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Cyclometalated Ir(III) complexes incorporating photoactive anthracene-based ligand: syntheses, crystal structures and luminescence switching by light irradiation

Abstract

Two cyclometalated complexes [Ir(dfppy)2(aip)](PF6) (1) and [Ir(ppy)2(aip)](PF6) (2) have been synthesized based on a photoactive anthracene-based ligand aip (Scheme 1) and cyclometalating ligands dfppyH and ppyH [dfppyH = (2-(2,4-difluorophenyl)-pyridine), ppyH = 2-phenyl-pyridine)]. Their crystal structures indicate that an aip ligand uses its phenanthroline moiety to chelate an {Ir(dfppy)2}+ unit in 1, while an {Ir(ppy)2}+ unit in 2. In CH2Cl2, the anthracene units in aip, 1 and 2 underwent photo-oxidation upon irradiation with 365 nm light, forming species aip-O, 1-O and 2-O, respectively. This photo-oxidation resulted in luminescence switching, from luminescent state (emission at 493 nm) to non-luminescent state for aip, while from non-luminescent state to luminescent state with an emission at 519 nm for 1 and 578 nm for 2. Additionally, the luminescence of aip, 1-O and 2-O in CH2Cl2 can be modulated by using TFA to protonate the imidazole units and/or non-coordinated phenanthroline moiety in these compounds. Upon adding TFA, aip showed luminescence quench, while species 1-O and 2-O revealed both luminescence-intensity decrease and emission-wavelength increase ( = 9 nm for 1-O, and  = 4 nm for 2-O). In this paper, we discuss the luminescence switching/modulation of aip, 1 and 2 by light-irradiation-induced photo-oxidation of their anthracene units and by TFA treatment.

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Publication details

The article was received on 10 Aug 2017, accepted on 10 Oct 2017 and first published on 10 Oct 2017


Article type: Paper
DOI: 10.1039/C7DT02967E
Citation: Dalton Trans., 2017, Accepted Manuscript
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    Cyclometalated Ir(III) complexes incorporating photoactive anthracene-based ligand: syntheses, crystal structures and luminescence switching by light irradiation

    T. Gao, Z. Qu, Z. Tang and D. Cao, Dalton Trans., 2017, Accepted Manuscript , DOI: 10.1039/C7DT02967E

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