title: Polymorphism of Zn[Au(CN)2]2 and its luminescent sensory response to NH3 vapor.
abstract: Four polymorphic forms of the complex Zn[Au(CN)2]2 have been synthesized and both structurally and spectroscopically characterized. In each of the four polymorphs, a zinc center in a tetrahedral geometry with a Au(CN)2(-) unit at each tetrahedral vertex is observed. All four structures contain three-dimensional networks based on corner-sharing tetrahedra. Because of the long Au(CN)2(-) bridging unit, the extra space not occupied by one network is filled by two to five additional interpenetrated networks. Short gold-gold bonds with lengths ranging from 3.11 to 3.33 A hold the interpenetrated networks together. Three of the four polymorphs are luminescent, having solid-state emissions with wavelengths ranging from 390 to 480 nm. A linear correlation between the emission energy and the gold-gold distance was observed. Upon exposure to ammonia vapor, the polymers altered their structures and emission energies, with the emission wavelength shifting to 500 nm for {Zn(NH3)2[Au(CN)2]2}, which adopts a two-dimensional layer structure with octahedral, trans-oriented NH3 groups. The adsorption route is dependent on the polymorph used, with NH3 detection limits as low as 1 ppb. Desorption of the ammonia occurred over 30 min at room temperature.
authors.affiliation: Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada V5A 1S6.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Katz
authors.forename: Taramatee
authors.initials: T
authors.lastname: Ramnial
authors.forename: Hua-Zhong
authors.initials: HZ
authors.lastname: Yu
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Leznoff