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Luminescent Pt II (bipyridyl)(diacetylide) Chromophores with Pendant Binding Sites as Energy Donors for Sensitised Near‐Infrared Emission from Lanthanides: Structures and Photophysics of Pt II /Ln III Assemblies
Author(s) -
Ronson Tanya K.,
Lazarides Theodore,
Adams Harry,
Pope Simon J. A.,
Sykes Daniel,
Faulkner Stephen,
Coles Simon J.,
Hursthouse Michael B.,
Clegg William,
Harrington Ross W.,
Ward Michael D.
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200600698
Subject(s) - lanthanide , luminescence , chromophore , chemistry , excited state , crystallography , adduct , covalent bond , photochemistry , ion , stereochemistry , materials science , physics , atomic physics , optoelectronics , organic chemistry
The complexes [Pt(bipy){CC‐(4‐pyridyl)} 2 ] ( 1 ) and [Pt( t Bu 2 bipy){CC‐(4‐pyridyl)} 2 ] ( 2 ) and [Pt( t Bu 2 ‐bipy)(CC‐phen) 2 ] ( 3 ) all contain a Pt(bipy)(diacetylide) core with pendant 4‐pyridyl ( 1 and 2 ) or phenanthroline ( 3 ) units which can be coordinated to {Ln(diketonate) 3 } fragments (Ln = a lanthanide) to make covalently‐linked Pt II /Ln III polynuclear assemblies in which the Pt II chromophore, absorbing in the visible region, can be used to sensitise near‐infrared luminescence from the Ln III centres. For 1 and 2 one‐dimensional coordination polymers [ 1⋅ Ln(tta) 3 ] ∞ and [ 2⋅ Ln(hfac) 3 ] ∞ are formed, whereas 3 forms trinuclear adducts [ 3⋅ {Ln(hfac) 3 } 2 ] (tta=anion of thenoyl‐trifluoroacetone; hfac=anion of hexafluoroacetylacetone). Complexes 1 – 3 show typical Pt II ‐based 3 MLCT luminescence in solution at ≈510 nm, but in the coordination polymers [ 1⋅ Ln(tta) 3 ] ∞ and [ 2⋅ Ln(hfac) 3 ] ∞ the presence of stacked pairs of Pt II units with short Pt⋅⋅⋅Pt distances means that the chromophores have 3 MMLCT character and emit at lower energy (≈630 nm). Photophysical studies in solution and in the solid state show that the 3 MMLCT luminescence in [ 1⋅ Ln(tta) 3 ] ∞ and [ 2⋅ Ln(hfac) 3 ] ∞ in the solid state, and the 3 MLCT emission of [ 3⋅ {Ln(hfac) 3 } 2 ] in solution and the solid state, is quenched by Pt→Ln energy transfer when the lanthanide has low‐energy f–f excited states which can act as energy acceptors (Ln=Yb, Nd, Er, Pr). This results in sensitised near‐infrared luminescence from the Ln III units. The extent of quenching of the Pt II ‐based emission, and the Pt→Ln energy‐transfer rates, can vary over a wide range according to how effective each Ln III ion is at acting as an energy acceptor, with Yb III usually providing the least quenching (slowest Pt→Ln energy transfer) and either Nd III or Er III providing the most (fastest Pt→Ln energy transfer) according to which one has the best overlap of its f–f absorption manifold with the Pt II ‐based luminescence.