作者:Wen-Juan Ma、Zhi-Yang Gao、Shu Zhu、Ben-Lai Wu
DOI:10.1016/j.poly.2014.02.021
日期:2014.5
Tetranuclear square grids, namely, [Cd-4(L-O)(4)]center dot 1.5DMF (1), [NI4(L-O)(4)]center dot H2O (2), [Zn-4(L-O)(4)]center dot 3H(2)O (3), [Zn-4(L-O)(4)] (4), [Cu-4(L-O)(4)]center dot H2O (5), and [Cu-4(L-O)(4)][Cu-4(L-O)(4)]}center dot 2.5DMF center dot 1.5H(2)O (6) (DMF = N,N-dimethylformarnide, H2L-O = 2,6-bis(pyrazine-2-carboxamido)pyridine-N-oxide), formed by the reactions of M ions (M = Cd-II, Ni-II, Zn-II and Cu-II) with pyridyldicarboxamide ligands 2,6-bis(pyrazine-2-carboxamido)pyridine (H2L), was fully characterized. Notably, the central pyridines of ligands H2L were oxidized into pyridine-N-oxides under air conditions, producing the new anionic ligands (L-O)(2-) to fabricate those grids. In those square grids every octahedrally coordinated metal node is chelated by two doubly deprotonated ligands (L-O)(2-) in the mer configuration, and each ligand (L-O)(2-) acts as a rigid bis(tridentate) linker with the N-carboxamide and one N-pyrazine in each arm chelating metal ions plus the O atom in the pyridine-N-oxide group bridging the two bound M ions. The Cd-II and Zn-II grids show uncommonly-excellent thermal stabilities and interesting green emissions. Magnetic studies upon grid [Ni-4(L-O)(4)] suggest an antiferromagnetic coupling between the adjacent Ni-II mainly exchanged through mu-O with a coupling constant of J = -15.06 cm(-1). (C) 2014 Elsevier Ltd. All rights reserved.