A UV birefringent crystal: RbNH4(H2C3N3O3)2·2H2O

Alkali-metal isocyanurate Cs3(H2C3N3O3)3(H3C3N3O3)·3H2O: synthesis and characterization

“…In general, alkali/alkaline earth metals without d–d or f–f transitions are also conducive to realize a wide band gap and large birefringence at the same time in isocyanurate. For example, RbNH 4 (H 2 C 3 N 3 O 3 ) 2 ·2H 2 O (Δ n cal = 0.4 at 1064 nm, E g = 4.72 eV) 25 and RbLi(HC 3 N 3 O 3 ) 2 ·H 2 O (Δ n cal = 0.18 at 514.6 nm, E g = 4.70 eV) 26 were reported as potential ultraviolet birefringent materials. As is well known, (H x C 3 N 3 O 3 ) x −3 groups are usually arranged in parallel, and the parallel arrangement of internal structures of compounds will lead to a large birefringence.…”

[C(NH2)3]2S2O8: combining delocalized and localized π-conjugate units to achieve strong optical anisotropy

“…10,11 Therefore, there are many strategies to design new birefringent crystal materials, including: (1) introducing planar π-conjugated groups ( e.g. , [BO 3 ], [B 3 O 6 ], [C 3 N 3 O 3 ] and [NO 3 ]); typical examples are Li 6 Zn 3 (BO 3 ) 4 , 12 BaTi(BO 3 ) 2 , 13 Ba 2 Mg(BO 3 ) 2 , 14 Ba 2 Mg(B 3 O 6 ) 2 , 15 Na 3 Ba 2 (B 3 O 6 ) 2 F, 16 AZn 4 (OH) 4 (C 3 N 3 O 3 ) 2 (A = Mg, Zn), 17 RbNH 4 (H 2 C 3 N 3 O 3 ) 2 ·2H 2 O, 18 Ba 3 (C 3 N 3 O 3 ) 2 , 19 Ba(NO 3 )Cl, 20 Cs 2 Pb(NO 3 ) 2 Br 2 , 21 (NH 4 ) 4 [B 12 O 16 F 4 (OH) 4 ], 22 Na[B 3 O 3 F 2 (OH) 2 ]·[B(OH) 3 ], 23 and A(H 3 C 3 N 3 O 3 )(NO 3 ); 24 (2) incorporating heteroanionic tetrahedral groups, such as [BO x F 4− x ]( x = 1–3), 25 [PO 3 F], 26,27 [PO 3 S], 28,29 and [SO 3 S]; 30,31 (3) adding d 0 metal cations with a second-order Jahn–Teller (SOJT) effect ( e.g. , Mo 6+ , V 5+ , and Nb 5+ ); 32–34 and (4) adding lone pair cations with stereoscopic activity ( e.g.…”