title: Negatively charged Ir(iii) cyclometalated complexes containing a chelating bis-tetrazolato ligand: synthesis, photophysics and the study of reactivity with electrophiles.
abstract: The bis-tetrazolate dianion [1,2 BTB](2-), which is the deprotonated form of 1,2 bis-(1H-tetrazol-5-yl)benzene [1,2-H2BTB], is for the first time exploited as an ancillary N^N ligand for negatively charged [Ir(C^N)2(N^N)](-)-type complexes, where C^N is represented by cyclometalated 2-phenylpyridine (ppy) or 2-(2,4-difluorophenyl)pyridine (F2ppy). The new Ir(iii) complexes [Ir(ppy)2(1,2 BTB)]- and [Ir(F2ppy)2(1,2 BTB)]- have been fully characterised and the analysis of the X-ray structure of [Ir(ppy)2(1,2 BTB)]- confirmed the coordination of the [1,2 BTB](2-) dianion in a bis chelated fashion through the N-atoms adjacent to each of the tetrazolic carbons. Both of the new anionic Ir(iii) complexes displayed phosphorescence in the visible region, with intense sky-blue (λmax = 460-490 nm) or aqua (λmax = 490-520 nm) emissions originating from [Ir(F2ppy)2(1,2 BTB)]- and [Ir(ppy)2(1,2 BTB)]-, respectively. In comparison with our very recent examples of anionic Ir(iii)tetrazolate cyclometalates, the new Ir(iii) tris chelate complexes [Ir(F2ppy)2(1,2 BTB)]- and [Ir(ppy)2(1,2 BTB)]-, display an improved robustness, allowing the study of their reactivity toward the addition of electrophiles such as H(+) and CH3(+). In all cases, the electrophilic attacks occurred at the coordinated tetrazolate rings, involving the reversible - by a protonation deprotonation mechanism - or permanent - upon addition of a methyl moiety - switching of their global net charge from negative to positive and, in particular, the concomitant variation of their photoluminescence output. The combination of the anionic complexes [Ir(F2ppy)2(1,2 BTB)]- or [Ir(ppy)2(1,2 BTB)]- with a deep red emitting (λmax = 686 nm) cationic Ir(iii) tetrazole complex such as [IrTPYZ-Me]+, where TPYZ-Me is 2-(2-methyl-2H-tetrazol-5-yl)pyrazine, gave rise to two fully Ir(iii)-based soft salts capable of displaying additive and O2-sensitive emission colours, with an almost pure white light obtained by the appropriate choice of the ionic components.
authors.affiliation: Department of Industrial Chemistry "Toso Montanari", University of Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy. valentina.fiorini5@unibo.it stefano.stagni@unibo.it.
authors.forename: Valentina
authors.initials: V
authors.lastname: Fiorini
authors.affiliation: Department of Industrial Chemistry "Toso Montanari", University of Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy. valentina.fiorini5@unibo.it stefano.stagni@unibo.it.
authors.forename: Stefano
authors.initials: S
authors.lastname: Zacchini
authors.affiliation: Department of Chemistry and Nanochemistry Research Institute, Curtin University, GPO Box U 1987, Perth, 6845, Australia. M.Massi@curtin.edu.au and Curtin Institute for Computation, Curtin University, GPO Box U 1987, Perth, 6845, Australia.
authors.forename: Paolo
authors.initials: P
authors.lastname: Raiteri
authors.affiliation: Department of Industrial Chemistry "Toso Montanari", University of Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy. valentina.fiorini5@unibo.it stefano.stagni@unibo.it.
authors.forename: Rita
authors.initials: R
authors.lastname: Mazzoni
authors.affiliation: Department of Industrial Chemistry "Toso Montanari", University of Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy. valentina.fiorini5@unibo.it stefano.stagni@unibo.it.
authors.forename: Valerio
authors.initials: V
authors.lastname: Zanotti
authors.affiliation: Department of Chemistry and Nanochemistry Research Institute, Curtin University, GPO Box U 1987, Perth, 6845, Australia. M.Massi@curtin.edu.au.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Massi
authors.affiliation: Department of Industrial Chemistry "Toso Montanari", University of Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy. valentina.fiorini5@unibo.it stefano.stagni@unibo.it.
authors.forename: Stefano
authors.initials: S
authors.lastname: Stagni