Different conjugated system Zn(II) Schiff base complexes: supramolecular structure, luminescent properties, and applications in the PMMA-doped hybrid materials

A series of Zn(II) complexes with different conjugated systems, [(ZnLCl2)-Cl-1](2) (Zn1), [(ZnLCl2)-Cl-1] (Zn2), [Zn(L-3)(2)]center dot(ClO4)(2) (Zn3), [(Zn2LCl4)-Cl-4] (Zn4), and [(ZnLCl2])-Cl-5 (Zn5), were synthesized and subsequently characterized via single crystal X-ray diffraction, H-1 and C-13 NMR, FT-IR, elemental analyses, melting point, and PXRD. The X-ray diffraction analyses revealed that the supramolecular frameworks of complexes Zn1Zn5 are constructed by C-H center dot center dot center dot O/Cl hydrogen bonds and pi center dot center dot center dot pi interactions. Complexes Zn1-Zn3 feature 3D 6-connected {4(12)center dot 6(3)} topological structures, whereas complex Zn4 exhibits a 3D 7-connected supramolecular framework with a {4(17)center dot 6(4)} topological structure. However, complex Zn5 shows one-dimensional " wave-like" chains. Based on these varied structures, the emission maximum wavelengths of complexes Zn1-Zn5 can be tuned in a wide range of 461-592 nm due to the red shift direction of lambda(em) caused by different conjugated systems and their electron donating abilities. Complex Zn3 shows a strong luminescence in the solid state and in the acetonitrile solution. Therefore, a series of Zn3-poly(methylmethacrylate) (Zn3-PMMA) hybrid materials were obtained by controlling the concentration of complex Zn3 in poly(methylmethacrylate) (PMMA). At an optimal concentration of 4%, the doped polymer film of Zn3-PMMA displays strong green luminescence emissions that are 19-fold in the luminescence intensities and 98 degrees C higher in the thermal stability temperature compared to the Zn3 film.