Structure and luminescent property of a novel one-dimensional organomercury complex

Article abstract of DOI:10.1016/j.inoche.2010.03.005

A novel organomercury complex, [Hg₂(μ-CH₃COO)(CH₃COO)(L)]_n (L = 1,3-bis(pyridine-2-ylmethoxy)benzene) 1, has been synthesized. Complex 1 has a one-dimensional chain structure formed by acetate anions bridging Hg

Full text of DOI:10.1016/j.inoche.2010.03.005

Inorganic Chemistry Communications 13 (2010) 630–632
Contents lists available at ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Structure and luminescent property of a novel one-dimensional
organomercury complex
⁎
⁎
Ying Liu, Peng-Fei Yan , Ying-Hui Yu, Guang-Feng Hou, Jin-Sheng Gao
Key Laboratory of Functional Inorganic Material Chemistry of Education Ministry, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A
novel organomercury complex, [Hg2(μ-CH3COO)(CH3COO)(L)]n (L = 1,3-bis(pyridine-2-ylmethoxy)
Received 18 December 2009
Accepted 2 March 2010
Available online 9 March 2010
benzene) 1, has been synthesized. Complex 1 has a one-dimensional chain structure formed by acetate
anions bridging Hg(II) atoms in crystallographical c-axis. The orthomercuration of the ligand takes place at
C-4 and C-6 of benzene ring rather than C-2 position. It shows intense fluorescent emission by solid-state
luminescent analysis.
Keywords:
© 2010 Elsevier B.V. All rights reserved.
Organomercury complex
Bipyridine ligand
X-ray structure
Luminescent property
In recent years, the compounds constructed by reacting d10 metal
ions with organic ligands have received considerable attention owing to
their characteristic luminescent response, which can be used for organic
light emitting diodes [1,2], photocatalysts [3,4] and fluorescent sensors
[5–7]. Like other metal ions of d10 (Zn(II) [8–12] and Cd(II) [13–17]), Hg
(II) ion with flexible coordination environment can be used to construct
coordination polymers and framework structures. The research of
complexes with Hg(II) ion, however, is rare compared with thatof Zn(II)
and Cd(II) complexes. Due to the fact that Hg(II) ion is hazardous to
environment and human health, it is an urgent task to determine the
concentration of mercury ions in the environment. Some organic
compounds can coordinate with mercury ions, which can change their
fluorescent properties markedly. The kind of compounds can be used for
high sensitive and selective mercury sensors. However, the crystal
structures and luminescent properties of such mercury complexes were
rarely reported.
The so-called pincer ligands and their complexes with the N–C–N
sequences of donor atoms, where C located at an anionic benzene ring,
have been investigated widely by far. The regioselective monometala-
tion usually takes place at C-2 of the benzene ring, as previously
reported for mercury, palladium, platinum, ruthenium and osmium.
Among those, reacting palladium with the N–C–N ligand generally
results in dimeric 4,6-bis-palladated derivatives [18,19], but it was not
the case for mercury and no 4,6-bis-mercuried derivatives have been
obtained. Herein we reported the synthesis and characterization of a
novel 4,6-metalated organomercury compound [Hg2(μ-CH3COO)
(CH3COO)(L)]n (1), where L is 1,3-bis(pyridine-2-ylmethoxy)
benzene.
The reaction of L and mercury(II) acetate in ethanol leads to the
formation of complex 1 [20,21]. Single crystal X-ray analysis reveals
that 1 shows a one-dimensional chain structure [22]. In the
asymmetrical unit of 1, there are two crystallographically indepen-
dent Hg2+ ions and two unique acetate anions with two different
coordination modes (Fig. 1). The Hg1 ion is four-coordinated and is
described as a distorted tetragon: three oxygen atoms from two
acetate anions and one carbon atom from the benzene spacer; the
Hg2 ion is three-coordinated like a distorted trigon: two oxygen
atoms from one acetate anion and one carbon atom from the benzene
spacer. The Hg1 is simultaneously coordinated to two adjacent
acetate anions with each adopting μ2–η2:η1-bridging coordination
mode, while Hg2 is not further coordinated with other acetate
anions. The Hg–C bond lengths range from 2.040(7) to 2.058(7) Å,
whereas the Hg–O distances vary from a normal value of 2.074(6) to
2.066(5) Å [23–25].
It is well known that mercury acetate could attack aromatic
compounds with metal–C (sp2) bond easily, and regioselective
monometalation takes place at C-2 of the benzene ring [26–28].
However, in this case it does not result in the formation of C-2 metal
bond, instead it leads to the formation of C-4 and C-6 metal bonds. It is
worth to note that nitrogen atoms of pyridine rings don't take part in
the coordination with Hg(II) atoms. The Hg1 atoms and bridging
acetate anions form an infinite chain with the adjacent ligands located
alternately on two sides of the chain (Fig. 2). The distance between
adjacent Hg atoms in the chain is 6.071 Å. The intramolecular Hg⋯O
distances between Hg atoms and the O atoms of 2.993 Å and 3.003 Å
are less than the sum of the van der Waals radii which suggests a weak
secondary interaction. It is the secondary interaction that produces
⁎
Corresponding authors. Tel.: +86 451 86609001; fax: +86 451 86609151.
E-mail addresses: yanpf@vip.sina.com (P.-F. Yan), gaojins@hlju.edu.cn (J.-S. Gao).
1387-7003/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2010.03.005

Y. Liu et al. / Inorganic Chemistry Communications 13 (2010) 630–632
631
Fig. 1. Asymmetric unit and atom labeling in complex 1 with thermal ellipsoids
represented at the 50% probability level.
Fig. 3. The powder XRD patterns for 1 (blue line: simulated from single-crystal X-ray
diffraction data; black line: as-synthesized solids).
the left–right alternate arrangement of the adjacent ligands to reduce
steric hindrance.
We also carried out the powder X-ray diffraction (PXRD)
experiment and the thermogravimetric analysis to investigate the
purity and stability of 1. The result of PXRD shows that the peak
positions and their intensities of as-synthesized solids are consistent
with the simulated pattern from the single-crystal X-ray diffraction
data, which proved that the powder sample has a single phase of the
complex 1 (Fig. 3). The TG curve shows that the complex 1 is stable up
to 70 °C at which temperature it starts to decompose and the first
weight loss is attributed to the release of two acetate anions per
formula unit (observed 13.95%, calcd. 14.56%). The next decomposi-
tion process takes place from 195 to 387 °C, indicating the release of
ligand (observed 35.80%, calcd. 36.05%). The solid residue HgO is
evaporated under higher temperature (Fig. S1).
The luminescent property of 1 was studied in the solid state at
room temperature. The ligand has shown a weak fluorescent
emission band with a maximum intensity at 420 nm upon
excitation at 365.5 nm (Fig. 4). In contrast to the ligand, 1 exhibits
a 20.5 nm red-shift in the emission spectrum and the increase of
emission intensity with an emission maximum at 440.5 nm upon
excitation at 387 nm. The observed emission of complex 1 is
probably assigned to the intraligand π–π* transition. The increase
of the fluorescent intensity of 1 can be attributed to the interactions
of Hg(II) atom with the ligand through Hg–C bond, which result in
the increase of ligand rigidity. The maximum emission locates in
the blue region so that it may have potential application as a blue
luminescent material.
In summary, a new mercury(II) complex [Hg2(μ-CH3COO)
(CH3COO)(L)]n (1) (L = 1,3-bis(pyridine-2-ylmethoxy)benzene) is
synthesized and characterized. In comparison with the similar
reactions between other bipyridine ligands and mercury acetate
salts, regioselective metalations in complex 1 take place at C-4 and C-6
of the benzene ring rather than C-2 position. The luminescent analysis
shows that 1 exhibits intense fluorescent emission in blue region,
which may have potential applications.
Acknowledgements
This research was supported by the National Natural Science
Foundation of China (Grant Nos. 20672032 and 20572018) and the
Specialized Research Funds for Technological Innovative Talent in
Harbin (RC2009XK018007). We thank the University of Heilongjiang
for supporting this study.
Appendix A. Supplementary data
CCDC 705198 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from the
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif. Supplementary data associated with this article can
be found, in the online version, at doi: 10.1016/j.inoche.2010.03.005.
Fig. 2. (a) One-dimensional chain structure of complex 1 is constructed by acetate anions bridging mercury atoms. The ligands located alternately on the right and left sides of the
chain are highlighted by blue and red atoms respectively. Hydrogen atoms are omitted for clarity; (b) One-dimensional polymeric chain of complex 1 viewed along the c-axis.

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Y. Liu et al. / Inorganic Chemistry Communications 13 (2010) 630–632
[15] Y.-Q. Gong, Y.-F. Zhou, L. Han, R.-H. Wang, B.-L. Wu, B.-Y. Lou, M.-C. Hong, J. Mol.
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[20] Synthesis of the ligand (L): A mixture of 1,3-dihydroxybenzene (resorcinol)
(1.1 g, 10 mmol), 2-chloromethylpyridine hydrochloride (3.28 g, 20 mmol) and
NaOH (1.6 g, 40 mmol) in acetonitrile (50 mL) was stirred at reflux under
nitrogen for 24 h. After cooling to room temperature, the reactant was filtered,
and the residue was washed with acetonitrile for several times. The mixed filtrate
was evaporated under reduced pressure and the red residue was dissolved in
dichloromethane and then washed twice with water, once with brine. The organic
layer was dried over anhydrous Na2SO4 and filtered. After the removal of the
solvent under reduced pressure, the residue was purified by chromatography on
silica gel to give colorless solid substance. Yield: 2.57 g (88% based on resorcinol).
Element Analysis: Calc. for C18H16O2N2: C, 73.95; H, 5.52; N, 9.58%. Found: C,
73.78; H, 5.50; N, 9.53%. IR (KBr, cm−1): 3062 (w), 3015 (w), 2918 (w), 1594 (s),
1574 (m), 1493 (s), 1433 (s), 1377 (m), 1271 (m), 1188 (s), 1161 (s), 1043 (m),
840 (m), 747 (s), 681 (m). 1H NMR (300 MHz, CDCl3): 5.21 (4H, s, CH2), 6.62 (1H,
t), 6.69 (2H, d), 7.24 (2H, q), 7.28 (1H, s), 7.53 (2H, d), 7.72 (2H, q), 8.62 (2H, t).
[21] The title complex was synthesized by reaction between a solution of the ligand
(0.0292 g, 0.10 mmol) in EtOH (5 mL) and a solution of Hg(CH3COO)2 (0.0319 g,
0.1 mmol) in EtOH (5 mL). The mixture is heated to 40 °C and stirred for about
one hour. After filtration, colorless block crystals suitable for X-ray diffraction
were obtained by slow evaporation under room temperature for several days in
40% yield. Element Analysis: Calc. for C22H20Hg2N2O6: C, 32.64; H, 2.49; N, 3.46%.
Found: C, 32.18; H, 2.43; N, 3.41%. IR (KBr, cm−1): 3379 (s), 3117 (w), 2922 (w),
1641 (s), 1599 (s), 1435 (s), 1354 (s), 1311 (s), 1294 (s), 1193 (s), 1052 (s), 756
(s), 683 (s).
Fig. 4. Photoluminescence emission spectra of complex
(dotted).
1 (solid) and the ligand
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