title: Structure and photoluminescence of silver(i) trinuclear halopyrazolato complexes.
abstract: Five halogen substituted pyrazolates, 4-chloro-3,5-diisopropylpyrazole (4-Cl-3,5-iPr2pzH), 4-bromo-3,5-diisopropylpyrazole (4-Br-3,5-iPr2pzH), 4-iodo-3,5-diisopropylpyrazole (4-I-3,5-iPr2pzH), 4-chloro-3,5-diphenylpyrazole (4-Cl-3,5-Ph2pzH), and 4-bromo-3,5-diphenylpyrazole (4-Br-3,5-Ph2pzH), were conveniently prepared by halogenation of the appropriate pyrazoles with N-halosuccinimides (NXS) (X = Cl, Br, and I) followed by complexation of the pyrazolate anions with silver(i) nitrate. Single crystal X-ray analysis revealed either dimeric trinuclear {[Ag(μ-4-X-3,5-R2pz)]3}2 (R = iPr, X = Cl, Br, and I) or trinuclear [Ag(μ-4-X 3,5-R2pz)]3 (R = iPr, X = I; R = Ph, X = Cl, R = Ph, X = Br) structures, the latter held together with argentophilic interactions (AgAg interactions) that could also be observed in the Raman spectra. The electronegativity of the halogen substituent could be correlated with the strength of the AgAg interaction and the wavelength of solid-state photoluminescence. All complexes were emissive on UV irradiation at low temperatures, with the colour of emission from the diisopropyl substituted analogues red shifted by the halogens in the order Cl (red) > Br (orange) > I (yellow). Emission from the diphenyl substituted analogues was dominated by the extended aromatic system and was largely invariant to the halogens.
authors.affiliation: Department of Chemistry, Ibaraki University, Mito 310-8512, Japan.
authors.forename: Yui
authors.initials: Y
authors.lastname: Morishima
authors.forename: David James
authors.initials: DJ
authors.lastname: Young
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Fujisawa