Pyrazinamide-IBr: An Organic-Inorganic Hybrid Crystal Exhibiting Giant Optical Anisotropy

Abstract

A novel organic-inorganic hybrid crystal, pyrazinamide-IBr (PZA-IBr, C5H5N3OIBr), was successfully synthesized using a facile in-situ reduction method. PZA-IBr exhibits remarkable birefringences (Δnexp= 0.524 at 550 nm，Δncal= 0.760 at 550 nm), surpassing those of commercially available birefringent crystals. PZA-IBr also has a moderate band gap of 2.32 eV. Structural and theoretical analyses reveal that the large birefringence originates from both the planar π-conjugated PZA and linear IBr molecules and is enhanced by the N-I halogen bonds, N–H⋯O hydrogen bonds, and C–H⋯π interactions. This work demonstrates the effectiveness of combining a heterocyclic molecule with an interhalogen molecule to create high-performance birefringent crystals.