Negatively charged Ir(III) cyclometalated complexes containing a chelating bis-tetrazolato ligand: synthesis, photophysics and the study of reactivity with electrophiles

摘要

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 (NN)-N-boolean AND ligand for negatively charged [Ir((CN)-N-boolean AND)(2)((NN)-N-boolean AND)](-)-type complexes, where (CN)-N-boolean AND is represented by cyclometalated 2-phenylpyridine (ppy) or 2-(2,4-difluorophenyl)pyridine (F(2)ppy). The new Ir(III) complexes [Ir(ppy)(2)(1,2 BTB)](-) and [Ir(F(2)ppy)(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 (lambda(max) = 460-490 nm) or aqua (lambda(max) = 490-520 nm) emissions originating from [Ir(F(2)ppy)(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(F(2)ppy)(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(F(2)ppy)(2)(1,2 BTB)](-) or [Ir(ppy)(2)(1,2 BTB)](-) with a deep red emitting (lambda(max) = 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 O-2-sensitive emission colours, with an almost pure white light obtained by the appropriate choice of the ionic components.