Co(II), Cu(II) and Zn(II) dinuclear complexes of a polypodal ligand containing phenolate and pyridyl donor groups

Article abstract of DOI:10.1016/j.poly.2010.06.005

Acetate and perchlorate dinuclear metal complexes of Co(II), Cu(II) and Zn(II) with the cresolate polypodal ligand having mixed phenolate and pyridyl pendant functionalities, H₃L, have been synthesized. The complexes were characterized by micro

Full text of DOI:10.1016/j.poly.2010.06.005

Polyhedron 29 (2010) 2651–2656
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Polyhedron
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Co(II), Cu(II) and Zn(II) dinuclear complexes of a polypodal ligand containing
phenolate and pyridyl donor groups
a
b
b
Jesús Martínez-Sánchez a, Rufina Bastida a, , Alejandro Macías , Harry Adams , David E. Fenton ,
*
Paulo Pérez-Lourido c, Laura Valencia c,
**
a Departamento de Química Inorgánica, Universidad de Santiago de Compostela, Avda. de las Ciencias s/n 15782, Santiago de Compostela (La Coruña), Spain
b Department of Chemistry, University of Sheffield, Dainton Building, Brook Hill, Sheffield S3 7HF, UK
c Departamento de Química Inorgánica, Facultad de Química, Universidade de Vigo, 36310 Vigo (Pontevedra), Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Acetate and perchlorate dinuclear metal complexes of Co(II), Cu(II) and Zn(II) with the cresolate polypodal
ligand having mixed phenolate and pyridyl pendant functionalities, H3L, have been synthesized. The com-
plexes were characterized by microanalysis, LSI mass spectrometry, IR, UV–Vis spectroscopy, magnetic
studies and conductivity measurements. Crystal structures of H3L, [Cu2(HL)(OAc)(H2O)2](OAc)ꢀ1.5H2O
and [Zn2L(CH3OH)3](ClO4)CH3OHꢀ2H2O complexes, have been also determined.
Received 6 May 2010
Accepted 10 June 2010
Available online 20 June 2010
Keywords:
The X-ray studies show the presence of dinuclear complexes with the metal ions joined by the bridging
cresolate group and coordinated to the tertiary amine nitrogen and their corresponding attached pyridyl
and phenol/phenolate pendant groups. The coordination environment for the metal ions is completed by
acetate, water or solvent molecules to generate mixed distorted coordination geometries; square plane/
square pyramidal for Cu(II) and octahedral/trigonal bipyramidal for Zn(II) complexes. Different intramo-
lecular interactions through hydrogen bonds are also observed in both complexes.
Metal complexes
Polypodal ligand
Cresolate-bridge
X-ray structure
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
methylphenol (H3L, Scheme 1) having cresol, phenol and pyridyl pen-
dant functionalities, have been reported [15–27]. It have been ob-
It is well-known that the important functional role of many
metalloproteins in the active sites is based in the polynuclear nat-
ure of the metal centers [1–3].
One strategy for the synthesis of multimetallic complexes in-
cludes the use of polypodal ligands, which allow accommodation
of two or more metal ions. They can be used to hold the metal cen-
ters at a fixed distance providing interesting properties. In this
sense, a considerable number of complexes of several polypodal
binucleating ligand systems have been reported as models of dif-
ferent metalloproteins from several decades ago [4–8].
served that the presence of coordinating anion usually drives to the
formation of an anion-based exogenous bridge, but non-coordinating
anion inhibit the formation of that exogenous bridge and instead,
encourages the interaction of the dinuclear core with the solvent.
In this way, the reaction of H3L and Co(II), Cu(II) and Zn(II) with
anions of different coordinative capabilities, as acetate and per-
chlorate, has been investigated in this paper.
The X-ray crystal structure of the polypodal ligand, H3L, and the
dinuclear crystal structures of Cu(II) acetate and Zn(II) perchlorate
complexes are also reported.
The presence in many of these polypodal ligands of a phenolate
group as a bridge to hold two metal ion centers in close proximity,
and also providing additional donor sites, have been required to
obtain suitable biomimetic complexes [9–14].
2. Experimental
2.1. Chemicals and starting materials
In another hand, the synthesis and characterization of new binu-
clear complexes with relevant N,O-donor ligands is an important area
of investigation. In last years the synthesis of dinuclear complexes of
different metal ions with the symmetric end-off compartmental li-
gand 2,6-bis[(2-hydroxybenzyl)(2-pyridylmethyl)amino)methyl]-4-
The precursors, 2,6-bis(chloromethyl)-4-methylphenol and (2-
hydroxybenzyl)-(2-pyridylmethyl)amine were synthesized follow-
ing a similar method as described in the literature [27,28]. Metal
salts were commercial products (from Alfa and Aldrich) and were
used without further purifications. Solvents were of reagent grade
and were purified by the usual methods.
Caution: Although no problems were encountered during the
course of this work, perchlorate salts must be handled with care
due to their potentially explosive nature.
* Corresponding author. Tel.: +34 981 591076; fax: +34 981597525.
** Corresponding author. Tel.: +34 986 812607; fax: +34 986 813797.
E-mail addresses: qibastid@usc.es (R. Bastida), qilaura@uvigo.es (L. Valencia).
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.06.005

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J. Martínez-Sánchez et al. / Polyhedron 29 (2010) 2651–2656
(C@C)ar], 623, 1103 [m /
(ClO4ꢂ)]. LSI-MS (m/z): 675 [Co2L]+. KM
X
ꢂ1 cm2 molꢂ1(in CH3CN): 205 (1:1). Colour: brown.
2.3.3. [Cu2L](OAc)ꢀ3H2O
Anal. Calc.: C, 55.7; H, 5.3; N, 7.0. Found: C, 55.4; H, 5.2; N, 6.8%.
Yield: 30%. IR (KBr, cmꢂ1): 1447, 1474, 1576, 1611 [
(C@N)py and
(C@C)ar], 1560
(OAcꢂ)]. LSI-MS (m/z): 684 [Cu2L]+. KM
ꢂ1 cm2 molꢂ1(in CH3CN): 190 (1:1). Colour: green.
m
[
m
/
X
2.3.4. [Cu2L](ClO4)ꢀCH3OHꢀ3H2O
Anal. Calc.: C, 49.8; H, 5.0; N, 6.4. Found: C, 49.5; H, 5.2; N, 6.2%.
Yield: 32% IR (KBr, cmꢂ1): 1450, 1477, 1597, 1610 [
(C@N)py and
(C@C)ar], 626, 1095 [
(ClO4ꢂ)]. LSI-MS (m/z): 684 [Cu2L]+. KM
ꢂ1 cm2 molꢂ1(in CH3CN): 200 (1:1). Colour: green.
m
m
/
X
2.3.5. [Zn2L](OAc)ꢀ2H2O
Anal. Calc.: C, 56.7; H, 5.1; N, 7.1. Found: C, 56.3; H, 5.2; N, 7.0%.
Yield: 26%. IR (KBr, cmꢂ1): 1453, 1492, 1602 [
(C@N)py and
(C@C)ar], 1560
(OAcꢂ)]. LSI-MS (m/z): 689 [Zn2L]+. KM
ꢂ1 cm2 molꢂ1(in CH3CN): 200 (1:1). Colour: colourless.
m
Scheme 1.
[
m
/
X
2.2. Synthesis of the ligand H3L
2.3.6. [Zn2L](ClO4)ꢀ3CH3OH
Anal. Calc.: C, 51.8; H, 5.1; N, 6.3. Found: C, 51.5; H, 5.3; N, 6.4%.
Yield: 28%. IR (KBr, cmꢂ1): 1437, 1460, 1577, 1610 [
(C@N)py and
(C@C)ar], 625, 1092 [
(ClO4ꢂ)]. LSI-MS (m/z): 689 [Zn2L]+. KM
ꢂ1 cm2 molꢂ1(in CH3CN): 196 (1:1). Colour: colourless.
The ligand, 2,6-bis[(2-hydroxybenzyl)(2-pyridylmethyl)amino)-
methyl]-4-methylphenol (H3L), was synthesized by modification
of the method of Krebs et al. [27].
m
m
/
A methanol (20 ml) solution of 2,6-bis(chloromethyl)-4-meth-
ylphenol (2.76 g, 14.6 mmol) was added slowly over a methanol
(100 mL) cooled solution at 0 °C of (2-hydroxybenzyl)-(2-pyridyl-
methyl)amine (6.17 g, 28.8 mmol) and Et3N (4.37 g, 43.2 mmol).
When the addition was completed, the resulting mixture was
warmed to room temperature and stirred for 12 h. The solution
was evaporated to dryness. The residue was dissolved in chloro-
form (60 mL) washed with water (3 ꢁ 30 mL). The organic layer
was dried over anhydrous MgSO4, filtered off and evaporated to
dryness to obtain a white solid characterized as H3L. Crystals
appropriate to be studied by X-ray diffraction could be obtained
by slow recrystallization of the compound from acetonitrile.
H3L: Anal. Calc. for C35H36N4O3: C, 75.0; H, 6.5; N, 10.0. Found: C,
74.7; H, 6.6; N, 10.1%. Yield: 75%. IR (KBr, cmꢂ1): 1431, 1489, 1572,
X
2.4. Physical measurements
Elemental analyses were performed in a Carlo-Erba EA micro-
analyser. Infra-red spectra were recorded as KBr discs on a Bruker
IFS-66V spectrophotometer. LSI-MS were recorded using a Micro-
mass Autospec spectrometer with 3-nitrobenzyl alcohol as the
matrix. Conductivity measurements were carried out in 10ꢂ3 mol
dmꢂ3 acetonitrile solutions at 20 °C using a WTW LF3 conductivi-
meter. Solid state electronic spectra were recorded on a Hitachi
4-3200 spectrophotometer using MgCO3 as reference. Magnetic
studies were determined at room temperature on a vibration sam-
ple magnetometer (VSM) Digital Measurement System 1660 with a
magnetic field of 5000 G.
1591 [m(C@N)py and (C@C)ar], 3070 [m(–OH)]. LSI-MS (m/z): 561
[H3L]+. Colour: white.
2.5. X-ray data collection, structure determination, and refinement
2.3. Synthesis of metal complexes
The details of the X-ray crystal data, and the structure solution
and refinement are given in Table 1. Measurements were made on
a Bruker Smart CCD area detector. All data were corrected for Lor-
entz and polarization effects and for absorption by semi empirical
methods based on symmetry-equivalent and repeated reflections.
Complex scattering factors were taken from the program package
SHELXTL [29]. The structures were solved by direct methods which
revealed the position of all non-hydrogen atoms. All the structures
were refined on F2 by a full-matrix least-squares procedure using
anisotropic displacement parameters for all non-hydrogen atoms.
The hydrogen atoms were located in their calculated positions
and refined using a riding model. For [Cu2(HL)(OAc)(H2O)2](OAc)ꢀ
1.5H2O data set was truncate to 50° in 2h.
To a heated at reflux methanolic solution (10 mL) of H3L
(0.056 g, 0.1 mmol), a solution of the corresponding acetate metal
salt (0.2 mmol) in methanol (5 mL) was slowly added. The reaction
mixture was refluxed for 30 min and stands to cool. The resulting
solution was concentrated until ca. 10 mL. The product obtained
was filtered off and dried under vacuum. In the case of the perchlo-
rate complexes, a solution of sodium perchlorate (0.2 mmol) in
methanol (5 mL) was added to the metallic acetate/ligand mixture,
and the resulting solution allowed to cool to room temperature
giving rise a precipitate. The precipitate obtained was filtered off
and dried under vacuum.
2.3.1. [Co2L](OAc)ꢀ6H2O
Anal. Calc.: C, 52.7; H, 5.7; N, 6.7. Found: C, 52.8; H, 5.5; N, 6.5%.
3. Results and discussion
Yield: 21%. IR (KBr, cmꢂ1): 1450, 1475, 1595, 1612 [
m
(C@N)py and
(OAcꢂ)]. LSI-MS (m/z): 675 [Co2L]+. KM
ꢂ1 cm2 molꢂ1(in CH3CN): 192 (1:1). Colour: brown.
(C@C)ar], 1558
X
[m
/
The polypodal ligand H3L was readily obtained in a one-pot syn-
thesis from the precursors reagents in satisfactory yield and purity.
Crystals suitable for X-ray diffraction of H3L were obtained from an
acetonitrile solution. Crystal data and structure refinement are gi-
ven in Table 1. Molecular structure and selected bond lengths and
angles for H3L are given in Fig. 1a. The structure belongs to mono-
2.3.2. [Co2L](ClO4)ꢀ3CH3OHꢀ2H2O
Anal. Calc.: C, 50.3; H, 5.4; N, 6.2. Found: C, 49.8; H, 5.6; N, 6.1%.
Yield: 24%. IR (KBr, cmꢂ1): 1450, 1476, 1595, 1612 [
(C@N)py and
m

J. Martínez-Sánchez et al. / Polyhedron 29 (2010) 2651–2656
2653
Table 1
Crystal data and structure refinement for H3L, [Cu2(HL)(OAc)(H2O)2](OAc)ꢀ1.5H2O and [Zn2L(CH3OH)3](ClO4)ꢀCH3OHꢀ2H2O.
H3L
[Cu2(HL)(OAc)(H2O)2](OAc)ꢀ1.5H2O
[Zn2L(CH3OH)3](ClO4)ꢀCH3OHꢀ2H2O
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C
35H36N4O3
C39H47N4O10.5Cu2
866.89
150(2)
0.71073
Orthorhombic
Pna21
C39H53ClN4O13Zn2
952.08
150(2)
0.71073
Monoclinic
P21/c
560.68
150(2)
0.71073
Monoclinic
P21/c
9.116(2)
12.227(3)
26.787(7)
13.0301(2)
29.667(3)
11.0106(7)
12.2162(10)
21.5446(17)
15.5498(2)
b (Å)
c (Å)
b (°)
97.725(5)
2958.3(12)
4
1.259
0.081
90.772(2)
4092.2(6)
4
1.516
1.305
Volume (Å3)
Z
4256.6(7)
4
1.395
1.058
Dcalc (mg/m3)
Absorption coefficient (mmꢂ1
Crystal size (mm3)
)
0.40 ꢁ 0.17 ꢁ 0.06
0.30 ꢁ 0.13 ꢁ 0.10
0.30 ꢁ 0.15 ꢁ 0.10
h Range for data collection (°)
1.53–27.56
1.37–25
1.62–27.50
Index ranges
ꢂ11 6 h 6 11
ꢂ15 6 k 6 15
ꢂ34 6 l 6 34
24921
ꢂ15 6 h 6 15
ꢂ35 6 k 6 35
ꢂ13 6 l 6 13
39768
ꢂ15 6 h 6 14
ꢂ27 6 k 6 23
ꢂ20 6 l 6 20
22974
Reflections collected
Independent reflections
Completeness to h (°)
Absorption correction
Maximum and minimum transmission
Refinement method
6725 [Rint = 0.1188]
99.9% (26.42)
Semi-empirical
0.9762 and 0.9503
Full-matrix least-squares on F2
6725/0/379
7499 [Rint = 0.1560]
100% (25)
Semi-empirical
0.9016 and 0.7420
Full-matrix least-squares on F2
7499/1/491
9165 [Rint = 0.0519]
97.4% (27.5)
Semi-empirical
0.8806 and 0.6956
Full-matrix least-squares on F2
9165/4/526
Data/restraints/parameters
Goodness-of-fit on F2
0.987
1.027
1.016
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0655, wR2 = 0.1398
R1 = 0.1750, wR2 = 0.1897
0.251 and ꢂ0.356
R1 = 0.0777, wR2 = 0.1896
R1 = 0.1404, wR2 = 0.2434
0.903 and ꢂ0.448
R1 = 0.0525, wR2 = 0.1183
R1 = 0.0997, wR2 = 0.1410
1.145 and ꢂ0.796
Largest difference in peak and hole (e Åꢂ3
)
clinic space group P21/c. All bond distances and angles are all with-
in the normal ranges.
The dihedral angles between the cresol ring [C2–C7–O1] and
the pyridyl rings, [C10–C14–N2 (rms 0.0103)] and [C24–C28–N4
(0.0072)], are 19.59° and 19.54°, respectively, whilst the phenol
groups, [C16–C21–O2 (rms 0.0063)] and [C30–C35–O3 (rms
0.0097)], form with the cresol ring dihedral angles of 81.4° and
78.3°, respectively.
Different intramolecular hydrogen bonding interactions be-
tween cresol, phenol, pyridine and amine groups are present in
the crystal lattice: (a) phenol groups and their corresponding ter-
tiary amine [O2–H2Aꢀ ꢀ ꢀN1 = 157.46°, 1.752 Å] and [O3–
H3Aꢀ ꢀ ꢀN3 = 1578.11°, 1.756 Å]; (b) cresol group and one pyridyl
ring [O1–H1Aꢀ ꢀ ꢀN2 = 157.39°, 1.914 Å].
Also, intermolecular offset (slipped)
p-stacking interactions be-
tween cresol groups of adjacent molecules, and face-to-face
p-
Fig. 1a. Crystal structure of H3L and selected bond lengths (Å) and angles (°). O(1)–C(5) 1.367(3), O(2)–C(21) 1.363(3), O(3)–C(35) 1.367(3), N(1)–C(9) 1.465(3), N(1)–C(15)
1.472(3), N(1)–C(8) 1.477(3), N(2)–C(10) 1.345(3), N(2)–C(14) 1.347(4), N(3)–C(23) 1.468(3), N(3)–C(29) 1.474(3), N(3)–C(22) 1.482(3), N(4)–C(24) 1.338(4), N(4)–C(28)
1.349(4), C(9)–N(1)–C(15) 110.9(2), C(9)–N(1)–C(8) 110.5(2), C(15)–N(1)–C(8) 111.5(2), C(10)–N(2)–C(14) 117.1(3), C(23)–N(3)–C(29) 109.0(2).

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J. Martínez-Sánchez et al. / Polyhedron 29 (2010) 2651–2656
stacking between phenol rings of different ligand molecules [30]
are observed (Fig. 1b). The distances between the centroids dc–c
have a value of 3.452 Å with a slipping angle (b) (defined by the
centroid–centroid vector and the normal to the planes containing
the rings) of 41°, in the first case, and 4.221 Å with b = 10.5° in
the second case.
Acetate and perchlorate metal complexes of Co(II), Cu(II) and
Zn(II) with H3L were synthesized in refluxing methanol. The com-
plexes were synthesized as described in Section 2 and, in general,
the reactions gave analytically pure products. The complexes
were characterized by elemental analysis, LSI mass spectrometry,
IR and UV–Vis spectroscopy, magnetic studies and conductivity
measurements.
3.1. Crystal structures of complexes
By slow recrystallization of the acetate dinuclear Cu(II) com-
pound in methanol, crystals of [Cu2(HL)(OAc)(H2O)2](OAc)ꢀ1.5H2O
were obtained. The crystal structure was studied by X-ray diffrac-
tion and the molecular structure of the complex is shown in Fig. 2,
together with the atomic numbering scheme adopted and selected
bond distances (Å) and angles (°). Crystal data and structure refine-
ment are given in Table 1.
The crystal structure is consistent with the dinuclear cation
complex [Cu2(HL)(OAc)(H2O)2]+ and one non-coordinated acetate
group involved in intramolecular hydrogen bonding with the dinu-
clear complex. Three half free water molecules of crystallization
complete the structure, which have been refined isotropically, ex-
cept for O2W.
Fig. 2. Crystal structure of [Cu2(HL)(OAc)(H2O)2](OAc)ꢀ1.5H2O and selected bond
lengths (Å) and angles (°): Cu(1)–O(1) 1.920(7), Cu(1)–O(2W1.976(7), Cu(1)–N(2)
2.010(9), Cu(1)–N(1) 2.037(9), Cu(1)–Cu(23.7284(17), Cu(2)–O(3) 1.918(7), Cu(2)–
O(4) 1.936(7), Cu(2)–N(4) 1.984(9), Cu(2)–N(3) 2.021(8), Cu(2)–O(1) 2.319(7),
O(1)–Cu(1)–O(2W) 90.1(3), O(1)–Cu(1)–N(2) 173.3(3), O(2W)–Cu(1)–N(2) 92.8(3),
O(1)–Cu(1)–N(1) 94.6(3), O(2W)–Cu(1)–N(1) 175.1(3), N(2)–Cu(1)–N(1) 82.6(3),
O(1)–Cu(1)–Cu(2) 31.5(2), O(2W)–Cu(1)–Cu(2) 66.19(17), N(2)–Cu(1)–Cu(2)
146.4(2), N(1)–Cu(1)–Cu(2) 118.7(2), O(3)–Cu(2)–O(4) 90.3(3), O(3)–Cu(2)–N(4)
175.4(4), O(4)–Cu(2)–N(4) 90.7(4), O(3)–Cu(2)–N(3) 94.0(3), O(4)–Cu(2)–N(3)
168.2(3), N(4)–Cu(2)–N(3) 84.1(4), O(3)–Cu(2)–O(1) 96.8(3), O(4)–Cu(2)–O(1)
99.1(3), N(4)–Cu(2)–O(1) 87.5(3), N(3)–Cu(2)–O(1) 91.3(3), O(3)–Cu(2)–Cu(1)
82.6(2), O(4)–Cu(2)–Cu(1) 78.0(3), N(4)–Cu(2)–Cu(1) 102.0(3), N(3)–Cu(2)–Cu(1)
113.4(2), O(1)–Cu(2)–Cu(1) 25.61(16).
The structural analysis of [Cu2(HL)(OAc)(H2O)2]+ cation shows
the presence of two Cu(II) ion with different coordination environ-
ment. Thus, Cu(1) presents a {N2O2} core, being the metal ion coor-
dinated to the cresolate oxygen atom, O1, which is acting as
asymmetric l
2-bridge between the copper ions, the tertiary amine
nitrogen, N1, and their corresponding attached pyridyl ring, N2,
and a water molecule, O2W. Bond lengths vary from 1.915 to 2.040
Å. The non-deprotonated phenol group [Cu(1)–O(2), 2.513(6) Å],
and another water molecule [Cu(1)–O(1W), 2.529(10) Å] are
slightly interacting with the metal center, commonly expected
due to the Jahn–Teller effect for d9 ions. The geometry around
Cu(1) can be described as square plane, N(1)–N(2)–O(1)–O(2W)
(rms 0.065), and the distance between the Cu(1) and the plane of
0.0361 Å. Instead, the Cu(2) ion presents a {N2O3} core, being coor-
dinated to the bridging cresolate oxygen atom, O1, the tertiary
amine nitrogen, N3, and their corresponding attached pyridyl ring,
N4, and phenolate group, O3. The fifth coordination position is
occupied by an oxygen atom from a monodentated coordinated
acetate anion, O4. The geometry around Cu(2) can be described
as slightly distorted square pyramidal [s = 0.11] [31] with Cu(2)
0.137 Å away from the best plane defined by N(3)–N(4)–O(3)–
O(4) (rms 0.052). Bond lengths vary from 1.917 to 2.019 Å for these
atoms. The apical position is occupied by the
l
2-cresolate group,
O1, at 2.322 Å from the metal. Banerjee et al. recently reported a
dinuclear Cu(II) crystal structure for L, [Cu2(HL)(O2CPh)(H2O)]Ph-
CO2ꢀ3H2O [26]. The structure shows a benzoate bridging group
and both Cu(II) ions in a pentacoordinated environment.
The distance between the copper ions Cu(1)ꢀ ꢀ ꢀCu(2) is 3.730 Å,
longer to consider the presence of intermetallic interactions.
In both cases, the main distortion from a regular geometries can
be attributed to the small bite of the five-membered chelate rings
formed by the tertiary amine and their corresponding pyridyl do-
nor group [N(2)–Cu(1)–N(1), 83.0(3)°] and [N(3)–Cu(2)–N(4),
84.0(4)°].
Inter and intramolecular hydrogen bonds interactions between
the free and coordinated acetate anions and water molecules and
the phenol group were found in the crystal structure (Table 2).
The complex [Zn2L(CH3OH)3](ClO4)ꢀCH3OHꢀ2H2O was obtained
by recrystallization of the perchlorate Zn(II) complex from metha-
Fig. 1b. Partial view of the ligand packing showing the different
interactions between cresolate and phenol rings of different molecules.
p-stacking

J. Martínez-Sánchez et al. / Polyhedron 29 (2010) 2651–2656
2655
nol. The molecular structure together with selected bond lengths
(Å) and angles (°) are given in Fig. 3. The crystal data and structure
refinement are given in Table 1. The X-ray crystal structure shows
also a dinuclear cation complex of type [Zn2L(CH3OH)3]+, similar to
that described by Fenton et al. for [Zn2L(H2O)3](ClO4) [21]. A meth-
anol and a water solvent molecule are disordered in two positions
with occupancies of 67/33% and 52/48%, respectively. They were
refined isotropically. A free perchlorate counterion is also present
in the crystal lattice. The metal centers present different coordina-
tion environment, six-coordinate {N2O4} core in a distorted octahe-
dral geometry for Zn(2) and five-coordinate {N2O3} core in a
distorted trigonal bipyramidal geometry [
The Zn(2) ion is bonded to the cresolato oxygen atom, O1, which
is acting as
2-bridge between the metal ions, a tertiary amine
s = 0.81] for Zn(1).
l
nitrogen, N3 and their corresponding attached pyridyl, N4, and ter-
minal phenolate group, O3. The coordination environment is com-
pleted by two methanol molecules, O5 and O6. The equatorial
plane of the octahedral geometry can be described by the amine
nitrogen, their corresponding attached pyridyl and terminal phe-
nolate groups, and one of the methanol molecules [N(3)–N(4)–
O(3)–O(5), rms 0.0257], with Zn(2) 0.0454 Å away from that plane.
The axial positions are determined by the oxygen atoms from the
central phenolate and the other methanol molecule, O1–Zn2–O6,
173.3°.
The equatorial plane of the distorted trigonal bipyramidal
geometry around Zn(1) can be defined by the bridging cresolate
oxygen atom and the pyridyl and phenolate group attached to
the other tertiary amine of the ligand, O(1)–N(2)–O(2). The axial
positions are occupied by the tertiary amine nitrogen and one
methanol molecule, N1–Zn1–O4, 170.13(11)°. In both cases, the
main distortion from a regular geometries can be also attributed
to the small bite of the five-membered chelate rings formed by
the amine and their corresponding pyridyl donor group [N(2)–
Zn(1)–N(1), 79.18(12)°] and [N(3)–Zn(2)–N(4), 81.47(13)°].
The Zn(1)ꢀ ꢀ ꢀZn(2) separation is 3.551 Å, not showing interaction
between the metal ions. This distance is also longer than others
Fig. 3. Crystal structure of [Zn2L(CH3OH)3](ClO4)ꢀCH3OHꢀ2H2O and selected bond
lengths (Å) and angles (°): Zn(1)–O(2) 1.970(3), Zn(1)–O(1) 1.981(2), Zn(1)–N(2)
2.091(3), Zn(1)–O(4) 2.097(3), Zn(1)–N(1) 2.148(3), Zn(1)–Zn(2) 3.5513(7), Zn(2)–
O(3) 1.985(3), Zn(2)–N(4) 2.095(3), Zn(2)–O(5) 2.109(3), Zn(2)–N(3) 2.138(3),
Zn(2)–O(1) 2.168(2), Zn(2)–O(6) 2.250(3), O(2)–Zn(1)–O(1) 110.25(11), O(2)–
Zn(1)–N(2) 125.95(12), O(1)–Zn(1)–N(2) 123.54(12), O(2)–Zn(1)–O(4) 93.08(11),
O(2)–Zn(1)–N(1) 93.43(12), O(1)–Zn(1)–N(1) 93.66(11), O(2)–Zn(1)–Zn(2)
87.96(8), O(1)–Zn(1)–Zn(2) 32.74(7), N(2)–Zn(1)–Zn(2) 141.90(10), O(4)–Zn(1)–
Zn(2) 67.95(7), N(1)–Zn(1)–Zn(2) 119.70(8), O(3)–Zn(2)–N(4) 172.57(13), O(3)–
Zn(2)–O(5) 93.12(12), N(4)–Zn(2)–O(5) 93.10(12), O(3)–Zn(2)–N(3) 92.24(12),
O(5)–Zn(2)–O(1) 90.29(10), N(3)–Zn(2)–O(1) 90.34(11), O(3)–Zn(2)–O(6)
90.13(11), N(4)–Zn(2)–O(6) 85.97(12), O(5)–Zn(2)–O(6) 88.54(11), O(1)–Zn(2)–
O(6) 173.32(11), O(3)–Zn(2)–Zn(1) 82.30(8), N(3)–Zn(2)–Zn(1) 116.70(8), O(1)–
Zn(2)–Zn(1) 29.62(6).
of the cooper complex described above. In both coordination
geometries, the longer bond lengths correspond to the atoms in ax-
ial positions, Zn1–N1 2.148(3) and Zn1–O4 2.097(3) Å; Zn2–O1
2.168(2) Å and Zn2–O6, 2.250(3) Å. The shortest bond length corre-
sponds, in both cases, for the terminal phenolate groups, Zn1–O2,
1.970(3) Å and Zn2–O3, 1.985(3) Å. For both metal ions, the Zn–Namine
bond lengths is quite longer [Zn1–N1, 2.148(3) and Zn2–N3, 2.138(3) Å]
than Zn–Npy [Zn1–N2, 2.091(3) and Zn2–N4, 2.095(3) Å], but similar in
both cases.
found in similar dinuclear complexes bearing also (
[19] or ( -phenolate) and additional exogenous bridge [22,32–
34], but shorter than that for [Zn2L(H2O)3](ClO4), 3.62 Å [21]. The
2-phenolate bridge is asymmetric, with Zn–O distances of
l-phenolate)
l
l
1.981(2) and 2.168(2) Å, but they are no so different as the case
Table 2
Hydrogen bond interactions (Å and °) for [Cu2(HL)(OAc)(H2O)2](OAc)ꢀ1.5H2O and
Inter- and intramolecular hydrogen bonds interactions between
phenolate groups, water and methanol molecules are present in
the crystal lattice (Table 2).
[Zn2L(CH3OH)3](ClO4)ꢀCH3OHꢀ2H2O.
Dꢀ ꢀ ꢀA
D–Hꢀ ꢀ ꢀA
[Cu2(HL)(OAc)(H2O)2](OAc)ꢀ1.5H2O
O2–H2ꢀ ꢀ ꢀO7
2.565
2.603
2.730
2.662
2.676
2.730
3.049
2.783
2.845
2.915
179.9
151.3
172.4
179.9
179.0
179.4
179.8
179.2
179.2
179.1
3.2. Spectroscopic and magnetic studies
O1W–H1WBꢀ ꢀ ꢀO4
O2W–H2WAꢀ ꢀ ꢀO3
O2W–H2WBꢀ ꢀ ꢀO8
Elemental analysis are consistent with the presence of dinuclear
compounds of the type [M2L](X)2ꢀxCH3OHꢀyH2O (M = Co(II), Cu(II)
or Zn(II); X = AcOꢂ or ClO4ꢂ).
O1W–H1WAꢀ ꢀ ꢀO4W_$1
O3W–H3WAꢀ ꢀ ꢀO5_$2
O3W–H3WBꢀ ꢀ ꢀO3_$2
O4W–H4WAꢀ ꢀ ꢀO8_$3
O5W–H5WAꢀ ꢀ ꢀO8_$4
O5W–H5WBꢀ ꢀ ꢀO1W_$5
The IR spectra of the complexes show m(C@N) vibration band of
the pyridine groups shifted to higher wavenumber than in the free
ligand suggesting coordination to the metal atom [35]. The IR spec-
tra of the perchlorate complexes feature absorptions attributable
to ionic perchlorate at 625 and 1100 cmꢂ1. The lack of splitting
of this band indicates that there is no coordination of these groups
to the metal centers [36,37].
Molar conductivity data, measured at room temperature using
acetonitrile as solvent showed the presence of ionic counterions,
since they are in the range reported in that solvent for 1:1 [38].
The results of LSI-MS of the complexes provide important evi-
dence of the formation of the dinuclear complexes as they feature
[Zn2L(CH3OH)3](ClO4)ꢀCH3OHꢀ2H2O
O4–H4ꢀ ꢀ ꢀO3
2.541
2.628
2.669
3.625
2.798
2.645
169.1
171.3
173.2
151.8
167.7
151.5
O5–H5ꢀ ꢀ ꢀO2
O1S–H1Sꢀ ꢀ ꢀO1W
O1S–H1Sꢀ ꢀ ꢀO1W0
O6–H6ꢀ ꢀ ꢀO1S0_$6
O6–H6ꢀ ꢀ ꢀO1S_$6
$1: x + 1/2, ꢂy ꢂ 1/2, +z ꢂ 1; $2: xꢂ1/2, ꢂy ꢂ 1/2, +z; $3: ꢂx + 1/2, +y + 1/2, +z + 1/2;
$4: x ꢂ 1/2, ꢂy ꢂ 1/2, +z ꢂ 1; $5: ꢂx + 1/2, +y + 1/2, +z ꢂ 1/2; $6: ꢂx + 1, ꢂy + 2,
ꢂz + 1.

2656
J. Martínez-Sánchez et al. / Polyhedron 29 (2010) 2651–2656
peaks attributable in all cases to the species [M2L]+ (M = Co, Cu or
Zn).
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CCDC 780194, 780195 and 780196 contains the supplementary
crystallographic data for H3L, [Cu2(HL)(OAc)(H2O)2](OAc)ꢀ1.5H2O
and [Zn2L(CH3OH)3](ClO4)ꢀCH3OHꢀ2H2O. These data can be ob-
tained free of charge via http://www.ccdc.cam.ac.uk/conts/retriev-
ing.html, or from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033;
or e-mail: deposit@ccdc.cam.ac.uk.
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Amsterdam, 1984.
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Lourido, Polyhedron 25 (2006) 783.
Acknowledgments
[41] B.N. Figgis, M.A. Hitchman, Introduction to Ligand Field Theory and Its
Applications, Wiley-VCH, 1999.
We thank Xunta de Galicia (PGIDT01PXI20901PR) for financial
support.