Unichromophoric platinum-acetylides that contain pentiptycene scaffolds: torsion-induced dual... - Abstract - Europe PMC
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Che-Jen Lin
Department of Chemistry, National Taiwan University , No 1, Sec 4, Roosevelt Rd, Taipei 10617, Taiwan.
Chih-Yuan Chen
Sandip Kumar Kundu
JYE-SHANE YANG
National Taiwan University Chemistry Department
Department of Chemistry, National Taiwan University , No 1, Sec 4, Roosevelt Rd, Taipei 10617, Taiwan.
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[03 Jan ):737-745]
Journal Article
The effect of the rigid bulky pentiptycene scaffolds on the photoluminescence, redox properties, and oxygen sensing behavior of unichromophoric Pt-acetylides is reported. When the pentiptycene groups are near the Pt(PBu3)2 center, the Pt-acetylides display both blue fluorescence and green phosphorescence with long phosphorescence lifetimes (90-202 &s) in THF. Their phosphorescence intensity is highly sensitive to molecular oxygen, and the emission color depends on the concentration of not only oxygen but also the complexes, which allows a feasible determination of oxygen in the range of 1-5% air volume. The dynamic quenching rate constants decrease linearly with increasing the number of pentiptycene groups, revealing the steric shielding effect of the peripheral rings of pentiptycene. A dependence of oxidation potential on the number of pentiptycene groups also revealed the steric shielding effect on the electron transfer between the complexes and the electrode. In a PMMA matrix, the dual emissive properties are diminished due to increased phosphorescence and decreased fluorescence intensity, and the phosphorescence lifetimes are significantly increased (up to &700 &s), leading to an &on-off& optical response to oxygen concentration. Both the dual emissive properties and long-lived triplet excitons are attributed to diminished spin-orbit couplings caused by twisting and steric shielding of the &-conjugated backbone around the Pt center.
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CitePeer Related ArticlesStereoselective formation of helical binuclear metal complexes: synthesis, characterization,... - Abstract - Europe PMC
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Ho-Lun Yeung
Wai-Yeung Wong
Chun-Yuen Wong
City University of Hong Kong
[01 May ):]
Research Support, Non-U.S. Gov't, Journal Article
A series of single-stranded helical Re(I) complexes, of formula [Re(2)(L)Br(2)(CO)(6)], were prepared by reacting [Re(CO)(5)Br] with chiral quaterpyridines L1-4. By (1)H and (13)C NMR analysis, all the crude complexes consisted of a pair of stereoisomers. Sterically more demanding ligand L4 induced a higher ratio (80:20) than L1-3 (about 56:44). Stereochemically pure complexes could be obtained by recrystallization in CH(2)Cl(2). X-ray crystallographic analysis of single crystals from purified complexes showed a single-stranded helical structure with a bridging ligand wrapped around two distorted octahedral rhenium metals, both of which possessed one bromide ligand and three carbonyl ligands in a fac coordination. The helical core is established by extensive noncovalent electrostatic interactions and chiral information is transmitted from the ligand to the helix through these interactions. Solution behavior was studied by CD spectroscopy, and the strong Cotton effect confirms the integrity of the helical structure in solution. The diastereoselectivity of helicates is proposed to be induced by steric interaction between the bromine atom and the substituent of the bridging ligand.
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