期刊
DALTON TRANSACTIONS
卷 48, 期 23, 页码 8068-8075出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c8dt04861d
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资金
- Global Science Campus program, Japan Science and Technology Agency (JST), through the High-grade Global Education Program for Sciences, Saitama University
The novel water-soluble monoanionic Ir(III) complex Na[Ir(ppy)(2)(SB-COO)] (2; Hppy = phenylpyridine; HSB-COOH = 4-carboxylanilinesalicylaldehyde Schiff base), which was obtained by the reaction of the novel Ir(III) complex [Ir(ppy)(2)(SB-COOH)] (1) with NaOEt, in its aqueous solution, showed hydrogen ion (H+)-responsive aggregation-induced enhanced phosphorescence (AIEP). Both these complexes exhibited very weak and relatively strong emissions in solution and solid states, respectively. The pH-responsiveness of 2 was evaluated from its emission spectra in aqueous solution in the pH range of 8.7-1.8. Above pH 6, 2 showed weak emission with a maximum at 508 nm. Upon decreasing the pH to 4.7, AIEP with a bathochromic shift to 618 nm was induced by the aggregation of 1, whereby the intensity at 618 nm was increased approximately by 50-fold compared to that at pH 6.0. This enhancement is due to restrictions of the geometrical changes in the six-membered chelate ring of the ancillary ligand (Ir-N-C-C-C-O-) and of the intramolecular rotations in the excited state. The enhanced luminescence originates from spin-forbidden metal-to-ligand-ligand charge transfer ((MLLCT)-M-3). Below pH 2.8, the emission intensity decreased owing to the decrease in the population of the emissive complex 1 upon dissociation of the ancillary ligand from the Ir(ppy)(2) unit.
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