From Pair Quadruple- to Single-Stranded Helices to Lines in a Mixed Ligand System via Adjusting the N‑Substituent of l‑Glu

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.