Synthesis and Molecular Structures of Two [1,4-bis(3-pyridyl)- 2,3-diazo-1,3-butadiene]-dichloro-zn(ii) Coordination Polymers

Two novel coordination polymers with 3D metal-organic frameworks (MOFs) have been synthesized by reacting 1,4-bis(3-pyridyl)-2,3-diazo-1,3-butadiene (L) with zinc dichloride. Both compounds have the same repeating unit consisting of a distorted tetrahedral Zn(II) center coordinated by two chlorides and two pyridyl nitrogen atoms of two bridging bismonodentate L ligands, however, different structural conformations have been found, one forming a helical chain and the other producing a square-wave chain. The intermolecular C−H···Cl hydrogen bonds in 1 and 2 play important roles in the formation of three-dimensional coordination polymers.


Results and Discussion
Compound 1 was synthesized by reacting of ZnCl 2 with L (molar ratio 1:1) under solvothermal conditions.Figure 1 1.It is noteworthy that the ligand L is not planar, but twisted around the -CH=N−N=CH− with a dihedral angle of 46.65 (13)° between the two pyridine rings and acts as a bis-monodentate mode to the Zn(II) ion.Hence, a 1D polymeric helical chain is formed.The distance between the neighboring zinc ions is 12.1834(4) Å.Table 1.Selected bond lengths and angles around the Zn(II) for compound 1.

X-ray techniques
Suitable single crystals were mounted on a glass fiber.The data collection was carried out on a NONIUS Kappa CCD diffractometer with Mo-Kα (λ = 0.71073 Å) radiation with the crystal cooled to 150K in a stream of N 2 from Oxford Cryostream-700 cooler.A preliminary orientation matrix and the unit cell parameters were determined from the 15 frames, each frame corresponding to a 1° ω scan in 20 sec.Data were measured (program COLLECT [11]) by using an ω scan of 0.5° per frame for 20 sec.until a complete data had been collected.Program DENZO-SMN [12] was used for cell refinement and data reduction.The SORTAV [13] program was used to apply absorption correction.The structure was solved by direct method with the SHELXS97 [14] and refined on F 2 with SHELXL97 [15].All non-hydrogen atoms were refined anisotropically.Hydrogen atoms were constrained to the ideal geometry applying an appropriate riding model.The molecular graphic were plotted using SHELXTL [16] and MERCURY [17].Crystallographic data are listed in Table 3. CCDC-605741 and 605742 contain the supplementary crystallographic data for this paper.These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html.[or from the CCDC, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223 336033; e-mail: deposit@ccdc.cam.ac.uk].

2 Figure 2 . 1 .
Figure 2. The packing diagram of compound 1, viewed along the c axis.Dotted lines indicate hydrogen bonds.

Figure 4 .
Figure 4.The packing diagram of compound 2, viewed along the c axis.Dotted lines indicate hydrogen bonds.

Table 3 .
Crystallographic and experimental data for compounds 1 and 2.