K₃C₆N₇O₃·2H₂O: A Multifunctional Nonlinear Optical Cyamelurate Crystal with Colossal π-Conjugated Orbitals

Abstract

The delocalized π-conjugated units are considered as an advantageous gene for improving the optical nonlinearity of acentric crystals. For the first time, we synthesized a new acentric SHG-active metal cyamelurate crystal K 3 C 6 N 7 O 3 •2H 2 O (I) by a facile solution method, containing a colossal planar π-conjugated (C 6 N 7 O 3 ) 3− unit. It displays a strong second-order harmonic generation (SHG) of 4 × KDP and a giant anisotropic birefringence of 0.446 at 1064 nm. The theoretical calculations reveal that such substantial improvement is contributed from the strong molecular susceptibility of (C 6 N 7 O 3 ) 3− units and their near-perfect coplanar arrangement. Moreover, I exhibits a broadband ultraviolet photoluminescence at 366 nm, suggesting its multifunctional capacity and great potential for compact highly integrated optoelectronic devices.

A UV solar-blind nonlinear optical crystal with confined π-conjugated groups

“…It is noted that the SHG efficiency of the reported RPNCO is relatively higher than that of previously reported compounds containing π-conjugated rings, such as Y 5 (C 3 N 3 O 3 )(OH) 12 (2.5 × KDP) and Yb 5 (C 3 N 3 O 3 )(OH) 12 (3.8 × KDP), 27 CsAlB 3 O 6 F (2.0 × KDP), 28 CsZn 2 B 3 O 7 (1.5 × KDP), 29 (C 5 H 6 ON) + (H 2 PO 4 ) − (3.0 × KDP), 11 NaRb 0.84 Cs 0.16 HC 3 N 3 O 3 •2H 2 O (3.0 × KDP), 30 (C 4 H 6 N 3 ) + (H 2 PO 3 ) − (2.0 × KDP), 31 and K 3 C 6 N 7 O 3 •2H 2 O (4.0 × KDP). 32 The birefringence value of RPNCO was estimated using a polarizing microscope. Fast and slow polarized lights were observed after passing light with a wavelength of 550 nm into an anisotropic single crystal.…”

ε-La(IO3)3: A Polar Iodate with High Thermal Stability and a Large Second-Harmonic-Generation Response Obtained by a Supercritical Hydrothermal Method

“…1−3 At present, researchers continue to explore new materials and methods to expand the laser band, which would provide rich laser light sources to meet the demand of modern economic and social development. 4,5 At the important mid-IR (3−5 and/ or 8−12 μm) atmospheric transparency windows, the mid-IR NLO crystals have been widely used in IR solid-state lasers, and they can produce a wide range of applications in various fields, such as IR medical instruments, atmospheric harmful gas monitoring, and photoelectric countermeasures. 6−9 The commercial mid-IR crystals AgGaS 2 10 and ZnGeP 2 11 both have their own shortcomings such as low laser-damage threshold and two-photon absorption, which cannot meet the high-performance demands of modern laser technology and limit their further wide applications.…”

“…Nonlinear-optical (NLO) crystals are one kind of the most important optoelectronic information functional materials that have been playing important roles in laser technology, such as laser communication, optical parametric oscillation, integrated circuits, military technology, and so on. − At present, researchers continue to explore new materials and methods to expand the laser band, which would provide rich laser light sources to meet the demand of modern economic and social development. , At the important mid-IR (3–5 and/or 8–12 μm) atmospheric transparency windows, the mid-IR NLO crystals have been widely used in IR solid-state lasers, and they can produce a wide range of applications in various fields, such as IR medical instruments, atmospheric harmful gas monitoring, and photoelectric countermeasures. − The commercial mid-IR crystals AgGaS 2 and ZnGeP 2 both have their own shortcomings such as low laser-damage threshold and two-photon absorption, which cannot meet the high-performance demands of modern laser technology and limit their further wide applications. Therefore, more efforts should be made to explore new NLO crystals in this region.…”

Rational Design of Noncentrosymmetric Organic–Inorganic Hybrids with a π-Conjugated Pyridium-Type Cation for High Nonlinear-Optical Performance

“…In the various fundamental building blocks, π-conjugated groups, such as (BO 3 ) 3– and (B 3 O 6 ) 3– , may be the most important and successful due to their large optical anisotropy and remarkable microscopic second-order susceptibility, which have been demonstrated in the excellent NLO crystals, e.g., KBBF, LBO, and BBO, and also encouraged the exploration of more π-conjugated units with appealing structural features, ,,− e.g., (C 3 N 3 O 3 ) 3– , (C 6 N 7 O 3 ) 3– , [C­(NH 2 ) 3 ] + , etc. For example, an intricate 2D [Li­(HC 3 N 3 O 3 )­O] − layer featuring KLi­(HC 3 N 3 O 3 )·2H 2 O shows a large second-harmonic-generation (SHG) response (5.3 × KDP) with a large birefringence (Δ n = 0.186 at 514 nm) .…”

“…For example, an intricate 2D [Li­(HC 3 N 3 O 3 )­O] − layer featuring KLi­(HC 3 N 3 O 3 )·2H 2 O shows a large second-harmonic-generation (SHG) response (5.3 × KDP) with a large birefringence (Δ n = 0.186 at 514 nm) . K 3 C 6 N 7 O 3 ·2H 2 O containing a colossal planar π-conjugated (C 6 N 7 O 3 ) 3– unit displays a strong SHG intensity of 4 × KDP and a giant anisotropic birefringence of 0.446 at 1064 nm …”