Explorations of New Second-Order Nonlinear Optical Materials in the Potassium Vanadyl Iodate System

Four new potassium vanadyl iodates based on lone-pair-containing IO3 and second-order Jahn−Teller distorted VO5 or VO6 asymmetric units, namely, α-KVO2(IO3)2(H2O) (Pbca), β-KVO2(IO3)2(H2O) (P212121), K4[(VO)(IO3)5]2(HIO3)(H2O)2·H2O (P1), and K(VO)2O2(IO3)3 (Ima2) have been successfully synthesized by hydrothermal reactions. α-KVO2(IO3)2(H2O) and β-KVO2(IO3)2(H2O) exhibit two different types of 1D [VO2(IO3)2]− anionic chains. Neighboring VO6 octahedra in the α-phase are corner-sharing into a 1D chain with the IO3 groups attached on both sides of the chain in a uni- or bidentate bridging fashion, whereas those of VO5 polyhedra in the β-phase are bridged by IO3 groups into a right-handed helical chain with remaining IO3 groups being grafted unidentately on both sides of the helical chain. The structure of K4[(VO)(IO3)5]2(HIO3)(H2O)2·H2O contains novel isolated [(VO)(IO3)5]2− units composed of one VO6 octahedron linked to five IO3 groups and one terminal O2− anion. The structure of K(VO)2O2(IO3)3 exhibits a 1D [(VO)2O2(IO3)3]− chain in which neighboring VO6 octahedra are interconnected by both oxo and bridging iodate anions. Most interestingly, three of four compounds are noncentrosymmetric (NCS), and K(VO)2O2(IO3)3 displays a very strong second-harmonic generation response of about 3.6 × KTP, which is phase matchable. It also has high thermal stability, a wide transparent region and moderate hardness as well as an excellent growth habit. Thermal analyses and optical and ferroelectric properties as well as theoretical calculations have also been performed.

基于含孤对电子的IO3和二阶Jahn−Teller畸变的VO5或VO6非对称单元，成功合成四种新型钒酸钾碘酸盐，分别为α-KVO2(IO3)2(H2O)（Pbca）、β-KVO2(IO3)2(H2O)（P212121）、K4[(VO)(IO3)5]2(HIO3)(H2O)2·H2O（P1）和K(VO)2O2(IO3)3（Ima2）。其中，α-KVO2(IO3)2(H2O)和β-KVO2(IO3)2(H2O)展现出两种不同类型的1D [VO2(IO3)2]−阴离子链。在α相中，相邻的VO6八面体以角共享方式形成一个1D链，IO3基团以单齿或双齿桥接方式附着在链的两侧；而在β相中，VO5多面体通过IO3基团桥接形成右手螺旋链，剩余的IO3基团以非单齿方式附着在螺旋链的两侧。K4[(VO)(IO3)5]2(HIO3)(H2O)2·H2O的结构包含新颖的孤立[(VO)(IO3)5]2−单元，由一个VO6八面体与五个IO3基团和一个终端O2−阴离子相连而成。K(VO)2O2(IO3)3的结构展示出1D [(VO)2O2(IO3)3]−链，其中相邻的VO6八面体通过氧和桥接碘酸盐阴离子相互连接。最为引人注目的是，四种化合物中有三种为非中心对称（NCS），且K(VO)2O2(IO3)3表现出约3.6 × KTP的非常强的二次谐波产生响应，可实现相位匹配。此外，它还具备高热稳定性、宽透明区域、适中的硬度和良好的生长习性。对该系列化合物还进行了热分析、光学和铁电性质以及理论计算。