Zinc Metal-Organic Frameworks Based on a Flexible Benzylaminetetracarboxylic Acid and Bipyridine Colinkers

Abstract

Three new metal-organic frameworks (MOFs), [Zn-2(L)( H2O)]center dot 3DMF center dot 1.5H(2)O (1), [Zn-2(L)(4,4' -bpy) (1.5)(H2O)(2)] center dot 2DMF center dot 2H(2)O (2), and [Zn-2(L)(2,2' -bpy)(2)(DMF)(2)] center dot 2DMF center dot 4H(2)O (3) [H4L = 5,5' -(2,3,5,6-tetramethyl-1,4-phenylene) bis(methylene) bis(azanediyl) diisophthalic acid, 4,4' -bpy = 4,4' -bipyridine, 2,2' -bpy = 2,2' -bipyridine, DMF = N, N-dimethylformamide], were synthesized under solvothermal conditions and characterized by single-crystal X-ray diffraction analysis, elemental analysis, IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). The L4-ligands in 1-3 display different coordination modes, and the introduction of bipyridine colinkers brings significant struc-tural variation into the frameworks. Complex 1 is constructed from dinuclear carboxylate [Zn2O(COO)(4)] secondary building units (SBUs) and H4L ligands and exhibits a binodal (4,4)connected pts net with 54.6% solvent-accessible void. Complex 2 exhibits an unprecedented tetranodal (3,4,4,4)-connected net, which is constructed from two types of crystallographically independent Zn-II ions, H4L ligands, and the 4,4' bipyridine colinker. Complex 3 is constructed from parallel 1D molecular ladders stacked along the a axis that generate 1D channels (7.8 Chi 10.4 angstrom) and are hydrogen bonded to form 2D layers. The thermal stabilities and luminescence properties of 1-3 have also been studied in detail