Electron-deficient moiety

Burn and coworkers [173] synthesized copolymer 143, containing a similar electron deficient moiety (triazole) incorporated in the PPV backbone. They have reported an efficient blue emission from this polymer (APL = 466 nm (solution), 486 nm (film), PL = 33% (film)) although the efficiency of the PLED fabricated as ITO/PPV/143/A1 was not very high (CT>j ) reached 0.08% at a luminance of 250 cd/m2). 

L.-S. Yu and S.A. Chen, Full-range tunability of electron and hole carrier mobilities and density ratios via incorporation of highly electron-deficient moieties in poly(phenylene vinylene) side chains, Adv. Mater., 16 744-748, 2004. 

Oligomers with 11 thiophene units showed an absorption maximum at 462 nm (91JA5887). The terthiophene derivative 21 and some other oli-gothiophene derivatives were studied because the coexistence of an electron-rich moiety (the terthiophene spine) and electron-deficient moiety (the dicyanomethylene groups on either side of the molecule) is expected to cause intramolecular charge-transfer (89BCJ1539 95BCJ2363 ... 

An empirical rule on a similar photoreactivity between mono- and di-olefin crystals (see Sect. II. a.) has been explained by correlating common molecular shape and packing with common intermolecular contacts between electron-rich and electron-deficient moieties in these olefin crystals. 

Replacement of 1,3,5-triscyanobenzene in 109 by 1,3,5-triazine results in 111 [428]. This TPA chromophore also exhibits large TPA. 1,3,5-Triazine is an electron-deficient moiety. It has a reduction potential of about —2 V [516], showing that reduction needs less energy in 1,4-cyanobenzene (Eted = — 1.6V[493]) but more in 1,2,4,5-tetrafluorobenzene (EItd = —2.4 V [342]). Thus, 111 exhibits an additional chromophore with three dipolar arms, in which each arm contributes... 

For PFs with HTM grafting as side chain, the alternating copolymer 18 with electron-deficient moiety (4-ferf-butylphcnyl-l,3,4-oxadiazole) functionalized fluorene and monomer of PFO was synthesized by Shu and coworkers [31]. The device with the configuration ITO/PEDOT PSS/18/Ca/Ag showed improved performance turn-on voltage of 5.3 V (defined as voltage needed for brightness of 1 cdm-2), maximum brightness 2770 cdm-2 at 10.8 V, and maximum external quantum efficiency 0.52% at 537 cdm-2 rela-... 

Another electron-deficient moiety, quinoline, was introduced into PF 19 by Su et al. [32]. However, the EL device performance (with the structure ITO/PEDOT PSS/19/l,3,5-tris-(M-phenylbenzimidazol-2-yl)benzene (TPBI)/ Mg Ag) remains low, with the maximum external quantum efficiency of 0.8%, maximum luminance of 1121 cd m-2 and high turn-on voltage of 7.2 V. Therefore, the introduction of electron-deficient moieties (either 4-ferf-butylphenyl-1,3,4-oxadiazol e or quinoline) cannot provide efficient EL performance, probably due to the large hole-injection barrier. 

Our group reported that capping both ends of the PFO chain with electron-deficient moieties (oxidazole, OXD, and triazole, TAZ), which can induce a minor amount of long conjugating length species (regarded as the /1-phase),... 

As mentioned in Sect. 2.2.1.3 [33], we proposed that a trace amount of /3-phase, induced by the use of an electron-deficient moiety (TAZ) as an end-capper for PFO, can improve device performance to give a better blue purity. Following the idea of /3-phase formation, we further proposed a novel simple physical method to generate /3-phase at a content of up to 1.32% in a PFO film spin-coated on a substrate (the remaining part is amorphous phase) by immersing it in a mixed solvent/non-solvent (tetrahydrofuran/methanol) for a few seconds [45]. The device based on PFO with 1.32% / -phase (ITO/PEDOT PSS/emitting polymer/CsF/Al) has a dramatically enhanced device efficiency and an improved blue-color purity of 3.85 cd A-1 (external quantum efficiency, 3.33%) and CIE of x+y = 0.283 (less than the limit of... 

For fluorene co-oligomers, the band gap often changes with concomitant changes to the energy levels of the compound [69]. Inclusion of electron-rich co-monomer units, predominantly raises the HOMO level [147,172], while electron-deficient moieties mostly lower the LUMO level [69,80,173]. Attachment through direct conjugation with electronically neutral cores has more... 

Trichothecene mycotoxins are secondary metabolites of various fungal species. Structures of some trichothecene mycotoxins of interest to the US ARMY are given in Figure 1. Several methods have been reported for the analysis of these toxins (1-11, 15). Of these, mass spectrometry techniques are both sensitive and definitive when applied to toxicologic and environmental samples. With current technology, the most sensitive and qualitatively definitive analytical technique for the determination of these toxins is derivatization with an electron deficient moiety followed by analysis with negative ion chemical ionization gas chromatography-mass spectrometry (NICI-GC/HS). 

Polyfluorene is one of the most attractive conjugated polymers for application in light-emitting devices [36-38], It is characterized by low electron affinity and, in consequence, several authors have inserted electron-deficient moieties into the aromatic chain to modify the position of the frontier orbital and increase the electron affinity in order to achieve a better balanced hole and electron injection in electroluminescent diodes. Among the electron-deficient groups, thienyl-5,5-dioxide and dibenzothienyl-5,5-dioxide have also been employed [16-18, 20-25, 27, 28],... 

M. C. Hung, J.L. Liao, S. A. Chen, S. H. Chen and A. C. Su, Fine tuning the purity of blue emission from polydioctylfluorene by end-capping with electron-deficient moieties, J. Am. Chem. Soc., 127,14576-14577 (2005). 

For electron transport/hole blocking purposes, a wide variety of electron-deficient moieties are well known, e.g., 1,3,4-oxadiazoles [12], 1,2,4-triazoles [13], 1,3-oxazoles, pyridines and quinoxalines [14] (see Scheme 3). Materials with conjugated 7i-electron system (e.g., styrylarylenes, arylenes, stilbenes, oligo- and poly(thiophene)s — see Scheme 3) are widely used as combined charge transport and luminescence layers as well [12,15]. 

Alkylation and Allylation. The use of TBAT as a fluoride source for the in situ formation of pentacoordinate silicates from silanes of alkyl and allyl substituents, generating electron-rich carbon centers capable of acting as nucleophiles toward electron deficient moieties, has been well documented for over a decade. Recently, A-acylhydrazones have been shown to undergo highly diastereoselective allylations when treated with allylsilanes, TBAT, and indium(III) trifluoromethanesulfonate (eq 10). ... 

Another wide family of purely organic interlocked systems has been developed by Stoddart s group, based on hydrogen bonding and on donor-acceptor interactions. Suitably sized crown ethers can form pseudorotaxane complexes with appropriate secondary dialkylammonium ions which rely on N —H - 0 and C—H - 0 hydrogen bonds for stabiUzation. Similarly, a r-electron rich component, in interaction with a r-electron deficient moiety (traditionally cyclobis(paraquat-p-phenylene), CBPQ T, 21, ... 

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