Doubling up on birefringence

One of the most birefringent solid materials known has been produced by researchers at Simon Fraser University in Canada using a coordination polymer based on the terpyridine ligand and the anisotropic, linear dicyanoaurate anion, rather than a mineral like calcite. Daniel Leznoff and Zuo-Guang Ye point out that the modular nature of coordination polymers offers great scope for fine-tuning their optical properties for particular applications, such as dual-focus lenses for optical disk readers. "The ability to judiciously choose a metal center, a chelating ligand, and a bridging ligand to tailor the overall physical and optical properties of the resulting polymer affords an exceptional design freedom in materials science," the researchers say.