Issue 28, 2016

Synthesis and photophysical properties of Ir(iii)/Re(i) dyads: control of Ir→Re photoinduced energy transfer

Abstract

A series of dinuclear Ir(III)/Re(I) complexes has been prepared based on a family of symmetrical bridging ligands containing two bidentate N,N′-chelating pyrazolyl–pyridine termini, connected by a central aromatic or aliphatic spacer. The Ir(III) termini are based on {Ir(F2ppy)2}+ units (where F2ppy is the cyclometallating anion of a fluorinated phenylpyridine) and the Re(I) termini are based on {Re(CO)3Cl} units. Both types of terminus are luminescent, with the Ir-based unit showing characteristic strong, structured phosphorescence in the blue region (maximum 452 nm) with a triplet excited state energy of 22 200 cm−1 and the Re-based unit showing much weaker and lower-energy phosphorescence (maximum 530 nm) with a triplet excited state energy of 21 300 cm−1. The energy gradient between the two excited states allows for partial Ir→Re photoinduced energy-transfer, with substantial (but incomplete) quenching of the higher-energy Ir-based emission component and sensitised emission – evidenced by an obvious grow-in component – on the lower-energy Re-based emission. The Ir→Re energy-transfer rate constants vary over the range 1–8 × 107 s−1 depending on the bridging ligand: there is no simple correlation between bridging ligand structure and energy-transfer rate, possibly because this will depend substantially on the conformation of these flexible molecules in solution. To test the role of ligand conformation further, we investigated a complex in which the bridging chain is a (CH2CH2O)6 unit whose conformation is known to be solvent-polarity dependent, with such chains adopting an open, elongated conformation in water and more compact, folded conformations in organic solvents. There was a clear link between the rate and extent of Ir→Re energy-transfer which reduced in polar solvents as the chain became elongated and the Ir/Re separation was larger; and increased in less polar solvents as the chain adopted a more compact conformation and the Ir/Re separation was reduced.

Graphical abstract: Synthesis and photophysical properties of Ir(iii)/Re(i) dyads: control of Ir→Re photoinduced energy transfer

Supplementary files

Article information

Article type
Paper
Submitted
26 Apr 2016
Accepted
27 Jun 2016
First published
27 Jun 2016

Dalton Trans., 2016,45, 11568-11579

Author version available

Synthesis and photophysical properties of Ir(III)/Re(I) dyads: control of Ir→Re photoinduced energy transfer

S. T. Saad, A. J. Metherell, E. Baggaley and M. D. Ward, Dalton Trans., 2016, 45, 11568 DOI: 10.1039/C6DT01614F

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements