Ferrocene Macrocyclic Schiff Base Complex: Synthesis, Structure and Recognition Properties for Dual Hg2+ and Cu2+

Article abstract of DOI:10.1134/S1070363217120428

A probe based on ferrocene structure has been designed, synthesized and elucidated from the single crystal X-ray method. It demonstrated fluorescence response to Hg²⁺ and Cu²⁺ in CH₃OH. The results indicated that the title complex could be applied in the multianalyte detection. Binding ability of receptor 3 in CH₃OH was tested for various cations (Fe³⁺, Co²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺, and Ba²⁺ in water). The computed binding constants for Hg²⁺ and Cu²⁺ indicated a distinct absorbance shift. The receptor is an attractive array due to its distinct absorbance shift profile in a semi-aqueous phase, making it applicable in biology, environmental sciences and material chemistry.

Full text of DOI:10.1134/S1070363217120428

ISSN 1070-3632, Russian Journal of General Chemistry, 2017, Vol. 87, No. 12, pp. 2986–2988. © Pleiades Publishing, Ltd., 2017.
Ferrocene Macrocyclic Schiff Base Complex:
Synthesis, Structure and Recognition Properties
for Dual Hg2+ and Cu2+ 1
Xiaoju Liu*, Yulin Xiang, Xiangrong Ma, Guoyu Ren, and Liguo Gao
Key Laboratory of Synthetic and Natural Chemistry of the Ministry of Education,
Chemical Engineering Institute, Yu-Lin University of Yulin,
Chongwen av. 4, Yulin, Shaanxi Province, 719000 China
*e-mail: liuxiaoju0628@163.com
Received November 5, 2017
Abstract―A probe based on ferrocene structure has been designed, synthesized and elucidated from the single
crystal X-ray method. It demonstrated fluorescence response to Hg2+ and Cu2+ in CH3OH. The results indicated
that the title complex could be applied in the multianalyte detection. Binding ability of receptor 3 in CH3OH
was tested for various cations (Fe3+, Co2+, Cu2+, Zn2+, Cd2+, Hg2+, Pb2+, and Ba2+ in water). The computed
binding constants for Hg2+ and Cu2+ indicated a distinct absorbance shift. The receptor is an attractive array due
to its distinct absorbance shift profile in a semi-aqueous phase, making it applicable in biology, environmental
sciences and material chemistry.
Keywords: ferrocene, ion recognition, fluorescence sensor, Hg2+ and Cu2+ cation sensing
DOI: 10.1134/S1070363217120428
Many heterocyclic compounds, including imidazo-
pyridine, benzimidazole and 8-aminoquinoline, have
been widely used in molecular recognition due to their
specific fluorescence properties. Ferrocene derivatives
have been rarely used in host-guest chemistry. In fact,
ferrocene derivatives are ideal platforms for
development of cations, anions and neutral molecules
recognition. In the current study we designed and
synthesized a ferrocene macrocyclic Schiff base
complex which demonstrated very high fluorescent
response to Hg2+ and Cu2+ions in aqueous media.
Other ions, including Fe3+, Co2+, Zn2+, Cd2+, Pb2+, and
Ba2+, had nearly no influence on the probing behavior.
Notably, this sensor can serve as a recyclable
component in sensing materials. Test strips based on
the sensor were produced and those exhibited high
selectivity to Hg2+ and Cu2+ in solutions.
monitoring). Upon removal of the solvent a crude
product was isolated. Column chromatography [silica
gel, V(CH3OH) : V(CH3Cl) = 1 : 2) gave the pure title
compound as deep-red powder. Yield 65 %, mp 198–
200°C. Found, %: C 63.23, H 5.34, N 10.58. C28H28Fe2N4.
Calculated, %: C 63.19, H 5.30, N 10.53. MALDI-
TOP MS: m/z: 533 [M]+.
A single crystal of the receptor 3 suitable for X-ray
diffraction studies was grown directly by slow
evaporation of 10 mL of the saturated neat CH2Cl2/
EtOH (1/4 v/v) solution. Its specific parameters are
available as Supplementary data. CCDC-1583117 contains
the supplementary crystallographic data that can be
obtained free of charge from www. Ccdc. Cam. Ac.
Uk / data_request/ cif.
RESULTS AND DISCUSSION
EXPERIMENTAL
The ORTEP drawing and packing diagram for
receptor 3 are presented in Figs. 1 and 2. Both
ferrocene units and the dimethyl substituted chains
have a staggered conformation. The point group of the
molecule is D2, as the molecule has three, two fold
axes (C2) perpendicular to each other. The main crystal
building force is the interaction between the nonpolar
ferrocene moieties.
Synthesis of the receptor 3. The intermediate
compound 2 (0.60 g, 2 mmol) was mixed with glacial
acetic acid (1 mL), used as a catalyst, in methanol
(20 mL). The mixture was stirred for 0.5 h at room
temperature and then refluxed for another 3 h (TLC
1 The text was submitted by the authors in English.
2986

FERROCENE MACROCYCLIC SCHIFF BASE COMPLEX
2987
Fe
Scheme 1. Synthetic route to the title compound.
N−NH2
COCH3
.
N N
N N
3
CH3COCl
N2H4 H2O
Reflux
CH3COOH
Reflux
Fe
Fe
Fe
Fe
AlCl3, CH2Cl
COCH3
N−NH2
1
2
The sensor 3 demonstrated selectivity and sensi-
tivity for Hg2+ and Cu2+ ions in a dual-channel mode
(fluorescence emission and UV/Vis). Mechanism of
the C=N isomerization, coupled with photoinduced
energy transfer, is proposed to explain the observed
spectral response. Probably the title complex could
have strong rigidity and self-assembly performance
with more binding sites. It exhibited a strong binding
force with the metals via nitrogen atoms orientated
towards Hg2 + and Cu2+.
receptor 3. The observed binding behavior of the
ligand (Fig. 3) could be attributed to the presence of
donor atoms that favor the binding with Hg2+ and Cu2+
in a tetrahedral fashion.
Fluorescence analysis. Fluorescence intensity was
recorded at λex/λem = 385/450 nm along with a reagent
blank. The excitation and emission slits were both set
to 5.0 nm. This was followed by a 5 min interval,
within which the reaction cell was left under
continuous stirring to ensure mixing, then the
fluorescence data were collected.
Sample preparation. A stock solution of receptor
3 (c = 1×10–6 mol/L) in CH3OH was prepared and the
solutions of metal ions (c = 1 × 10–5 mol/L) were
prepared by diluting with H2O. All solutions were
prepared in ultrapure water and spectroscopic grade
methanol.
The receptor 3 demonstrated a strong fluorescence
emission at 450 nm when excited at 385 nm. Upon
addition of Fe3+, Co2+, Cu2+, Zn2+, Cd2+, Hg2+, Pb2+,
and Ba2+, receptor 3 showed no change in the
fluorescence intensity at 450 nm. However, there was a
notable change when Hg2+ and Cu2+ were present
(Figs. 4, 5). Colour of the solution also changed from
colourless to yellow under illumination with a 385 nm
UV lamp. Reason for the fluorescence change of the
receptor 3 could be due to the occurrence of either an
electron transfer or an electronic energy transfer
involving the transition metal and the excited fluoro-
phore, as it had been observed in the other Hg2 and
Cu2+ recognition sensors.
UV-Vis analysis. UV-Vis experiments were carried
out in a CH3OH solvent system at room temperatures
(298 K) with the aim of determining the selectivity
among the metal ions (Fe3+, Co2+, Cu2+, Zn2+, Cd2+,
Hg2+, Pb2+ and Ba2+ in water) with the receptor/ligand.
The absorbance intensity was recorded at 200–800 nm.
The accumulated data demonstrated that metal ions
such as Fe3+, Co2+, Zn2+, Cd2+, Pb2+ and Ba2+
(10 equiv.) did not change absorption peaks of the
C26
C20
C8
C9
N3
C24
N4
C10
C21
C22
C28
C6
C7
C25
C27
C23
Fe2
Fe1
C12
C17
C16
C5
N2
N1
C14
C13
C3
C11
C18
C15
C2
C1
C19
Fig. 1. Ortep diagram of the sensor 3. Only non-hydrogen
atoms are labelled. The molecule has three, two fold axes
perpendicular to each other (point group D2). The ellipsoid
probability is 30%.
Fig. 2. Molecular packing of the receptor 3.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 12 2017

2988
XIAOJU LIU et al.
N N
Fe
Fe
Fe
1.4
Fe
1
N N
M
1.2
1.0
0.8
N N
N N
Fe
0.6
0.4
0.2
0.0
2
N N
M
Fe M : Hg2+ or Cu2+
250
300
350
400
450
Wavelength, nm
N N
Fig. 4. Absorption spectra of the receptor 3 (c = 1×
10–6 mol/L) in CH3OH solution upon addition of various
metal ions: (1) Hg2+ and (2) Cu2+ (10.0 equiv, c = 1×
10–5 mol/L) in water.
Fig. 3. Two possible types of recognizing mechanism of
Hg2+ and Cu2+ with 3 as a probe.
1000
ACKNOWLEDGMENTS
800
1
This study was supported by Instrumental Analysis
Center of the Chemical engineering institute, the Yu-
Lin University, the Scientific research fund Project
(grant no. 2016NY-221), the Key Laboratory
Project Foundation of Shaanxi Provincial Education D
epartment in China (17JS144).
600
2
400
200
0
REFERENCES
1. Ermakova, E., Michalak, J., Meyer, M., Arslanov, V.,
Tsivadze, A., and Guilard, R., Org. Lett., 2013, vol. 15,
p. 662. doi 10.1021/ol303499v
380
420 460 500 540 580
Wavelength, nm
Fig. 5. Fluorescence emission spectra of 3 (CH3OH, c =
1 × 10–6 mol/L ) in the absence and presence of 10 equiv.
of various cations (c = 1 × 10–5 mol/L) in H2O solution
(λex = 385 nm): (1) Hg2+ and (2) Cu2+.
2. Schmidtchen, F.P. and Berger, M., Chem. Rev., 1997,
vol. 97, p. 1609. doi 10.1021/cr9603845
3. Beer, P.D. and Gale, P.A., Angew. Chem. Int. Ed., 2001,
vol. 40, p. 486. doi 10.1002/1521-3773(20010202)
40:3<486::AID-ANIE486>3.0.CO;2-P
4. Vicente, M.C., Burguete, M.I., Galindo, F., Izquierdo, M.A.,
Kumar, D.K., and White, A.J., J. Org. Chem., 2012,
vol. 77, p. 490. doi 10.1021/jo202077v
5. Jin, C., Zhang, M., Deng, C., Guan, Y.F., Gong, J., and
Zhu, D.R., Tetrahedron. Lett., 2013, vol. 54, p. 796. doi
10.1016/j.tetlet.2012.11.117
Despite certain attempts, single crystals of both Hg2
and Cu2+ complexes with the receptor 3 suitable for
diffraction study, could not be obtained.
CONCLUSIONS
6. Kondo, S.I., Bie, Y., and Yamamura, M., Org. Lett.,
2013, vol. 15, p. 520. doi 10.1021/ol303332k
7. Chandra, B., Mahanta, S.P., Pati, N.N., Baskaran, S.,
Kanaparthi, R.K., and Sivasankar, C., Org. Lett., 2013,
vol. 15, p. 306. doi 10.1021/ol3032158
8. Wei, T.B., Zhang, P., Shi, B.B., Chen, P., Lin, Q., Liu, J.,
and Zhang. Y.M., Dyes Pigm., 2013, vol. 97, p. 297. doi
10.1016/j.dyepig.2012.12.025
We have synthesized the selective and sensitive
fluorescent chemical sensor 3, based on ferrocene,
efficient in detection of Hg2+ and Cu2+ in CH3OH
medium. Receptor 3 could be applied directly to real
environmental samples because of its working ability
in semi-aqueous solutions. The sensor is not affected
by common interference of other ions.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 12 2017