TY - JOUR
T1 - Phosphorescent, liquid-crystalline complexes of platinum(ii)
T2 - influence of the β-diketonate co-ligand on mesomorphism and emission properties
AU - Spencer, Matthew
AU - Santoro, Amedeo
AU - Freeman, Gemma R
AU - Díez, Alvaro
AU - Murray, Paul R
AU - Torroba, Javier
AU - Whitwood, Adrian C
AU - Yellowlees, Lesley J
AU - Williams, J A Gareth
AU - Bruce, Duncan W
PY - 2012
Y1 - 2012
N2 - 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.
AB - 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.
U2 - 10.1039/c2dt31525d
DO - 10.1039/c2dt31525d
M3 - Article
C2 - 22975927
SN - 1477-9234
VL - 41
SP - 14244
EP - 14256
JO - Dalton Transactions
JF - Dalton Transactions
IS - 47
ER -