- Fine tuning of emission color of iridium(iii) complexes from yellow to red via substituent effect on 2-phenylbenzothiazole ligands: Synthesis, photophysical, electrochemical and DFT study
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Four novel iridium(iii) complexes bearing biphenyl (7a-7c) or fluorenyl (7d) modified benzothiazole cyclometallate ligands are synthesized. In comparison with the yellow parent complex, bis(2-phenylbenzothiozolato-N,C 2′) iridium(iii) (acetylacetonate) [(pbt)2Ir(acac)] (λPLmax = 557 nm, φPL = 0.26), 7a-7d show 20-43 nm bathochromic shifted orange or red phosphorescence in solution, with maximum photoluminescence (PL) quantum yield of 0.62, and PL lifetime of 1.8-2.0 μs. Meanwhile, the resulting complexes also exhibit intense orange or red phosphorescence of λPLmax = 588-611 nm in solid films. The complex 7c with two tert-butyl substituents possesses the highest phosphorescent efficiency both in dilute solution and thin solid films, therefore may be a prospective candidate for both doping and host emitting electrophosphorescent material. Furthermore, despite the observation of severe oxygen quenching for 7a-7d in solution, 7a and 7c even show efficient emission intensity quenching by oxygen in their solid state due to the existence of void channels in crystals; consequently, they are promising molecular oxygen sensor reagents. Electrochemical measurement and DFT calculation results suggest that all these chelates own declined LUMOs of 0.1 eV relative to that of (pbt) 2Ir(acac) owing to the contribution of the phenyl substituents; whereas only 7d shows a more destabilized HOMO (～0.1 eV) compared with the parent chelate.
- Li, Ming,Zeng, Hui,Meng, Yanyan,Sun, Huiqin,Liu, Song,Lu, Zhiyun,Huang, Yan,Pu, Xuemei
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experimental part
p. 7153 - 7164
(2011/09/12)
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- NMR-based discovery of lead inhibitors that block DNA binding of the human papillomavirus E2 protein
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The E2 protein is required for the replication of human papillomaviruses (HPVs), which are responsible for anogenital warts and cervical carcinomas. Using an NMR-based screen we tested compounds for binding to the DNA-binding domain of the HPV-E2 protein. Three classes of compounds were identified which bound to two distinct sites on the protein. Biphenyl and biphenyl ether compounds containing a carboxylic acid bind to a site near the DNA recognition helix and inhibit the binding of E2 to DNA. Benzophenone- containing compounds which lack a carboxylic acid group bind to the β- barrel formed by the dimer interface and exhibit negligible effects on the binding of E2 to DNA. Structure-activity relationships from the biphenyl and biphenyl ether compounds were combined to produce a compound [5-(3'- (3'',5''-dichlorophenoxy)-phenyl)-2,4-pentadienoic acid] with an IC50 value of approximately 10 μM. This compound represents a useful lead for the development of antiviral agents that interfere with HPV replication and further illustrates the usefulness of the SAR by NMR method in the drug discovery process.
- Hajduk, Philip J.,Dinges, Jürgen,Miknis, Gregory F.,Merlock, Megan,Middleton, Tim,Kempf, Dale J.,Egan, David A.,Walter, Karl A.,Robins, Terry S.,Shuker, Suzy B.,Holzman, Thomas F.,Fesik, Stephen W.
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p. 3144 - 3150
(2007/10/03)
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- Carbanions. 21. Reactions of 2- and 3-p-Biphenylylalkyl Chlorides with Alkali Metals. Preparation of Labile Spiro Anions
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The present work was undertaken to see if (3-p-biphenylylpropyl)- and (2-p-biphenylethyl)cesium cyclize like (4-p-biphenylbutyl)cesium to stable spiro anions.Reaction of 1-p-biphenylyl-3-chloropropane (5) with Cs-K-Na alloy in THF at -75 deg C gave, under the optimum conditions found, 36percent of 7-phenylspironona-6,5-dien-5-yl anion (8) besides 3-p-biphenylylpropyl (7), 1-p-biphenylylpropyl (9), and p-biphenylylmethyl (10) anions, according to the products of carbonation.The spiro anion 8 (Cs+ as the counterion) has a half-life of about 13 min at -75 deg C.Incontrast, 5 reacts with lithium to give predominantly (3-p-biphenylylpropyl)lithium.Reaction of 1-p-biphenylyl-2-chloroethane with Cs-K-Na alloy gave no appreciable spiro anion under conditions which were successful with 5.In the reaction of 1-p-biphenylyl-2-chloro-2-methylpropane (28) with Cs-K-Na alloy the α-gem-dimethyl group accelerates migration of the p-biphenylyl group to give products similar to those from 2-p-biphenylyl-1-chloro-2-methylpropane (24); however, the expected intermediate spiro anion 26 was undetectable by the carbonation technique.With both α- and β-gem-dimethyl groups, 2-p-biphenylyl-3-chloro-2,3-dimethylbutane (41) reacts with Cs-K-Na alloy to give 1,1,2,2-tetramethyl-6-phenylspiroocta-5,7-dien-4-yl anion (43) and 2-p-biphenylyl-1,1,2-trimethylpropyl anion (42) in about a 2:1 ratio according to the results of carbonation.The open anion 42 and the spiro anion 43 appear to be in mobile equilibrium (Cs+ as the counterion) with half-lives of about 22 min in THF at -75 deg C.With lithium as counterion, only the open product (2-p-biphenylyl-1,1,2-trimethylpropyl)lithium (50) was detectable by carbonation.
- Grovenstein, Erling,Lu, Pang-Chia
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p. 2928 - 2939
(2007/10/02)
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