The coordination chemistry of two symmetric double-armed oxadiazole-bridged organic ligands with copper salts

Abstract

Two new symmetric double-armed oxadiazole-bridged ligands, 4-methyl-{5-[5-methyl-2-(pyridin-3-ylcarbonyloxy)phenyl]-1,3,4-oxadiazol-2-yl}phenyl pyridine-3-carboxylate (L1) and 4-methyl-{5-[5-methyl-2-(pyridin-4-ylcarbonyloxy)phenyl]-1,3,4-oxadiazol-2-yl}phenyl pyridine-4-carboxylate (L2), were prepared by the reaction of 2,5-bis(2-hydroxy-5-methylphenyl)-1,3,4-oxadiazole with nicotinoyl chloride and isonicotinoyl chloride, respectively. Ligand L1 can be used as an organic clip to bind Cu(II) cations and generate a molecular complex, bis(4-methyl-{5-[5-methyl-2-(pyridin-3-ylcarbonyloxy)phenyl]-1,3,4-oxadiazol-2-yl}phenyl pyridine-3-carboxylate)bis(perchlorato)copper(II), [Cu(ClO4)2(C28H20N4O5)2], (I). In compound (I), the Cu(II) cation is located on an inversion centre and is hexacoordinated in a distorted octahedral geometry, with the pyridine N atoms of two L1 ligands in the equatorial positions and two weakly coordinating perchlorate counter-ions in the axial positions. The two arms of the L1 ligands bend inward and converge at the Cu(II) coordination point to give rise to a spirometallocycle. Ligand L2 binds Cu(I) cations to generate a supramolecule, diacetonitriledi-μ3-iodido-di-μ2-iodido-bis(4-methyl-{5-[5-methyl-2-(pyridin-4-ylcarbonyloxy)phenyl]-1,3,4-oxadiazol-2-yl}phenyl pyridine-4-carboxylate)tetracopper(I), [Cu4I4(CH3CN)2(C28H20N4O5)2], (II). The asymmetric unit of (II) indicates that it contains two Cu(I) atoms, one L2 ligand, one acetonitrile ligand and two iodide ligands. Both of the Cu(I) atoms are four-coordinated in an approximately tetrahedral environment. The molecule is centrosymmetric and the four I atoms and four Cu(I) atoms form a rope-ladder-type [Cu4I4] unit. Discrete units are linked into one-dimensional chains through π-π interactions.

Temperature-driven structural phase transitions in 0.05(Na0.50Bi0.50)TiO3-0.95NaNbO3 solid solution via amplitude mode analysis

“…Several studies have been carried out to study the effect of external strain on the properties of NaNbO3. It is found that the strain induced by the homovalent ion (Li x Na 1−x NbO 3 , K x Na 1−x NbO 3 ) and hetrovalent (Na 0.5 Bi 0.5 )TiO 3 (xNBT) [8,9,[20][21][22][23][24][25][26], BaTiO 3 [17,18,[27][28][29] CaTiO 3 [30,31], SrTiO 3 [7], BiFeO 3 [32,33], PbTiO 3 [34], etc., showed improvement in the ferroelectric and piezoelectric properties alongwith stabilization of various crystal structure.…”