- Strongly blue luminescent cationic iridium(III) complexes with an electron-rich ancillary ligand: Evaluation of their optoelectronic and electrochemiluminescence properties
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Two strongly blue luminescent cationic heteroleptic iridium complexes 1b and 2b bearing a 4,4′-bis(dimethylamino)-2,2′-bipyridine (dmabpy) ancillary ligand and either 1-benzyl-4-(2,4-difluorophenyl)-1H-1,2,3-triazole (dFphtl) or 2-(2,4-difluorophenyl)-5-methylpyridine (dFMeppyH), respectively, have been synthesized and fully characterized. In comparison with other analogues, the interplay of the triazole unit with the dmabpy unit and methylation of the pyridine ring are discussed with respect to the photophysical, electrochemical, and electrochemiluminescent (ECL) properties of the complexes. The two complexes, 1b and 2b, are blue emitters with λmax = 495 and 494 nm, respectively. The nature of the excited states was established by various photophysical and photochemical experiments as well as DFT calculations. Both complexes emit from a ligand-centered state, however, the emission of 1b possesses significant charge-transfer character, which is absent in 2b. The presence of the methyl group on the cyclometalating ligand leads only to a modest increase in the radiative rate constant, k r, but otherwise does not appreciably influence the optoelectronic properties of the complex compared with the non-methylated analogue. In contrast, the efficacy of the ECL emission when scanning to 2.50 V is strongly influenced by the presence of the methyl group. ECL emission is also enhanced in complexes bearing dmabpy ancillary ligands compared with those containing dtBubpy ligands. The two complexes exhibit similar electrochemical behavior. Incorporation of the dmabpy ligand shifts both the oxidation and reduction cathodically. The combination of the dmabpy and dFphtl groups increases the redox potential difference and thus the HOMO-LUMO gap but the emission is not further blueshifted. Thus, the structural modification of the cyclometalating ligand, although only modestly tuning the emission energy, modulates the nature of the excited state and the efficiency of the ECL process. The synthesis, photophysical, electrochemical, and electrochemiluminescent properties of two highly emissive cationic blue-emitting Ir complexes are reported. Variation of the ligand results in a change in the nature of the emission. The decoration on both the cyclometalating and ancillary ligands strongly influences the ECL efficiencies. A detailed DFT/TDDFT study corroborates experiment. Copyright
- Ladouceur, Sebastien,Swanick, Kalen N.,Gallagher-Duval, Shawn,Ding, Zhifeng,Zysman-Colman, Eli
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- A NOVEL REARRANGEMENT OF 2,2'-BIPYRIDINE N,N'-DIOXIDES THE CHARACTERISATION OF DIPYRIDO ISOXAZOLINIUM SALTS AS INTERMEDIATES IN THE FORMATION OF 3-HYDROXY-2,2'-BIPYRIDINES
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The reactions of 2,2'-bipyridine N,N'-dioxides with POCl3 and SO2Cl2 have been investigated, and the products shown to be synthetically useful halogenated derivatives.The presence of substituents in the 4 position favours an intramolecular cyclisation to form dipyrido-isoxazolinium salts, which have been characterised for the first time.
- Constable, Edwin C.,Seddon, Kenneth R.
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- Novel di- and tetra(pyrazolyl)bipyridine ligands and their Co (II)-complexes for electrochemical applications
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Novel di- and tetra(pyrazolyl)bipyridine ligands have been prepared from available bipyridine N-oxide and N,N′-dioxide nitro derivatives via nucleophilic substitution reactions. The ligands were converted to the corresponding homoleptic octahedral cobalt
- Zavozin, Alexander G.,Simirskaya, Nina I.,Nelyubina, Yulia V.,Zlotin, Sergei G.
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- Electronic effects on reactivity and anticancer activity by half-sandwich N,N-chelated iridium(iii) complexes
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The synthesis and characterization of a series of organometallic half-sandwich N,N-chelated iridium(iii) complexes bearing a range of electron-donating and withdrawing substituents were described. The X-ray crystal structures of complexes 1, 3 and 5 have been determined. This work demonstrated how the aqueous chemistry, catalytic activity in converting coenzyme NADH to NAD+ and anticancer activity can be controlled and fine-tuned by the modification of the ligand electronic perturbations. In general, the introduction of an electron-withdrawing group (-Cl and-NO2) on the bipyridine ring resulted in increased anticancer activity, whereas an electron-donating group (-NH2,-OH and-OCH3) decreased the anticancer activity. Complex 6 bearing a strongly electron-withdrawing NO2 group displayed the highest anticancer activity (7.3 ± 1.2 μM), ca. three times as active as cisplatin in the A549 cell line. Notably, selective cytotoxicity for cancer cells over normal cells was observed for complexes 1 and 6. DNA binding does not seem to be the primary mechanism for cancer fighting. However, the aqueous chemistry, cell apoptosis and cell cycle, which show similar dependence on the ligand electronic perturbations as the anticancer activity, appear to together contribute to the anticancer potency of theses complexes. This work may provide an alternative strategy to enhance anticancer activity for these N,N-chelated organometallic half-sandwich iridium(iii) complexes.
- Guo, Lihua,Zhang, Hairong,Tian, Meng,Tian, Zhenzhen,Xu, Yanjian,Yang, Yuliang,Peng, Hongwei,Liu, Peng,Liu, Zhe
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p. 16183 - 16192
(2018/10/04)
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- Synthesis and in vitro evaluation of diverse heterocyclic diphenolic compounds as inhibitors of DYRK1A
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Dual-specificity tyrosine phosphorylation-related kinase 1A (DYRK1A) is a dual-specificity protein kinase that catalyses phosphorylation and autophosphorylation. Higher DYRK1A expression correlates with cancer, in particular glioblastoma present within the brain. We report here the synthesis and biological evaluation of new heterocyclic diphenolic derivatives designed as novel DYRK1A inhibitors. The generation of these heterocycles such as benzimidazole, imidazole, naphthyridine, pyrazole-pyridines, bipyridine, and triazolopyrazines was made based on the structural modification of the lead DANDY and tested for their ability to inhibit DYRK1A. None of these derivatives showed significant DYRK1A inhibition but provide valuable knowledge around the importance of the 7-azaindole moiety. These data will be of use for developing further structure-activity relationship studies to improve the selective inhibition of DYRK1A.
- Zhou, Qingqing,Reekie, Tristan A.,Abbassi, Ramzi H.,Indurthi Venkata, Dinesh,Font, Josep S.,Ryan, Renae M.,Munoz, Lenka,Kassiou, Michael
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p. 5852 - 5869
(2018/11/10)
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- Isomer Dependence of Efficiency and Charge Recombination in Dye-Sensitized Solar Cells Using Ru Complex Dyes Bearing Halogen Substituents
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We have synthesised Ru(H2-dcbpy)(N,N′-Y2-bpy)(NCS)2 dyes (where N = 4, 5; Y = F, Cl, Br; N is the position on the bipyridyl ring where the halogen substituent is located) for dye-sensitised solar cells. We show that careful consideration of the position of the substituent, in conjunction with the nature of the substituents, on a bpy ring is important to optimize the solar cells performance. Changing the position (from 4,4′ to 5,5′) along with the nature of the halogen (F, Cl, or Br) substituents were observed to cause changes in the electronic and spectroscopic properties of the dyes as well as influence the recombination rates at the TiO2-dyes-I-/I3- interface affecting the performance of the dyes in DSSCs. Changing the position (from 4,4′ to 5,5′) along with the nature of the halogen (F, Cl, or Br) substituents affects the electronic and spectroscopic properties of the Ru(H2-dcbpy)(N,N′-Y2-bpy)(NCS)2 dyes as well as the recombination rates at the TiO2-dyes-I-/I3- interface hence affecting the performance of the dyes in DSSCs.
- Chadwick, Nina,Kumar, D. Kishore,Ivaturi, Aruna,Grew, Benjamin A.,Upadhyaya, Hari M.,Yellowlees, Lesley J.,Robertson, Neil
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p. 4878 - 4884
(2015/11/02)
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- TBAF-Catalysed silver oxide-mediated cross-coupling of functional trimethysilylpyridines: Access to arylpyridines and bihetaryl compounds
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The concomitant use of silver oxide and catalytic amount of TBAF allowed the efficient and chemoselective coupling of readily available 4-chloro- and 4-methyl-2-trimethyl-silyl-pyridines with heteroaromatic and aromatic halides. Based on control experiments, a mechanism involving the formation of a pyridylsilver intermediate and TBAF recycling is postulated.
- Louerat, Frederic,Tye, Heather,Napier, Spencer,Garrigou, Michael,Whittaker, Mark,Gros, Philippe C.
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scheme or table
p. 1768 - 1773
(2011/04/26)
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- Functional polypyridine ligands from copper-mediated room temperature coupling of 4-chloro-2-trimethylsilylpyridine
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A range of functional polypyridine ligands (bipyridines and terpyridine) has been synthesized by copper-mediated oxidative homocoupling of 4-chloro-2-trimethylsilylpyridine or cross-coupling with functional bromopyridines. The reaction proceeded smoothly at room temperature.
- Lou?rat, Frédéric,Gros, Philippe C.
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supporting information; experimental part
p. 3558 - 3560
(2010/08/07)
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- Conversion of solar energy to chemical energy
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The rate of evolution of hydrogen from water by photochemical process using solar energy has been investigated employing fourteen metal complexes as catalysts, ten electron relays, three electron donors and two co-catalysts in different permutation and combinations. The effect of varying reaction conditions like temperature, concentration and pH have also been investigated for the optimum production of hydrogen by the photochemical cleavage of water molecules.
- Ranganayakulu,Murthy
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p. 309 - 316
(2011/08/09)
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- Synthesis of 2,4-dibromopyridine and 4,4'-dibromo-2,2'-bipyridine. Efficient usage in selective bromine-substitution under palladium-catalysis
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We report an efficient method for preparing 2,4-dibromopyridine and 4,4'-dibromo-2,2'-bipyridine from the corresponding nitroazine N-oxide in one step via a tandem nucleophilic substitution-N-oxide reduction process. The one step preparation of 4,4'-dihalo-2,2'-bipyridines from dihalopyridines via a Stille reaction is also described. 4,4'-Dibromo-2,2'-bipyridine undergoes selective mono- or disubstitution processes under palladium catalysis. This short synthetic procedure is an efficient and reliable process for preparing conjugated pyridine and 2,2'-bipyridine building blocks for applications in coordination chemistry and materials science.
- Garcia-Lago, Ramon,Alonso-Gomez, Jose-Lorenzo,Sicre, Cristina,Cid, Maria-Magdalena
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- Syntheses, characterizations, and properties of electronically perturbed 1,1′-dimethyl-2,2′-bipyridinium tetrafluoroborates
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The syntheses of three new 2,2′-bipyridinium tetrafluoroborate sensitizers are reported. Their preliminary electrochemical and photophysical properties are compared to the properties of the more widely used pyrylium cation sensitizers. In addition, the first examples of triplet-triplet absorption spectra of 2,2′-bipyridinium ions are presented.
- Zhang, Dong,Dufek, Eric J.,Clennan, Edward L.
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p. 315 - 319
(2007/10/03)
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- Hiyama cross-coupling of chloro-, fluoro-, and methoxypyridyltrimethylsilanes: Room-temperature novel access to functional bi(het)aryl
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(Chemical Equation Presented) The incorporation of chloro, fluoro, or methoxy substituents on the pyridine ring of pyridyltrimethylsilanes allowed us to perform efficient Hiyama cross-coupling with various (het)aryl halides. The reactions proceeded smoothly at room temperature leading to the corresponding functional bis(het)aryl in fair to excellent yields. The presence of pyridine nitrogen α to the trimethylsilyl group was requisite to achieve the cross-coupling.
- Pierrat, Philippe,Gros, Philippe,Fort, Yves
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p. 697 - 700
(2007/10/03)
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- Catalytic Conversions in Water. Part 22: Electronic Effects in the (Diimine)palladium(II)-Catalysed Aerobic Oxidation of Alcohols
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The electronic effects in the (diimine)Pd-(II)-catalysed aerobic oxidation of alcohols were investigated from the viewpoint of both the catalyst and the alcohol. A 'push-pull' mechanism is operative, where both electron-donating substituents on the benzyl alcohol (ρ = -0.58) and electron-withdrawing groups on the 4,4′-disubstituted-2,2′-bipyridine ligand (ρ = +0.18) increase the reaction rate. The results indicate partial reduction of the palladium centre in the transition state of the rate-limiting step.
- Ten Brink, Gerd-Jan,Arends, Isabel W. C. E.,Hoogenraad, Marcel,Verspui, Goeran,Sheldon, Roger A.
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p. 497 - 505
(2007/10/03)
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- LUMINESCENT METAL COMPLEXES. PART 1. TRIS-CHELATES OF SUBSTITUTED 2,2'-BIPYRIDYLS WITH RUTHENIUM(II) AS DYES FOR LUMINESCENT SOLAR COLLECTORS
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Ruthenium(II) and osmium(II) complexes of 2,2'bipyridyls (bipy) and 1,10-phenanthrolines (phen) are identified as feasible dyes for use in luminecsent solar collectors.Twenty-seven RuII)bipy)32+ complexes are prepared and the absorption and emission spectra of their solutions in EtOH-MeOH at room temperature are reported.Quantum efficiencies, wich are sensitive to oxygen quenching, vary between 0.002 and 0.306 depending upon substituents.The effect of the medium on the spectral properties of selected compounds has also been investigated.Measured quantum yields of non-aqueous solutions are higher than those for aqueous solutions but lower than for doped plastic films.
- Cook, Michael J.,Lewis, Anthony P.,McAuliffe, Glenn S. G.,Skarda, Vladimir,Thomson, Andrew J.,et. al.
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p. 1293 - 1302
(2007/10/02)
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- Studies of 2,2'-Bipyridyl N,N'-Dioxides
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2,2'-Bipyridyl N,N'-dioxide, its derivatives substituted at the 4- and/or 4'-positions by methoxy, nitro, chloro, and bromo groups, and the corresponding N,N'-deoxygenated compounds have been synthesized.The N,N'-dioxides were examined in a number of refluxing solvents and under sublimation to investigate a potential liberation of singlet oxygen.All N,N'-dioxides were found to be stable under such conditions with no production of the corresponding N,N'-deoxygenated compounds.
- Wenkert, David,Woodward, R. B.
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p. 283 - 289
(2007/10/02)
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- SUBSTITUTED 2,2'-BIPYRIDINES AS LIGANDS. PREPARATION AND CHARACTERIZATION OF 4,4'-DISUBSTITUTED 2,2'-BIPYRIDINE DERIVATIVES OF THE HEXACARBONYLS OF CHROMIUM, MOLYBDENUM AND TUNGSTEN
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The preparation of cis- (M=Cr, Mo, W; biL is 4,4'-X2-2,2'-bipyridine; X=NMe2, NH2, OMe, CMe3, Me, H, Ph, CH=CHPh, Cl, CO2H, CO2Me, NO2) is reported.The ligands and complexes are characterized by spectroscopy (IR, electronic absorption and emission, NMR (1H, 13C, 15N, 95Mo)) and microanalysis.The variations observed in the spectroscopic properties of these complexes are strongly correlated with electronic substituent parameters of the group X.This is most apparent in the lowest energy (visible) absorption which changes by ca. 0.8 eV between the extremes of donor and off acceptor substituent used.
- Connor, Joseph P.,Overton, Colin
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p. 165 - 174
(2007/10/02)
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