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.