Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 42:9–13, 2012
Copyright ꢀ Taylor & Francis Group, LLC
C
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2011.609220
A Linear Piperazine-Containing Ligand and Its Hg
Coordination Polymer
Wen-Juan Chu, Rui-Jun Li, Yao-Ting Fan, and Hong-Wei Hou
Department of Chemistry, Zhengzhou University, Zhengzhou, P. R. China
with flexible units. In this article, we synthesized the biden-
tate ligand: (N,Nꢁ-bis(1-H-1,2,4-triazole-1-yl)piperazine) (btp),
in which the two triazole groups are held in transconformation in
the equatorial position to the piperazine. The btp ligand adopts
didentate bridging mode to connect Hg ions leading to a 1D
infinite zigzag chain. In addition, polymer 1 and btp are syn-
thesized and characterized by X-ray single crystal diffraction
analysis, elemental analysis, IR, solid-state UV-Vis, and so on
in the context.
Reactions of piperazine hexahydrate with triazol and
paraformaldehyde afford a new piperazine-containing ligand:
(N,Nꢀ-bis(1-H-1,2,4-triazole-1-yl)piperazine) (btp). X-ray crystal
diffraction reveals that btp is an overall linear structure. Its Hg2+
polymer displays a zigzag chain in which piperazine is held in the
chair conformation. In addition, the spectra properties of the btp
and 1 are investigated, the strong luminescence characteristics of
btp and 1 are found.
Keywords crystal structure, luminescence property, polymer,
solid-state UV-Vis
EXPERIMENTAL
Materials and Physical Measurements
INTRODUCTION
All chemicals were of reagent-grade quality and obtained
from commercial sources and used without further purification.
Elemental analyses (C, H, N) were performed on a Carlo-Erba
1160 Elemental Analyzer. IR spectra were recorded in the re-
gion of 4000–400 cm−1 on a FTS-40 infrared spectrophotometer
with pressed KBr pellets. Powder XRD patterns were recorded
with CuKa1 radiation by using a PANalytical X’Pert PRO
diffractometer. Emission spectra were recorded on an F-4500
HITACHI fluorescence spectrophotometer. UV-Vis absorption
spectra in the solid state were taken using a Cary 5000 UV-Vis-
NIR spectrophotometer.
In recent years, nitrogen-containing heterocycles are fre-
quently employed as building blocks such as triazole, tetra-
zole, piperazine, triazine, and tetrazine have been widely used
for the construction of MOFs as a result of their variety of
intriguing structure and potential applications in the areas of
catalysis, magnetism, luminescence, and gas storage.[1–13] As
is known to us all, substituted 1,4-piperazine can assume dif-
ferent types of bridging conformations in both boat and chair
forms, of which the latter is thermodynamically more favorable,
though the boat form can coordinate one or bridge two metal
ions to give mononuclear and cis-dinuclear complexes, respec-
tively.[11–17] Compared with the rigid nitrogen heterocycle lig-
ands, the incorporation of flexible units, for example, –CH2–
group, has recently received increasing attention because the
freedom of the C-C single-bond connection between two ni-
trogen heterocycles in favor of the ligands serving as useful
building blocks.[18]
Synthesis of Ligand
(N,Nꢀ-bis(1-H-1,2,4-triazole-1-yl)piperazine) (btp)
Mixture of triazole (3.04 g, 44 mmol), paraformaldehyde
(1.47 g, 49 mmol), and 3 drops of triethylamine were heated at
80◦ several hours until viscous residues appear. Then the
residues were dissolved by methanol and stirred with piperazine
(1.85 g, 22 mmol). Coreless crystals (4.22 g) were obtained
by filtration and recrystallization in methanol. (yield: 77.34%).
Anal. Calcd. for C8H14N8 (%): C, 48.37; H, 6.50; N, 45.13;
Found: C, 47.93; H, 6.96; N, 45.11. M.P.: 228∼230◦C. IR (KBr,
cm−1): 3430(s), 3117(s), 3079(m), 2960(s), 2837(s), 11511(m),
1453(m), 1360(s), 1322(m), 1171(s), 1130(m), 1033(m),
1011(s), 959(w), 889(w), 797(s), 639(s). 1HNMR(CDCl3):
δ 2.687 (8H), 5.480 (4H), 8.531 (4H). Scheme 1
Taking the previous into consideration, we are exploring
the design and preparation of nitrogen heterocycles ligands
Received 10 May 2011; accepted 4 June 2011.
The authors gratefully acknowledge the financial support from the
National Natural Science Foundation of China (No. 20871106 and
90610001).
Address correspondence to Yao-Ting Fan, Department of Chem-
istry, Zhengzhou University, Henan 450052, P. R. China. E-mail:
Complex 1 is synthesized by the reactions of HgI2 (454.4 mg,
1 mmol) and btp (25.0 mg, 0.1 mmol) in methanol (8 mL), then
colorless rod-like crystals were obtained upon slow evaporation
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