Synthesis, crystal structure, and fluorescence of a novel trinuclear zinc(II) complex derived from 2-ethoxy-6-[(2-phenylaminoethylimino)methyl]phenol

Article abstract of DOI:10.1080/15533174.2013.867881

A novel trinuclear zinc(II) complex, [Zn3L3 (3μ-O)] ClO₄H₂O, where L is the anionic form of 2-ethoxy-6-[(2-phenylaminoethylimino)methyl]phenol, has been synthesized and characterized by elemental analysis, FT-IR spectra, and single-c

Full text of DOI:10.1080/15533174.2013.867881

ACCEPTED MANUSCRIPT
Synthesis, Crystal Structure, and Fluorescence of a Novel Trinuclear Zinc(II) Complex
Derived from 2-Ethoxy-6-[(2-phenylaminoethylimino)methyl]phenol
Xiao-Ming Hua, Ling-Wei Xuea,*, Cai-Xia Zhangb, Wei-Chun Yanga
a College of Chemistry and Chemical Engineering, Pingdingshan University, Pingdingshan
Henan 467000, P.R. China
b Coal Chemical Industry Branch of Shenhua Ningxia Coal Group, Yinchuan Ningxia 750411,
P.R. China
* Corresponding author. E-mail: pdsuchemistry@163.com
Abstract
A novel trinuclear zinc(II) complex, [Zn3L3(µ3-O)]·ClO4·H2O, where L is the anionic form of 2-
ethoxy-6-[(2-phenylaminoethylimino)methyl]phenol, has been synthesized and characterized by
elemental analysis, FT-IR spectra, and single crystal X-ray determination. The crystal of the
complex is cubic: space group P213, a = b = c = 17.6479(2) Å, V = 5496.4(1) Å3, Z = 4, R1 =
0.0759, wR2 = 0.1963. The Zn···Zn distance is 3.134(1) Å. The Zn atom is coordinated by one
imino N, one amino N, and two phenolate O atoms from the Schiff base ligand, and one bridging
O atom, forming distorted trigonal-bipyramidal geometry. Fluorescence of the complex was also
studied.
Keywords zinc complex, trinuclear complex, Schiff base, crystal structure, fluorescence
1
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
INTRODUCTION
Schiff bases are a kind of versatile ligands which have widely been used in coordination
chemistry.[1–3] It has been shown that the Schiff base complexes derived from salicylaldehyde
and its derivatives with primary amines, bearing the N2O, N2S, NO2, or NSO donor sets, have
interesting biological activity.[4–7] In addition, metal complexes with Schiff bases have also been
widely studied for their catalytic properties of various organic reactions,[8-10] magnetic exchange
materials,[11-13] as well as photoluminescence applications.[14-16] As an extension of work on the
structures and photoluminescence of Schiff base complexes, in the present paper, a novel
trinuclear zinc(II) complex, [Zn3L3(µ3-O)]·ClO4·H2O, where L is the anionic form of 2-ethoxy-6-
[(2-phenylaminoethylimino)methyl]phenol (HL), has been prepared, characterized, and
investigated for its luminescence property.
EXPERIMENTAL
Materials and methods
3-Ethoxysalicylaldehyde and N-phenylethane-1,2-diamine were purchased from Fluka. Other
reagents and solvents were analytical grade and used without further purification. Zinc
perchlorate was prepared by the reaction of perchloric acid with zinc carbonate in water.
Elemental (C, H, and N) analyses were made on a Perkin-Elmer Model 240B automatic analyzer.
IR spectra were recorded on an IR-408 Shimadzu 568 spectrophotometer. Luminescence was
reported on a JASCO FP-6500 spectrofluorimeter (solid) in the range of 200–850 nm.
Synthesis of the complex
3-Ethoxysalicylaldehyde (0.1 mmol, 16.6 mg) and N-phenylethane-1,2-diamine (0.1 mmol,
13.6 mg) were reacted in methanol (10 mL). To the solution was added with stirring a
2
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
methanolic solution (10 mL) of Zn(ClO4)2·7H2O (0.1 mmol, 39.0 mg). The mixture was stirred at
refluxed for 30 min to give a clear solution. The solution was left still at room temperature in air
to give colorless block-shaped single crystals, which were collected by filtration and dried in air.
The yield is 28.3 mg (72%). Elemental analysis found: C, 51.7; H, 5.1; N, 7.3%,
C51H59ClN6O12Zn3 calcd: C, 51.9; H, 5.0; N, 7.1%.
X-ray diffraction
Data were collected from a selected crystal mounted on a glass fiber. The data for the complex
were processed with SAINT[17] and corrected for absorption using SADABS.[18] Multi-scan
absorption corrections were applied with ψ scans.[19] The structure of the complex was solved by
direct method using the SHELXS-97 program and refined by full-matrix least-squares techniques
on F2 using anisotropic displacement parameters.[20] All non-hydrogen atoms were refined
anisotropically. Hydrogen atoms were placed at the calculated positions. Crystallographic data
for the complexes are listed in Table 1. Selected bond lengths and angles are given in Table 2.
RESULTS AND DISCUSSION
Reaction of the Schiff base ligand with zinc perchlorate in methanol affords the complex
(Scheme 1). The complexes are soluble in DMF, DMSO, methanol, ethanol, and acetonitrile. We
have attempted to grow diffraction quality crystals from various solvents. However, well-shaped
single crystals suitable for X-ray diffraction were finally obtained from methanol.
Crystal structure description of the complex
The asymmetric unit of the complex contains a trinuclear [Zn3L3(µ3-O)]+ cation (Fig. 1), a
disordered perchlorate anion, and a disordered water molecule of crystallization. The trinuclear
zinc complex cation has a crystallographic three-fold rotation axis symmetry, with the axis
3
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
passing through the central O bridging atom. The Zn···Zn distance is 3.134(1) Å. The Schiff base
ligands coordinate to the Zn atoms through phenolate O, imino N, and amino N atoms, forming a
six- and a five-membered chelate rings with Zn atoms. Each Zn atom has a trigonal-bipyramidal
coordination, with the equatorial atoms defined by one imino N atom of one Schiff base ligand,
one phenolate O atom of another Schiff base ligand, and the bridging O atom, and with the two
axial positions defined by the amino N and phenolate O atom of the Schiff base ligand. The three
equatorial donor atoms show a high degree of planarity. The Zn1 atom deviates from the least-
squares plane defined by the three equatorial donor atoms by 0.004(2) Å. The angular distortion
in the trigonal-bipyramidal coordination comes from the bites O1A-Zn1-O4 (80.5(2)º), O1-Zn1-
O4 (79.2(2)º) and O1-Zn1-N2 (80.8(5)º). The bond values related to the coordination are within
normal ranges when compared to other zinc(II) complexes with Schiff bases.[21,22]
Infrared spectra
For the IR spectrum of the complex, the medium band centered at 3568 cm-1 can be assigned
to O-H stretching vibrations of the disordered water molecule. The sharp band at 3283 cm-1 is
clearly attributed to the N-H stretching vibrations. The strong band observed at 1635 cm-1 is
assigned to the typical azomethine group vibration.[23] The intense absorption at 1090 cm-1 is
aroused by the perchlorate anion.[24]
Fluorescence property
The fluorescence property of the complex was studied at room temperature (298 K) in the
solid state. Figure 2 is the emission spectrum of the complex. The emission band of the complex
is from 400 nm to 570 nm, with λmax = 453 nm (λex = 360 nm). For zinc(II) complexes, no
4
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
emission originating from metal-centered MLCT/LMCT excited states are expected, since the
Zn(II) ion is difficult to oxidize or reduce due to its stable d10 configuration. Thus, the emission
observed in the complex is tentatively assigned to the π–π* intra-ligand fluorescence.[25]
SUPPLEMENTARY MATERIALS
CCDC-967474 contain the supplementary crystallographic data for this paper. The data can be
obtained free of charge at http://www.ccdc.cam.ac.uk/const/retrieving.html or from the
Cambridge Crystallographic Data Centre (CCDC), 12 Union Road, Cambridge CB2 1EZ, UK;
fax: +44(0)1223-336033 or e-mail: deposit@ccdc.cam.ac.uk.
ACKNOWLEDGEMENTS
This research was supported by the National Sciences Foundation of China (No. 20676057
and 20877036) and Top-class foundation of Pingdingshan University (No. 2008010).
5
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
REFERENCES
1. Pradeep, C.P.; Das, S.K. Coordination and supramolecular aspects of the metal complexes of
chiral N-salicyl-beta-amino alcohol Schiff base ligands: Towards understanding the roles of
weak interactions in their catalytic reactions. Coord. Chem. Rev. 2013, 257, 1699-1715.
2. Ourari, A.; Aggoun, D.; Ouahab, L. A novel copper(II)-Schiff base complex containing
pyrrole ring: Synthesis, characterization and its modified electrodes applied in oxidation of
aliphatic alcohols. Inorg. Chem. Commun. 2013, 33, 118-124.
3. Ghosh, S.; Biswas, S.; Bauza, A.; Barcelo-Oliver, M.; Frontera, A.; Ghosh, A. Use of
metalloligands [CuL] (H2L = Salen type di-Schiff bases) in the formation of heterobinnetallic
copper(II)-uranyl complexes: Photophysical investigations, structural variations, and
theoretical calculations. Inorg. Chem. 2013, 52, 7508-7523.
4. Paiva, I.L.; de Carvalho, G.S.G.; da Silva, A.D.; Corbi, P.P.; Bergamini, F.R.G.; Formiga,
A.L.B.; Diniz, R.; do Carmo, W.R.; Leite, C.Q.F.; Pavan, F.R.; Cuin, A. Silver(I) complexes
with symmetrical Schiff bases: Synthesis, structural characterization, DFT studies and
antimycobacterial assays. Polyhedron 2013, 62, 104-109.
5. Fleck, M.; Layek, M.; Saha, R.; Bandyopadhyay, D. Synthetic aspects, crystal structures and
antibacterial activities of manganese(III) and cobalt(III) complexes containing a tetradentate
Schiff base. Transition Met. Chem. 2013, 38, 715-724.
6. Farag, A.M.; Guan, T.S.; Osman, H.; Majid, A.M.S.A.; Iqbal, M.A.; Ahamed, M.B.K.
Synthesis of metal(II) [M = Cu, Mn, Zn] Schiff base complexes and their Pro-apoptotic
activity in liver tumor cells via caspase activation. Med. Chem. Res. 2013, 22, 4727-4736.
6
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
7. Lee, S.M.; Ali, H.M.; Sim, K.S.; Malek, S.N.A.; Lo, K.M. Synthesis, characterization and
biological activity of diorganotin complexes with ONO terdentate Schiff base. Inorg. Chim.
Acta 2013, 406, 272-278.
8. Banerjee, A.; Guha, A.; Adhikary, J.; Khan, A.; Manna, K.; Dey, S.; Zangrando, E.; Das, D.
Dinuclear cobalt(II) complexes of Schiff-base compartmental ligands: Syntheses, crystal
structure and bio-relevant catalytic activities. Polyhedron 2013, 60, 102-109.
9. Pasa, S.; Ocak, Y.S.; Temel, H.; Kilicoglu, T. Synthesis, characterization and catalytic
behavior in the Suzuki reaction of Schiff base and its complexes and the optical properties of
nickel complex used in the fabrication of a photodiode. Inorg. Chim. Acta 2013, 405, 493-
504.
10. Pattanayak, P.; Pratihar, J.L.; Patra, D.; Brandao, P.; Mal, D.; Felix, V. Synthesis, crystal
structure, spectral properties and catalytic activity of a binuclear copper(II) complex
containing a Schiff base ligand. Polyhedron 2013, 59, 23-28.
11. Shit, S.; Nandy, M.; Rosair, G.; Gomez-Garcia, C.J.; Almenar, J.J.B.; Mitra, S. A
ferromagnetically coupled single hydroxido bridged tetranuclear nickel(II) Schiff base
complex incorporating a Ni4O4 cubane core: Crystal structure and magnetic study.
Polyhedron 2013, 61, 73-79.
12. Puterova-Tokarova, Z.; Mrazova, V.; Boca, R. Magnetism of novel Schiff-base copper(II)
complexes derived from aminoacids. Polyhedron 2013, 61, 87-93.
13. Shaabani, B.; Khandar, A.A.; Dusek, M.; Pojarova, M.; Mahmoudi, F.; Feher, A.;
Kajnakova, M. Two coordination polymers based on semicarbazone Schiff base and azide:
7
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
synthesis, crystal structure, electrochemistry, magnetic properties and biological activity. J.
Coord. Chem. 2013, 66, 748-762.
14. Feng, X.; Zhou, L.L.; Shi, Z.-Q.; Shang, J.-J.; Wu, X.-H.; Wang, L.-Y.; Zhou, J.-G.
Synthesis, crystal structure, and luminescence property of a new zinc(II) complex with
Schiff-base containing triazole propane ancillary ligand. Synth. React. Inorg. Met.-Org.
Nano-Met. Chem. 2013, 43, 1093-1098.
15. Roy, S.; Sarkar, B.N.; Bhar, K.; Satapathi, S.; Mitra, P.; Ghosh, B.K. Syntheses, structures
and luminescence behaviors of zinc(II) complexes containing a tetradentate Schiff base:
Variation in nuclearity and geometry with the change of halide/pseudohalide/carboxylate and
counter anion. J. Mol. Struct. 2013, 1037, 160-169.
16. Marinescu, G.; Madalan, A.M.; Tiseanu, C.; Andruh, M. New d(10) heterometallic
coordination polymers based on compartmental Schiff-base ligands. Synthesis, structure and
luminescence. Polyhedron 2011, 30, 1070-1075.
17. Bruker, SMART and SAINT. Area Detector Control and Integration Software; Bruker
Analytical X-ray Instruments Inc.: Madison, WI, USA, 1997.
18. Sheldrick, G. M. SADABS. Program for Empirical Absorption Correction of Area Detector
Data; University of Göttingen: Göttingen, Germany, 1997.
19. North, A. C. T.; Phillips, D. C.; Mathews, F. S. A semi-empirical method of absorption
correction. Acta Crystallogr., 1968, A24, 351-359.
20. Sheldrick, G. M. SHELXL-97. Program for the Refinement of Crystal Structures; University
of Göttingen: Göttingen, Germany, 1997.
8
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
21. Tandon, S.S.; Chander, S.; Thompson, L.K. Ligating properties of tridentate Schiff base
ligands, 2-[[(2-pyridinylmethyl)imino]methyl] phenol (HSALIMP) and 2-[[[2-(2-
pyridinyl)ethyl]imino]methyl]phenol (HSALIEP) with zinc(II), cadmium(II), nickel(II) and
manganese(III) ions. X-ray crystal structures of the [Zn(SALIEP)(NO3)]2 dimer,
[Mn(SALIEP)2](ClO4), and [Zn(AMP)2(NO3)2]. Inorg. Chim. Acta 2000, 300, 683-692.
22. Garcia-Raso, A.; Fiol, J.J.; Lopez-Zafra, A.; Mata, I.; Espinosa, E. Synthesis of ZnN-
salicylidene-L-aminoacidatos: X-ray structure of [(N-salicylidene-L-alaninato)
(aqua)zinc(II)]·0.25H2O and [(N-salicylidene-L-valinato) (aqua)zinc(II)]. Polyhedron 2000,
19, 673-680.
23. Lal, R.A.; Choudhury, S.; Ahmed, A.; Chakraborty, M.; Thakur, R.B.; Kumar, A. Synthesis
and spectral studies of nickel(II) complexes derived from disalicylaldehyde
oxaloyldihydrazone. J. Coord. Chem. 2009, 62, 3864-3874.
24. Qian, J.; Tian, J.-L.; Feng, L.; Gu, W.; Zhao, X.-J.; Yan, S.-P. Syntheses, structures, and
spectroscopic properties of binuclear copper(II) complexes containing N,N-bis(2-
pyridylmethyl)amine ligands. J. Coord. Chem. 2009, 62, 3276-3283.
25. Das, D.; Chand, B.G.; Sarker, K.K.; Dinda, J.; Sinha, C. Zn(II)-azide complexes of diimine
and azoimine functions: Synthesis, spectra and X-ray structures. Polyhedron, 2006, 25, 2333-
2340.
9
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
TABLE 1
Crystal and structure refinement data for the complex
Molecular formula
C51H57ClN6O12Zn3
1177.6
Molecular weight
Crystal system
Space group
a /Å
Cubic
P213
17.6479(2)
17.6479(2)
17.6479(2)
5496.4(1)
b /Å
c /Å
V /Ǻ3
Z
4
Dcalc (g cm-3)
Crystal dimensions (mm)
µ (mm-1)
1.423
0.20 × 0.20 × 0.18
1.411
F000
2432
Radiation λ
Tmin/Tmax
Mo Kα (0.71073 Ǻ)
0.7656/0.7853
27586
Reflections measured
Range/indices (h, k, l)
θ limit (°)
-20, 20; -19, 20; -20, 18
1.63–24.65
3087 [Rint = 0.0532]
Unique reflections
10
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Observed reflections (I > 2σ(I))
Parameters
2143
242
Restraints
64
Goodness of fit on F2
R1, wR2 [I  2(I)]a
1.062
0.0759, 0.1963
R1, wR2 (all data)a
0.1101, 0.2385
2
2 2 1/2
a R1 = Fo-Fc/Fo, wR2 = [w(Fo -Fc2)2/w(Fo ) ]
11
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
TABLE 2
Selected bond lengths (Å) and angles (°) for the complex
Bond lengths
Zn1-O1A
1.972(6)
2.028(6)
2.260(13)
Zn1-N1
Zn1-O4
1.995(11)
2.094(5)
Zn1-O1
Zn1-N2
Bond angles
O1A-Zn1-N1
N1-Zn1-O1
N1-Zn1-O4
O1A-Zn1-N2
O1-Zn1-N2
139.3(4)
89.2(4)
O1A-Zn1-O1
O1A-Zn1-O4
O1-Zn1-O4
N1-Zn1-N2
O4-Zn1-N2
102.7(4)
80.5(2)
79.2(2)
80.8(5)
92.4(4)
140.1(4)
101.3(4)
152.8(4)
Symmetry operation to generate related atoms: A: 3/2 – z, 1 – x, 1/2 + y.
12
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
+
N
H
N
O
Zn
H
O
N
N
O
_
Zn(ClO4)2
+
OH
ClO4
O
O
O
Zn
HN
Zn
N
N
H
O
N
O
H2O
SCH. 1. The preparation of the complex.
13
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
FIG. 1. Molecular structure of the complex at 30% probability displacement. Atoms labeled with
the suffix A and B are at the symmetry operations 3/2 – z, 1 – x, 1/2 + y and 1 – y, –1/2 + z, 3/2 –
x, respectively.
14
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
400
453 nm
350
300
250
200
150
100
50
0
400
450
500
550
600
Wavelength (nm)
FIG. 2. Emission spectrum of the complex.
15
ACCEPTED MANUSCRIPT