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Issue 35, 2008
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Luminescence properties of Pt(ii) complexes containing polypyridine ligands with extended aromatic moieties

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Abstract

The luminescence properties of eleven Pt(II) complexes containing polypyridine ligands with extended aromatic moieties have been studied, both in acetonitrile fluid solution at 298 K and in butyronitrile rigid matrix at 77 K. For comparison purposes, also the phosphorescence properties of three free ligands at 77 K in butyronitrile have been investigated. The absorption spectra of all the compounds exhibit intense bands (ε in the range 104–105 M−1 cm−1) in the UV region, which are attributed to spin-allowed ligand-centered (LC) transitions, and moderately intense bands (ε in the range 103–104 M−1 cm−1) in the visible region, which receive contribution from both spin-allowed LC transitions and spin-allowed metal-to-ligand charge-transfer (MLCT) transitions. At low energy, less intense spin-forbidden MLCT bands are also present. At 77 K in rigid matrix, all the studied compounds exhibit structured and long-lived (lifetimes from 840 μs on the millisecond timescale) luminescence, which is attributed to triplet LC states in all cases. At room temperature in fluid solution the luminescence lifetime of all the compounds is largely shortened (nanosecond timescale), and most of the emission spectra are unstructured and red-shifted. For species exhibiting structured emission spectra even at room temperature, low luminescence quantum yields are always obtained (Φ < 104), and their emission is assigned to triplet LC states, which mainly deactivate to the ground state by thermal-activated surface crossing to a closely-lying metal-centered (MC) triplet state. Compounds exhibiting unstructured emission show relatively high emission quantum yields (about 0.1) and their emission is assigned to a mixed LC/MLCT state.

Graphical abstract: Luminescence properties of Pt(ii) complexes containing polypyridine ligands with extended aromatic moieties

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Supplementary files

Article information


Submitted
17 Mar 2008
Accepted
09 May 2008
First published
27 Jun 2008

Dalton Trans., 2008, 4762-4769
Article type
Paper

Luminescence properties of Pt(II) complexes containing polypyridine ligands with extended aromatic moieties

F. Cucinotta, M. L. Di Pietro, F. Puntoriero, A. Giannetto, S. Campagna and M. Cusumano, Dalton Trans., 2008, 4762
DOI: 10.1039/B804574G

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