title: Proton-induced reversible modulation of the luminescent output of rhenium(I), iridium(III), and ruthenium(II) tetrazolate complexes.
abstract: One of the distinct features of metal-tetrazolate complexes is the possibility of performing electrophilic additions onto the imine-type nitrogens of the coordinated five-membered ring. These reactions, in particular, provide a useful tool for varying the main structural and electronic properties of the starting tetrazolate complexes. In this paper, we demonstrate how the use of a simple protonation-deprotonation protocol enables us to reversibly change, to a significant extent, the light-emission output and performance of a series of Re(I)-tetrazolate-based phosphors of the general formulation fac-[Re(N(∧)N)(CO)3L], where N(∧)N denotes diimine-type ligands such as 2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen) and L represents a series of different 5-aryl tetrazolates. Indeed, upon addition of triflic acid to these neutral Re(I) complexes, a consistent blue shift (Δλmax ca. 50 nm) of the emission maximum is observed and the protonated species also display increased quantum yield values (4-13 times greater than the starting compounds) and longer decay lifetimes. This alteration can be reversed to the initial condition by further treating the protonated Re(I) complex with a base such as triethylamine. Interestingly, the reversible modulation of luminescent features by the same protonation-deprotonation mechanism appears as a quite general characteristic of photoactive metal tetrazolate complexes, even for compounds in which the 2-pyridyl tetrazolate ligands coordinate the metal center with a bidentate mode, such as the corresponding Ir(III) cyclometalates [Ir(C(∧)N)2L] and the Ru(II) polypyridyl derivatives [Ru(bpy)2L](+). In these cases, the protonation of the starting materials leads to red-shifted and more intense emissions for the Ir(III) complexes, while almost complete quenching is observed in the case of the Ru(II) analogues.
authors.affiliation: Department of Chemistry, Curtin University , GPO Box U 1987, Perth, Australia , 6845.
authors.forename: Melissa V
authors.initials: MV
authors.lastname: Werrett
authors.forename: Sara
authors.initials: S
authors.lastname: Muzzioli
authors.forename: Phillip J
authors.initials: PJ
authors.lastname: Wright
authors.forename: Antonio
authors.initials: A
authors.lastname: Palazzi
authors.forename: Paolo
authors.initials: P
authors.lastname: Raiteri
authors.forename: Stefano
authors.initials: S
authors.lastname: Zacchini
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Massi
authors.forename: Stefano
authors.initials: S
authors.lastname: Stagni