Coordination Polymers of Copper and Zinc Ions with a Linear Linker Having Imidazole at Each End and an Azo Moiety in the Middle: Pedal Motion, Gas Adsorption, and Emission Studies

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• 作者：Ruchi Singh ; Musheer Ahmad ; Parimal K. Bharadwaj
• 刊名：Crystal Growth & Design
• 出版年：2012
• 出版时间：October 3, 2012
• 年：2012
• 卷：12
• 期：10
• 页码：5025-5034
• 全文大小：736K
• 年卷期：v.12,no.10(October 3, 2012)
• ISSN：1528-7505

文摘

The imidazole donor ligand bis(4-imidazol-1-yl-phenyl)-diazene (azim) reacts readily with M(ClO₄)₂路6H₂O [M(II) = Zn(II) and Cu(II)] salts at room temperature to afford {[Zn(azim)₂]路(ClO₄)₂路3DMF}_n (1) and {[Cu(azim)₂(DMF)₂]路(ClO₄)₂路2DMF}_n (2) (DMF = N,N鈥?dimethylformamide). With MCl₂路6H₂O [M(II) = Zn(II) and Cu(II)] salts under solvothermal conditions, compounds {[Zn(azim)(HCOO)₂]}_n (3) and {[Cu(azim)(Cl)]}_n (4) are obtained in moderate yields. Complexes 1 and 2 crystallize as 2D four-connected 4⁴ sql networks with rectangular and rhombus grids, respectively. The frameworks are stabilized by an intricate array of hydrogen bonding interactions with guest molecules that also results in overall 3D frameworks. On the other hand, complexes 3 and 4 form 1D zigzag infinite chain structures. All compounds have been characterized by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric analysis (TGA), and powder X-ray diffraction (PXRD) measurements. The TGA and PXRD measurements reveal that the integrity of the frameworks 1 and 2 is maintained upon guest removal. N₂ and CO₂ adsorption measurements were carried out for evacuated frameworks 1 and 2, and the adsorption studies show CO₂ selectivity over N₂ at low pressure in the case of 2. Interestingly, heat and guest induced bicycle pedal motion of the azo moiety can be observed in 1 and 4 without loss of crystallinity. Upon excitation at 304 nm, compounds 1鈥?b>4 and 4鈥?/b> exhibit solid-state luminescence at room temperature.