Abstract:

Four novel Salen-type mono-and bi-nuclear complexes were synthesized by a metal template method, and were characterized by elemental analyses, hydrogen nuclear magnetic resonance (1H NMR), electrospray ionization mass spectroscopy (ESI-MS), Fourier transforminfrared (FT-IR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, and circular dichroism(CD)spectroscopy. The thermodynamic behavior of the Salen-type Ni (II) complexes were studied by UV-Vis and CD spectra. We found that the coordination numbers for imidazole (Im) and N-methylimidazole (N-MeIm)were 2, but for 2-Et-4-MeImand 2-MeImthey were 1. The association constants of the systems decrease according to the following order: KΘ(Im) >KΘ(N-MeIm) >KΘ(2-Et-4-MeIm) >KΘ(2-MeIm). The thermodynamic parameters △rHΘm and △rSΘm were also determined. Results showed that the axial coordination process was driven by enthalpy and entropy.

Key words: Metal template method, Novel Salen-type complexes, Synthesis and characterization, Thermodynamics of axial coordination, Circular dichroismspectrum