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Bimetallic Pt(II)-bipyridyl-diacetylide/Ln(III) tris-diketonate adducts based on a combination of coordinate bonding and hydrogen bonding between the metal fragments: syntheses, structures and photophysical properties

Al-Rasbi, N.K., Derossi, S., Sykes, D., Faulkner, S. and Ward, M.D. (2009) Bimetallic Pt(II)-bipyridyl-diacetylide/Ln(III) tris-diketonate adducts based on a combination of coordinate bonding and hydrogen bonding between the metal fragments: syntheses, structures and photophysical properties. Polyhedron, 28 (2). pp. 227-232. ISSN 0277-5387

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Abstract

The luminescent Pt(II) complex [Pt(4,4'-Bu-t(2)-bipy){CC-(5-pyrimidinyl)}(2)] (1) was prepared by coupling of [Pt(4,4'-Bu-t(2)-bipy)Cl-2] with 5-ethynyl-pyrimidine, and contains two pyrimidinyl units pendant from a Pt(H) bipyridyl diacetylide core; it shows luminescence at 520 nm which is typical of Pt(II) luminophores of this type. Reaction with [Ln(hfac)(3)(H2O)(2)] (hfac = anion of hexafluoroacetylacetone) affords as crystalline solids the compounds [1 center dot {Ln(hfac)(3)(H2O)}{Ln(hfac)(3)(H2O)(2)}] (Ln = Nd, Gd, Er, Yb), in which the {Ln(hfac)(3)(H2O)} unit is coordinated to one pyrimidine ring via an N atom, whereas the {Ln(hfac)(3)(H2O)(2)} unit is associated with two N atoms, one from each pyrimidine ring of 1, via N center dot center dot center dot HOH hydrogen-bonding interactions involving the coordinated water ligands on the lanthanide centre. Solution spectroscopic studies show that the luminescence of 1 is partly quenched on addition of [Ln(hfac)(3)(H2O)(2)] (Ln = Er, Nd) by formation of Pt(II)/Ln(III) adducts in which Pt(II)-> Ln(III) photoinduced energy-transfer occurs to the low-lying f-f levels of the Ln(Ill) centre. Significant quenching occurs with both Er(Ill) and Nd(III) because both have several f-f states which match well the (MLCT)-M-3 emission energy of 1. Time-resolved luminescence studies show that Pt(II)-Er(III) energy-transfer (7.0 x 10(7) M-1) is around three times faster than Pt(II)-> Nd(III) energy-transfer (approximate to 2 x 10(7) M-1) over the same distance because the luminescence spectrum of l overlaps better with the absorption spectrum of Er(111) than with Nd(III). In contrast Yb(111) causes no significant quenching of 1 because it has only a single f-f excited level which is a poor energy match for the Pt(II)-based excited state.

Item Type: Article
Copyright, Publisher and Additional Information: © 2009 Elsevier. This is an author produced version of a paper subsequently published in 'Polyhedron'. Uploaded in accordance with the publisher's self-archiving policy.
Keywords: Platinum; Lanthanides; Crystal structure; Luminescence; Energy-transfer
Institution: The University of Sheffield
Academic Units: The University of Sheffield > Faculty of Science (Sheffield) > Department of Chemistry (Sheffield)
Depositing User: Miss Anthea Tucker
Date Deposited: 16 Mar 2009 16:54
Last Modified: 18 Jun 2014 13:35
Published Version: http://dx.doi.org/10.1016/j.poly.2008.10.046
Status: Published
Publisher: Elsevier
Refereed: Yes
Identification Number: 10.1016/j.poly.2008.10.046
URI: http://eprints.whiterose.ac.uk/id/eprint/7970

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