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NMR and X-ray Study Revealing the Rigidity of Zeolitic Imidazolate Frameworks
Morris, William,Stevens, Caitlin J.,Taylor, R. E.,Dybowski, C.,Yaghi, Omar M.,Garcia-Garibay, Miguel A. American Chemical Society 2012 The Journal of Physical Chemistry Part C Vol.116 No.24
<P>NMR relaxation studies and spectroscopic measurements of zeolitic imidazolate framework-8 (ZIF-8) are reported. The dominant nuclear spin–lattice relaxation (<I>T</I><SUB>1</SUB>) mechanism for ZIF-8 in air arises from atmospheric paramagnetic molecular oxygen. The <SUP>13</SUP>C <I>T</I><SUB>1</SUB> measurements indicate that the oxygen interacts primarily with the imidazolate ring rather than the methyl substituent. Similar relaxation behavior was also observed in a ZIF with an unsubstituted ring, ZIF-4. Single-crystal X-ray diffraction was used to provide data for the study of the thermal ellipsoids of ZIF-8 at variable temperatures from 100 to 298 K, which further confirmed the rigid nature of this ZIF framework. These results highlight a rigid ZIF framework and are in contrast with dynamic metal–organic frameworks based on benzenedicarboxylate linking groups, for which the relaxation reflects the dynamics of the benzenedicarboxylate moiety.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-24/jp303907p/production/images/medium/jp-2012-03907p_0003.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp303907p'>ACS Electronic Supporting Info</A></P>