A series of sulfates A2Bi2(SO4)2Cl4 (A = NH4, K, Rb) were synthesized, achieving a subtle balance of a large SHG effect and sufficient birefringence.

PO 4 ] 3− possesses small microscopic secondorder susceptibility and polarizability anisotropy, which inherently result in weak second-harmonic generation (SHG) and small birefringence. Herein, a new noncentrosymmetric phosphate, [C(NH 2 ) 3 ] 3 PO 4 •2H 2 O, was successfully designed and synthesized by a solution evaporation method. [C(NH 2 ) 3 ] 3 PO 4 •2H 2 O without metal ions is composed of planar conjugated guanidine cations and PO 4 tetrahedrons, which are connected by hydrogen bonds, forming a three-dimensional network. Physical property measurements indicate that the title compound displays an SHG response of 1.5 × KH 2 PO 4 (KDP) and a larger birefringence (0.055@546.1 nm) compared with most reported ultraviolet nonlinear optical phosphates. Furthermore, first-principles calculations reveal that the π-conjugated planar [C(NH 2 ) 3 ] + cations and [PO 4 ] 3− groups are responsible for its excellent linear and NLO properties.

To obtain new nonlinear optical (NLO) materials with a large second harmonic generation (SHG) effect has always been a great challenge. We have synthesized the first metal borate-iodate NLO crystal, Be 2 (BO 3 )(IO 3 ) (BBIO), by multicomponent modification of KBe 2 BO 3 F 2 (KBBF), in which the structural features of KBBF were maintained and (IO 3 ) À groups were connected to honeycomb [Be 2 BO 3 O 2 ] 1 layers. As the first KBBF family member with mixed anionic groups, BBIO benefited from the synergistic effect of (IO 3 ) À , (BO 3 ) 3À and (BeO 4 ) 6À groups, and exhibited a very strong SHG response of % 7.2 KH 2 PO 4 (KDP, @1064 nm) and a large birefringence (Dn) of 0.172 at 1064 nm. BBIO may, unexpectedly, optimize growth habits via van der Waals forces. This study presents borate-iodate as a new NLO material and it demonstrates opportunities in KBBF structural engineering. Creatinganewtypeofpolarornon-centrosymmetric(NCS)inorganic compounds is of great significance in the development of piezoelectric, pyroelectric, ferroelectric, and especially nonlinear optical (NLO) materials. Although significant efforts have been devoted to looking for new NLO crystals from various types of compounds, such as borates, carbonates, iodates, phosphates, sulfates, etc., [1] it is still very challenging to rationally design and synthesize polar or NCS crystals with large second harmonic generation (SHG) effects, sufficient birefringence, and wide band gaps from these traditional compound systems. Recently, mixing two types of NLO-active anionic groups in the same crystal has been proved as a convenient molecular design strategy for designing new NLO materials. Besides, it is possible to precisely tailor the physical and chemical properties of crystalline materials by hybridizing anionic groups with different properties. This strategy afforded several excellent NLO compounds with mixed anionic groups, such as Bi 3 TeBO 9 , [2] B 2 S 2 O 9 , [3] Pb 2 (BO 3 )(NO 3 ), [4] Ba 3 (ZnB 5 O 10 )PO 4 , [5] Nb 2 O 3 (IO 3 ) 2 (SO 4 ), [6] Sc(IO 3 ) 2 (NO 3 ). [7] However, borate-iodate mixed NLO materials have never been reported due to the difficulty in synthesis, though the combination of diverse B-O groups and (IO 3 ) À group with super large, microscopic second-order NLO susceptibility may lead to novel NLO crystals with excellent optical properties. Herein, the first borate-iodate NLO crystal will be reported.According to our previous report of the two centrosymmetric metal borate-iodates, Sr[B(OH) 4 ](IO 3 ) and Li 4 Sr 5 [B 12 O 22 (OH) 4 ](IO 3 ) 2 , [8] in which the B-O and (IO 3 ) À groups were isolated from each other and formed pseudotwo-dimensional (2D) layered structures with borate and iodate layers stacked alternately, a new synthesis strategy has been designed in this study. To obtain NCS borate-iodates, it may be better to construct a stable polar borate layer first as a polar structure inducer. Therefore, the most famous deepultraviolet (deep-UV) NLO crystal KBBF with honeycomb 2D [Be 2 BO 3 F 2 ] 1 layers was chosen...

An ammonium‐containing metal iodate fluoride compound, (NH4)Bi2(IO3)2F5, featuring a two‐dimensional double‐layered framework constructed by [BiO2F5]6− and [BiO4F4]9− polyhedra, as well as [IO3]− groups, was successfully synthesized. The well‐ordered alignment of these SHG‐active units leads to an extraordinary strong SHG response of 9.2 times that of KDP. Moreover, this compound possesses a large birefringence (Δn=0.0690 at 589.3 nm), a wide energy band gap (Eg=3.88 eV), and a high laser damage threshold (LDT; 40.2×AgGaS2). In particular, thermochromic behavior was observed for the first time in this type of compound. Such multifunctional crystals will expand the application of nonlinear optical materials.