Synthesis And Characterization Of Novel Schiff Bases And Their Metal Complexes

Schiff base has become a subject of research and attention due to its good biological activity.As a main feature,the structural flexibility of Schiff bases broadens their applications,including antibacterial,anti-cancer,catalytic,materials,anti-corrosion,fluorescence probes etc.Meanwhile,Schiff base has potential coordination ability,so its complexes are now becoming an important part of coordination chemistry,and the application field is constantly being expanded.This paper mainly introduces the preparation of ketone Hydrazone from benzoin or 4'-phenyl-acetophenon by reacting with hydrazine hydrate respectively.Then the Schiff base ligands were prepared by reacting with aromatic aldehydes or ketones.The structure of ligands was determined by elemental analysis,Nuclear Magnetic Resonance and X-ray single crystal diffraction,and then the obtained Schiff bases coordinated with transition metal ions.In the end,two kinds of copper ion complexes with good crystallinity were successfully synthesized by changing the reaction conditions,reaction solvents and other methods.An unexpected global disorder has been discovered during an X-ray investigation of the crystal structure of(E)-(1-(biphenyl-4-yl)ethylidene)hydrazine(BEH)at room temperature.But when the temperature decreases to 273 K,the disorder disappears.The results of this study establish the order and disorder crystal structures of BEH and,thereby,identify the nature of the phase transition.It is shown that the order-disorder transition is due to the onset of molecule rotation and glide under proper conditions.Generally,in order for a molecule to be present with this type of disorder in crystal structure,it must satisfy two criteria: First,it must have one or more flexible bonds that can rotate freely with energy barriers low enough so that it is preferably populated in several conformations at the ambient temperature.Second,it must have enough spaces separating adjacent molecules away that required movements will not encounter insurmountable collisions.Experimental and theoretical studies on UV-Vis and fluorescence spectra impart an understanding on the prediction methods of optical properties,which are essential for rational design of the biphenyl based materials with pre-defined properties.