Jump to main content
Jump to site search

Issue 25, 2017
Previous Article Next Article

Cyclometalated Ir(III) complexes based on 2-(2,4-difluorophenyl)-pyridine and 2,2′-(2-phenyl-1H-imidazole-4,5-diyl)dipyridine: acid/base-induced structural transformation and luminescence switching, and photocatalytic activity for hydrogen evolution

Author affiliations

Abstract

Based on ligands dfppyH and pidpyH, cyclometalated Ir(III) complexes [Ir(dfppy)2(pidpyH)](PF6) (1·PF6) and [Ir(dfppy)2(pidpy)] (2) have been synthesized. The crystal structures indicate that each {Ir(dfppy)2}+ unit is coordinated by a neutral ligand pidpyH in 1·PF6, while by a pidpy anion in 2. The packing structure of 1·PF6 only exhibits electrostatic interactions and van der Waals interactions among [Ir(dfppy)2(pidpyH)]+ cations and PF6 ions. In contrast, the neighboring molecules in 2 are linked into a supramolecular chain structure through aromatic stacking interactions between two dfppy ligands. In solution, 1·PF6 and 2 show acid/base-induced structural transformation due to the protonation/deprotonation of their pyridyl groups and/or imidazole units, which can be confirmed by their 1H NMR spectra. At room temperature, compounds 1·PF6, 2 and pidpyH in CH2Cl2 reveal TFA-induced luminescence switching behaviors, from a non-luminescence state to a luminescence state with an emission at 582 nm for both 1·PF6 and 2, and emission switching from 392 nm to 502 nm for pidpyH. These switching behaviors are associated with the protonation of pyridyl groups and/or imidazole units in 1·PF6, 2 and pidpyH. Moreover, compounds 1·PF6 and 2 were used as photosensitizers (PS) for reduction of water to hydrogen under the same experimental conditions. It was found that the amount of evolved hydrogen and the PS turnover number are 512 μmol and 102 for 1·PF6, and 131 μmol and 26 for 2, respectively. Thus, compound 1·PF6 has better photocatalytic activity than 2. In this paper, we discuss the modulation of luminescence and photocatalytic activities of 1·PF6 and 2 by varying the coordination mode and/or protonation extent of pidpyH/pidpy ligands.

Graphical abstract: Cyclometalated Ir(iii) complexes based on 2-(2,4-difluorophenyl)-pyridine and 2,2′-(2-phenyl-1H-imidazole-4,5-diyl)dipyridine: acid/base-induced structural transformation and luminescence switching, and photocatalytic activity for hydrogen evolution

Back to tab navigation

Supplementary files

Publication details

The article was received on 13 Apr 2017, accepted on 29 May 2017 and first published on 29 May 2017


Article type: Paper
DOI: 10.1039/C7DT01337J
Citation: Dalton Trans., 2017,46, 8180-8189
  •   Request permissions

    Cyclometalated Ir(III) complexes based on 2-(2,4-difluorophenyl)-pyridine and 2,2′-(2-phenyl-1H-imidazole-4,5-diyl)dipyridine: acid/base-induced structural transformation and luminescence switching, and photocatalytic activity for hydrogen evolution

    T. Gao, Q. Fan, Z. Yu and D. Cao, Dalton Trans., 2017, 46, 8180
    DOI: 10.1039/C7DT01337J

Search articles by author

Spotlight

Advertisements