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Dual visible/NIR emission from organometallic iridium(III)complexes

Dual visible/NIR emission from organometallic iridium(III)complexes
Dual visible/NIR emission from organometallic iridium(III)complexes

A series of four substituted benzo[g]quinoxaline species have been synthesised and utilised as cyclometalating ligands for iridium(III). The ligands (L1-L4) were synthesised and isolated in good yield following the condensation of 2,3-diaminonaphthalene with benzil and three of its derivatives. The substituent modulated electronic properties of L1-L4 were dominated by intraligand π−π* transitions, with the fluorescence profile demonstrating vibronic features attributed to the highly conjugated nature of the chromophore. Iridium(III) complexes of the form [Ir(L)2 (bipy)]PF6 were synthesised from L1-L4 in two steps. The electronic properties of the complexes reveal absorption in the UV-vis. region with spin forbidden metal-to-ligand charge transfer (MLCT) transitions possibly contributing at longer wavelengths to ca. 600 nm. Steady state luminescence (aerated, room temperature) on solutions of the complexes showed dual emissive properties in the visible and near-infra red (NIR) regions. Firstly, a vibronically structured emission in the visible region (ca. 525 nm) was attributed to ligand centred fluorescence (lifetime < 10 ns). Secondly, a broad emission peak in the NIR (ca. 950 nm) which extended to around 1200 nm was observed with corresponding lifetimes of 116–162 ns, indicative of triplet excited state emission.

DFT, Iridium, Ligands, Luminescence
0022-328X
11-20
Phillips, Kaitlin A.
6a551edd-88e5-492c-86ab-88fa5e3214f3
Stonelake, Thomas M.
c72d5105-aa44-48fe-9641-5d43aa810eb0
Horton, Peter N.
154c8930-bfc3-495b-ad4a-8a278d5da3a5
Coles, Simon J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Hallett, Andrew J.
36cc4f6a-74d4-4894-8a65-8dd9d7803593
O'Kell, Sean P.
01ff0d06-c93a-455d-9586-c62b101eefc8
Beames, Joseph M.
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Pope, Simon J.A.
db9a489c-29ba-41cd-a96a-623bace0889d
Phillips, Kaitlin A.
6a551edd-88e5-492c-86ab-88fa5e3214f3
Stonelake, Thomas M.
c72d5105-aa44-48fe-9641-5d43aa810eb0
Horton, Peter N.
154c8930-bfc3-495b-ad4a-8a278d5da3a5
Coles, Simon J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Hallett, Andrew J.
36cc4f6a-74d4-4894-8a65-8dd9d7803593
O'Kell, Sean P.
01ff0d06-c93a-455d-9586-c62b101eefc8
Beames, Joseph M.
73b04545-4859-44ad-999e-551f82924c29
Pope, Simon J.A.
db9a489c-29ba-41cd-a96a-623bace0889d

Phillips, Kaitlin A., Stonelake, Thomas M., Horton, Peter N., Coles, Simon J., Hallett, Andrew J., O'Kell, Sean P., Beames, Joseph M. and Pope, Simon J.A. (2019) Dual visible/NIR emission from organometallic iridium(III)complexes. Journal of Organometallic Chemistry, 893, 11-20. (doi:10.1016/j.jorganchem.2019.04.019).

Record type: Article

Abstract

A series of four substituted benzo[g]quinoxaline species have been synthesised and utilised as cyclometalating ligands for iridium(III). The ligands (L1-L4) were synthesised and isolated in good yield following the condensation of 2,3-diaminonaphthalene with benzil and three of its derivatives. The substituent modulated electronic properties of L1-L4 were dominated by intraligand π−π* transitions, with the fluorescence profile demonstrating vibronic features attributed to the highly conjugated nature of the chromophore. Iridium(III) complexes of the form [Ir(L)2 (bipy)]PF6 were synthesised from L1-L4 in two steps. The electronic properties of the complexes reveal absorption in the UV-vis. region with spin forbidden metal-to-ligand charge transfer (MLCT) transitions possibly contributing at longer wavelengths to ca. 600 nm. Steady state luminescence (aerated, room temperature) on solutions of the complexes showed dual emissive properties in the visible and near-infra red (NIR) regions. Firstly, a vibronically structured emission in the visible region (ca. 525 nm) was attributed to ligand centred fluorescence (lifetime < 10 ns). Secondly, a broad emission peak in the NIR (ca. 950 nm) which extended to around 1200 nm was observed with corresponding lifetimes of 116–162 ns, indicative of triplet excited state emission.

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Accepted/In Press date: 20 April 2019
e-pub ahead of print date: 25 April 2019
Published date: 15 August 2019
Keywords: DFT, Iridium, Ligands, Luminescence

Identifiers

Local EPrints ID: 432799
URI: https://eprints.soton.ac.uk/id/eprint/432799
ISSN: 0022-328X
PURE UUID: b685d06b-b863-4dca-9951-8ec4e97b4770
ORCID for Peter N. Horton: ORCID iD orcid.org/0000-0001-8886-2016
ORCID for Simon J. Coles: ORCID iD orcid.org/0000-0001-8414-9272

Catalogue record

Date deposited: 26 Jul 2019 16:30
Last modified: 16 Aug 2019 00:37

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Contributors

Author: Kaitlin A. Phillips
Author: Thomas M. Stonelake
Author: Peter N. Horton ORCID iD
Author: Simon J. Coles ORCID iD
Author: Andrew J. Hallett
Author: Sean P. O'Kell
Author: Joseph M. Beames
Author: Simon J.A. Pope

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