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An interesting complex ethanolic formed from Sudan red G and the
cobalt ion
Humberto C. Garcia, Gilson Rodrigues, and Luiz Fernando C. de
Oliveira*
Ncleo de Espectroscopia e Estrutura Molecular, Departamento de
Qumica,
Universidade Federal de Juiz de Fora, Campus Universitrio s/n,
Martelos, Juiz de Fora,
MG, 36036-900, Brazil
*Corresponding author. Electronic
address:[email protected]
Tel: +55 (32) 3229-3310 Fax: +55 (32) 3229-3310
mailto:[email protected]:[email protected]:[email protected]:[email protected]
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Abstract
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Introduction
During the last years the study of crystalline systems
denominated
supramolecular has attracted much attention of many researchers
group [1, 2]. The
importance in understanding these new arrangements also called
non-covalent have arole in trying to propose a direct association
between structure and their property, as in
processes related to gas adsorption, catalytic, magnetic and
currently related to
nanotechnology [3, 4]. Thus the use of organic molecules known
as building blocks also
has a great importance for the synthesis of these new materials,
from the different
building blocks that can be used in the synthesis, we mention
the interesting class of
Sudan dyes.
Sudan dyes are a family of lipophilic synthetic organic
colorants, characterizedby a chromophoric azo group (N=N),
extensively used in industrial as additives in
gasoline, grease, oils, plastics and scientific application, but
banned as food colorants
due generate metabolites that are converted to active mutagens
and carcinogens in
humans[5, 6]. Thereby the International Agency for Research on
Cancer (IARC)
classified these azo compounds as category 3 carcinogens because
they can induce some
forms of liver and bladder cancer in animals [7, 8].
Among the different azo compounds existing in diverse scientific
papers in the
literature, we can mention for use in this work of the
1-(2-methoxyphenyl-azo)-2-
naphthol or simply Sudan Red G (also known commercially as Oil
Red 113), can also
be found in the hidrazo form, due to an tautomeric effect able
occur in structure
(Scheme 1). From the point of view supramolecular we can say
that this building block
has significant physical and chemical characteristics as: its
molecule has a certain
planarity, with the presence of electrons that cause a large
electronic delocalization
system, responsible for the absorption of its electronic
spectrum in the visible region.Another very important feature
related to the coordination chemistry refers to the
presence of adequate sites coordination in the structure as
oxygen and nitrogen atoms,
providing strongly it coordination especially when considering
the transition metals [9].
Thus we can say that this work describes the synthesis,
structural and
spectroscopic characterization of a new supramolecular compound
obtained from the
reaction between the Sudan red G and the metal ion copper. This
article additionally
will involve a study of the supramolecular compound synthesized
in order to attempt toexplain the stability of the crystalline
arrangement formed.
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Experimental Section
Chemicals and reagents
Synthesis
Physical measurements
Infrared spectra were obtained using a Bomem MB-102 spectrometer
fitted with a CsI
beam splitter, with the samples dispersed on KBr disks and the
spectral resolution was
acquired at 4 cm-1. Good signal-to-noise ratios were obtained
from the accumulation of
128 spectral scans. Fourier-transform Raman spectroscopy was
performed using a
Bruker RFS 100 instrument, Nd3+/YAG laser operating at 1064 nm
in the near-infrared
region and a CCD detector cooled with liquid N2. Good
signal-to-noise ratios were
obtained from 2000 scans that were accumulated over a period of
30 min with a spectral
resolution of 4 cm-1. All spectra were obtained at least twice
to show reproducibility,
and there were no changes in the band positions or intensities
observed. X-ray powder
data were obtained using a Bruker D8 Advance (-) diffractometer:
Bragg-Brentano
geometry, with CuK(= 1.5406 ). The scan range, step size and
time per step were
2= 5.00 to 65, 0.02 and 1.00 s, respectively. Single crystal
X-ray data were collected
using an Oxford GEMINI A Ultra diffractometer with MoK(= 0.71073
) at room
temperature (112 K) for compound 2 and 3. Data collection,
reduction and cell
refinement were performed by CrysAlis RED, Oxford diffraction
Ltda, Version
1.171.32.38 program [10]. The structures were solved and refined
using SHELXL-97
[11].The empirical isotropic extinction parameterxwas refined
according to the method
previously described by Larson [12], and a Multiscan absorption
correction was applied
[13]. The structures were drawn by ORTEP-3 for windows [14] and
Mercury [15]
programs. CCDC 937901 contained the supplementary
crystallographic data for
compounds 1. These data can be obtained free of charge
athttp://www.ccdc.cam.ac.uk
or from the Cambridge Crystallographic Data Centre, 12, Union
Road, Cambridge CB2
IEZ, UK [Fax: (internat.) 1 44-1223/336-033;
E-mail:[email protected]].
http://www.ccdc.cam.ac.uk/http://www.ccdc.cam.ac.uk/http://www.ccdc.cam.ac.uk/mailto:[email protected]:[email protected]:[email protected]:[email protected]://www.ccdc.cam.ac.uk/
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Results and Discussions
The crystalline nature of supramolecular of compound
Co(SRG)2.CH3CH2OH,
obtained from reactions involving the
1-(2-methoxyphenyl-azo)-2-naphthol and
chloride of cobalt followed by further crystallisation from a
solvent ethanolic have beenrevealed by X-ray single crystal
analysis. The data crystalline compound is described in
Table 1, and some bond distances, bond angles and hydrogen
interactions are displayed
in Table 2.
The compound named Co(SRG)2.CH3CH2OH crystallizes in a
monoclinic
system presenting space group P21/c; Fig. 1 represents the
repeating unit for this
structure, formed by two building blocks distinct. The first of
these building blocks was
formed through coordination between two azo dye Sudan Red G and
cobalt ion; themetallic site appears coordinated in a slightly
distorted octahedral geometry, with the
bond angles between the atoms O1Co1O4, O3Co1O2 and N1Co1N3,
present
values of 155.2, 163.1 and 173.8, respectively. These values
when compared to the
same angles of a perfect octahedral geometry show a lower value,
this result may be
explained by the formation in the structure of five-member
rings, between atoms Co1
O1C6C1N1 and Co1O2C23C18N3 of the system synthesized, requiring
a
greater curvature in these bond angles, which does not happen if
all the rings formedwere of six members. We can also observe that
this building block, both ligand Srg
molecules are not so completely plane, introducing a small angle
of torsion between the
ring of the naphthol and phenyl group, coordinates to the
metallic sites and forming a
meridional isomer with both ligands perpendicular to each other.
The formation of a
facial isomer is more difficult to occur due to steric
impediment of the structure and
change of planarity of this ligand used. Due to the presence of
planarity of the molecule
Srg in the complex formed, we observe that the distance bonds
Co1O1 = 2.194(3) and
Co1O2 = 2.186(3) of each ligand are large than CoO4(O3) =
1.984(3) and Co
N1(N3) = 2.046(3) , showing that the molecule must undergo
further disruption to
maintain their geometry.
The other building block seen in the repeating unit of the
structure refers to a
molecule of ethanol, obtained from the recrystallization of the
product synthesized in
the same ethanolic solvent. We can also observe through the
repeat unit that the
interaction between the two independent building blocks formed
occurs with an
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interaction of hydrogen of 2.817(5) , between atoms O5O4 and
classified as medium
intensity following works of literature [16].
The supramolecular arrangement of compound obtained may be
observed across
Fig. 2. Presence of other supramolecular interactions occurring
effectively from thebuilding blocks formed by metal complexes and
ethanol solvent were not found; as an
example of this fact can be seen the distance centroid-centroid
of the aromatic rings that
have values of 5.295 and 4.857 , which does not correspond to a
packaging type -
stacking as noted in the literature are in the range of
approximately 3.80 [17]. A
second hydrogen bond classified as unconventional can also be
observed in the form
intramolecular ligand SRG, occurring between donor and acceptor
atoms C16H16N2
with distance of 2.754(5) and angle bond of 99.58. The low value
of this anglehydrogen bond occurs due to hybridization of the C16
that is sp2, which because to the
conformation of the molecule precludes a direct orientation
between atoms C16
H16N2 to form an angle of 180, resulting in a connection
hydrogen considered more
effective [18, 19].
Figure 3 shows the two-dimensional arrangement of the compound
synthesized
along bc-plane. For this structure can be along the c-axis that
both building blocks
consisting of the metal complex and the ethanol molecule have
only two possiblespecial orientations. These two orientations have
as main characteristic provide a greater
proximity between metal complexes, which has a higher volume of
building blocks,
thus providing better system stability tridimensional formed,
with the main objective of
minimizing the maximum of the volume occupied. Along the
a-crystallographic axis
can be seen that every building blocks have the same orientation
in space, both for the
metal complex as ethanol present as a solvent molecule in the
structure.
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Conclusions
Acknowledgements
The authors thank CNPq, CAPES, FAPEMIG (PRONEX 04370/10,
CEX-APQ-00617) and FINEP (PROINFRA 1124/06) for financial support
and also LabCri
(Departamento de Fsica UFMG) and LDRX (Instituto de Fsica UFF)
for the X-ray
facilities.
References
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Scheme Captions
Scheme 1.The tautomrica inversion of Sudan III: (a) the azo form
and (b) the hydrazo
form.
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Figures Captions
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 1.
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Figure 2
Figure 3
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Tables Captions
Table 1.
Table 2.
Table 3.
Table 1
Compound Co(SRG)2.CH3CH2OH
Formula C36H32CoN4O5
Formula weight/g mol-1 659.59
Crystal system Monoclinic
Space group P21/c
a/ 18.7874(16)
b/ 11.5005(5)
c/ 15.0000(10)
90.00
108.669(9)
90.00
V/3 3070.4(4)
Z 4
Crystal size/mm 0.68x0.24x0.20
Dcalc/g cm-3 1.427
(Mo K)/cm-1 0.610
Transmission factors (min/max) 0.839/0.885
Reflections measured/unique 16338/6287
Observed reflections [Fo2>2(Fo
2)] 4277
N. of parameters refined 420
R[Fo>2(Fo)] 0.0798wR[Fo2>2(Fo)
2] 0.1936
S 1.055
RMS peak/ 0.155
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Table 2
Bond distance/ Co(SRG)2.CH3CH2OH Bond distance/
Co(SRG)2.CH3CH2OH
Co1 O3 1.955(3) O4 O9 1.297(5)
Co1 O4 1.984(3) N3 N4 1.285(5)
Co1 N3 2.031(4) N3 C18 1.423(5)
Co1 N1 2.046(3) N1 N2 1.292(5)
Co1 O2 2.186(3) N1 C1 1.419(5)
Co1 O1 2.194(3) O3 C26 1.291(5)
O1 C6 1.375(5) N4 C25 1.349(5)
O1 C7 1.431(5) N2 C8 1.378(6)
Average of bond angles/
O3
Co1
O4 103.95(13) O3
Co1
O2 163.08(12)O3 Co1 N3 88.62(13) O4 Co1 O2 87.89(12)
O4 Co1 N3 99.39(13) N3 Co1 O2 77.40(13)
O3 Co1 N1 89.38(13) N1 Co1 O2 103.53(13)
O4 Co1 N1 86.74(13) O3 Co1 O1 93.52(12)
N3 Co1 N1 173.85(14) O4 Co1 O1 155.18(12)
Hydrogen bond (DA/)
O5 H5OO4 2.817(5)
C16 H16N2 2.754(5)
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Table 3
SRG CH3CH2OH Co(SRG)2.CH3CH2OH(1)
IR R IR R IR R Tentativeassignment
i.p CO(h)o.p. CH+wag CH2
i.p C=O
CCwag. NH2o.p CHringringi.p CHC-O(h)i.p OH(h)CC(c)
ring+ o.p CHCCCC
CC/CNC=OC=OCH2CHCHCHNH2syNH2as
