Syntheses and crystal structures of two new nickel (II) metal-organic frameworks with a polydentate ligand

Two metal-organic frameworks {Na 2 [Ni(L) 2 (H 2 O)]} n ( 1 ) and {[Ni(L)(H 2 O)]·2H 2 O} n ( 2 ) (H 2 L = N -pyrazinesulfonyl-glycine) have been prepared by reaction of the same proportion Ni(CH 3 COO) 2 ·4H 2 O and H 2 L but with different pH values in water-ethanol mixed solution, and were characterized by X-ray diffraction, elemental analysis, IR spectrum. X-ray analysis indicates that 1 is a 3-D polymeric structure containing two different secondary building units (SBUs, NiN 4 O 2 and Na 2 O 8 ), in which two deprotonated L ligands coordinate in a facial tridentate arrangement about the Ni II atom. While complex 2 is a 1-D chain structure, in which three N atoms of two L ligands coordinate to one Ni II atom but its pyrazyl N atom monodentate-bridge to adjacent Ni II atom. Thus SBUs Ni(L)(H 2 O) 2 are obtained between two neighboring Ni II atoms and they connect one another to form this new polymer. In the crystal, two different hydrogen bond motifs and π ··· π stacking are found in 1 and 2 .