The Crystal Structures of two Linearly Polymeric Copper(II) Complexes of
2,2⬘-Bipyridine with threefold Glycolato and Oxalato Bridges
Alfonso Castiñeirasa,*, Susana Balboaa, Rosa Carballob, and Juan Niclósc
a
Santiago de Compostela/Spain, Universidad de Santiago de Compostela, Departamento de Quı́mica Inorgánica
b
Vigo/Spain, Universidad de Vigo, Departamento de Quı́mica Inorgánica, Facultad de Ciencias
Granada/Spain, Universidad de Granada, Departamento de Quı́mica Inorgánica, Facultad de Farmacia
c
Received May 3rd, 2002.
Dedicated to Professor Dieter Fenske on the Occasion of his 60th Birthday
Abstract. The complex [Cu(HGLYO)2(bipy)] (I) and two new copper(II) coordination polymers with the formulas {[Cu(GLYO)1x(ox)x(bipy)]·2.5H2O}n [GLYO ⫽ glycolato dianion, ox ⫽ oxalato
dianion, bipy ⫽ 2,2⬘-bipyridine, x ⫽ 0.56 (in II) or 0.71 (in III)]
were synthesized using copper(II) glycolate as starting material and
were characterized by IR, UV-Vis and EPR spectrometry, by magnetic measurements (II and III), and by single-crystal X-ray diffractometry. Both II and III crystallized as one-dimensional polymers composed of Cu2O2-centred dimers with a Cu-Cu distance of
3.282(1) Å (mean of II and III) that are linked by Cu2(OCO)2 rings
with a Cu-Cu distance of 5.237(1) Å (mean of II and III), both
dianions acting as (µ-1,1,2,3) three-way bridges connecting the two
copper atoms of one dimer with one copper atom of a neighbouring dimer. Each copper atom is coordinated tetragonally in a
CuN2O4 chromophore. In the mononuclear complex I the copper
atom has a tetragonally distorted octahedral environment.
Keywords: Copper; mixed Copper(II) carboxylates; 2,2⬘-Bipyridine
complexes; Crystal structures; Coordination polymers.
Die Kristallstrukturen von zwei linear-polymeren Kupfer(II)-Komplexen des
2,2⬘-Bipyridins mit dreifachen Glycolat- und Oxalat-Brücken
Inhaltsübersicht. Der Komplex [Cu(HGLYO)2(bipy)] (I) und die
zwei neuen Kupfer(II)-Koordinationspolymere der Formel
{[Cu(GLYO)1-x(ox)x(bipy)]·2.5H2O}n [GLYO ⫽ Glycolat-Dianion,
ox ⫽ Oxalat-Dianion, bipy ⫽ 2,2⬘-Bipyridine, x ⫽ 0,56 (in II) or
0,71 (in III)] wurden ausgehend von Kupfer(ii)-glycolat synthetisiert und durch IR-, UV-Vis- und EPR-spektroskopische Messungen, durch magnetische Messungen (II und III) sowie durch Röntgen-Einkristallstrukturanalysen charakterisiert. II und III kristallisieren als eindimensionale Polymere aus Cu2O2-zentrierten Dime-
ren mit einem Cu⫺Cu-Abstand von 3,282(1) Å (Mittel bei II und
III), die durch Cu2(OCO)2-Ringe mit einem Cu⫺Cu-Abstand von
5,237(1) Å (Mittel bei II und III) verbunden sind. Beide Dianionen
bilden (µ-1,1,2,3)-Dreiwegbrücken und verbinden die zwei Kupferatome des einen Dimeren mit einem Kupferatom eines Nachbardimeren. Jedes Kupferatom ist in einem CuN2O4-Chromophor tetragonal koordiniert. In dem einkernigen Komplex I hat das Kupferatom eine tetragonal verzerrte oktaedrische Umgebung.
Introduction
sis [3] and magnetochemistry [4]. The coordination modes
of the oxalato ligand, both in solution [5] and in the solid
state [6], are accordingly well known. By contrast, the possibilities of α-hydroxycarboxylato anions as bridging ligands in polynuclear complexes have been much less thoroughly explored: a few scattered papers have reported the
formation of the coordination polymers [Cu(HGLYO)2]n
[7], [Pb(HGLYO)2]n [8], [Ag2(HGLYO)2]n·1/2H2O [9],
[Co(HGLYO)2]n [10] and [Zn(HLACO)2]n [11] (H2GLYO ⫽
glycolic acid, H2LACO ⫽ lactic acid), in which the only
ligand is an α-hydroxycarboxylato anion, but it was only
recently that Xiong et al. [12] reported the preparation of
(S-(-)-lactato)(isonicotinato)zinc(II), the first α-hydroxycarboxylato-bridged coordination polymer featuring a second
bridging ligand.
In previous work by our group on complexes of divalent
cations containing both α-hydroxycarboxylato ligands and
another
ligand,
we
prepared
the
dimer
In recent years, intense research on the synthesis and
characterization of coordination polymers of transition metals has led to significant advances in both their theoretical
description and the search for potential applications of
these new materials [1]. Many studies have concerned polynuclear complexes with bridging oxalato ligands, which display a great variety of structural motifs and have applications in fields that include biological chemistry [2], cataly-
* Prof. Dr. A. Castiñeiras
Departamento de Quı́mica Inorgánica
Facultad de Farmacia
Universidad de Santiago de Compostela
E-15706 Santiago de Compostela
Fax: ⫹34 981 547163
E-mail: [email protected]
Z. Anorg. Allg. Chem. 2002, 628, 2353⫺2359  WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 0044⫺2313/02/628/2353⫺2359 $ 20.00⫹.50/0
2353
A. Castiñeiras, S. Balboa, R. Carballo, J. Niclós
[Cu(GLYO)(bipy)]2·nH2O (bipy ⫽ 2,2⬘-bipyridine), in
which the deprotonated glycolato hydroxyl oxygen acts as
a single-atom bridge while joining with one of the carboxylato oxygens in chelating one of the copper atoms [13].
Copper(II) was used in this work because of the plasticity
of its coordination sphere [14], and the chelating aromatic
diamine bipy because it is of general interest in coordination chemistry [15], being capable of both the formation
of species that are stable in solution [16] and of the stabilization of solid state systems through stacking interactions
[17]. We report here that further exploration of the above
reaction, under different conditions, has afforded two new
coordination polymers, both of which contain bipy, glycolato dianion (GLYO2⫺) and, as the result of oxidation of
the latter, oxalato dianion (ox2⫺), and in both of which the
glycolato and oxalato dianions both act as three-way
bridges.
Results and Discussion
Synthesis and non-structural characteristics
In ethanol, Cu2(OH)2(CO3), H2GLYO and bipy react to
form the mononuclear complex [Cu(HGLYO)2(bipy)] or
the dinuclear species [Cu(GLYO)(bipy)]2·nH2O (n ⫽ 4 or
6) [13], depending on the mole ratios of the reagents in
the reaction mixture. However, in the present study their
reaction for 3⫺5 h in refluxing water afforded linearly
polymeric species in which a proportion of the glycolato
dianion had been oxidized to oxalato dianion. In the light
of the structures described below, it seems likely that
initial formation of the above dimers (in which one of
the carboxylato oxygens is uncoordinated) was followed,
in the presence of air and at the working temperatures
used, by oxidation of glycolato to oxalato and coordination of the previously “free” carboxylato oxygen to a
copper atom of a neighbouring dimer. The analytical data
of the two new complexes show them to differ as regards
the proportion of glycolato that has been oxidized to
oxalato, II being {[Cu(GLYO)0.44(ox)0.56(bipy)]·2.5H2O}n
and III {[Cu(GLYO)0.29(ox)0.71(bipy)]·2.5H2O}n.
In the IR spectra, carboxylato bands can be identified in
the 1700⫺1300 cm⫺1 region (at 1610, 1598, 1492, 1445,
1402, 1382 and 1307 for I, at 1655, 1604, 1478, 1446, 1396
and 1317 cm⫺1 for II and at 1657, 1605, 1447, 1401 and
1316 cm⫺1 for III), but in II and III more precise identification is prevented by the fact that there are four different
types of oxygen atoms (uncoordinated, dicoordinated, and
chelating and non-chelating monocoordinated) and by the
presence of bipy bands in the same region of the spectrum.
A broad band characteristic of OH stretching appears at
3430 cm⫺1 because of the involvement of the water molecules or hydroxyl groups in hydrogen bonds. A medium
band appearing around 780 cm⫺1 is assigned to CO2 deformation. The bipy ring deformation bands, which lie around
625 and 405 cm⫺1 in the spectrum of free bipy [18,19], have
shifted to higher frequencies in those of the complexes due
2354
to the N,N⬘-coordination of bipy. The far IR spectra show
two weak-to-medium bands: one lies at 310 cm⫺1 in I and
at 339 cm⫺1 in II and III and may be attributed to ν(CuO),
the other lies at 231 cm⫺1 in I, 266-234 cm⫺1 in II and at
243 cm⫺1 in III and may be attributed to ν(CuN) [20,21].
The reflectance spectra show two bands near 25000 and
23000 cm⫺1 that may be due either to charge transfer from
carboxylato to copper or to intraligand transitions. The dd bands typical of (4⫹1⫹1)-coordinate species with a
CuN2O4 chromophore [22] appear in the spectrum of I as
a single band at 15013 cm⫺1, in that of II as a broad band
at 15528 cm⫺1 with a shoulder at 16103 cm⫺1, and in that
of III as a broad band at 15600 cm⫺1 with a shoulder at
16260 cm⫺1 and another band at 14327 cm⫺1.
The room-temperature EPR spectra of polycrystalline
samples have no medium-field signals and show axial symmetry, with g储 ⫽ 2.29 and g⬜ ⫽ 2.06 for I, g储 ⫽ 2.22 and
g⬜ ⫽ 2.06 for II, and g储 ⫽ 2.20 and g⬜ ⫽ 2.04 for III,
values that are typical of copper(II) ions with predominantly tetragonal coordination and a dx2-dy2 ground state
[23]. The values of G [⫽ (g储 - 2)/(g⬜ - 2)] lie in the range
3.5-5.0 indicative of probable magnetic exchange [24] of the
kind observed in {[Cu(ox)(bipy)]·2.5H2O}n, for which G ⫽
4.5.
At room temperature the magnetic moment of II is 1.63
BM and that of III 1.64 BM. These values are both rather
smaller than the spin-only value, possibly because of weak
antiferromagnetic interaction or, as in {[Cu(ox)(bipy)] ·
2.5H2O}n [25], alternating ferromagnetic and antiferromagnetic interactions.
Crystal structures
Selected interatomic distances and angles are listed in Table
1, and the main hydrogen bonds in Table 2. Figures 1 and
2 show drawings of the structures of compounds I and II,
respectively, together with the atom-numbering schemes
used.
The crystals of I are based on neutral [Cu(HGLYO)2(bipy)] molecules. The copper ions are six-coordinate (Fig.
1), being bound to the nitrogen atoms of the 2,2⬘-bipyridine
ligand and to one carboxy and one hydroxyl oxygen of each
of two HGLYO⫺ anions. There are thus three five-membered chelate rings. The copper atom has elongated octahedral coordination geometry with the two nitrogen atoms
and the mutually cis Ocarboxy atoms equatorial and the two
α-hydroxyl oxygen atoms axial, the difference between the
average equatorial and axial bond lengths being 0.445 Å.
This elongation of the coordination polyhedron, due to a
Jahn-Teller effect, is also observed in polymeric complexes
containing lactato or 2-methyllactato ligands and 4,4⬘-bipyridine [26]. Additional deviation from ideal octahedral
geometry is shown by the chelating angles, which range
from 72.35(11)° to 80.52(15)° (Table 1), and by some of the
trans angles, such as Ohydroxyl-Cu-Ohydroxyl [149.70(10)°] and
Ocarboxy-Cu-N [172.61(12)° and 173.88(14)°]. The CuOcarboxy distances fall within the range usually observed in
Z. Anorg. Allg. Chem. 2002, 628, 2353⫺2359
Crystal Structures of two Linearly Polymeric Copper(II) Complexes
Table 1 Selected lengths/Å and angles/° in [Cu(HGLYO)2(bipy)]
{[(GLYO)0.29(ox)0.71(bipy)}]·2.5H2O}n (III) and related compounds
(I),
{[Cu(GLYO)0.44(ox)0.56(bipy)]·2.5H2O}n
(II),
and
Compound
[Cu(GLYO)(bipy)2]2·nH2Oa)
Ib)
II
III
{[Cu(ox)(bipy)]·2.5H2O}nc)
Cu(1)-N(11)
Cu(1)-N(12)
Cu(1)-O(11)
Cu(1)-O(21)
Cu(1)-O(21)#1
Cu(1)-O(12)#2
Cu(1)-Cu(1)#1
Cu(1)-Cu(1)#2
O(21)-O(21)#1
1.987(1)/1.990(1)
2.017(1)/2.010(2)
1.929(1)/1.945(2)
1.925(1)/1.923(2)
2.341(1)/2.401(2)
⫺
3.047(1)/3.084(1)
⫺
⫺
2.008(4)
2.001(3)
1.951(3)
1.943(3)
2.333(3)
2.508(3)
⫺
⫺
⫺
1.982(3)
1.992(3)
1.939(2)
1.923(2)
2.562(3)
2.837(3)
3.242(1)
5.265(1)
3.165(5)
1.986(2)
1.973(3)
1.932(2)
1.921(2)
2.646(3)
2.817(3)
3.322(1)
5.209(1)
3.218(5)
1.973(2)
1.966(2)
1.935(2)
1.927(2)
2.711(3)
2.784(3)
3.451
5.058
⫺
N(11)-Cu(1)-N(12)
N(11)-Cu(1)-O(11)
N(11)-Cu(1)-O(21)
N(11)-Cu(1)-O(21)#1
N(11)-Cu(1)-O(12)#2
N(12)-Cu(1)-O(11)
N(12)-Cu(1)-O(21)
N(12)-Cu(1)-O(21)#1
N(12)-Cu(1)-O(12)#2
O(11)-Cu(1)-O(21)
O(11)-Cu(1)-O(21)#1
O(11)-Cu(1)-O(12)#2
O(21)-Cu(1)-O(21)#1
O(21)-Cu(1)-O(12)#2
O(21)#1-Cu(1)-O(12)#2
80.94(6)/80.99(8)
92.68(6)/95.06(7)
176.22(5)/179.55(7)
94.34(5)/90.27(7)
⫺
164.39(6)/168.99(7)
99.48(5)/98.57(7)
95.58(5)/97.24(7)
⫺
85.97(5)/85.38(7)
⫺/93.04(6)
⫺
89.35(5)/89.72(6)
⫺
⫺
80.52(15)
172.61(12)
93.36(13)
97.94(12)
104.65(12)
93.17(13)
173.88(14)
104.59(12)
98.89(12)
92.93(12)
87.33(12)
72.35(11)
76.09(11)
82.60(11)
149.70(10)
81.58(11)
96.74(11)
176.83(11)
88.75(10)
87.91(10)
171.64(11)
96.98(11)
95.41(10)
89.45(9)
85.09(10)
92.73(9)
82.30(9)
88.57(10)
94.91(10)
173.65(8)
81.51(10)
172.70(9)
97.14(10)
93.47(8)
89.72(8)
97.14(10)
176.15(9)
88.39(9)
88.11(9)
84.65(9)
93.66(9)
83.06(8)
88.08(10)
95.51(10)
174.87(7)
82.01(9)
⫺
⫺
⫺
⫺
⫺
⫺
⫺
⫺
84.75(8)
⫺
⫺
⫺
⫺
177.88(6)
a)
Ref. [13]
O(11), O(21)#1 and O(12)#2 are O(31), O(23) and O(33), respectively for [Cu(HGLYO)2(bipy)].
Ref. [25]
Symmetry transformations used to generate equivalent atoms: #1, ⫺x⫹1, ⫺y⫹1, ⫺z⫹1; #2, ⫺x, ⫺y⫹1, ⫺z⫹1, for I; #1, ⫺x⫹1, ⫺y⫹1, ⫺z; #2, ⫺x⫹2,
⫺y⫹1, ⫺z, for (II); #1 ⫺x⫹2, ⫺y⫹1, ⫺z or ⫺x⫹1/2, ⫺y⫹3/2, ⫺z, for [Cu(GLYO)(bipy)2]2·nH2O; #1, ⫺x, ⫺y⫹1, ⫺z; #2, ⫺x⫺1, ⫺y⫹1, ⫺z for
{[Cu(ox)(bipy)]·2.5H2O}n .
b)
c)
Table 2 Hydrogen bonds in [Cu(HGLYO)2(bipy)] (I),
{[Cu(GLYO)0.44(ox)0.56(bipy)]·2.5H2O}n (II) and
{[(GLYO)0.29(ox)0.71(bipy)}]·2.5H2O}n (III).
D-H···A
d(D-H)/Å
d(H···A)/Å d(D···A)/Å <(DHA)/°
Compound I
O(23)-H(23)···O(32)#1
O(33)-H(33)···O(22)#2
1.00
0.99
1.69
1.76
2.683(5)
2.727(5)
172.0
164.0
Compound II
O(1)-H(10A)···O(3A)#2
O(1)-H(10A)···O(3B)#2
O(1)-H(10B)···O(12)#1
O(1)-H(10B)···O(11)#1
O(2)-H(20A)···O(1)#3
O(3B)-H(3B)···O(22)
0.80
0.80
0.99
0.99
1.00
0.83
2.15
2.27
2.00
2.47
2.15
2.17
2.811(8)
3.069(10)
2.866(5)
3.305(4)
2.586(8)
2.989(10)
139.8
170.5
145.6
141.8
175.6
168.6
Compound III
O(1)-H(10A)···O(12)#1
O(1)-H(10A)···O(11)#1
O(1)-H(10B)···O(3A)#2
O(1)-H(10B)···O(3B)#2
O(3B)-H(30B)···O(22)#1
0.96
0.96
1.05
1.05
0.91
2.00
2.50
2.04
2.09
2.15
2.914(5)
3.314(4)
2.921(11)
3.109(14)
2.972(10)
158.4
142.8
139.6
163.5
149.3
Symmetry transformations used to generate equivalent atoms: #1, ⫺x⫹1,
⫺y, ⫺z⫹2; #2, ⫺x, ⫺y⫹1, ⫺z⫹2 (I); #1, ⫺x⫹1, ⫺y⫹1,⫺z⫹1; #2, x⫹1, y,
z; #3, ⫺x⫹1, ⫺y, ⫺z⫹1 (II); #1, ⫺x⫹1, ⫺y⫹1, ⫺z; #2, ⫺x, ⫺y⫹1, ⫺z;
#3, ⫺x⫹1, ⫺y, ⫺z (III)
similar copper(II) complexes (1.90-1.97 Å) [26⫺30]. The
lengths of the Cu-Ohydroxyl bands depend on the involvement of the hydroxyl oxygen atoms in hydrogen bonds, as
in other complexes with a CuN2O4 core [26,27,30]. The CuZ. Anorg. Allg. Chem. 2002, 628, 2353⫺2359
Figure 1 Prespective view of [Cu(HGLYO)2(bipy)] (I) showing the
numbering scheme adopted for the atoms.
N distances (ca. 2.000 Å) are slightly shorter than in polymeric copper(II) complexes containing 4,4⬘-bipyridine [26],
but are nevertheless within the normal range for complexes
with N,N-chelating ligands [27,28].
In spite of the different steric requirements of the glycolato and oxalato ligands, the structures of both the new
polymeric complexes are isotypic with that of
2355
A. Castiñeiras, S. Balboa, R. Carballo, J. Niclós
Figure 2 Ball-and-stick representation of a fragment of a one-dimensional chain, showing the coordination environment in II.
Figure
3 The
packing
diagram
of
the
complex
{[(GLYO)0.29(ox)0.71(bipy)]·2.5H2O}n (III), viewed perpendicularly
to the ac plane. For clarity, water of crystallization molecules are
omitted.
{[Cu(ox)(bipy)]·2.5H2O}n [25], being composed of [Cu(GLYO)1-x(ox)x(bipy)]n chains and water of crystallization.
Fig. 2 shows a fragment of II with the atom numbering
used, and Table 1 lists the main bond lengths and angles in
II, III and related copper(II) complexes.
The linear chains can be considered as composed of
Cu2O2-centred [Cu(carboxylato)(bipy)]2 dimers (carboxylato ⫽ glycolato or oxalato dianion), the dimers being
linked by Cu2(OCO)2 rings. Each copper atom is linked to
the other Cu of its own dimer via two single-oxygen bridges,
and to a Cu atom of a neighbouring dimer via two OCO
bridges formed by carboxylato groups (one belonging to its
own monomer, the other to the neighbouring dimer); while
each dianion acts as a (µ-1,1,2,3) three-way bridge, chelating the Cu atom of its own monomer and bridging asymmetrically between the two Cu atoms of its own dimer and
between these and a Cu atom of a neighbouring dimer.
Each monomer is based on a distorted square-planar
CuN2O2 unit in which the oxygen atoms are the chelating
atoms of a glycolato or oxalato dianion. In II the Cu-bound
nitrogen and oxygen atoms lie ±0.093(1) Å from the leastsquares plane defined by the CuN2O2 kernel, and in III
±0.091(1) Å; the copper atom lies 0.047(1) Å from this
plane in II and 0.031(1) Å from it in III. As a result of these
deviations, the dihedral angles between the CuN2O2 plane
and those of the bipy and carboxylato ligands are respectively 6.7(1)° and 13.2(2)° in II and 6.2(1)° and respectively
12.4(2)° in III. Distorsion is also apparent in the bond
angles around the metal atom, which range from 81.6(1)°
to 97.0(1)° in II and from 81.5(1)° to 97.1(1)° in III for
angles that are ideally 90°, and from 171.6(1)° to 176.8(1)°
2356
Figure 4 The solid state structure of
{[Cu(GLYO)0.44(ox)0.56(bipy)]·2.5H2O}n (II), in the bc plane.
in II and from 172.7(1)° to 176.2(1)° in III for angles that
are ideally 180°.
Z. Anorg. Allg. Chem. 2002, 628, 2353⫺2359
Crystal Structures of two Linearly Polymeric Copper(II) Complexes
The coordinating bond lengths within each monomer [average Cu-N ⫽ 1.987(3) Å for II, 1.980(3) Å for III; average
Cu-O ⫽ 1.931(2) Å for II, 1.927(2) Å for III] are very similar to those found in other copper(II) complexes with
square planar primary coordination, but the influence of
charge delocalization in the oxalato ligands is nevertheless
apparent in that the Cu-N bonds in II and III are intermediate in length between those of I, in which there is no
delocalization, and those of {Cu(ox)(bipy)]·2.5H2O}n [average 1.970(2) Å], in which all the carboxylato ligands are oxalatos (Table 1). In fact, delocalization is even reflected in
the difference in coordination bond lengths between II, in
which 56 % of carboxylato ligands are oxalato, and III, in
which this proportion rises to 71 %, since it is II that has
slightly the longer Cu-N and Cu-O bonds.
Within each dimer, the Cu-O distance between each Cu
and the bridging glycolato CH2O oxygen or oxalato COO
oxygen of the other monomer is 2.562(3) Å in II and
2.646(3) Å in III, and the resulting Cu···Cu distances are
3.242(1) Å and 3.322(1) Å, respectively. The between-dimer
Cu-O bonds have lengths of 2.837(3) Å in II and 2.817(3) Å
in III, and the Cu···Cu distances mediated by the corresponding OCO bridges are 5.265(1) Å and 5.209(1) Å,
respectively. Thus the Cu···Cu distances in each polymer
chain are alternately long (between dimers) and short
(within dimers), as in {Cu(ox)(bipy)]·2.5H2O}n.
Taking all interactions into account, each copper atom is
tetragonally coordinated, with the bonds with ligands of its
own monomer equatorial and the axial Cu-O bonds with
the other monomer of its dimer and with the neighbouring
dimer longer by about 0.68 Å and 0.90 Å, respectively (averages of II and III). The longest Cu-O bond length is very
close to the sum of the Van der Waals radii of oxygen and
copper [rVdW(Cu) ⫽ 1.40 Å, rVdW(O) ⫽ 1.50 Å [31].
The polymer chains extend in the [100] direction with the
bipy ligands intercalating slightly with those of the neighbouring ligands in the [001] direction (Fig. 2). The molecules of water of crystallization, located in the spaces between neighbouring chains in the [010] direction (Fig. 3),
are involved in hydrogen bonds with each other and with
the carboxylato oxygens of neighbouring polymer chains
(Table 2).
Experimental Section
netometer. X-band (9300 MHz) EPR spectra were obtained at
room temperature with a Bruker ESP 300E spectrometer.
Synthesis and crystallization of the compounds
[Cu(HGLYO)2(bipy)] (I). A mixture of Cu2CO3(H2O)2 (0.50 g,
2.26 mmol) and H2GLYO (0.69 g, 9.10 mmol) in 35 mL of ethanol
was refluxed for 3 h at 75 °C. 2,2⬘-Bipyridine (0.71 g, 4.52 mmol)
was added and refluxing was continued for 2 h, after which the
mixture was stirred for 7 days. The blue solid formed was filtered
out, washed with ethanol and dried over CaCl2. Single crystals were
obtained by slow concentration of a solution in CH3CN/H2O at
room temperature.
Anal. Found: C, 45.1; H, 3.6; N, 7.6 %. Calc. for
C14H14CuN2O6.(369.81): C, 45.5; H, 3.8; N, 7.6 %.
IR/(KBr, ν/cm⫺1): 3428m ν(OH), 1610s νas(CO2), 1598vs ν(bipy, CC), 1492w,
1470w, 1445m, ν(C⫽C), 1402m, 1382m νs(CO2), 1307m, 1250w, 1171w,
1104w, 1074m, 1062m, 1031m, 934w, 921w, 777m δ(CO2), 732m, 711w, 656w,
638w 움(CCC, ring), 540w, 417w φ(CC, ring), 373w, 311m ν(CuO), 231w
ν(CuN), 190w, 178m. UV-vis (ν/cm⫺1): 2743, 23697, 15015.
{[Cu(GLYO)0.44(ox)0.56(bipy)]·2.5H2O}n (II). To a suspension of
0.50 g (2.26 mmol) of Cu2CO3(OH)2 in 25 mL of distilled water
was added, with stirring, an aqueous solution of 0.35 g (4.60 mmol)
of glycolic acid. The mixture was refluxed for 2 h, 1.42 g
(9.09 mmol) of 2,2⬘-bipyridine was added, and refluxing was continued for a further 3 h and stirring for a further 7 days. The resulting blue solution was filtered, and slow evaporation of the solvent in air at room temperature afforded blue crystals.
Anal. Found: C, 41.6; H, 3.5; N, 8.0 %. Calc. for
C12H13.89CuN2O6.06.(346.64): C, 41.6; H, 4.0; N, 8.1 %.
IR/(KBr, ν/cm⫺1): 3429m ν(OH), 1655s νas(CO2), 1604vs ν(bipy, CC), 1478w,
1446m ν(C⫽C), 1396m νs(CO2), 1317w, 1258w, 1232w, 1163w, 1109w,
1065m, 1030m, 920w, 874w, 779m δ(CO2), 732m, 695w, 660w 움(CCC, ring),
588w, 549w, 491m, 422w φ(CC, ring), 368w, 339m ν(CuO), 266w, 234w
ν(CuN), 204w, 178m. UV-vis (ν/cm⫺1): 25000, 23148, 16103sh, 15527.
{[Cu(GLYO)0.29(ox)0.71(bipy)]·2.5H2O}n (III). To a suspension
of 0.25 g (1.13 mmol) of Cu2CO3(OH)2 in 25 mL of H2O was added 0.177 g (1.13 mmol) of 2,2⬘-bipyridine and, later, 0.086 g
(1.13 mmol) of glycolic acid dissolved in 5 mL of H2O. The mixture
was refluxed for 3 h and stirred for a further 10 days, and the resulting blue solution was filtered and centrifuged. Slow evaporation
of the solvent in air at room temperature afforded crystals suitable
for structural analysis by X-ray diffractometry.
Anal. Found: C, 41.4; H, 3.6; N, 8.0 %. Calc. for
C12H13.57CuN2O6.21(348.80): C, 41.3; H, 3.9; N, 8.0 %.
IR/(KBr, ν/cm⫺1): 3433s ν(OH), 1657vs νas(CO2), 1605s ν(bipy, CC), 1447m
ν(C⫽C), 1401m νs(CO2), 1316w, 1259w,1161w, 1098w, 1062m, 1034m, 781m
δ(CO2), 731m, 662w 움(CCC, ring), 638w, 548w, 519w, 493m, 443w φ(CC,
ring), 339m ν(CuO), 243w ν(CuO),146w. UV-vis (ν/cm⫺1): 27248, 23148,
16260sh, 15600, 14327.
General
Chemicals were purchased from commercial sources and used without further purification. Elemental analyses (C, H, N) were performedin a Carlo Erba 1108 microanalyser. Melting points were
measured in a Büchi melting point apparatus and are uncorrected.
The IR spectra of samples incorporated in KBr discs
(4000⫺400 cm⫺1) or polyethylene-sandwiched Nujol mulls
(500⫺100 cm⫺1) were recorded on a Bruker IFS66v spectrophotometer. A Shimadzu UV-3101PC spectrophotometer was used to obtain electronic spectra in the region 900-350 nm. Magnetic susceptibility measurements were made at room temperature using a Johnson Matthey magnetic susceptibility balance with a DSM-10 magZ. Anorg. Allg. Chem. 2002, 628, 2353⫺2359
Crystal structure determination
Crystals of [Cu(HGLYO)2(bipy)] (I), {[Cu(GLYO)0.44(ox)0.56(bipy)]
· 2.5H2O}n (II) and {[Cu(GLYO)0.29(ox)0.71(bipy)}] · 2.5H2O}n (III)
were mounted on glass fibres for data collection in an Enraf Nonius CAD4 automatic diffractometer. Cell constants and an orientation matrix were obtained by least-squares refinement of the diffraction data for 25 reflections in the ranges 16.76° < θ < 26.34°
(I),18.66° < θ < 46.22° (II) and 12.96°< θ < 28.74° (III) [32]. Data
were collected at 213 K (I and II) or 293 K (III) using CuKα radiation (λ ⫽ 1.54184 Å) and the ω/2θ-scan technique, and were cor2357
A. Castiñeiras, S. Balboa, R. Carballo, J. Niclós
Table 3 Crystal and structure refinement data for [Cu(HGLYO)2(bipy)] (I), {[Cu(GLYO)0.44(ox)0.56(bipy)]·2.5H2O}n (II) and
{[(GLYO)0.29(ox)0.71(bipy)}]·2.5H2O}n (III).
Compound
I
II
III
Empirical formula
Formula weight
Wavelength / Å
Crystal size /mm
Crystal shape
Crystal system
Space group
a / Å
b / Å
c / Å
움/°
β/°
γ/°
V / Å3
Z, Dcalcd. /Mg/m3
F(000)
θ range / °
Temperature / K
hmin/hmax
kmin/kmax
lmin/lmax
µ / mm⫺1
Max. / min. transmissions
Refl. collected / unique
Rint
Data / parameters
Final R
Final wR2
GOOF
Max. ∆ρ / eÅ!3
C14H14CuN2O6
369.81
1.5418
0.20 ⫻ 0.15 ⫻ 0.10
prismatic
triclinic
P1̄ (No. 2)
8.3735(7)
9.9706(5)
10.2379(8)
72.033(5)
70.924(6)
65.771(5)
721.42(9)
2, 1.702
378
5.96⫺65.08
213(2)
⫺1 / ⫺9
⫺11 / 11
⫺11 / 12
2.469
0.933 / 0.717
2894 / 2348
0.061
2348 / 209
0.052
0.134
1.053
0.517
C12H13.89CuN2O6.06
346.64
1.54184
0.35 ⫻ 0.30 ⫻ 0.05
needle
triclinic
P1̄ (No. 2)
7.0774(9)
9.6587(7)
10.4432(13)
93.624(10)
109.603(9)
91.358(10)
670.39(13)
2, 1.717
355
6.19⫺64.96
213(2)
⫺8 / 1
⫺11 / 11
⫺11 / 12
2.609
0.881 / 0.462
2862 / 2276
0.058
2276 / 208
0.046
0.121
1.173
0.539
C12H13.57CuN2O6.21
348.80
1.54184
0.96 ⫻ 0.24 ⫻ 0.08
needle
triclinic
P1̄ (No. 2)
7.1206(4)
9.6672(4)
10.4706(8)
93.885(7)
109.525(5)
91.447(4)
676.87(7)
2, 1.711
357
4.50⫺73.64
293(2)
⫺8 / 8
⫺12 / 0
⫺12 / 12
2.598
0.819 / 0.189
5898 / 2694
0.075
2694 / 209
0.055
0.159
1.094
0.463
rected for Lorentz and polarization effects [33]. A semi-empirical
absorption correction (γ-scans) was also made [34].
The structures were solved by direct methods [35] and subsequent
difference Fourier maps, and refined on F 2 by a full-matrix leastsquares procedure using anisotropic displacement parameters [36].
All hydrogen atoms were located in difference Fourier maps and
included as fixed contributions riding on attached C atoms with
isotropic thermal displacement parameters 1.2 times those of the
respective C atom. Since the variable oxidation of glycolato caused
considerable disorder in structures II and III, with high anisotropic
and thermal displacement parameters for O(22), a model was set
up with either an oxygen atom or a pair of H atoms [H(2A) and
H(2B)] bound to C(2); with this model the occupancy factors for
the oxygen and hydrogen atoms refined to 0.56(1) for O(22) and
0.44 for H(2A) and H(2B) in II, and to 0.71(1) for O(22) and 0.29
for H(2A) and H(2B) in III. The oxygen atoms of the water of
crystallization are also disordered: one, O(2), varies between two
symmetry-related positions, each with a 50 % occupation factor;
while O(3) varies between two positions with occupancies that refined to 0.54(1) for O(3A) and 0.46(1) for O(3B) for II and to
0.83(6) for O(3A) and 0.17(6) for O(3B) for III. Atomic scattering
factors were taken from International Tables for X-ray Crystallography [37]. Molecular graphics were produced using PLATON [38]
and SCHAKAL [39]. The crystal data, experimental details and
refinement results are summarized in Table 3.
Crystallographic data have been deposited at the Cambridge Crystallographic Data Centre with CCDC Nos 187584 for
[Cu(HGLYO)2(bipy)], 184302 for {[Cu(GLYO)0.44(ox)0.56(bipy)] ·
2.5H2O}n and 184303 for {[Cu(GLYO)0.29(ox)0.71(bipy)}] ·
2.5H2O}n. Copies of this information may be obtained free of
2358
charge from The Director, CCDC, 12 Union Road, Cambridge,
CB2 1EZ, UK (Fax: ⫹44-1223-336033; e-mail: [email protected] or www:http://www.ccdc.cam.ac.uk).
Acknowledgements. We thank the Spanish Ministry of Education,
Cultureand Sports and the Xunta de Galicia for financial support
(Refs. PB98-0605-C03 andPGIDT00PXI20302PN, respectively).
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