Construction Of New Supramolecular Systems Based On Bipyridine - (piperazine) - Ligand

A series of oxadiazole-containing dipyridyl linkers, including 2,5-bis(2-pyridyl)-1,3,4-oxadiazole (L1), 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (L2) and 2,5-bis(4-pyridyl)-l,3,4-oxadia-zole (L3), are introduced to prepare novel metal supramolecular complexes, which were characterized by IR, UV-vis, elemental analysis, thermogravimetric (TG) analysis and X-ray diffraction technique. The reaction of L1 with Cu(OAc)2·H2O in a CH3OH/CH3CN medium produces a new monometallic CuⅡ complex 1 [Cu(L4)(OAc)(H2O)](H2O)2(CH3CN), where HL4 = N-(a-hydroxyl-2-pyridyl)-N'-(a-methoxy-2-pyridyl)ketazine (C13H12N4O2). The results revealed that metal-assisted alcoholysis of L1 leads to the open of the central oxadiazole ring to give a new ligand HL4 during this course. The reaction of L2 with CuⅡ(BF4)2 or CuⅠ(ClO4) salt affords a bimetallic macrocyclic compound [Cu2(L2)2(H2O)6](BF4)4·(H2O)3·(CH3OH)0.5 (2) (similar to its CuⅡ(ClO4)2 complex) or a novel trigonal-prismatic cage-shape species [(H2O)(?) Cu2(L2)3(CH3CN)2](ClO4)2 (3), respectively. However, substituting L2 with its analogous L3 to react with Cu'(BF4) yields a 1-D infinite chain array {[Cu(L3)2(CH3CN)](BF4)-(H2O)i.5}n (4), being similar to its CuⅠ(ClO4) compound. A new supramolecular compound [Zn(H2EDTA) (H2O)](Q)2(H2O)2 (5), in which H4EDTA = ethylenediaminetetraacetic acid and Q = 4-(carboxylate)pyridinium, has been prepared by mild hydrothermal reaction and X-ray single-crystal diffraction of 5 revealed that the ZnⅡ ion coordinates to the chelating tetradentate ligand H2EDTA and a water molecule, taking a distorted trigonal bipyramid geometry. The reaction of L2 with Fe(ClO4)2-6H2O and auxiliary NH4SCN in a H2O/CH3CN medium affords a new mononuclear complex [Fe(L2)2(NCS)2(H2O)2] (6), and the subunits are linked to form a three-dimensional array through hydrogen bonds and π stacking interactions.Reaction of 2,5-bis(pyrazine)-l,3,4-oxadiazole (bpzo) with a series of inorganic AgX salt in CHCl3/OH(CH2)2OH/CH3OH gave products 7-10 with general formula {[Ag(bpzo)]X-solvent}n (X = BF4-, AsF6-, CF3SO3- and SbF6-, respectively, and solvent = 1.5H2O for 7). Alternatively, reaction of bpzo with AgBF4 in CH3CN generated quite unstable crystals of {[Ag(bpzo)](BF4)1/2(OH)1/2·(CH3CN)1/4}n 11. The crystal structures of all five complexes consist...