ABSTRACT: Birefringence and second harmonic generation (SHG) are important optical properties of functional crystals. However, it is relatively rare for a compound to exhibit both enhanced properties simultaneously. In this study, we used DFT calculations to discover an ideal functional gene: protonated 3,5-dipicolinic acid (C7H4NO4, HDPA). By combining HPDA with the traditional IO3- anion, we obtained a non-centrosymmetric and polar semiorganic iodate, namely HDPA(IO3). The organic cations and iodate anions in HDPA(IO3) are bridged via the N-H···O and O-H···O hydrogen bonds, forming the wave-shaped layers. The synergistic effect between the expanded π-conjugation of the organic cation and the stereochemically active lone pair electrons in the inorganic iodate anion results that HDPA(IO3) exhibiting a strong SHG effect, 3.6 times that of KH2PO4, and an unusually large birefringence of 0.35 at 546 nm, larger than most of SHG-active iodates. Additionally, HDPA(IO3) has a wide bandgap of 4.12 eV with a corresponding cutoff edge at 269 nm, indicating its potential as a promising short-wave ultraviolet (UV) optical crystal.
文章链接：https://doi.org/10.1016/j.cclet.2024.110513
