Hydrothermal synthesis, crystal structures and effect of non bonding interactions in crystal packing of two mixed-ligand metal complexes with glycolato and 2,2′-dipiridylamine and with benzilato and imidazole

Article abstract of DOI:10.1002/zaac.200570007

Two new mixed-ligand complexes [Fe(HG)₂(dipyam)] (1) (HG = glycolato and dipyam = 2,2′-dipyridylamine) and [Cu(HB) ₂(im)₂]·2H₂O (2) (HB = benzilato and im = imidazole) have been hydrothermally synthesized and st

Full text of DOI:10.1002/zaac.200570007

Hydrothermal Synthesis, Crystal Structures and Effect of Non Bonding
Interactions in Crystal Packing of Two Mixed-Ligand Metal Complexes with
Glycolato and 2,2Ј-Dipiridylamine and with Benzilato and Imidazole
a,
a
a
a
b
´
´
´
´
˜
Rosa Carballo *, Berta Covelo , Ezequiel M. Vazquez-Lopez , Emilia Garcıa-Martınez , Alfonso Castineiras ,
and Christoph Janiakc
a
´
´
´
Vigo/Spain, Departamento de Quımica Inorganica, Facultade de Quımica, Universidade de Vigo
b
´
´
Santiago de Compostela/Spain, Departamento de Quımica Inorganica, Facultade de Farmacia, Universidade de Santiago de
Compostela
c Freiburg/Germany, Institut für Anorganische und Analystiche Chemie, Universität Freiburg
Received November 19th, 2004; accepted March 10th, 2005.
Abstract. Two new mixed-ligand complexes [Fe(HG)2(dipyam)] (1)
(HG glycolato and dipyam 2,2Ј-dipyridylamine) and
two oxygen atoms of the carboxylate group in 2. The complexes
ϭ
ϭ
are extended into 2D frameworks through hydrogen bonding and
π···π or C-H···π interactions. The complexes were also characteri-
zed by elemental analysis, FT-IR and UV-vis spectroscopy and
room temperature magnetic measurements.
[Cu(HB)2(im)2]·2H2O (2) (HB ϭ benzilato and im ϭ imidazole)
have been hydrothermally synthesized and structurally characteri-
sed by X-ray diffraction. In both cases the metallic centre is in an
octahedral environment, strongly distorted in 2 (4ϩ2 coordina-
tion). The α-hydroxycarboxylato ligands (glycolato or benzilato)
present different coordinative behaviour, bidentade chelate through
the hydroxyl oxygen and one carboxy oxygen in 1 and through the
Keywords: Hydrothermal synthesis; Copper; Iron; Mixed-ligand
complexes; Supramolecular chemistry; Crystal structures
Introduction
7 by hydrothermal reaction. Compound 1 has been ob-
tained by reaction of iron(II) chloride, glycolic acid, 2,2Ј-
dipyridylamine and sodium carbonate in 1:2:1:1 ratio, and
compound 2 by reaction of copper(II) hydroxide-carbonate,
benzilic acid and imidazole in 0.5:2:2 ratio. Both com-
pounds are stable in air and have high melting points. Com-
pound 1 is very poorly soluble in both polar and apolar
solvents, however 2 is soluble in methanol and ethanol.
Extended frameworks of coordination compounds based
on non-covalent intermolecular interactions like hydrogen
bonds [1, 2], π···π [3] and/or C-H···π interactions [3, 4], are
currently of great interest because of their intriguing top-
ologies and their potential applications. α-hydroxycar-
boxylato ligands may exhibit various coordination modes
and provide potential intermolecular interactions such as
hydrogen bonds involving the hydroxyl and carboxylate
functionalities, and π···π and C-H···π interactions when pre-
sent aromatic substituents. The possibilities of formation of
supramolecular arrays can be also promoted by the use of
auxiliary ligands such as: imidazole and 2,2Ј-dipyridylam-
ine, with N-H groups potentially donors in hydrogen bonds
and with aromatic rings suitable to establish π···π and/or C-
H···π interactions. In this paper, we report the preparation,
properties and a detailed structural analysis of two new
mixed-ligand complexes with iron(II) and copper(II).
Structural analysis
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 structures of compounds 1 and 2,
respectively, together with the atom-numbering schemes
used.
The structure of 1 is based on neutral units [Fe(HG)2(di-
pyam)], where two monoanionic O,OЉ-bidentade glycolato
ligands (HGϪ) chelate the iron(II) ion through one carboxy
and the hydroxyl oxygen atoms to form two five-membered
chelate rings (Figure 1). The octahedral coordination
around each iron(II) ion is completed by two nitrogen
atoms of one 2,2Ј-dipyridylamine ligand that forms a six-
membered chelate ring with a boat conformation. The main
deviations from the ideal coordination polyhedron are the
chelating angles Ohydroxyl-Fe-Ocarboxy [74.57 and 76.95°] and
N-Fe-N [81.76°]. The configuration around the iron(II) ion
can be described with the configuration index[OC-6-32] [5],
whereas in similar glycolato complexes the configuration
around the metal atom is different, for instance,
[Cu(HG)2(2,2Ј-bipy)] [6] where the hydroxyl groups of the
Results and Discussion
Crystalline compounds [Fe(HG)2(dipyam)] (1) and
[Cu(HB)2(im)2]·2H2O (2) were synthesized in water at pH ഠ
* Prof. Dra. Rosa Carballo
Departamento de Quımica Inorganica
Facultade de Quımica-Edificio de Ciencias Experimentais
Universidade de Vigo
E-36310 Vigo/Spain
Fax: ϩ34 986 812556
E-mail: rcrial@uvigo.es
´
´
´
2006
© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
DOI: 10.1002/zaac.200570007
Z. Anorg. Allg. Chem. 2005, 631, 2006Ϫ2010

Two Mixed-Ligand Metal Complexes
˚
Table 1 Selected interatomic bond distances/A and angles/° for 1
and 2.
1
2
Fe-O11
Fe-O13
Fe-O21
Fe-O23
Fe-N1
Fe-N3
O11-Fe-O13
O13-Fe-O23
O13-Fe-O21
O11-Fe-N3
O23-Fe-N3
O11-Fe-N1
O23-Fe-N1
N1-Fe-N3
O11-Fe-O23
O11-Fe-O21
O23-Fe-O21
O13-Fe-N3
O21-Fe-N3
O13-Fe-N1
O21-Fe-N1
2.0949(15)
2.1352(15)
2.1423(14)
2.1378(16)
2.1466(17)
2.1425(17)
76.95(6)
92.78(6)
160.83(6)
96.80(6)
165.94(6)
175.06(6)
90.37(6)
81.76(6)
91.96(6)
88.94(6)
74.57(6)
99.87(6)
94.56(6)
98.60(6)
95.88(6)
Cu-O11
Cu-O12
Cu-O21
Cu-O22
Cu-N1
Cu-N3
N3-Cu-N1
N1-Cu-O11
N1-Cu-O21
N3-Cu-O12
O11-Cu-O12
N3-Cu-O22
O11-Cu-O22
O12-Cu-O22
N3-Cu-O11
N3-Cu-O21
O11-Cu-O21
N1-Cu-O12
O21-Cu-O12
N1-Cu-O22
O21-Cu-O22
2.002(3)
2.547(3)
2.006(3)
2.563(3)
1.952(4)
1.951(4)
178.15(19)
90.09(19)
88.89(13)
92.57(15)
56.17(11)
93.75(14)
121.66(11)
173.38(11)
91.13(14)
89.84(16)
177.61(14)
89.27(14)
125.96(11)
84.42(14)
56.08(11)
Figure 1 Molecular structure of [Fe(HG)2(dipyam)] (1).
derivates ligands [9Ϫ13]. The four closest donor atoms are
two nitrogen atoms of imidazole ligands and two oxygen
atoms of the carboxylate groups forming a distorted
square-planar arrangement. Two longer out-of-plane Cu-O
bonds from the remaining oxygen atoms of the carboxylate
groups complete the strongly distorted octahedral coordi-
nation of the copper(II) ion. The configuration around the
copper(II) ion is [OC-6-11]. The Cu-N bond lengths agree
to those reported in other copper(II) complexes with imi-
dazole [9, 13Ϫ15]. The Cu-O distances are in close agree-
ment to those found similar copper(II) complexes with a
4ϩ2 coordination type [9Ϫ13]. The longest Cu-O bond
glycolato
ligand
are
trans,
[OC-6-33],
and
[Ni(HG)2(py)2]·2H2O [7] where the carboxylate groups are
trans [OC-6-13]. Note that, when the α-hydroxycarboxylato
ligand acts as O,OЉ-bidentade the chelate metal-Ocarboxylate
distances are usually shorter than the metal-Ohydroxyl dis-
tances, however in 1, one of the glycolato ligands shows
similar metal-Ocarboxylate and metal-Ohydroxyl distances [Fe-
˚
O21 ϭ 2.1423 and Fe-O23 ϭ 2.1378 A]. The Fe-N bond
distances are similar to those found in 1ϱ[Fe(oxa)(dipyam)]
(oxa ϭ oxalato) [8].
In compound 2 the asymmetric unit is composed of the
˚
lengths [2.547 and 2.563 A] are shorter than the sum of the
neutral complex [Cu(HB)2(im)2], where HB is
a
van der Waals radii of oxygen and copper {rvdw(Cu) ϭ
1.40 A and rvdw(O) ϭ 1.50 A [16]}.
˚
˚
monoanionic O,OЈ-bidentade benzilato ligand, and two
crystal water molecules (Figure 2). The coordinated car-
boxylate groups of the benzilate ligands form four-mem-
bered unsymmetrical chelate rings. The copper(II) ion ad-
opts a distorted octahedral coordination (4ϩ2) similar to
the mixed-ligand complexes with imidazole and carboxylate
In both compounds, the nature of the α-hydroxycar-
boxylato (glycolato and benzilato), imidazole and 2,2Ј-dipy-
ridylamine ligands allows the formation of supramolecular
architectures based on hydrogen bonding (Table 2) and π···π
or C-H···π interactions.
˚
Table 2 Main intermolecular hydrogen bond distance/A and angles/°.
D-H...A
d(D-H)
d(H...A)
d(D...A)
<(DHA)
Compound 1
N2-H20···O12i
0.846(15)
0.867(17)
0.868(16)
2.060(16)
1.752(17)
1.789(17)
2.902(2)
2.610(2)
2.657(2)
174(2)
171(3)
179(3)
O23-H23···O22ii
O13-H13···O21ii
i: x, Ϫy, zϪ1/2; ii: x, yϩ1, z;
Compound 2
O13-H13···O12
0.82
0.82
0.82
0.82
0.89(2)
0.76(4)
0.67(4)
0.91(6)
0.88(2)
0.97(5)
2.13
2.19
2.09
2.09
1.90(2)
2.00(4)
2.22(4)
1.94(6)
1.95(3)
1.76(5)
2.611(4)
2.917(4)
2.601(4)
2.810(4)
2.773(6)
2.747(6)
2.844(6)
2.848(6)
2.809(5)
2.720(5)
117.6
147.6
119.9
146.6
170(5)
170(5)
156(5)
174(6)
165(7)
170(4)
O13-H13···O22i
O23-H23···O22
O23-H23···O12ii
N2-H20···O1w
N4-H40···O2wiii
O1w-H12···O11iv
O1w-H11···O13v
O2w-H21···O21
O2w-H22···O23i
i: xϩ1,y,z; ii: xϪ1, y, z; iii: x, y, zϩ1; iv: x, y, zϪ1; v: xϪ1, y, zϪ1
Z. Anorg. Allg. Chem. 2005, 631, 2006Ϫ2010
zaac.wiley-vch.de
© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
2007

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R. Carballo, B. Covelo, E. M. Vazquez-Lopez, E. Garcıa-Martınez, A. Castin˜eiras, C. Janiak
Figure 4 View of the two-dimensional structure generated by π···π
interactions in 1.
Figure 2 Molecular structure of [Cu(HB)2(im)2]·2H2O (2). Water
molecules omitted for clarity.
edge-to-face C-H···π interactions, one of them promotes the
formation of intramolecular interactions between one C-H
group of the benzilato as donor and one imidazole ligand
as acceptor [C204-H204···Cg(1), Cg(1): N1-C1-N2-C2-C3,
In 1, the shortest hydrogen bonds, between the hydroxyl
groups of the glycolato ligands and the oxygen atoms (coor-
dinated and non-coordinated) of one carboxylate group of
adjacent molecules, form a polymeric chain along the crys-
tallographic b axis. These chains are linked by additional
hydrogen bonds involving the NH groups of the 2,2Ј-dipyri-
dylamine ligands as donors and non-coordinated car-
boxylate oxygen atoms as acceptors, resulting in an infinite
two-dimensional network in the crystallographic bc plane
(Figure 3). On the other hand, π···π interactions are also
observed between one pyridine ring [Cg(1): N3-C6-C7-C8-
C9-C10] of the 2,2Ј-dipyridylamine ligand and an anal-
ogous ring of a neighbouring molecule {d[Cg(1)···Cg(1)i]:
˚
˚
d(H···Cg): 3.01 A, d(C...Cg): 3.92 A], and the other ben-
zilato ligand generates intermolecular C-H···π interactions
between one C-H group as donor and one phenyl ring of
neighbouring analogous benzilato ligand as acceptor
[C106-H106···Cg(2)i, Cg(2): C109-C110-C111-C112-C113-
˚
C114, symmetry code i: x, y, zϩ1, d(H···Cg): 2.97 A,
˚
d(C...Cg): 3.77 A] creating a polymeric chain along the
crystallographic c axis (Figure 5). Compound 2 adopts a
non-centrosymmetric packing (chiral space group P21) and
the different C-H···π interactions involving the ligands
could be responsible of this spontaneous resolution as has
been also observed in other compounds [17]. Several hydro-
gen bonds involving the water molecule as donor and as
acceptor (Figure 5 and Table 2) stabilize the chains gener-
ated by C-H···π interactions. Also other hydrogen bonds
involving the hydroxyl group as donor and as acceptor, and
carboxy oxygen atoms as acceptor and the water molecule
as donor (Table 2), respectively, join the chains forming a
two-dimensional network in the crystallographic ac plane
(Figure 6).
˚
3.8 A, symmetry code i: Ϫx, Ϫy, Ϫz, dihedral angle α:
0.02°}. These π···π interactions join two sheets resulting a
new two-dimensional supramolecular organization (Figure
4).
In 2, the intramolecular hydrogen bonds involving the
hydroxyl group and the non-coordinated carboxy oxygen
atoms of the same benzilato ligand are the strongest. In this
case, the supramolecular organization is a consequence of
the existence of intermolecular hydrogen bonds and C-H···π
interactions. Each benzilato ligand establishes different
Infrared spectroscopy
The infrared spectra of 1 and 2 show sharp bands in the
3000-3200 cmϪ1 region, which are assigned to the NH
Figure 3 View of the 2D structure generated by hydrogen bonds
in 1.
Figure 5 View of the 1D network obtained by C-H···π interactions
and hydrogen bonds of 2.
2008
© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
zaac.wiley-vch.de
Z. Anorg. Allg. Chem. 2005, 631, 2006Ϫ2010

Two Mixed-Ligand Metal Complexes
Experimental Section
All reagents and solvents were obtained commercially, glycolic acid
(H2G), 2,2Ј-dipyridylamine (dipyam) and imidazole (im) from Ald-
rich, benzilic acid (H2B) from Avocado, FeCl2·4H2O and Na2CO3
from Fluka and CuCO3·Cu(OH)2·0.5H2O from Riedel-deHae¨n. All
were used as supplied.
Microanalyses (C, H, N) were carried out with a Fisons EA-1108
elemental analyser. Melting points (m. p.) were carried out with a
Gallenkamp MBF-595 apparatus. FT-IR spectra were recorded
from KBr pellets (4000-400 cmϪ1) or polyethylene-sandwiched Nu-
jol mulls (500-100 cmϪ1) on a Bruker Vector 22 and on a Bruker
IFS66v spectrometers, respectively. A Shimadzu UV-3101PC spec-
trophotometer was using to obtain the electronic spectra in the
region 250-1500 nm. Magnetic susceptibility measurements were
performed at 25 °C using Johnson Matthey Alfa MSB-MK1
Gouy balance.
Synthesis of the complexes
[Fe(HG)2(dipyam)] (1)
Figure 6 View of the 2D architecture generated by hydrogen bonds
in 2. (Some hydrogen atoms and phenyl groups have been omitted
for clarify).
Under a positive pressure of argon FeCl2·4H2O (1.0 mmol) was
dispersed in 10 mL of degassed water in a Schlenk flask to give a
yellowish-green solution. To this solution were added with continu-
ous stirring glycolic acid (H2G, 2.0 mmol), Na2CO3 (1 mmol) and
2,2Ј-dipyridylamine (dipyam, 1 mmol). The mixture was trans-
ferred to a Teflon-lined stainless-steel autoclave and heated at
stretching frequency. Compound 1 shows a broad band at
3437 cmϪ1 and compound 2 at 3477 and 3356 cmϪ1, which
correspond to ν(OH) of the hydroxyl groups of the ligands
and the crystallisation water molecule in 2 [18]. The intense
bands appearing around 1600 cmϪ1, which overlap with
bands associated with the aminoaromatic ligands, are as-
signed to the asymmetric COOϪ vibration. The bands
found at 1368 cmϪ1 for 1 and 1392 cmϪ1 for 2 are assigned
to the symmetric COOϪ vibration. The value of Δ ϭ
[νasym(COOϪ)-νsym(COOϪ)], 235 cmϪ1 for 1 is typical of
monodentade carboxylate groups [19] but the value for 2,
208 cmϪ1, is too high for a bidentade-chelate coordination
of the carboxylate group, in agreement with the strong un-
symmetrical chelate behaviour observed by X-ray studies
[19]. In both compounds the band observed in the 420-
450 cmϪ1 region is attributed to ν(MO) [20].
130 °C for 5 hours followed by slow cooling at a rate of 3 °C·hϪ1
Green crystals of 1 were collected by filtration, washed with water
and dried in air.
.
Data for 1: Yield: 30 %; m.p. >250 °C; Anal. Found: C 44.5, H 4.0,
N 11.0. Calc. for C14H15FeN3O6 (377.14): C 44.6, H 4.0, N 11.1 %.
IR (ν, cmϪ1): 3437s, b; 3167m, 3083m, 3023m, 1635vs, 1603s, 1476s, 1432m,
1368s, 1046m, 1010m, 773m, 557m, 280m. UV-vis (λ, nm): 825, 1060. μeff at
25 °C: 5.6 B.M.
[Cu(HB)2(im)2] (2)
CuCO3·Cu(OH)2·0.5H2O (0.5 mmol), benzilic acid (H2B,
2.0 mmol) and imidazole (im, 2.0 mmol) were dispersed in 10 mL
of water in a flask with continuous stirring to give a green suspen-
sion. The mixture was transferred to a Teflon-lined stainless-steel
autoclave and heated at 140 °C for 10 hours followed by slow cool-
ing at a rate of 1.5 °C·hϪ1. Blue crystals of 2 were collected by
filtration, washed with water and dried in air.
Electronic and magnetic properties
Data for 2: Yield: 36 %; m.p. 200 °C; Anal. Found: C 59.5, H 5.2,
N 8.1. Calc. for C34H34CuN4O8 (690.19): C 59.2, H 5.0, N 8.1 %.
IR (ν, cmϪ1): 3478m, b; 3356s, b; 3144m, 1613vs, 1600sh, 1550m, 1513m,
1489m, 1448m, 1392m, 1325s, 1169m, 1102m, 750s, 702s 423w, 275m. UV-
vis (λ, nm): 630. μeff at 25 °C: 1.9 B.M.
The electronic spectra of 1 and 2 in the range 250-1500 nm
were recorded in the solid state by diffuse reflectance. The
spectrum of 1 consists of two broad bands at 825 and
1060 nm. The observed absorption features are in conson-
ance with those predicted and reported in the literature for
a FeII high spin d6 octahedral species with a cis disposition
of the ligands [21]. The electronic spectrum of 2 shows an
asymmetric broad band attributable to d-d transitions at
630 nm, as expected for octahedral CuII complexes with a
tetragonal distortion [21].
X-ray Crystallography
Crystallographic data were collected on a Bruker Smart CCD dif-
fractometer at 243 K (1) and at 293 K (2) using graphite monochro-
˚
mated Mo Kα radiation (λ ϭ 0.71073 A), and were corrected for
The magnetic effective moments at room temperature, 5.6
B.M. in 1 is close to the value typical of high-spin FeII
centres [22] and 1.9 B.M. in 2 is typical of CuII species with
no Cu···Cu interactions [23, 24].
Lorentz and polarisation effects. The frames were integrated with
the Bruker SAINT [25] software package and the data were cor-
rected for absorption using the program SADABS [26]. The struc-
tures were solved by direct methods using the program SHELXS97
Z. Anorg. Allg. Chem. 2005, 631, 2006Ϫ2010
zaac.wiley-vch.de
© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
2009

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´
´
´
R. Carballo, B. Covelo, E. M. Vazquez-Lopez, E. Garcıa-Martınez, A. Castin˜eiras, C. Janiak
Table 3 Crystal and structure refinement data.
Compound
1
2
Empirical formula
Formula weight
Crystal system
Space group
Unit cell dimensions /A, °
a
C14H15FeN3O6
377.14
monoclinic
P2/c
C34H34CuN4O8
690.19
monoclinic
P21
˚
15.210(3)
7.8245(16)
b
c
5.8118(12)
17.563(4)
23.520(5)
9.0209(18)
β
106.656(4)
0.29 x 0.10 x 0.04
1.4-30.0
Ϫ14/21, Ϫ8/7, Ϫ23/22
9412
4000 [R(int)ϭ 0.0317]
1.000/0.842
4000/ 229
1.005
R1 ϭ 0.0378 wR2 ϭ 0.0744
94.68(3)
0.23 x 0.17 x 0.10
1.7-28.1
Ϫ10/8, Ϫ31/31, Ϫ11/9
10231
7036, [R(int)ϭ 0.0396]
1.000/0.878
7036/451
0.995
R1 ϭ 0.0619 wR2 ϭ 0.0935
Crystal size /mm3
θ Range /°
Index ranges
Reflections collected
Independent reflections
Max/min transmission
Data/parameters
Goodness-of-fit on F2
Final R indices [I>2σ(I)]
[27]. All non-hydrogen atoms were refined with anisotropic thermal
parameters by full-matrix least-squares calculations on F2 using
the program SHELXL97 [28]. Hydrogen atoms were inserted at
calculated positions and constrained with isotropic thermal param-
eters, except for the hydrogen atoms of hydroxyl groups, NH groups
and water molecules, which were located from a Fourier-difference
map and refined isotropically (in some cases the distances O-H and
N-H were restrained with DFIX 0.9). For 2, which crystallized in
the chiral space group P21, the analysis established unambiguously
the absolute structure {Flack’s Parameter [29] 0.000(14)}. Drawings
were produced with SCHAKAL99 [30]. Special computations for
the crystal structure discussions were carried out with PLATON
[31]. Crystal data and structure refinement parameters are summar-
ised in Table 3.
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Supplementary crystallographic data have been deposited with the
Cambridge Crystallographic Data Centre, CCDC No 252927 and
252928 for compounds 1 and 2, respectively. Copies of this infor-
mation may be obtained free of charge from The Director, CCDC,
12 Union Road, Cambridge, CB2 1EZ, UK (Fax: ϩ44-1223-
336033; e-mail:or www:
Acknowledgements. Financial support from ERDF (EU) and DGI-
MCYT (Spain) (research project BQU200203543) is gratefully
acknowledged.
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