The Crystal and Molecular Structure and Properties of
DiaquajN-salicylidene—(S )—( + ) —glutamato]copper(II) Monohydrate
J. K rätsm ár-Šmogrovič*, F. Pavelčik3, J. Soldánováa, J. Sivýa, V. Seressová , and M. Žemlička
Department o f Inorganic and Organic Chemistry and
a Department o f Analytical Chemistry, Faculty o f Pharmacy, Comenius University,
83232 Bratislava, Czechoslovakia
Z. Naturforsch. 46b, 1 3 2 3 - 1327 (1991); received December 14, 1990/A pril 22, 1991
D iaq u a[N -salicylid en e-(S )-( + )-glutam ato]copper(II) M onohydrate, X -R ay, Dehydration,
Cryomagnetic Properties
The crystal and molecular structure o f the title complex was determinated by single crystal
X-ray diffraction (R = 0.066 for 1059 observed reflections). The approximately square-pyram­
idal coordination o f Cu(II) results from donor atom s 0 (1 2 ), 0 (1 ), N (l), 0 (5 ) o f one H 20 m o­
lecule as well as the tridentate Schiff base dianion ligand and from the weakly bonded 0 (1 1 )
donor atom o f one other H 20 molecule in the apical site.
The magnetic behaviour o f the complex studied obeys the C u rie-W eiss law in the tempera­
ture range 9 4 -3 0 9 K with a small value o f the Weiss constant, 0 = 1.4 K. A similar cryomag­
netic behaviour is also characteristic for the anhydrous com pound, [N -s a lic y lid e n e -(S )-(+ )glutamato]copper(II), obtained by thermal dehydration o f the title complex.
Introduction
Copper(II) N -salicylidene-(S)-glutam ate as a
“trihydrate” has been described [1] and character­
ized by the formula
[C u{sal-(S )-g lu }(H 20 )]-2 H 20 . On the basis of
the LF band maximum position it has been con­
cluded that this complex has a similar molecular
structure as aqua(N-salicylideneglycinato)copper(II) [2]. The [Cu(salgly)(H20)] complex itself is
known in two forms; as a hemihydrate [3] (“poly­
meric” in its crystal structure) and as a so-called
tetrahydrate [4]. The crystal structure of the latter
shows monomers. The square-pyramidal coordi­
nation of Cu(II) in this complex is completed by an
axially weakly linked H 20 ligand (the equatorially
coordinated H 20 is strongly bonded) and thus its
correct formula is [Cu(salgly)(H20 ) 2] •3 H 20 [4].
The IR spectrum of
[C u{sal-(S )-g lu }(H 20 )]-2 H 20 confirmed that
the terminal carboxylic group of the amino acid
moiety of the Schiff base ligand does not partici­
pate in the coordination in this complex [1],
By modification of the reaction mode, based on
slow crystallization of the final product (during
about a m onth) from a diluted reaction mixture,
Abbreviations: s a l- ( S ) - g lu = N -sa lic y lid e n e -(S )-g lu ­
ta m a te ^ -), salgly = N -salicylideneglycinate(2-).
* Reprint requests to Dr. J. Krätsmär-Smogrovic.
Verlag der Zeitschrift für Naturforschung, D-7400 Tübingen
0932-0776/91 /1000—1323/$ 01.00/0
containing originally ( S ) - ( + ) - glutamic acid,
the racemic complex
[Cu3{ s a l-(R S )-g lu } 2(H 20 ) 4]-7 H 20 has been ob­
tained [5], As proven by X-ray structure analysis
[5], in the polymeric crystal structure of this com ­
plex two different coordination geometries around
Cu(II), square-pyram idal and distorted octa­
hedral, are formed by the participation o f both
carboxylic groups of the Schiff base ligand. An
antiferrom agnetically coupled, probably dimeric
copper(II)
N-salicylidene - (S) - (+ ) - glutamate
m onohydrate has also been described besides the
above mentioned complexes [6],
In order to study the syntheses, properties and
structure o f N-salicylideneaminoalkanoatocopper(II) complexes as im portant bioactive species
we have given attention also to the N-salicylideneglutam atocopper(II) complexes [(S)- and
(RS)-forms] containing various additional ligands.
In the present paper we investigate the precise (re­
producible) conditions of the
C u [sal-(S )-g lu ] •3 H 20 synthesis and its conver­
sion into the anhydrous compounds. We also re­
port on the cryomagnetic behaviour of both these
complexes down to liquid nitrogen temperature,
and on the structure of
[C u { sal-(S )-g lu } (H 20 ) 2] •H 20 .
Experim ental
The complex C u [sa l-(S )-g lu ]• 3H 20 was pre­
pared by reaction of 4.0 g (2.0 10 2mol) copper(II) acetate m onohydrate, 2.6 g (2 .2 -10“2 mol)
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1324
J. K rätsm är-S m ogrovic et at. ■ D ia q u a [N -sa lic y lid e n e -(S )-( + )-g lu ta m a to ]c o p p e r(II)
salicylaldehyde and 2.9 g (2 .0 -10-2 mol) (S)-glutamic acid in a warm water solution. The parent
com pounds were gradually dissolved in 80 ml of
water at 6 0 -6 5 C with stirring for 0.5 h. The re­
sulting dark green solution was filtered and al­
lowed to cool to room temperature. The crude
crystalline product separated from the reaction
mixture was deposited, washed with cool water
and recrystallized from hot water.
Analysis fo r C r H I7N 0 8Cu (366.82)
' Calcd C 39.29' H 4.67 N 3.82,
Found C 39.20 H 4.35 N 3.93.
The anhydrous compound C u [sal-(S )-g lu ] was
obtained by thermal dehydratation of the trihy­
drate in a therm ostat at 110 °C, and a 14.68% to ­
tal weight loss has been registered (14.73% calcu­
lated). The same anhydrous com pound was pre­
pared by heating a suspension of powdered
C u [sa l-(S )-g lu ]-3 H 20 in toluene to the boiling
point and removing the liberated water by azeotropic destination with the solvent.
Analysis fo r C r H n NO 5Cu (312.76)
Calcd C 46.08' H 3.54 N 4.48,
Found C 45.95 H 3.64 N 4.60.
The magnetic susceptibilities of both complexes
(the trihydrate and the anhydrous com pound)
were measured by G ouy’s method in the tem pera­
ture range of 9 4 -300 K, using commercial equip­
ment (Newport Instruments Ltd.). Measuring con­
ditions were similar to those reported in [7],
A crystal of size 0.3 x 0.2 x 0.1 mm was selected
for data collection. Weissenberg photographs
showed the crystal to be monoclinic, with system­
atic absences OkO for k = 2n+ \ indicating P2,
space group (noncentrosymmetry expected on ba­
sis of chiral ligand). Unit cell param eters were re­
fined by a least-squares fit of positional angles o f 9
reflections 5 < 29 < 14 . Intensities were meas­
ured for 0 < 29 < 50 on a Syntex P2, four-circle
diffractom eter with graphite m onochrom ated
M oK a radiation, by the 9 - 2 9 technique at scan
rate 4.88 to 29.3° m in-1 in 2 9 , scan range
2.0° + 2 0 (K a ,) -2 # (K a 2). The background was
measured at each end of the scan for one half of
the scan time. 1806 reflections were measured with
h = 0 to 13, k = 0 to 12, / = - 7 to 7, the data were
averaged, Rml = 0.12, to give 1684 unique and 1059
observed reflections with I > 1.96er(I). Two stand­
ard reflections monitored after every 98 scans
showed that no correction for instrum ent instabili­
ty or crystal decay was required.
Crystal data: Formula weight M r = 366.82,
monoclinic, space group P 2 b a = 1.1305(8), b =
1.0919(9), c = 0.5991(4) nm,/? = 104.31(5)°, Z = 2,
H = 1.56 m m -1, qx = 1.68 M g-cm -3, F(000) = 372,
M oK a, a = 0.071069 nm, room temperature, V =
0.7165 nm 3.
The structure was solved by Patterson and
Fourier m ethods and refined by the block-diago­
nal least-squares with anisotropic thermal param e­
ters assigned to all nonhydrogen atoms. The hy­
drogen atom s were included at their calculated
position with B = 0.03 nm2. The function
I w ( |F 0| - 1F c|)2 was minimized; a weighting
scheme w-1 = er2(F) + (0.03 |F 0|)2 was used, <r(F)
from counting statistics. Final residuals were R =
0.066 and 0.116, w R = 0.070 and 0.114 for ob­
served and all reflections, respectively. S = 1.63,
(^AOmax = 0.1, (/le)max = 1 .20.1030 em“3, (Ag)min =
-0 .8 3 .1030 em 3. The scattering factors for the
neutral atom s were taken from the International
Tables for X-ray Crystallography [8]. The neutral
atomic scattering factors with anomalous disper­
sion for Cu atom were used. All crystallographic
calculations were carried out with the Syntex XTL
and X RC83 [9] program packages on ES-1045
computer.
The final atomic coordinates are given in
Table I, selected bond lengths and bond angles in
Table II.
Table I. Final atom ic coordinates (x 104) with estimated
standard deviations in parentheses and equivalent
isotropic thermal parameters B defined as Bec| =
4/3 ZZBijäj-äj.
J
> j
Atom
x/a
C u (l)
0 (1 )
0 (2 )
0 (3 )
0 (4 )
0 (5 )
N (l)
C (l)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C ( ll)
C( 12)
0 (1 1 )
0 (1 2 )
0 (1 3 )
2244( 1)
1547(5)
1421(5)
2079(6)
1266(5)
3107(5)
3048(5)
1823(6)
2589(7)
1815(7)
2445(6)
1843(7)
3920(5)
4418(6)
3977(6)
4305(7)
5343(7)
5751(8)
5199(6)
555(4)
1688(6)
987(6)
y/b
2500(0)
1905(5)
272(5)
-3 3 3 6 (6 )
-3 4 5 7 (5 )
3179(5)
951(5)
793(7)
117(7)
971(7)
-16 7 2 (6 )
-2 9 1 2 (7 )
2599(9)
1418(7)
731(7)
3142(7)
940(8)
1489(9)
2612(10)
2213(4)
416(5)
4536(5)
z/c
737(1)
3186(8)
5321(8)
-29 90 (1 0 )
32(9)
-1 3 5 6 (9 )
993(9)
3777(10)
2463(12)
1177(13)
- 447(11)
-11 0 0 (1 2 )
-2 1 96(10)
-1 3 88(11)
226( 11)
-4 0 3 7 (1 2 )
-23 1 9 (1 4 )
-4 0 54(13)
-4 9 47(11)
-2 3 1 6 (7 )
1493(10)
5512(9)
Beq(A 2)
2.76(2)
3.42(6)
3.57(7)
4.99(9)
3.81(6)
3.67(5)
2.24(2)
2.56(3)
2.91(4)
3.22(6)
2.45(2)
3.13(5)
3.09(5)
2.65(2)
2.71(2)
3.13(6)
3.79(7)
4.05(7)
3.89(6)
3.34(5)
4.77(9)
4.48(9)
J. K rätsm är-S m ogrovic et al. - D ia q u a [N -sa lic y lid e n e -(S )-( + )-g lu ta m a to ]c o p p e r(II)
Interatomic distances
C u ( l) - 0 ( 1 )
C u ( l) - 0 ( 5 )
C u ( l) - N ( l)
C u O )- O (ll)
C u ( l) - 0 ( 1 2 )
0 (1 ) -C ( 1 )
0 ( 2 ) —C (l)
0.1942(7)
0.1919(8)
0.1908(8)
0.2315(7)
0.2007(8)
0.1284(13)
0.1259(12)
0 ( 3 ) —C(5)
0 ( 4 ) -C (5 )
N ( l) - C ( 2 )
N ( l) - C ( 8 )
C (7 )-C (8 )
0 (5 )-C (6 )
C (l) -C ( 2 )
0.1309(13)
0.1209(13)
0.1449(13)
0.1268(13)
0.1409(14)
0.1321(13)
0.1501(14)
172.2(3)
85.2(3)
98.2(3)
85.6(2)
94.9(3)
89.4(3)
92.2(3)
103.1(3)
N (l) -C u ( l)- 0 (1 2 )
0 ( 11 ) - C u ( l ) - 0 ( 1 2 )
C u (l) -0 (1 )- C ( l)
C u ( l) - 0 ( 5 ) - C ( 6 )
C u ( l) - N ( l) - C ( 2 )
C u ( l) - N ( l) - C ( 8 )
C (2 )-N (l)-C (8 )
0 ( l ) - C ( l ) —0 (2 )
162.2(3)
93.3(3)
114.2(6)
125.2(7)
111.9(6)
123.8(7)
123.7(8)
121.4(9)
1325
Table II. Selected interatomic distan­
ces (nm) and bond angles (°) with esti­
mated standard deviations in parenthe­
ses.
Bond angles
O ( l)- C u d ) O O ) - C u ( l) 0 (1 ) -C u (l)0 (1 )-C u (l)0 (5 )-C u (l)0 (5 )-C u (l)0 (5 )-C u (l)N (l) -C u ( l)-
0 (5 )
N (l)
0 (1 1 )
0 (1 2 )
N (l)
0 (1 1 )
0 (1 2 )
0 (1 1 )
Results and Discussion
The molecular structure o f the title complex is
similar to those of [Cu(salgly)(H20 ) 2] *3 H 20 [4],
and of the square-pyramidally coordinated centres
in the polymeric complex
[Cu3{ sa l-(R S )-g lu } 2(H 20 ) 4] [5]. The basal, but
not strictly coplanar part o f the complex molecule
is given by the fused five- and six-membered ring
systems of the N -salicylidene-(S)—glutam atocopper(II) chelate and one strongly coordinated H 20
molecule (Fig. 1). The distorted square-pyram idal
coordination of Cu(II) is apically completed by a
weakly bonded water molecule. The bond dis­
tances of the copper environment are: Cu( 1) - 0 ( 1) =
0.1942(7), C u (l)-0 (5 ) = 0.1919(8), C u (l)-N (l) =
0.1908(8), C u (l)-0 (1 2 ) = 0.2007(8) and C u (l)0(11) = 0.2315(7) nm.
The in-plane bond lengths involving the copper
atom in the title complex are fairly close to those
found [5] in the square-pyramidally coordinated
units of the polymeric complex
[Cu3{ sa l-(R S )-g lu } 2(H 20 ) 4] •7 H 20 . Differences
of the comparable bond lengths arranged in the
above-mentioned sequence are: -0.0020, 0.0006,
-0.0020 and 0.0030 nm, respectively.
Table III. The deviations (nm) o f atom s from the leastsquare planes in the crystal structure o f
[C u { sa l-(S )-g lu } (H 20)2] • H20 (standard deviations are
in parentheses).
Deviations from the plane
The benzene ring:
C(6)
C(9)
C(12)
-0.0031(10)
0.0009(10)
0.0015(11)
C ( ll)
C(10)
C(7)
-0 .0 0 1 5 (1 2 )
-0 .0 0 1 0 (1 2 )
0.0025(10)
C u (l)
0 (5 )
C(6)
-0 .0 0 0 0 (1 0 )
-0 .0 0 0 2 (8 )
0.0078(10)
The six-membered chelate ring:
C ;0t3
Fig. 1. The molecular structure o f
[C u {sa l-(S )-g lu }(H 20)2] • H 20 and the atom ic number­
ing scheme. Hydrogen atom s o f the coordinated O i l ,
O 12) and uncoordinated (O 13) H 20 molecules are om it­
ted.
C(7)
C(8)
N (l)
-0.0030(10)
-0.0090(10)
0.0074(7)
The five-membered Cu chelate ring:
N (l)
C(2)
C (l)
-0.0 0 7 3 (7 )
0.0112(10)
-0.0000(10)
0 (1 )
C u (l)
-0 .0 0 3 6 (7 )
0.0000(10)
J. K rätsm är-S m ogrovic et al. ■D ia q u a [N -sa lic y lid e n e -(S )-( + )-g lu ta m a to ]c o p p e r(II)
1326
The length of the apical C u (l)-0 (1 1 ) bond is
significantly shorter (-0.0170 nm) in the title com­
plex as the com parable bond in the polymeric
[Cu3{ s a l-(R S )-g lu } 2(H 20 ) 4] H 20 [5] complex,
although the same ligand (H 20 ) is coordinated
here in both cases. The copper ion is displaced
from the plane of equatorially coordinated donor
atom s in the direction o f 0(11) atom by
0.0193(1) nm. Bond lengths and angles within the
rings o f the title complex are normal.
D ata on the least-squares planes through the in­
dividual rings of the title complex are listed in T a­
ble III. The six-membered chelate ring is almost
planar (within standard deviation). The five-membered Cu(am inoacidato) chelate ring is in nearly
planar gauche conform ation; N (l) and C(2) are
the out-of-plane atoms. The maximum deviations
from the least-squares planes are: the five-membered chelate ring 0.0112(10), the six-membered
one 0.0090(10).
The side chain of the Schiff base ligand is in
rra«s-conform ation with C (2 )-C (3 )-C (4 )-C (5 )
torsion angle of 166°.
The shortest copper to copper distance is
0.5991(2) nm in the crystal structure o f the title
complex (Fig. 2).
Table IV. The hydrogen bond contacts (nm) with esti­
mated standard deviations in parentheses.
sym. code
X -H -Y
d
0 (2 )--0 (1 1 )
0 (2 )-0 (1 3 )
0 (3 )--0 (1 3 )
0 (4 ) - 0 (1 2 )
0 (4 ) 0 (1 1 )
0 (1 1 )-0 (1 3 )
0 (1 2 ) —0 (1 3 )
0.2853(10)
0.2761(12)
0.2676(12)
0.2750(11)
0.2834(11)
0.2945(10)
0.2747(12)
[C u { s a l-(S )-g lu } (H 20 )] • H 20
T/K
/'Mx 10"/m 3 m ol-1
H jli*
94
5965
1-88
.v, y , z + 1
- x , y - 1/2, l - z
x , y —l , z ~ 1
x ,y - l,z
- x ,y - l/2 ,- z
x .y .z - 1
x, y, z
Fig. 2. A view showing the molecular packing in the unit
cell o f [C u { s a l-(S )-g lu } (H 20 ) 2] • H 20 .
The protonized side chain carboxylic group is
not involved in the coordination o f the copper
ions, but it forms a strong hydrogen bond
0 ( 3 ) - H •••0(13) which is 0.2676(12) nm long. The
oxygen atom s o f this carboxylic group participate
also on the hydrogen bond contacts to the coordi­
nated H 20 molecules of the adjacent complex
units in the crystal structure. Thus the crystal
structure o f the title complex consists of discrete
[C u { sal-(S )-g lu } (H 20 ) 2] m olecular units and of
uncoordinated H 20 molecules (present in ratio
1:1), m utually connected by a three dimensional
network o f hydrogen bonds, listed in Table IV.
From this point of view the crystal structure of the
title complex is rather similar to that o f the
[Cu(salgly)(H20 ) 2] •3 H 20 complex [4], than of the
polymeric [Cu3{ sa l-(R S )-g lu } 2(H 20 ) 4]-7 H 20 [5].
In the latter the deprotonized carboxylic groups of
the side chains also participate bidentately on the
M r = 366.82; Z>dia = -2 2 0 .5 x 10"" m 3 m o l“1
121
4670
1.88
151
3736
1.88
182
3120
1.88
210
2702
1.87
240
2357
1.87
270
2111
1.87
298
1930
1.88
272
2178
1.91
301
1956
1.90
Table V. Magnetic properties o f
the complex
[C u { s a l-(S )-g lu } (H 20 ) J H 20
and the anhydrous
[C u { sa l-(s)-g lu } ].
0 = 1 .4 K ;C = 5.44x 10“6 m3 m ol-1; g = 2.15
[C u {sa l-(S )-g lu }]
T/K
/'Mx 10"/m 3 m ol“1
MefT/u B
M r = 312.76; £ / dia = - 171.5 x 10-" m3 m o l'1
96
6374
1.96
123
4887
1.94
152
3911
1.93
183
3233
1.92
212
2793
1.91
242
2445
1.91
Ö = 8 K ; C = 5.52x 10~6 m3 m o F 1; g = 2.165
Anisotropic thermal parame­
ters, H-atom coordinates and F0/
Fc tables are available from the
authors.
J. K rätsm är-S m o grovic et al. • D ia q u a [N -sa lic y lid e n e -(S )-( + )-g lu tam ato ]c o p p e r(II)
1327
coordination to form distorted octahedral coordi­
nation centres, contacted with the square-pyram i­
dal polyhedra by the bridging coordinated
a-carboxylic group o f a “hexadentate” Schiff base
ligand [sa l-(R S )-g lu ]3-.
The room tem perature magnetic moments of
both the title complex and the corresponding
anhydrous com pound are greater than the “spinonly” value of Cu(II): //eff - 1 .88 //B (T = 2 9 8 K)
and / / efr = 1 .9 0 - / zb, respectively. But these com­
plexes differ from one another in their cryomagnetic behaviour (tem perature range 3 0 9 - 9 4 K)
quite perceptibly. The param eters o f the cryomagnetic properties are listed in Table V.
The magnetic mom ent of
[Cu {sal - (S) - glu} (H 20 ) 2] • H 20 is invariable in the
entire tem perature range of magnetic susceptibility
measurements. Its cryomagnetic behaviour obeys
the C urie-W eiss law used in form / ' M = C /T - 0
with the Weiss constant 0 = 1.4 K: Currie constant
C = 5.4 4 -106 m 3 m ol-1. From the latter the g =
2.15 has been evaluated. Such magnetic properties
are usual for Cu(II) complexes o f tetragonal sym­
metry in which a perceptible spin-exchange cou­
pling is absent between the copper ions (down to
the liquide nitrogen temperature).
The cryomagnetic behaviour of the anhydrous
C u [sal-(S )-g lu ] obeys the C urie-W eiss law, too.
However, a slight ferromagnetic interaction be­
tween the Cu ions could be assumed on the basis of
an enlarged value o f the Weiss constant: 0 = 8 K
and inappreciable tem perature dependence of the
magnetic moment: 1.96 //B (96 K) —> 1.90 -//B
(301 K). Hence, an efficient antiferrom agnetic
coupling is absent in both [C u { sal-(S )glu} •(H 20 ) 2] • H 20 and the anhydrous C u[sal(S)-glu]. Such type o f magnetic coupling has been
observed in the probably dimeric Cu(II)
N -salicylidene-(S)-glutam ate m onohydrate [6]
(1.26 •//B; room temperature) isolated from a ho­
mogenous reaction system in a solvent mixture:
methanol - ethyl acetate - water (after cooling
and concentration). If the antiferromagnetically
coupled binuclear [Cu2{ sa l-(S )-g lu } 2]-2 H 20
crystallizes from a solution directly, it appears that
no crystal structure effects hinder the form ation of
the necessary bridge-system for an efficient spinspin exchange coupling between the Cu(II) ions.
On the other hand the preparation o f the stud­
ied anhydrous com pound C u [sal-(S )-g lu ] has
been realized by thermal dehydratation of the par­
ent [C u{sal-(S )-glu}(H 20 ) 2] H 20 in the solid
state. In this case probably the side chain carboxylic group oxygen atom s replace the H 20 molecules
in the coordination polyhedron of a neighbouring
complex unit liberated during the dehydratation.
The possibility o f such replacement is based on intermolecular hydrogen bonds in the crystal struc­
ture of the parent complex
[C u{sal-(S)-glu} (H20 ) 2] H 20 fixing its side
chain carboxylic group oxygen atom s nearly to
the coordinated H 20 molecules of neighbouring
structure unit. E.g. the “magnetically diluted”
[C u-(salgly)(H 20 ) 2]-3 H 20 complex [4] lacks a
convenient side chain carboxylic group for intermolecular crystal structure contacts and its ther­
mal dehydratation in the solid state gave rise to an
antiferromagnetically coupled binuclear anhy­
drous compound [Cu2(salgly)2] [10], containing an
approximately planar Cu20 2 network as the
bridge-system.
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The authors are indebted to Mrs J. M atovska,
Mrs M. Svrbickä and Mrs O. Durcekovä for their
expert technical assistance.