Browsing by Author "Wen, Yuh-Sheng"

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Carbodicarbenes: Unexpected pi-Accepting Ability during Reactivity with Small Molecules
(2017-09-13)
Chen, Wen-Ching
;
Shih, Wei-Chih
;
Jurca, Titel
;
Zhao, Lili
;
Andrada, Diego M.
An investigation of carbodicarbenes, the less explored member of the carbenic complex/ligand family has yielded unexpected electronic features and concomitant reactivity. Observed 1,2-addition of E-H bonds (E = B, C, Si) across the carbone central carbon and that of the flanking N-heterocyclic carbene (NHC) fragment, combined with single-crystal X-ray studies of a model Pd complex strongly suggests a significant level of pi-accepting ability at the central carbon of the NHC moiety. This feature is atypical of classic NHCs, which are strong sigma-donors, with only nominal pi-accepting ability. The unanticipated pi-acidity is critical for engendering carbodicarbenes with reactivity more commonly observed with frustrated Lewis pairs (FLPs) rather than the more closely related NHCs and cyclic (alkyl)(amino)carbenes (CAACs).
Dibenzothiophene/oxide and quinoxaline/pyrazine derivatives serving as electron-transport materials
(2006-07-21)
Huang, Tai-Hsiang
;
Whang, Wha-Tzong
;
Shen, Jiun Yi
;
Wen, Yuh-Sheng
;
Lin, Jiann T.
A series of 2,8-disubstituted dibenzothiophene and 2,8-disubstituted dibenzothiophene-SS-dioxide derivatives containing quinoxaline and pyrazine moieties are synthesized via three key steps: i) palladium-catalyzed Sonogashira coupling reaction to form dialkynes; ii) conversion of the dialkynes to diones; and iii) condensation of the diones with diamines. Single-crystal characterization of 2,8-di(6,7-dimethyl-3-phenyl-2-quinoxalinyl)-5H-5 lambda(6)-dibenzo[b,d]thiophene-5,5-dione indicates a triclinic crystal structure with space group P1 and a non-coplanar structure. These new materials are amorphous, with glass-transition temperatures ranging from 132 to 194 degrees C. The compounds (Cpd) exhibit high electron mobilities and serve as effective electron-transport materials for organic light-emitting devices. Double-layer devices are fabricated with the structure indium tin oxide (ITO)/Qn/Cpd/LiF/Al, where yellow-emitting 2,3-bis[4-(N-phenyl-9-ethyl-3-carbazolylamino)phenyl]quinoxaline (Qn) serves as the emitting layer. An external quantum efficiency of 1.41 %, a power efficiency of 4.94 lm W-1, and a current efficiency of 1.62 cd A(-1) are achieved at a current density of 100 mA cm(-2).
Influence of molecular dipoles on the photoluminescence and electroluminescence of dipolar spirobifluorene
(2007-01-01)
Chiang, Chih-Long
;
Tseng, Shih-Min
;
Chen, Chin-Ti
;
Hsu, Chao-Ping
;
Wen, Yuh-Sheng
Here we study a series of strongly fluorescent spirobifluorene compounds, red PhSPDCV and blue PhSPDPV, together with their spiro "dimer" analogs, BisPhSPDCV and blue BisPhSPDPV. We found that the fluorescence quantum yield as well as the OLED performance of the strongly dipolar red PhSPDCV decrease significantly in the "dimeric" analog BisPhSPDCV, but not in the weakly dipolar PhSPDPV and BisPhSPDPV. On the other hand, by doping the highly dipolar PhSPDCV to an isolated environment having low polarity Alq3 as the host matrix and avoiding the emission-quenching dipole from the neighboring molecules, very high performance of saturated yellow OLEDs has been obtained as well.
Interface-Controlled Synthesis of Au-BINOL Hybrid Nanostructures and Mechanism Study
(2018-11-13)
Patlolla, Shashank Reddy
;
Kao, Chen-Rui
;
Yeh, Ai-Hsuan
;
Lin, Hung-Min
;
Chuang, Yu-Chun
The combined functionality of components in organic inorganic hybrid nanomaterials render them efficient nanoreactors. However, the development in this field is limited due to a lack of synthetic avenues and systematic control of the growth kinetics of hybrid structures. In this work, we take advantage of an ionic switch for regio-control of Au-BINOL(1,1'-Bi-2-naphthol) hybrid nanostructures. Aromatic BINOL molecules assemble into nanospheres, concomitant with the growth of the Au nanocrystals. The morphological evolution of Au nanocrystals is solely controlled by the presence of halides in the synthetic system. Here we show that quaternary ammonium surfactants (CTAB or CTAC), not only bridging Au and BINOL, but also contributing to the formation of concentric or eccentric structures when their concentrations are tuned to the range of 10(-5) to 10(-3) M. This facile strategy offers the potential advantage of scalable production, with diverse functional organic inorganic hybrid nanocomposites being produced based on the specific archetype of Au-BINOL hybrid nano composites.
Synthesis and characterization of donor-acceptor-substituted fluorene fluorophores for non-doped red organic light emitting diodes
(2006-12-01)
Chiang, Chih-Long
;
Wen, Ya-Ju
;
Wen, Yuh-Sheng
;
Shu, Ching-Fong
;
Chen, Chin-Ti
A series of fluorene fluorophores bearing bis(4-methoxyphenyl)amino electron donating substitutent as well as bisbenzothiazolylvinyl (AFDB), benzothiazolylcyanovinyl (AFCB), or dicyanovinyl (AFDC) electron accepting substituent were synthesized and characterized. A non-doped red organic light-emitting diode (OLED) device based on AFCB exhibited deep red (lambda(el)(max) = 670 nm, CIE, x = 0.65, y = 0.34) electroluminescence with brightness over 2380 cd/m(2) and an external quantum efficiency higher than 1.2%.