Issue 47, 2015

Cyclometalated Ir(iii) complexes of deprotonated N-methylbipyridinium ligands: effects of quaternised N centre position on luminescence

Abstract

Six new tricationic IrIII complexes of cyclometalating ligands derived from 1-methyl-2-(2′-pyridyl)pyridinium or 1-methyl-4-(2′-pyridyl)pyridinium are described. These complexes of the form [IrIII(C^N)2(N^N)]3+ (C^N = cyclometalating ligand; N^N = α-diimine) have been isolated and characterised as their PF6 and Cl salts. Four of the PF6 salts have been studied by X-ray crystallography, and structures have been obtained also for two complex salts containing MeCN and Cl or two Cl ligands instead of N^N. The influence of the position of the quaternised N atom in C^N and the substituents on N^N on the electronic/optical properties are compared with those of the analogous complexes where C^N derives from 1-methyl-3-(2′-pyridyl)pyridinium (B. J. Coe, et al., Dalton Trans., 2015, 44, 15420). Voltammetric studies reveal one irreversible oxidation and multiple reduction processes which are mostly reversible. The new complexes show intramolecular charge-transfer absorptions between 350 and 450 nm, and exhibit bright green luminescence, with λmax values in the range 508–530 nm in both aqueous and acetonitrile solutions. In order to gain insights into the factors that govern the emission properties, density functional theory (DFT) and time-dependent DFT calculations have been carried out. The results confirm that the emission arises largely from triplet excited states of the C^N ligand (3LC), with some triplet metal-to-ligand charge-transfer (3MLCT) contributions.

Graphical abstract: Cyclometalated Ir(iii) complexes of deprotonated N-methylbipyridinium ligands: effects of quaternised N centre position on luminescence

Supplementary files

Article information

Article type
Paper
Submitted
25 Sep 2015
Accepted
15 Oct 2015
First published
20 Oct 2015
This article is Open Access
Creative Commons BY license

Dalton Trans., 2015,44, 20392-20405

Author version available

Cyclometalated Ir(III) complexes of deprotonated N-methylbipyridinium ligands: effects of quaternised N centre position on luminescence

B. J. Coe, M. Helliwell, J. Raftery, S. Sánchez, M. K. Peers and N. S. Scrutton, Dalton Trans., 2015, 44, 20392 DOI: 10.1039/C5DT03753K

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