From pair quadruple- to single-stranded helices to lines in a mixed ligand system via adjusting the N-substituent of L-Glu.

ABSTRACT

Utilizing the mixed-ligand strategy, a novel fourfold-interpenetrated 3D homochiral metal-organic framework (1) with rare pair quadruple-stranded helices was assembled from bpee (1,2-bis(4-pyridyl)ethylene) and NCG (N-carbamyl-l-glutamate). Changing the carbamyl substituent of NCG with benzoyl group (NBzG N-benzoyl-l-glutamate), a non-interpenetrated 3D homochiral coordination polymer (2) composed of alternate right-handed and left-handed single helix was obtained. When p-tolylsulfonyl substituent was used instead, an interesting homochiral linear structure (3) was formed from mixed-ligand bpee and NTsG (N-p-tolylsulfonyl-l-glutamate), with all individual NTsG being lined up orderly. The steric hindrance of N-substituent of l-glu has a tremendous impact on the construction of these diverse frameworks. Complexes 1-3 display second harmonic generation (SHG) efficiencies, which are approximately 0.32, 0.45, and 0.55 times as much as that of KDP powder.