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C4H5N3O5, triclinic, P1‾ $P\overline{1}$ (no. 2), a = 6.3017(7) Å, b = 6.9235(7) Å, c = 8.2333(8) Å, α =100.604(3)°, β = 90.862(4)°, γ = 108.102(4)°, V = 334.60(6) Å3, Z = 2, R gt(F) = 0.0616, wR ref(F 2) = 0.1414, T = 170.0 K.

C4H5N3O2, monoclinic, P21/c (no. 14), a = 4.0668(13) Å, b = 11.198(4) Å, c = 6.137(2) Å, β = 97.033(11)°, V = 277.40(16) Å3, Z = 2, Rgt(F) = 0.0444, wRref(F2) = 0.1048, T = 170.00 K.

Recently, diverse twisting structures have been discovered to be a potential approach to design liquid crystal polarization gratings and lenses (LCPGs and LCPLs) with a high diffraction efficiency, broad bandwidth, wide view, and large diffraction angle. In this review, we divide these twisting structures into two main types, namely, multi-layer twisting structures with phase compensation and twisting structures forming Bragg diffraction. We found that multi-layer twisting structure LCPGs and LCPLs presented a broader bandwidth and a wider view angle by phase compensation. While for transmissive or reflective Bragg LCPGs, a large diffraction angle with high diffraction efficiency could be achieved. Based on the theoretical analysis in the review, potential research directions on novel twisting structures were prospected.

C20H20ClN5OS, triclinic, P1̅ (no. 2), a = 8.668(1) Å, b = 8.733(1) Å, c = 13.554(2) Å, α = 94.673(9)°, β = 94.73(1)°, γ = 101.841(9)°, V = 995.6 Å3, Z = 2, Rgt(F) = 0.0410, wRref(F2) = 0.1118, T = 296 K.

C12H10Br3NO3, orthorhombic, Pbca (no. 61), a = 12.942(2) Å, b = 10.304(2) Å, c = 21.527(3) Å, V = 2870.5 Å3, Z = 8, Rgt(F) = 0.0385, wRref(F2) = 0.0868, T = 296 K.