The Study Of Coordination Complexes With Asymmetric Schiff Base Based On Diaminomaleonitrile-acyl Chloride

Schiff bases and its complexes are extensively studied for biological activity, catalytic activity, optical property and have a wide range of applications in catalyst, advanced materials, bio- medicine, so they have aroused great interest among researchers. Due to its special structure, asymmetric Schiff bases have important research value and implementation prospect in the area of particular properties, for example catalyst, fluorescent switch and the design of functional supermolecule. Compared to symmetric Schiff bases, the synthesis of asymmetric Schiff bases is relatively difficulty and guided by little references. Looking for appropriate reaction conditions and synthetic methods to prepare asymmetric Schiff bases and its metal complexes is a challenging task.This paper studies the synthesis of asymmetric Schiff bases and its complexes based on diaminomaleonitrile-acyl chloride on the basis of Hui Li group’s previous work. We obtained single acylation product N-acetyl condensing diaminomaleonitrile（Ac-DAMN） using diaminomaleonitrile and acyl chloride. Then, we synthesized N-acetyl-N’-salicylaldehyde condensing diaminomaleonitrile（H₂L1） and N-acetyl-N’-（2-hydroxyl-1-naphthaldehyde） condensing diaminomaleonitrile（H₂L2） by condensation of Ac-DAMN and salicylaldehyde, 2-hydroxy-1-naphthaldehyde, respectively. We also obtained single acylation product N- furoyl condensing diaminomaleonitrile（O-DAMN） using diaminomaleonitrile and 2-furoyl chloride. Then, we synthesized N-furoyl-N’-salicylaldehyde condensing diaminomaleonitrile（H₂L3） by condensation of O-DAMN and salicylaldehyde.We obtained seven kinds of metal complexes: complex Zn L1·CH3OH（1）, complex Co-L2（2）, complex N i L2·2CH3OH·CH3CN（3）, complex Cu-L2（4）, complex Zn-L2（5）, complex Cd L2·CH3CH₂OH（6） and complex Mn-L2（7）. We obtained the single crystal structure of complex（1）,（3）,（5）,（6） and studied their single crystal structure by the X-ray single crystal diffraction analysis. Complex（1） is one-dimensional structure through coordinating with oxygen atom of acetyl; complex（3） is hexa-coordinate mononuclear structure; complex（5） is symmetric structure which is different from the expected and need more studies; complex（6） is dual- nuclei spatial structure through coordinating with oxygen atom of hydroxyl and form one-dimensional structure by connecting with nitrogen atom of cyanogroup. The experimental results show that complex（2） and（3） are isomorphic. We also try to synthesize complex of H₂L3, but we haven’t obtained and need more experiments. These ligands and coordination complexes are characterized by IR, element analysis, 1H-NMR, UV-Vis absorption, fluorescence spectra, TGA, X-ray single crystal diffraction analysis and PXRD. However, we need study more functional properties of complexes.At present, the synthetic method of asymmetric Schiff bases controlled by acyl chloride is unusual. This paper provide a new method of synthesis asymmetric Schiff bases.