Issue 47, 2012

Phosphorescent, liquid-crystalline complexes of platinum(ii): influence of the β-diketonate co-ligand on mesomorphism and emission properties

Abstract

Two series of rod-like ortho-platinated complexes bound to a range of β-diketonate co-ligands are reported of the form [Pt(N^C)(O^O)]. The liquid crystal and luminescent properties are influenced through the introduction of different β-diketonates (O^O) as well as through the presence of a fused cyclopentene ring on the N^C-coordinated 2-phenylpyridine ligand. For metal complexes, smectic phases are dominant but no mesomorphism is exhibited when the β-diketonate is hexafluorinated acetylacetonate (1,1,1-5,5,5-hexafluoro-2,4-pentandione). The introduction of an unsymmetrical trifluoroacetyl acetonate (1,1,1-trifluoro-2,4-pentandione) ligand is particularly interesting due to the discovery of the β-diketonate as a dynamic system that readily isomerises to a 1 : 1 ratio under thermal conditions, from an initial ratio of 3 : 1 formed during the synthesis. As expected, the presence of the 3,5-heptanedionato co-ligand decreases the transition temperatures due to the introduction of a larger lateral substituent. Unfortunately complexes based on 2-phenylpyridine ligands with a fused cyclopentene ring are, with one exception, not mesomorphic. With the exception of the hexafluoroacetyl acetonate complexes, the materials are brightly luminescent and have excited state lifetimes between 13 and 30 μs with emission quantum efficiencies exceeding 0.5, with one as high as 0.7. A time-dependent density functional theory (TD-DFT) study suggests that the lack of emission from the hexafluoroacetyl acetonate complexes may be associated with large structural distortion upon formation of the excited state, as well as to poorer overlap of orbitals leading to a lower radiative rate constant. The same analysis provides an explanation for the apparently quite different emission efficiencies of the two isomers of the trifluoroacetyl acetonate complexes.

Graphical abstract: Phosphorescent, liquid-crystalline complexes of platinum(ii): influence of the β-diketonate co-ligand on mesomorphism and emission properties

Supplementary files

Article information

Article type
Paper
Submitted
11 Jul 2012
Accepted
30 Aug 2012
First published
13 Sep 2012

Dalton Trans., 2012,41, 14244-14256

Phosphorescent, liquid-crystalline complexes of platinum(II): influence of the β-diketonate co-ligand on mesomorphism and emission properties

M. Spencer, A. Santoro, G. R. Freeman, Á. Díez, P. R. Murray, J. Torroba, A. C. Whitwood, L. J. Yellowlees, J. A. G. Williams and D. W. Bruce, Dalton Trans., 2012, 41, 14244 DOI: 10.1039/C2DT31525D

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