrystallisation of 1 from water yielded crystals suitable for an
X-ray crystallographic study. The asymmetric unit of 1 is shown
in Fig. 1.5
some calix[4]arene Schiff base derivatives as potential ligands for
fluorescence studies.2 As part of our current studies, we targeted
the attachment of functional groups, which did not contain imine
functionalities, to the lower rim of our calix[4]arene scaffolds. We
have reported our observations of the reactions of three Schiff base
ligands, not calix[4]arene derivatives, with various MX2 salts (M =
Cu, Ni or Zn; X = chloride, perchlorate or acetate) which resulted
in the cleavage of the imine bond and formation of metal-amine
complexes.3 With this in mind, we decided to investigate the use
of the compound N-(2-aminoethyl)-2-hydroxy-5-nitrobenzamide
(1), an amine which contains an amide functional group. This
compound has not been reported previously but a derivative
N-(2-aminoethyl)-2-hydroxybenzamide has been reported as a
starting material for unsymmetrical Schiff bases.4 Herein we report
the synthesis, characterisation and metal complexation reactions
of 1 as well as X-ray crystal structures of N-(2-aminoethyl)-2-
hydroxy-5-nitrobenzamide (1), its HCl salt (2) and two copper(II)
complexes (3 and 4).
Fig. 1 Molecular structure of 1 showing selected labels. Ellipsoids are
displayed at 50% probability level; the H-bond is represented by a dashed
line.
The compound is a zwitterion with a complex, three-
dimensional, H-bonding network (see Fig. 2), which is probably
responsible for the conformation of the molecule. This also
Results and discussion
1
Ligand 1 was synthesised by the reaction of methyl 2-hydroxy-5-
nitrobenzoate with 1,2-diaminoethane in a 1:1 methanol:toluene
mixture. The compound showed the expected H NMR signal
pattern with three aromatic proton signals, two signals for the
explains why the hydroxyl signal in the H NMR spectrum is
not observed. A difference map showed that the H atom in the
hydrogen bond between the phenoxy oxygen O1 and the amide
nitrogen N2 was localised on the N atom, indicating that the
O atom is negatively charged. The phenoxy C-O bond (C1-O1)
1
aChemistry Department, National University of Ireland Maynooth,
Maynooth, Co. Kildare, Ireland. E-mail: john.mcginley@nuim.ie; Fax: +353
1 708 3815; Tel: +353 1 708 4615
˚
is very short at 1.3003(16) A, whereas the typical C-O bond in a
7
˚
phenol is 1.362 A. The ammonium nitrogen N3 is involved in three
intermolecular H-bonds, two of which involve interactions with
two neighbouring phenoxide oxygens while the third interaction
is with an amide oxygen.
The hydrochloride salt of N-(2-aminoethyl)-2-hydroxy-5-
nitrobenzamide was readily synthesised by the reaction of 1
with HCl in water. Broad signals are clearly observed in the H
NMR spectrum for the hydroxyl and the ammonium groups, as
well as signals for the aromatic and methylene protons. A slow
bDepartment of Chemistry, Loughborough University, Loughborough,
Leicestershire, LE11 3TU, England. E-mail: v.mckee@lboro.ac.uk;
Fax: +44 1509 223 925; Tel: +44 1509 222 565
cDepartment of Physics and Chemistry, University of Southern Denmark,
Campusvej 55, 5230, Odense M, Denmark. E-mail: hto@ifk.sdu.dk;
Fax: +45 6615 8760; Tel: +45 6550 2543
† CCDC reference numbers 720239, 720240, 720241 and 722041 for 1, 2,
3 and 4, respectively. For crystallographic data in CIF or other electronic
format see DOI: 10.1039/b905226g
1
8406 | Dalton Trans., 2009, 8406–8412
This journal is
The Royal Society of Chemistry 2009
©

View Article Online
Fig. 4 Partial packing diagram for 2, to illustrate H-bonding interactions.
As a result of these interactions, the structure consists of H-bonded
sheets running diagonally across the unit cell.
Metal complexation reactions of 1 with Cu(ClO4)2·6H2O,
CuCl2·2H2O, Cu(OAc)2·H2O, Zn(ClO4)2·6H2O and Zn(OAc)2·
2H2O were carried out in a 1:2 metal:ligand ratio in water, initially.
The reaction of 1 with Cu(ClO4)2·6H2O using a 1:2 metal:ligand
ratio resulted in the formation of a brown solid (3) and a green solid
(4). The X-ray crystal structure of 3 was obtained from crystals
grown from a water solution.
The asymmetric unit revealed that the copper(II) ion is bound
within one ligand in a square-planar geometry to the phenoxide
oxygen, the amide nitrogen and the terminal amine (Fig. 5).10
The remaining coordination site is occupied by a water solvate
molecule. The overall structure consists of H-bonded layers
between the water molecule and the neighbouring nitro group
and amide carbonyl of two different molecules, which are further
sandwiched into a double layer by H-bonding between one of
the amine hydrogens and a neighbouring phenoxide oxygen. As a
result of these H-bonded layers there are no further interactions
between the copper centre and any other atom, reinforcing the fact
that the copper atom occupies a square-planar geometry (Fig. 6
and 7).
Fig. 2 Partial packing diagram for 1, to illustrate H-bonding interactions.
recrystallisation of 2 from water yielded crystals suitable for X-ray
crystallographic analysis. The asymmetric unit of 2 is shown in
Fig. 3.8
Fig. 3 Molecular structure of 2 showing selected labels. Ellipsoids are
displayed at 50% probability level; dashed lines represent H-bonds.
Several structural differences between this structure and that
of 1 are clearly obvious. The structure is not zwitterionic but is
instead a charged species. The most striking feature of the structure
involves the orientation of the ammonium amide arm. In 2, a
rotation has occurred, compared to the orientation of the arm in
1, so that the carbonyl group points towards the phenol instead
of away from it, as in 1. As a result of this rotation there is an
Fig. 5 Molecular structure of 3 showing selected labels, ellipsoids are
shown at 50% probability level.
The coordinating role of the ligand is unusual in that it acts in a
double role through loss of both the phenolic proton and the amide
proton. While this loss of the amide proton has been observed
in compartmental ligands11 and in the copper(II) complexes of
peptides,12 it has not previously been reported for such a simple
ligand as 1. The mode of coordination to a metal ion through the
loss of the amide proton has been observed for hydroxamic acids,
˚
intramolecular H-bond (2.5471(17) A) linking the phenol oxygen
(O1) and the amide oxygen (O4), which is within the reported range
for this type of H-bond.9 Each chloride ion acts as an acceptor for
+
H-bonds to three symmetry-related R-NH3 groups (Fig. 4). The
cations are paired by two, symmetry-related, H-bonds (N2. . .O3¢).
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 8406–8412 | 8407
©

View Article Online
Fig. 8 Molecular structure of 4 showing selected labels and the disorder
of the perchlorate ions. Hydrogen atoms are omitted for clarity, dashed
lines represent H-bonds. Atoms with labels ending in A or B are generated
1
2
by symmetry operation 1 - x, y, - z.
occupancy over two overlapping sites. The molecules are linked
into H-bonded chains via the water solvate molecule, as well as
further, complicated H-bonding (see Fig. 9). Interestingly, as a
result of the coordination of the ligand to the copper ion, both
pendant arms are on the same side of the molecule, or cis to each
other, but point in opposite directions. From a symmetry point of
view, it might be expected that having the ligands bound in such a
way to have the pendant arms on opposite sides of the molecule,
or trans to each other, would be more energetically favoured. If no
steric crowding was occurring which would prevent the formation
of the cis isomer, then the trans isomer would be the favoured
conformation. Presumably, the hydrogen bonding interaction
between the ammonium nitrogen and the water molecule, that
is, the additional solvation energy of the more polar cis form, is
largely responsible for the cis configuration.
Fig. 6 Partial packing diagram for 3, to illustrate H-bonding interactions.
Fig. 7 Second packing diagram for 3, to illustrate square planar geometry
of copper(II) ion.
but the most common mode of metal binding for hydroxamic
acids is through the deprotonated hydroxamate and carbonyl
oxygen atoms, to form very stable five-membered chelate rings.13
Presumably, the copper ion, in our case, is stripping the amide
proton under these mild conditions in order to form stable five-
and six-membered chelate rings. The alternative coordination
possibility through the amide oxygen would result in the formation
of a more unstable seven- and six-membered rings as opposed to
the five- and six-membered rings depicted in the X-ray structure
(Fig. 5).
A slow recrystallisation of the copper perchlorate complex
(4) from water yielded green crystals which were structurally
characterised. The asymmetric unit of 4 shows the metal in
an octahedral environment with the two ligands forming the
equatorial plane and the two perchlorate anions occupying the
axial positions (Fig. 8).14
Both the copper ion and the water solvate molecule (O1w) lie
on 2-fold axes. Neutrality in the molecule is maintained as the two
ammonium groups and the copper(II) cation counteract the two
negatively charged ligands and the two perchlorate anions. The
perchlorate anions are disordered, and were modeled with 60:40
Fig. 9 Partial packing diagram for 4, to illustrate H-bonding interactions.
The metal complexation reactions of 1 with CuCl2·2H2O and
Cu(OAc)2·H2O in water yielded green (5) and purple (6) solids
respectively. Elemental analyses suggested the presence of a 1:2
metal:ligand complex in the case of the green complex 5 formed
from the copper chloride salt. A comparison of the IR spectra
of both 4 and 5 showed that the spectra were very similar,
apart from the obvious difference of the anions used in each
case. This would suggest that the copper ion is involved in a
8408 | Dalton Trans., 2009, 8406–8412
This journal is
The Royal Society of Chemistry 2009
©

View Article Online
Fig. 10 ESR spectrum of 4 as a solid at RT.
similar coordination mode to that in 4, with the anion axially
bonded to the copper ion centre. EPR spectra of 4 and 5
were obtained at both room temperature and liquid nitrogen
temperature as solid samples. Both EPR spectra were consistent
with copper(II) being present (see Fig. 10) and were almost
identical, showing jagged four-line spectra. These spectra indicate
that the coordination of Cu(II) is very similar in each case. The
spectrum of 4 shows a well resolved anisotropic spectrum, typical
for an axially elongated octahedral geometry. The parameters
(g(ꢀ) = 2.30 and g(^) = 2.08, A = 0.016 cm-1) are typical for
a nearly square planar N2O2 coordination environment. UV-vis
spectra of 4 and 5 obtained in either water or acetonitrile were
also very similar, with all spectra showing metal to ligand charge
transfer bands at 600 nm.
Elemental analyses suggested the presence of a 1:1 metal:ligand
complex for the purple copper complex (6), formed from the
copper acetate reaction, with no acetate anions present in the
complex. One molecule of water is also included in the structure,
based on the elemental analysis data. The IR spectrum of 6, when
compared to that of 3, which is the four coordinate structure,
show that both spectra are almost identical, suggesting that the
complexes contain the metal ion in a four coordinate geometry
similar to that found in 3 with a water molecule occupying
the fourth coordination site. No solution UV-vis spectra could
be obtained for 3 or 6 because, as soon as either compound
was placed into solution (water, methanol or acetonitrile), the
colour of the solution turned immediately to a green colour,
indicating a change in the coordination geometry about copper
from four to six co-ordination, with two molecules of solvent
occupying the axial positions in the octahedral geometry formed.
All efforts to get either solid to dissolve in a non-polar solvent
failed.
The zinc complexes (7 and 8), which were obtained from the
reaction of 1 with Zn(ClO4)2·6H2O and Zn(OAc)2·2H2O, were
both pale yellow in colour. Elemental analyses suggested the
presence of 1:1 metal:ligand complexes for both zinc complexes.
A comparison of the IR spectrum of 3 with those of the two 1:1
zinc complexes (7 and 8) showed that all spectra are very similar to
each other, suggesting that the zinc complexes contain the metal
ion in a four coordinate geometry similar to that found in 3. This
structural assignment was confirmed when the 1H NMR spectra
of the zinc complexes were run in d6-DMSO. When the 1H NMR
spectrum of 1 was compared with those of the zinc complexes, the
triplet signal of the amide proton was completely absent in the
metal complexes. Furthermore, the multiplicity of the methylene
group attached to the amide was reduced from a multiplet to a
triplet, suggesting that the zinc ion was bonded to the amide via
a Zn-N bond. It also implied that the structural integrity was
retained in solution. The EPR spectrum of 8 showed a radical
signal with g = 2.005, due possibly to an impurity formed by air
oxidation. The copper(II) doped zinc(II) complexes were prepared
in the same way as the neat zinc(II) complexes with the addition of
a few percent of copper(II) salt. Dilution of the copper(II) complex
into the Zn host did not change the parameters of 4 significantly.
The hyperfine lines are more narrow, but are not resolved into a
superhyperfine pattern.
We repeated the copper complexation studies using acetonitrile
as solvent instead of water. The complexation reaction of 1 with
Cu(ClO4)2·6H2O was carried out in a 1:1 metal:ligand ratio at
room temperature. A moss green solution resulted from which
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 8406–8412 | 8409
©

View Article Online
no solid precipitated after several days. On removing some of
the solvent under reduced pressure, a green solid (9) resulted.
This green solid had an IR spectrum that was very similar to 4,
including the presence of bands due to the perchlorate anions
and elemental analysis suggested that the complex had a 1:2
metal:ligand ratio, again similar to 4. The difference in colour
between 4 and 9 is due to the different solvent molecules present in
each complex. The complexation reaction of 1 with Cu(OAc)2·H2O
in a 1:1 metal:ligand ratio resulted in a dark green solid (10)
precipitating from solution after several hours. The IR spectrum
of 10 was very different to the IR spectra of both 3 and 4,
allowing for the differences in anion, implying that the copper
ion was neither in a four coordinate square-planar geometry as
in 3 nor in a six coordinate octahedral geometry as in 4. It also
confirmed the presence of an acetate group. Despite using different
solvents, it proved impossible to grow crystals suitable for an X-ray
crystallographic study. Elemental analysis of 10 suggested that the
complex was a 1:1 metal:ligand complex with one acetate anion
and one molecule of acetonitrile and one water molecule also
present. The dimer, shown in Fig. 11, is a plausible structure for
the data available, with the extra water molecules being present in
the lattice. The reaction of 1 with CuCl2·2H2O was also carried
out in a 1:1 metal:ligand ratio in acetonitrile, which resulted in
a neon green solid (11) precipitating from the reaction solution
after a few hours. The IR spectrum of 11 was very similar to the
structure of 4 and elemental analysis on the complex suggested the
presence of a 1:1 metal:ligand complex similar to the structure of
4, previously described. The UV-vis spectra of the three complexes
(9-11) were run in DMSO. All three showed metal to ligand
charge transfer bands centered at 580 nm. Interestingly, in these
reactions, there is no sign of a four coordinate copper species as
we saw when the reactions were carried out using water as the
solvent.
explosive and should be manipulated with care and used only in
small quantities.
General procedures
1H and 13C NMR (d ppm; J Hz) spectra were recorded on a
Bruker Avance 300 MHz NMR spectrometer using saturated
CDCl3 solutions with Me4Si reference, unless indicated otherwise,
with resolutions of 0.18 Hz and 0.01 ppm, respectively. The
X-band EPR spectra were recorded with a Bruker EMX Plus
X spectrometer. The samples were solid powders in all cases.
Infrared spectra (cm-1) were recorded as KBr discs or liquid
films between KBr plates using a Perkin Elmer System 2000
FT-IR spectrometer. Melting point analyses were carried out
using a Stewart Scientific SMP 1 melting point apparatus and are
uncorrected. Microanalysis was carried out at the Microanalytical
Laboratory of either University College, Dublin, the National
University of Ireland Cork or the National University of Ireland
Maynooth. Standard Schlenk techniques were used throughout.
Syntheses
Synthesis of N-(2-aminoethyl)-2-hydroxy-5-nitro-benzamide (1).
Methyl 2-hydroxy-5-nitrobenzoate (2 g, 10.14 mmol) and 1,2-
diaminoethane (1.82 g, 30.42 mmol) were heated to reflux
temperature in a toluene:methanol system (1:1, 80 cm3) under
nitrogen for 4 h. The resulting suspension was cooled to room
temperature. The yellow precipitate was removed by filtration and
dried in an oven overnight. Analytical data for 1: yellow solid,
yield = 2.06 g (91%); Found: C, 47.89; H, 4.93; N, 18.53. Calc.
for C9H11N3O4 C, 47.98; H, 4.93; N, 18.66; m.p. 230-234 (dec.) ◦C;
nmax (KBr) 3441, 3193, 2914, 1626, 1590, 1557, 1430, 1341, 1298,
1201, 1151, 1131, 842, 755, 678 cm-1; dH (300 MHz, d6-DMSO):
11.43 (1 H, t, J 5.7 Hz, CONH), 8.65 (1 H, d, J 3.3 Hz, Ar-H),
7.80 (1 H, dd, J 9.5 & 3.3 Hz, Ar-H), 7.71 (2 H, br s, NH2), 6.27
(1 H, d, J 9.5 Hz, Ar-H), 3.50 (2 H, m, NHCH2), 2.96 (2 H, t, J
7.5 Hz, CH2NH2); dC (75 MHz, d6-DMSO): 178.2, 167.8, 129.8,
128.4, 127.3, 122.6, 117.5, 39.5, 36.5.
Experimental
Materials
The following chemicals were used without further purification
from commercial sources: methyl 2-hydroxy-5-nitrobenzoate, 1,2-
diaminoethane, copper perchlorate hexahydrate, copper chloride
dihydrate, copper acetate monohydrate, zinc perchlorate hexahy-
drateandzinc acetatedihydrate. Caution! Althoughnot encountered
in our experiments, perchlorate salts of metal ions are potentially
Synthesis of 1·HCl (2). 1 (0.15 g, 0.67 mmol) was suspended in
water (5 cm3). 1 M HCl (7 cm3) was added dropwise with stirring
until the yellow solid has dissolved. Stirring was continued for
1 h. The solvent was reduced until a white solid precipitated. The
white solid was removed by filtration, washed with cold water and
dried in the air. Analytical data for 2: white solid, yield = 0.14 g
Fig. 11 Proposed structure of 11 containing bridging acetates and coordinating solvent molecules.
8410 | Dalton Trans., 2009, 8406–8412 This journal is The Royal Society of Chemistry 2009
©

View Article Online
(82%); Found: C, 41.19; H, 4.61; N, 15.79. Calc. for C9H12ClN3O4
C, 41.29; H, 4.62; N, 16.06; m.p. 268-270 (dec.) ◦C; nmax (KBr)
3383, 2969, 1641, 1605, 1557, 1497, 1329, 1207, 1172, 1159, 844,
749 cm-1; dH (300 MHz, d6-DMSO): 13.45 (1 H, br s, OH), 9.28 (1
H, t, J 4.8 Hz, CONH), 8.86 (1 H, d, J 2.9 Hz, Ar-H), 8.27 (1 H,
dd, J 9.2 & 2.7 Hz, Ar-H), 8.17 (3 H, br s, NH3), 7.22 (1 H, d, J
9.2 Hz, Ar-H), 3.61 (2 H, m, CH2NH3), 3.02 (2 H, m, NHCH2);
dC (75 MHz, d6-DMSO): 166.9, 164.6, 139.1, 128.5, 125.5, 118.2,
116.6, 38.2, 37.0.
by filtration, washed with water and dried in air. Analytical data
for 7: yellow solid, yield = 0.11 g (78%); Found: C, 35.45; H, 3.58;
N, 13.45. Calc. for C9H11N3O5Zn C, 35.26; H, 3.62; N, 13.71; nmax
(KBr) 3443, 2915, 1613, 1590, 1448, 1431, 1341, 1301, 1131, 843,
678 cm-1; dH (300 MHz, d6-DMSO): 8.65 (1 H, d, J 2.9 Hz, Ar-H),
7.88 (1 H, dd, J 9.3 & 2.9 Hz, Ar-H), 6.56 (1 H, d, J 9.3 Hz, Ar-H),
3.43 (2 H, br s, CH2NCO), 2.83 (2 H, br s, CH2NH).
Reaction of 1 with Zn(OAc)2·2H2O
Similar procedure to that of 7, except that 0.096 g (0.44 mmol)
zinc acetate dihydrate was used, with similar analytical results.
Analytical data for 8: yellow solid, yield = 0.12 g (85%); Found:
C, 35.54; H, 3.84; N, 13.95. Calc. for C9H11N3O5Zn C, 35.26; H,
3.62; N, 13.71; nmax (KBr) 3515, 3227, 3147, 1609, 1570, 1528, 1449,
1435, 1315, 1232, 1142, 1131, 834, 706 cm-1.
Reaction of 1 with Cu(ClO4)2·6H2O
To 1 (0.1 g, 0.44 mmol) in 15 cm3 water was added copper
perchlorate hexahydrate (0.34 g, 0.89 mmol) in water (5 cm3) and
the resulting green solution was stirred for 1 h. The resulting
purple/brown precipitate was removed by filtration and dried
in air. The solid was redissolved in water and allowed to stand
overnight, resulting in brown crystals (3) and some starting
material. Analytical data for 3: brown solid, yield = 0.02 g (31%);
Found: C, 35.45; H, 3.58; N, 13.45. Calc. for C9H11CuN3O5 C,
35.47; H, 3.64; N, 13.79; nmax (KBr) 3438, 3225, 1611, 1569, 1525,
1435, 1317, 1283, 1231, 1142, 1131, 834, 696 cm-1. The original
green filtrate was allowed to stand, resulting in the formation of
green crystals (4) after several days. The crystals were removed
by filtration and dried in air. Analytical data for 4: green solid,
yield = 0.10 g (59%); Found: C, 29.40; H, 3.01; N, 11.20. Calc. for
C18H24Cl2CuN6O17 C, 29.58; H, 3.31; N, 11.50; nmax (KBr) 3391,
3083, 1608, 1545, 1483, 1471, 1436, 1307, 1141, 1120, 1110, 1086,
834, 749 cm-1.
Reaction of 1 with Cu(ClO4)2·6H2O
To 1 (0.1 g, 0.44 mmol) in 5 cm3 acetonitrile was added
copper perchlorate hexahydrate (0.18 g, 0.45 mmol) in acetonitrile
(15 cm3) and the resulting moss green solution was stirred for
10 h. No precipitate resulted and the solvent was partially removed
under reduced pressure. The green solid which then precipitated
was removed by filtration and dried in air (9). Analytical data for
9: moss green solid, yield = 0.08 g (78%); Found: C, 31.40; H,
3.03; N, 13.20. Calc. for C20H25Cl2CuN7O16 C, 31.86; H, 3.34; N,
13.00; nmax (KBr) 3398, 1610, 1550, 1467, 1439, 1308, 1231, 1141,
1122, 834, 783, 755, 696 cm-1.
Reaction of 1 with Cu(OAc)2·H2O
Reaction of 1 with CuCl2·2H2O
To 1 (0.1 g, 0.44 mmol) in 5 cm3 acetonitrile was added copper
acetate monohydrate (0.1 g, 0.49 mmol) in acetonitrile (15 cm3)
and the resulting green suspension was stirred for 10 h. The solid
(10) was removed by filtration and dried in air. Analytical data
for 10: dark green solid, yield = 0.12 g (78%); Found: C, 38.24;
H, 4.03; N, 13.46. Calc. for C26H30Cu2N8O14 C, 38.76; H, 3.75; N,
13.91; nmax (KBr) 3433, 3324, 3260, 1600, 1574, 1533, 1471, 1427,
1310, 1146, 1131, 1084, 859, 755, 706, 678 cm-1.
To 1 (0.1 g, 0.44 mmol) in 15 cm3 water was added copper chloride
dihydrate (0.15 g, 0.88 mmol) in water (5 cm3) and the resulting
green solution was stirred for 1 h. A green solid precipitated from
solution. The solid was removed by filtration and dried in air.
Analytical data for 5: green solid, yield = 0.07 g (51%); Found:
C, 36.95; H, 3.79; N, 14.24. Calc. for C18H22Cl2CuN6O8 C, 36.96;
H, 3.79; N, 14.37; nmax (KBr) 3378, 3006, 1604, 1579, 1558, 1466,
1307, 1271, 1161, 839, 750 cm-1.
Reaction of 1 with CuCl2·2H2O
Reaction of 1 with Cu(OAc)2·H2O
To 1 (0.1 g, 0.44 mmol) in 5 cm3 acetonitrile was added copper
chloride dihydrate (0.08 g, 0.48 mmol) in acetonitrile (15 cm3) and
the resulting orange solution was stirred for 10 h. After 5 h, a
yellow/green solid precipitated from solution. The solid (11) was
removed by filtration and dried in air. Analytical data for 11: neon
green solid, yield = 0.11 g (84%); Found: C, 36.38; H, 4.21; N,
14.45. Calc. for C18H22Cl2CuN6O8 C, 37.04; H, 4.15; N, 14.41; nmax
(KBr) 3375, 1610, 1556, 1465, 1358, 1321, 1273, 1163, 839, 777,
752 cm-1.
To 1 (0.1 g, 0.44 mmol) in 15 cm3 water was added copper acetate
monohydrate (0.18 g, 0.89 mmol) in water (5 cm3) and the resulting
purple/brown solution was stirred for 1 h. A pale purple solid
precipitated from solution within 2 mins. The solid was removed
by filtration and dried in air. Analytical data for 6: purple solid,
yield = 0.11 g (79%); Found: C, 35.45; H, 3.58; N, 13.45. Calc. for
C9H11CuN3O5 C, 35.47; H, 3.64; N, 13.79; nmax (KBr) 3515, 3227,
3147, 1609, 1570, 1528, 1449, 1435, 1315, 1232, 1142, 1131, 834,
706 cm-1.
Conclusions
Reaction of 1 with Zn(ClO4)2·6H2O
In summary, we have shown that the simple ligand N-(2-
aminoethyl)-2-hydroxy-5-nitrobenzamide (1) exhibits several co-
ordination modes depending on the reaction conditions. It acts
as a zwitterion on its own and is ionic in the presence of acid.
Furthermore, depending on the concentration of metal present in
a reaction, it can coordinate to the metal in either a 1:1 (as in 3) or
To a zinc perchlorate hexahydrate (0.17 g, 0.44 mmol) in water
(5 cm3) solution was added dropwise a solution of 1 (0.1 g,
0.44 mmol) and sodium hydroxide (0.018 g, 0.44 mmol) in
water (5 cm3). An immediate yellow precipitate resulted and the
resulting suspension was stirred for 1 h. The solid was removed
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 8406–8412 | 8411
©

View Article Online
3
V = 1908.5(3) A , Z = 8, Dcalcd = 1.568 Mg/m3, m = 0.125 mm-1,
GoF = 1.030, Rint = 0.0359, R1 = 0.0445, wR2(all) = 0.1307. CCDC
720239.
˚
a 1:2 (as in 4) metal:ligand mode. The coordination mode is also
dependent on the type of metal ion present. Furthermore, when
we repeat the copper complexation reactions using acetonitrile as
solvent instead of water, we only get the formation of six coordinate
species and no four coordinate complexes are formed.
6 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr., 2007,
64, 112.
7 F. H. Allen, O. Kennard, D. G. Watson, L. Brammer, A. G. Orpen and
R. Taylor, J. Chem. Soc., Perkin Trans. 2, 1987, S1.
8 Single-crystal structure analysis of 2. The structure was solved by
direct methods and refined on F2 using all the reflections.6 Hydrogen
atoms bonded to O1 and N2 were located from difference maps and
Acknowledgements
˚
their coordinates refined. C9H12ClN3O4 M = 261.67, l = 0.71073 A,
We are thankful to North Tipperary County Council and NUIM
for financial assistance. The authors would like to acknowledge
Dr Malachy McCann and Dr Bernie Creaven for useful dis-
cussions.
˚
˚
˚
triclinic, P-1,◦a = 5.8346(5) A, b◦= 8.1575(8) A, c = 11.8171(11) A, a =
◦
3
˚
105.3490(10) , b = 92.1640(10) , g = 91.2740(10) , V = 541.69(9) A ,
Z = 2, Dcalcd = 1.604 Mg/m3, m = 0.361 mm-1, GoF = 1.047, Rint
=
0.0247, R1 = 0.0374, wR2(all) = 0.0976. CCDC 720240.
9 (a) X.-S. Tai, J. Yin, M.-Y. Hao and Z.-P. Liang, Acta Crystallogr., Sect.
E: Struct. Rep. Online, 2007, 63, o1727; (b) H.-M. Liu, L. He, X.-L. Luo
and W.-Q. Zhang, Acta Crystallogr., Sect. C: Cryst. Struct. Commun.,
2006, 62, o104.
Notes and references
1 (a) B. S. Creaven, M. D. Deasy, P. M. Flood, J. McGinley and B. A.
Murray, Inorg. Chem. Commun., 2008, 11, 1215; (b) A. D. Bond, B. S.
Creaven, D. F. Donlon, T. L. Gernon, J. McGinley and H. Toftlund,
Eur. J. Inorg. Chem., 2007, 749; (c) B. S. Creaven, T. L. Gernon,
J. McGinley, A.-M. Moore and H. Toftlund, Tetrahedron, 2006, 62,
9066; (d) B. S. Creaven, T. L. Gernon, T. McCormac, J. McGinley,
A.-M. Moore and H. Toftlund, Inorg. Chim. Acta, 2005, 358, 2661;
(e) B. S. Creaven, M. F. Mahon, J. McGinley and A.-M. Moore,
Inorg. Chem. Commun., 2006, 9, 231; (f) B. S. Creaven, M. D. Deasy,
J. F. Gallagher, J. McGinley and B. A. Murray, Tetrahedron, 2001, 57,
8883.
10 Single-crystal structure analysis of 3. The structure was solved by
direct methods and refined on F2 using all the reflections.6 Hydrogen
atoms on the water molecule were located from difference maps and
˚
the coordinates refined. C9H11CuN3O5 M = 304.75, l = 0.71073 A,
˚
˚
orthorhombic, Pbca, a = 13.5511(6) A, b = 10.4268(4) A, c =
3
14.7843(6) A, V = 2088.94(15) A , Z = 8, Dcalcd = 1.938 Mg/m3,
m = 2.111 mm-1, GoF = 1.034, Rint = 0.0428, R1 = 0.0332, wR2(all) =
0.1027. CCDC 720242.
˚
˚
11 (a) See, for example, J. Y. Yang and D. G. Nocera, Tetrahedron Lett.,
2008, 49, 4796; (b) R.-J. Tao, F.-A. Li, Y.-X. Cheng, S.-Q. Zang, Q.-L.
Wang, J.-Y. Niu and D.-Z. Liao, Inorg. Chim. Acta, 2006, 359, 2053;
(c) S. Brooker, D. J. de Geest and G. S. Dunbar, Inorg. Chim. Acta, 1998,
282, 222; (d) S. K. Mandal, L. K. Thompson, M. J. Newlands, A. K.
Biswas, B. Adhikary, K. Nag, E. J. Gabe and F. L. Lee, Can. J. Chem.,
1989, 67, 662.
2 M. F. Mahon, J. McGinley, A. D. Rooney and J. M. D. Walsh,
Tetrahedron, 2008, 64, 11058.
3 M. F. Mahon, J. McGinley, A. D. Rooney and J. M. D. Walsh, Inorg.
Chim. Acta, 2009, 362, 2353.
4 (a) E. A. Djurendic´, T. M. Sura´nyi and D. A. Miljkovic´, Collect. Czech.
Chem. Commun., 1991, 56, 1446; (b) W. Adam, C. R. Saha-Moeller and
P. A. Ganeshpure, Indian J. Chem., Sect. A: Inorg., Bio-inorg., Phys.,
Theor. Anal. Chem., 2004, 43A, 56; (c) T. Kido, Y. Ikuta, Y. Sunatsuki,
Y Ogawa, N. Matsumoto and N. Re, Inorg. Chem., 2003, 42, 398; (d) Q.
Yu, Y. Tang, Y.-H. Feng, M.-Y. Tan and K.-B. Yu, Acta Crystallogr.,
Sect. E: Struct. Rep. Online, 2003, 59, o577.
12 W. Kaim and B. Schwederski, Bioinorganic Chemistry: Inorganic
Elements in the Chemistry of Life, Wiley, Chichester, 1994.
13 C. J. Marmion, D. Griffith and K. B. Nolan, Eur. J. Inorg. Chem., 2004,
3003.
14 Single-crystal structure analysis of 4. The structure was solved by
direct methods15 and refined on F2 using all the reflections.6 The
single independent proton bonded to the oxygen atom of a water
molecule was located from difference maps and not further refined.
5 All data sets were collected at 150(2) K on a Bruker APEXII CCD
diffractometer. Single-crystal structure analysis of 1. The structure was
solved by direct methods and refined on F2 using all the reflections.6
Hydrogen atoms bonded to nitrogen were located from difference maps,
those bonded to N3 were then inserted at calculated positions, but
the coordinates of the hydrogen bonded to N2 were freely refined.
˚
C18H24Cl2CuN6O17 M = 730.87, l = 0.71073 A, monoclinic, C2/c, a =
◦
˚
˚
˚
10.2850(5) A, b = 14.9501(7) A, c = 18.1501(9) A, b = 92.915(1) , V =
2787.2(2) A , Z = 4, Dcalcd = 1.742 Mg/m3, m = 1.066 mm-1, GoF =
3
˚
1.073, Rint = 0.0268, R1 = 0.0327, wR2(all) = 0.0951. CCDC 720241.
15 M. C. Burla, R. Caliandro, M. Camalli, B. Carrozzini, G. L. Cascarano,
L. D. Caro, C. Giacavazzo, G. Polidori and R. Spagna, J. Appl.
Crystallogr., 2005, 38, 381.
˚
C9H11N3O4 M = 225.21, l = 0.71073 A, monoclinic, C2/c, a =
◦
˚
˚
˚
15.5904(13) A, b = 9.6611(8) A, c = 13.7196(11) A, b = 112.550(1) ,
8412 | Dalton Trans., 2009, 8406–8412
This journal is
The Royal Society of Chemistry 2009
©