Browsing by Author "Liu, Yi-Hung"

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Bis(diphenylamino)-9,9 '-spirobifluorene functionalized Ir(III) complex: a conceptual design en route to a three-in-one system possessing emitting core and electron and hole transport peripherals
(2011)
Chen, Hsiao-Fan
;
Wong, Ken-Tsung
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Liu, Yi-Hung
;
Wang, Yu
;
Cheng, Yi-Ming
Conceptual design of a three-in-one (luminescence chromophore with electron and hole transports) system was demonstrated by a functionalized Ir(III) complex 3, in which 4,5-diazafluorene and bis(diphenylamino) serve as electron and hole transporting sites, respectively. The poor emission quantum yield of 3 was systematically examined via a series of photophysical studies in combination with theoretical approaches. The far lifting of the pi-electron from -NPh(2) renders virtually no (3)MLCT contribution to the lowest transition in the triplet manifold as compared with that of the parent model 2 without amino substituents. With an empirical approach, we conclude that an energy gap law may account for the major deactivation process. A light-emitting electrochemical cell (LEC) device based on 3 shows peak EQE, peak current efficiency and peak power efficiency at 2.4 V of 0.020%, 0.013 cd A(-1) and 0.017 lm/W, respectively. The low device efficiencies are in accordance with the low PL quantum yield, stemming from the ligand-centered radiationless deactivation. The conceptual design presented here should provide valuable information for future progress en route to an ideal three-in-one system suited for OLEDs.
Cationic Iridium Complexes with Intramolecular pi-pi Interaction and Enhanced Steric Hindrance for Solid-State Light-Emitting Electrochemical Cells
(2012-11-19)
Chen, Hsiao-Fan
;
Hung, Wen-Yi
;
Chen, Shou-Wei
;
Wang, Ting-Chih
;
Lin, Shih-Wei
Cationic iridium complexes incorporated 4,5-diaza-9,9'-spirobifluorene as N<^>N ancillary ligands, in which one (2) or two (3) phenyl groups were introduced onto 4,5-diazafluorene to afford intraligand pi-pi interactions. The X-ray crystal structures of complexes 2 and 3 show that the pendant phenyl ring forms strong intramolecular face-to-face pi-stacking with the difluorophenyl ring of the cyclometalated ligand with distances of 3.38 angstrom for complex 2 and 3.40 and 3.46 angstrom for complex 3. This pi-pi stacking interaction minimizes the expansion of the metal ligand bonds in the excited state, resulting in a longer device lifetime in the light-emitting electrochemical cell (LEC) devices.
Cooperative Recognition of a Copper Cation and Anion by a Calix[4]arene Substituted at the Lower Rim by a beta-Amino-alpha,beta-Unsaturated Ketone
(2009)
Senthilvelan, Annamalai
;
ho, I. -Ting
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Chang, Kai-Chi
;
Lee, Gene-Hsiang
;
Liu, Yi-Hung
We report herein a new ditopic calix[4]arene receptor 25,27-bis{[4-amino-4-(1-naphthyl)-2-oxo-3-butenyl]oxy}-26,28-dihydroxycalix[4]arene (2) for the simultaneous complexation of anionic and cationic species. The host molecule 25,27-bis{[3-(1-naphthyl)-5-isoxazolyl]methoxy}-26,28-dihydroxycalix[4]arene (1) was synthesised first and was followed by a [Mo(CO)(6)]mediated ring-opening reaction to give the target receptor 2. The binding properties of ligands 1 and 2 towards metal ions in CH(3)CN were investigated by UV/Vis and fluorescence spectroscopies. The results showed that both ligands I and 2 were highly selective for Cu(II) ions. Upon titration with Cu(II), the fluorescence of I was severely quenched, whereas 2 showed strong fluorescence enhancement because the metal ions help to lock the conformation of the fluorophores. During the complexation of 2 with Cu(II), the Cu(II) was reduced to Cu(I) by the free phenolic OH of 2, whereas the phenol was oxidised by Cu(II), after which it assisted in the trapping of Cu(I). Ditopic behaviour was observed for the complex 2 center dot Cu(I), which showed further enhancement of its fluorescence intensity upon complexation with anions such as acetate or fluoride.
Cooperativity and Site-Selectivity of Intramolecular Hydrogen Bonds on the Fluorescence Quenching of Modified GFP Chromophores
(2015-12-18)
Chang, Deng-Hsiang
;
Ou, Chun-Lin
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Hsu, Hung-Yu
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Huang, Guan-Jhih
;
Kao, Chen-Yi
This paper provides the first example of experimentally characterized hydrogen-bond cooperativity on fluorescence quenching with a modified green fluorescence protein (GFP) chromophore that contains a 6-membered C=N center dot center dot center dot H-O and a 7-membered C=O center dot center dot center dot H-O intramolecular H-bonds. Variable-temperature H-1 NMR and electronic absorption and emission spectroscopies were used to elucidate the preference of intra- vs intermolecular H-bonding at different concentrations (1 mM and 10 mu M), and X-ray crystal structures provide clues of possible intermolecular H-bonding modes. In the ground state, the 6-membered H-bond is significant but the 7-membered one is rather weak. However, fluorescence quenching is dominated by the 7-membered H-bond, indicating a strengthening of the H-bond in the excited state. The H-bonding effect is more pronounced in more polar solvents, and no intermediates were observed from femtosecond fluorescence decays. The fluorescence quenching is attributed to the occurrence of diabatic excited-state proton transfer. Cooperativity Of the two intramolecular H-bonds on spectral shifts and fluorescence quenching is evidenced by comparing with both the single H-bonded and the non-H-bonded counterparts. The H-bond cooperativity does not belong to the conventional patterns of sigma- and pi-cooperativity but a new type of polarization interactions, which demonstrates the significant interplay of H-bonds for multiple H-bonding systems in the electronically excited states.
Editorial Message: Special Issue on Fuzzy Brain-Computer Interface Systems
(2017-04-01)
Liu, Yi-Hung
;
Jung, Tzyy-Ping
;
Lin, Chin-Teng
;
Liao, Lun-De
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交大名義發表
Iptycenes with an acridinone motif developed through [4+2] cycloaddition of tethered naphthalene and iminoquinone via a radical reaction
(2017-06-11)
Raju, Selvam
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Annamalai, Pratheepkumar
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Chen, Pei-Ling
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Liu, Yi-Hung
;
Chuang, Shih-Ching
A new class of iptycenes was developed by combining 2-(naphthalen-1-yl) anilines and p-benzoquinones through copper( II)-mediated radical cyclisation. This unusual cyclisation reaction resulted in the robust and efficient syntheses of iptycenes with an acridinone motif. These iptycenes can be further transformed into planar acridinone heterocyclics through the Diels-Alder reaction.
Mathematical Methods Applied to Digital Image Processing
(2014)
Liu, Yi-Hung
;
Chen, Chung-Hao
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Chao, Paul C. -P.
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Palladium(II)-Catalyzed Mono- and Bis-alkenylation of N-Acetyl-2-aminobiaryls through Regioselective C-H Bond Activation
(2018-04-06)
Annamalai, Pratheepkumar
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Hsu, Kou-Chi
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Raju, Selvam
;
Hsiao, Huan-Chang
;
Chou, Chih-Wei
We developed palladium-catalyzed oxidative coupling of olefins with N-acyl 2-aminobiaryls through a sequence of ortho C-H bond activation/alkene insertion/reductive elimination. Furthermore, we controlled the selectivity of mono- and bis-alkenylation products with the solvent effect. The developed protocol was promising for a broad substrate scope ranging from activated olefins with a wide variety of functional groups to unactivated olefins.
Palladium-Catalyzed C-H Bond Activation by Using Iminoquinone as a Directing Group and an Internal Oxidant or a Co-oxidant: Production of Dihydrophenanthridines, Phenanthridines, and Carbazoles
(2017-08-04)
Raju, Selvam
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Annamalai, Pratheepkumar
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Chen, Pei-Ling
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Liu, Yi-Hung
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Chuang, Shih-Ching
A palladium-catalyzed C-H bond activation reaction, via a redox-neutral pathway, for the preparation of dihydrophenanthridine, phenanthridine, and carbazole derivatives from biaryl 2-iminoquinones is developed. The preinstalled iminoquinone was designed to act as a directing group for ortho C-H activation and an internal oxidant or a co-oxidant. This catalysis proceeded through the following sequence: C-H bond activation, coordination and insertion of activated olefins, beta-hydride elimination, H-shift, insertion, and protonation or beta-hydride elimination. using this method without the addition of external oxidants. In addition, carbazoles can be prepared efficiently by
Synthesis, Isolation, and Characterization of Mono- and Bis-norbornene-Annulated Biarylamines through Pseudo-Catellani Intermediates
(2019-02-15)
Annamalai, Pratheepkumar
;
Hsiao, Huan-Chang
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Raju, Selvam
;
Fu, Yi-Hsuan
;
Chen, Pei-Ling
A palladium-catalyzed C-H functionalization of an external ring of N-acyl 2-aminobiaryl with bicyclo[2.2.1]-hept-2-ene (norbornene) via multiple C-H bond activations was developed. This study is the first report of the formation of bis-norbornene annulated biarylamines isomers (syn-3a'/anti-3a' = 36:64) from multiple C-H bond functionalizations. Additionally, nondirected C-H bond functionalization at the C-4' position with alkenes rendered complete C-H functionalization of five C-H bonds that formed a stable hexasubstituted benzene ring.