ZnII and CdII Metal Organic Frameworks Based on 2-Methyl-6-oxygen-1,6-dihydro-3,4'bipyridine-5-carbonitrile

To investigate the coordination chemistry of modbc (2-methyl-6-oxygen-1,6-dihydro-3,4'-bipyridine-5-carbonitrile) with Zn^II and Cd^II salts under the solvothermal conditions, six new MOFs with the formulas Zn(modbc)₂(mpa)]_n ( 1 ), Zn(modbc)(mpa)(H₂O)]_n ( 2 ), Zn(modbc)(pa)_0.5(H₂O)]_n ( 3 ), Cd(modbc)(pa)_0.5(H₂O)]_n ( 4 ), Zn(modbc)₂(tpa)]_n ( 5 ), and Cd(modbc)₂(pda)(H₂O)]_n ( 6 ) (mpa = m-phthalic acid; pa = pyromellitic acid; tpa = terephthalic acid; pda = pentane diacid) were successfully synthesized by solvothermal reaction and fully characterized by elemental analysis, IR spectroscopy, single crystal, powder X-ray diffraction, thermal and photoluminescence properties. Though MOFs 3 and 4 have the same structure, we have obtained three different kinds of coordination configurations by the X-ray diffration analysis. Compared with 1 and 2 , coordination water has no effect on the solid fluorescence emission of MOFs. It is worth noting that the fluorescence intensity of 3 containing central Zn^II atoms is very strong, whereas that of isomorphism 4 containing central Cd^II atoms has almost no fluorescence emission, showing that metal ions have very important influence on the fluorescence emission. Further, we found that solvents had an important effect on the fluorescence emission in liquid fluorescence of MOFs 1 – 6 .