(C₁₀N₂H₁₀)(HI₂O₆)(HIO₃)(IO₃): A Birefringent Material Featuring Large π-Conjugated Organic Cation and Two Types of Iodate Anions

Abstract

Birefringent crystals, which can modulate and polarize light, play a vital role in the development of optical sensors and optoelectronic devices. Herein, we synthesized a new birefringent crystal [(C 10 N 2 H 10 )-(HI 2 O 6 )(HIO 3 )(IO 3 )] with large birefringence by integrating the large πconjugated 4,4′-bipyridine group with two types of iodates anions ([IO 3 ] − and [HI 2 O 6 ] − ) characterized by high polarizability anisotropy and strong stereochemically active lone pairs (SCALP).The crystal exhibits a large measured birefringence of 0.171 at 550 nm, surpassing most organic− inorganic hybrid iodate birefringent materials reported in the literature. Theoretical analyses reveal that the optical properties of the crystal arise primarily from the synergistic interactions between the π-conjugated 4,4′-bipyridine group and I−O groups. This research presents an effective method for the strategic integration of large π-conjugated organic cations into iodates, facilitating the design of novel birefringent materials and encouraging further exploration of superior birefringent substances.