A pair of novel helical Zn(II) enantiomers constructed from l- and d-threonine Schiff bases: Synthesis, crystal structures and properties

• Assembly of l- and d-threonine Schiff bases with Zn2 + gave a pair of enantiomers.
• Compound 1 exhibits a 1D right-handed helical chain and 2 is left-handed.
• Both complexes exhibit 2D homochiral supramolecular structures via hydrogen bonds.
• 1 and 2 exhibit blue shift behavior and enhanced luminescence phenomenon.

Two novel homochiral helical Zn(II) coordination polymers, {[Zn2(nap-l-thr)2(H2O)2]·H2O}n (1) and {[Zn2(nap-d-thr)2(H2O)2]·H2O}n (2) (H2nap-l-thr = N-(2-hydroxy-1-naphthylmethylidene)-l-threonine, H2nap-d-thr = N-(2-hydroxy-1-naphthylmethylidene)-d-threonine) have been successfully synthesized and characterized by elemental analysis, IR, UV–visible and single-crystal X-ray diffraction. It is interesting to note that both complexes are a pair of enantiomers: 1 exhibits 1D right-handed helical chain of [Zn-COO−]∞ and 2 is 1D left-handed helical chain of [Zn-COO−]∞. There are various hydrogen bonds between the adjacent helical chains which result in a 2D homochiral supramolecular layer structure. Notably, under similar synthetic procedure by using the NO3−, CH3COO−, Cl− salts of Zn2 + ion as a starting reagent, and identical compounds were obtained. In addition, the chiral nature of complexes 1 and 2 are confirmed by the results of circular dichroism (CD) spectra measurements. Thermal stability and luminescence properties were also investigated.

A pair of enantiomers of Zn(II) coordination polymers have been constructed from l- and d-threonine Schiff bases, and two Zn(II) complexes 1 and 2 exhibit interesting 1D right- and left-handed helical chains, respectively. Both complexes were characterized by X-ray crystallography, PXRD, TGA, CD measurements and luminescence properties.Figure optionsDownload as PowerPoint slide