Synthesis,Structures And Properties Of Metal Complexes Based On Pyrazine Hybroxamic Acid And Pyrazinoxime

The pyrazine-oximes ligands contain more than one N and O atoms which makes them easily to coordinate with various metal ions to form lots of stable complexes and some of them are metallacrown which contain the M-N-O repetivive unit forming a annular structure.In-depth studies have revealed that this kind of complex exhibits unique chemical properties in terms of reaction catalysis,biological activity and magnetic.Some metallacrowns which contain the transition metal ions such as Cu^II,Mn^III,Co^II,Fe ^III,Ni^II and so on will exhibit the single-molecular magnetic behavior.Based on the study of metal crown ether monomolecular magnets,the selection of suitable ligands and metal salts to construct complexes with unique structure is expected to make a breakthrough in the study of monomolecular magnets.Besides,the pyrazine-oximes ligands could be not only the terminal-ligand but also the bridge-ligand because of the double N atoms in the pyrazine ring and the existence of this characteristic might bring some new metal complexes with novel structures.Therefore,we chose these ligands to react with metal salts to obtain metal complexes and their structures were characteristiced by NMR,elemental analysis,infrared spectroscopy,X-ray single crystal diffraction.The main work of this paper is as follows:1.We synthesized the pyrazinohybroxamic acid ligand?H₂pyzha?.Six 3d-4f complexes were obtained by reactions with cobalt nitrate and rare-earth nitrate:[Dy?pyzic?{Dy₃Co₂?pyzha?₆?*pyzha??NO₃?₂?H₂O??MeOH?₂}]₂?2?NO₃??10H₂O?8MeOH?1?,[Ho?pyzic?{Ho₃Co₂?pyzha?₆?*pyzha??NO₃?₂?H₂O??MeOH?₂}]₂?2?NO₃??10H₂O?8MeOH?2?,[Tm?pyzic?{Tm₃Co₂?pyzha?₆?*pyzha??NO₃?₂?H₂O?₂?MeOH?}]₂?2?NO₃??14H₂O?8MeOH?3?,[Y?pyzic?{Y₃Co₂?pyzha?₆?*pyzha??NO₃?₂?2H₂O??MeOH?₂}]₂?2?NO₃??10H₂O?8MeOH?4?[Er?pyzic?{Er₃Co₂?pyzha?₆?*pyzha??NO₃??H₂O?₃?OH?}]₂?2?NO₃??26H₂O?4MeOH?5?,[Yb?pyzic?{Yb₃Co₂?pyzha?₆?*pyzha??NO₃??H₂O?₃?OH?}]₂?2?NO₃??18H₂O?8MeOH?6?.These complexes have the similar butterfly topology.The wing of the butterfly contains a new 12-MC-4 metallacrown with Co-N-O-Ln repetitive unit.Unexpectedly,there is a new coordination mode of the pyrazinohybroxamic acid founded in this structure.Magnetic measurement reveals that the complex 1 exhibits slow magnetic relaxation.2.The pyrazinohybroxamic acid ligand?H₂pyzha?reacted with copper trifluoromethane sulfonate and rare-earth trifluoromethane sulfonate and obtained seven3d-4fcomplexes:{[Gd?H₂O?₃{Cu?pyzha?}₅?MeOH?₃]?3?TfO??3?H₂O?}_n?7?,{[Tb?H₂O?₃{Cu?pyzha?}₅?H₂O?₂]?3?TfO??6?H₂O?}_n?8?,{[Dy?H₂O?₃{Cu?pyzha?}₅?H₂O?₂]?3?TfO??5?H₂O?}_n?9?,{[Gd?H₂O?₂?MeOH?₂{Cu?pyzha?}₅?MeOH?₂]?3?TfO??5H₂O}_n?10?,{[Tb?H₂O?₂?MeOH?₂{Cu?pyzha?}₅?H₂O??MeOH?₃]?3?TfO??2H₂O?MeOH}_n?11?,{[Tb?H₂O?₃{Cu?pyzha?}₅?H₂O?₃]?3?TFO??3?H₂O???MeOH?}?12?,{[Dy?H₂O?₃{Cu?pyzha?}₅?H₂O?₃]?3?TFO??3?H₂O???MeOH?}?13?.The spatial structuers of complexes 7-9 presented a 2D network and complexes 10 and 11 were 1D chain-like structuer.The repetitive unit of complexes 7-11 was the 15-MC-5 metallacrown which connected with each other by the coordination of the Cu ion that located in the ring of the metallacrown and theouter N atom in the ring of pyrazine.The complexes 12 and 13 were common 15-MC-5 metallacrown.Magnetic measurement reveals that the complex 9exhibits single-molecular magnet behavior.The analysis of N₂ gas adsorption of complexes7-9 reveals that they are non-porous coordination polymers.3.We synthesized the 2-pyrazilaldoximato ligand?Hpyzaox?.Four complexes were obtained by reactions with transition metal salts and rare-earth salts:[Fe₂?pyzaox?₃?H₂O?₃]?2?NO₃???OH??5?H₂O??14?,[Fe₂?pyzaox?₃?H₂O?₃]?2?NO₃???OH??2?H₂O???Dy?NO₃?₃3?H₂O???15?,[Fe₃?pyzaox?₆]?6?TfO??3?H₃O??10?H₂O??2?MeOH??16?,[{Cu₂?pyzaox?₂?H₂O?₂}?2?TfO??2?H₂O???MeOH?]_n?17?.The complexes 14 and 15contained twoFe³⁺ions and the complexes 16 cotained three Fe³⁺ions respectively.The complex 17 is a 2D complex whose repetitive unit is a binuclar Cu component which is connected with each other by the coordination of the Cu ion and the outer N atom in the ring of pyrazine.Magnetic measurement reveals that the complex 16 exhibits slow magnetic relaxation.