Synthesis,Structures And Study On Properties Of Mixed-Valent Mutlinuclear Complexes Based On Salicylaldehyde Schiff Base Ligands

Multinuclear coordination complexe with mixed oxidation states continues to attract much attention from groups around the world for its wide application prospects in the fields of magnetic chemistry,catalysis chemistry,biochemistry,as well as for the aesthetically pleasing structures it often produces.Salicylaldehyde Schiff base,one kind of ligand with excellent bioactivity and physicochemical properties,have many coordination sites and diverse coordination forms,which can form varieties of complexes with fascinating structure.Here,series of mixed-valent Mn-contained trinuclear complexes,Co-contained dinuclear complexes and hexamers of mononuclear have been prepared by using salicylaldehyde Schiff base and Mn???/or Co???salts as start materials.These coordination complexes have been characterized by X-ray diffraction,IR spectra,UV spectra,thermogravimetric analysis,and so on.In addition,the electrochemical and magnetic properties of these compounds are also studied.The main results are listed as follows:1.Two series of ligands containing salicylaldehyde Schiff base have been obtained by the reaction of alkylol amine and salicylaldehyde/or its derivatives,as follows:2-hydroxyethylimidogen methyl-4-X-phenol?X=H,Cl and Br;L=H₂mSea,H₂mSeb and H₂mSec,respectively?and 2-[?1,3-two hydroxypropane-2-imine?methyl]-4-X phenol?X=H,Cl and Br;L=H₃dSea,H₃dSeb and H₃dSec,respectively?.Computational chemistry and UV spectra of these ligands proved that the electron transfer in these ligands is influenced by the solvent.2.These salicylaldehyde Schiff base ligands reacted with Mn? salts in ethanol to produce six coordination complexes and single X-ray diffraction showed 2-2-2-6 are trinuclear-manganese compounds with line core[Mn?Mn?Mn?]:[Mn₃?mSeb?₂?OAc?4?H₂O?₂][Mn₃?mSeb?₂?OAc?4?CH3CH₂OH?₂]·8H₂O·2CH3CH₂OH?2-2?,[Mn₃?mSec?₂?O Ac?4?CH3CH₂OH?₂]·4H₂O?2-3?,[Mn₃?HdSea?₂?OAc?4?H₂O?₂]·4H₂O?2-4?,[Mn₃?Hd Seb?₂?OAc?4?CH3CH₂OH?₂]·4H₂O?2-5?and[Mn₃?HdSec?₂?OAc?4?CH3CH₂OH?₂]·4H₂O?2-6?.And there are multiple hydrogen bonds between trinuclear-manganese compounds and crystal-lattice solvent/or among these solvent molecules in the crystalic complexes.The magnetic properties show that there are antiferromagnetic behaviors between neighboring manganese atoms in all of these complexes.Electrochemical analysis indicated that the redox processes of these five compounds were reversible and the Mn???cation in them are more stable.3.The ligands 2-[?1,3-two hydroxypropane-2-imine?methyl]-4-X phenol reacted with Co?NO₃?₂·6H₂O in ethanol at room temperature to get three dinuclear Co-contained complexes with different oxide states?Co?Co??:[Co₂?HdSea?₂?H₂O?₂]·?NO₃?·H₂O?3-1?,[Co₂?HdSeb?₂]·?NO₃?·?5-ClSa?·4H₂O?3-2?,[Co₂?HdSec?₂]·?NO₃?·?5-ClSa?·4H₂O?3-3??5-ClSa=5-Chlorosalicylaldehyde?.These complexes are similar to amphiphile in hydrophilic and hydrophobic poles due to the difference of coordinate environment to cobalt cations,which reduced to hydrophobic chain/or layer in crystalic state.When the ligands were changed to 2-hydroxyethylimidogen methyl-4-X-phenol,three hexamers of mononuclear cobalt coordination complexes were gained:[Co?mSea?₂?HmSea?]6·12H₂O?4-1?,[Co?mSeb??HmSeb?]6?4-2?,[Co?mSec??HmSec?]6?4-3?.These hexamers were formed by strong hydrogen bonds between neighboring mononuclears in different asymmetric units around the sixfold rotation axes,and their structures are alike to the metallacrowns with six[M-N-O]and[M-N-N]repeat units.Interestedly,in compound 4-1,crystalic lattice waters join together to chair-form doube-layer?H₂O?12 water cluster.Then,the hexamers are linked by these water clusters through hydrogen bonds in?AB?.mode resulting to 1D tublar structure.Electrochemical analysis discovers the fact that the redox processes of these six Co-contained complexes were completely irreversible.