Proton-induced reversible modulation of the luminescent output of rhenium(I), iridium(III), and ruthenium(II) tetrazolate complexes

Melissa V. Werrett, Sara Muzzioli, Phillip John Wright, Antonio Palazzi, Paolo Raiteri, Stefano Zacchini, Massimiliano Massi, Stefano Stagni

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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.
Original languageEnglish
Pages (from-to)229 - 243
Number of pages15
JournalInorganic Chemistry
Issue number1
Publication statusPublished - 2014
Externally publishedYes


  • Tricarbonyl complexes
  • Rhenium
  • Ligands

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