AZn₄(OH)₄(C₃N₃O₃)₂ (A = Mg, Zn): Two Zn-Based Cyanurate Crystals with Various Cation Coordination and Large Birefringence

Abstract

Cyanurate crystals have recently become a research hot spot in birefringent materials owing to the large structural and optical anisotropy of the planar π-conjugated (H x C 3 N 3 O 3 ) x−3 (x = 0−3) groups. In this study, two new Zn-based cyanurate crystals, Zn 5 (OH) 4 (C 3 N 3 O 3 ) 2 and MgZn 4 (OH) 4 (C 3 N 3 O 3 ) 2 , were synthesized by the hydrothermal method. In Zn 5 (OH) 4 (C 3 N 3 O 3 ) 2 , the d 10 Zn 2+ cations have three different coordinating environments, which has never been found in cyanurates. These compounds have wide band gaps (∼5 eV) and large birefringence (∼0.32 at 400 nm), indicating their potential as ultraviolet birefringence crystals.

Crystal clear: unveiling giant birefringence in organic–inorganic cocrystals

“…43 Organic six-membered ring groups (6-MRs) have been identified as excellent birefringence-active groups with considerably larger Δα, such as [H x C 3 N 3 O 3 ] (3-x)-(x = 0 -3) and C 3 N 6 H 7 + . [44][45][46][47] As a result, organic 6-MRs compounds with substantial birefringence have been reported. [48][49][50] However, although NO 3and organic 6-MRs have attractive Δα, these groups will red-shift the bandgaps, posing an obstacle to their potential application in the UV regions.…”

[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.…”

Zn(C6H4NO2)2·4H2O: A Solar-Blind Birefringent Crystal

“…33,34 For example, the birefringence of AZn 4 (OH) 4 (C 3 N 3 O 3 ) 2 (A = Mg, Zn) is slightly less than 0.32@400 nm, and the birefringence of A 2 Zn(H 2 C 3 N 3 O 3 ) 4 •4H 2 O (A = K, Cs) is 0.264−0.305@800 nm. 35,36 And in the given example, the crystal alignment is a parallel or quasi-two-dimensional structure arrangement, which also means that the potential of birefringence in the cyanate system has been excavated almost completely. But be that as it may, the birefringence of the above two is lower than that of 1 by 0.05, in the case of also belonging to the solar-blind crystal.…”