Browsing by Author "Hsu, Chao-Ping"

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An incoherent feed-forward loop switches the Arabidopsis clock rapidly between two hysteretic states
(2018-09-17)
Joanito, Ignasius
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Chu, Jhih-Wei
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Wu, Shu-Hsing
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Hsu, Chao-Ping
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生物科技學系
In higher plants (e.g., Arabidopsis thaliana), the core structure of the circadian clock is mostly governed by a repression process with very few direct activators. With a series of simplified models, we studied the underlying mechanism and found that the Arabidopsis clock consists of type-2 incoherent feedforward loops (IFFLs), one of them creating a pulse-like expression in PRR9/7. The double-negative feedback loop between CCA1/LHY and PRR5/TOC1 generates a bistable, hysteretic behavior in the Arabidopsis circadian clock. We found that the IFFL involving PRR9/7 breaks the bistability and moves the system forward with a rapid pulse in the daytime, and the evening complex (EC) breaks it in the evening. With this illustration, we can intuitively explain the behavior of the clock under mutant conditions. Thus, our results provide new insights into the underlying network structures of the Arabidopsis core oscillator.
Carbodicarbenes: Unexpected pi-Accepting Ability during Reactivity with Small Molecules
(2017-09-13)
Chen, Wen-Ching
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Shih, Wei-Chih
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Jurca, Titel
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Zhao, Lili
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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).
Influence of molecular dipoles on the photoluminescence and electroluminescence of dipolar spirobifluorene
(2007-01-01)
Chiang, Chih-Long
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Tseng, Shih-Min
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Chen, Chin-Ti
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Hsu, Chao-Ping
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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.
Influence of molecular dipoles on the photoluminescence and electroluminescence of dipolar spirobifluorenes
(2008-01-24)
Chiang, Chih-Long
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Tseng, Shih-Min
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Chen, Chin-Ti
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Hsu, Chao-Ping
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Shu, Ching-Fong
This Full Paper investigates a series of strongly fluorescent donor-acceptor-substituted spirobifluorene compounds, red 2-diphenylamino-7-(2,2-dicyanovinyl)-9,9'-spirobifluorene (DCV), green 2-diphenylamino-9,9'-spirobifluorene7-carxoxaldehyde (CHO), and blue 2-diphenylamino-7-(2,2-diphenylvinyl)-9,9'-spirobifluorene (DPV), together with their spiro-linked "dimeric" analogs, 2DCV, 2,2'-bis(diphenylamino)-9,9'-spirobifluorene-7,7'-dicarboxaldehyde (2CHO), and 2,2'-bis(diphenylamino)-7,7'bis(2,2-diphenylvinyl)-9,9'-spirobifluorene (2DPV), respectively. The emission optical density and, hence, the intensity of photoluminescence (PL) or electroluminescence (EL) of the "dimeric" analogs is presumed to increase, which is beneficial for organic light-emitting diode (OLED) applications. The physical properties, including the dipole moments obtained from quantum chemistry calculations, emission solvatochromism, fluorescence quantum yield (Of) as well as the EL of these six spirobifluorene compounds have been examined in detail. We found that Of as well as OLED performance (EL efficiency and intensity) of the strongly dipolar DCV decrease significantly in the "dimeric" analog 2DCV, but less so in the moderately dipolar CHO and 2CHO, and only slightly in the weakly dipolar DPV and 2DPV. This is parallel to the intramolecular dipole moment, which is large for 2DCV, medium for 2CHO, and very small for 2DPV. Here, we show for the first time systematically that the luminescence intensity is closely correlated with the local electric field induced by the molecular dipole. A strong electric field may facilitate radiationless decay channels with a charge-transfer nature, leading to a high quenching rate. Consistent with this conclusion, which is derived from the red DCV/2DCV and green CHO/2CHO, our new blue fluorophore DPV with an essentially zero dipole moment has successfully achieved one of the best electrofluorescent blue OLEDs. At the same time, by doping the highly dipolar DCV into an isolated environment with the low-polarity Alq(3) as the host matrix, we obtained a very high performance of saturated yellow OLEDs as well, This is possibly due to the reduction of emission-quenching dipoles from the neighboring molecules. Our results have provided an important insight in designing luminescent materials, as follows: molecular dipole moments should be kept at a low magnitude to avoid quenching induced by a strong local electric field in the chromophore.
Influence of Phenylethynylene of Push-Pull Zinc Porphyrins on the Photovoltaic Performance
(2016-02-10)
Chou, Hsien-Hsin
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Reddy, Kamani Sudhir K.
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Wu, Hui-Ping
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Guo, Bo-Cheng
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Lee, Hsuan-Wei
A series of zinc porphyrin dyes YD22-YD28 were synthesized and used for dye-sensitized solar cells. Dyes YD26-YD28 consist of zinc porphyrin (ZnP) as core unit, arylamine (Am) as electron-donating group, and p-ethynylbenzoic add (EBA) as an electron-withdrawing/-anchoring group. The dyes YD22-YD25 contain additional phenylethynylene group (PE) bridged between Am and ZnP units. The influence of the PE unit on molecular properties as well as photovoltaic performances were investigated via photophysical and electrochemical studies and density functional calculations. With the insertion of PE unit, the dyes YD22-YD25 possess better light-harvesting properties in terms of significantly red-shifted Q-band absorption. The conversion efficiencies for dyes YD22-YD25 are better than those of dyes YD26-YD28 owing to larger J(SC) output. Natural transition orbitals and Mulliken charge analysis were used to analyze the electron injection efficiency for porphyrin dyes upon time-dependent DFT calculations. The results indicated that insertion of additional PE unit is beneficial to higher J(SC) by means of improved light-harvesting property due to broadened and red-shifted absorption.
LWD-TCP complex activates the morning gene CCA1 in Arabidopsis
(2016-10-13)
Wu, Jing-Fen
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Tsai, Huang-Lung
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Joanito, Ignasius
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Wu, Yi-Chen
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Chang, Chin-Wen
A double-negative feedback loop formed by the morning genes CIRCADIAN CLOCK ASSOCIATED1 (CCA1)/LATE ELONGATED HYPOCOTYL (LHY) and the evening gene TIMING OF CAB EXPRESSION1 (TOC1) contributes to regulation of the circadian clock in Arabidopsis. A 24-h circadian cycle starts with the peak expression of CCA1 at dawn. Although CCA1 is targeted by multiple transcriptional repressors, including PSEUDO-RESPONSE REGULATOR9 (PRR9), PRR7, PRR5 and CCA1 HIKING EXPEDITION (CHE), activators of CCA1 remain elusive. Here we use mathematical modelling to infer a co-activator role for LIGHT-REGULATED WD1 (LWD1) in CCA1 expression. We show that the TEOSINTE BRANCHED 1-CYCLOIDEA-PCF20 (TCP20) and TCP22 proteins act as LWD-interacting transcriptional activators. The concomitant binding of LWD1 and TCP20/TCP22 to the TCP-binding site in the CCA1 promoter activates CCA1. Our study reveals activators of the morning gene CCA1 and provides an action mechanism that ensures elevated expression of CCA1 at dawn to sustain a robust clock.
Molecular design of near-infrared fluorescent Pdots for tumor targeting: aggregation-induced emission versus anti-aggregation-caused quenching
(2019-01-07)
Tsai, Wei-Kai
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Wang, Chun-I.
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Liao, Chia-Hsien
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Yao, Chun-Nien
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Kuo, Tsai-Jhen
Semiconducting polymer dots (Pdots) have recently emerged as a new type of ultrabright fluorescent probe that has been proved to be very useful for biomedical imaging. However, Pdots often suffer from serious fluorescence aggregation-caused quenching (ACQ) especially for near-infrared (NIR) fluorescent Pdots. This article compared two strategies to overcome the ACQ effect in near-infrared emissive Pdot systems: aggregation-induced emission (AIE) and anti-aggregation-caused quenching (anti-ACQ). The results show that the anti-ACQ platform outperforms the AIE system. The fluorescence quantum yield of anti-ACQ-based Pdots can be over 50% and the average per-particle brightness of the Pdots is about 5 times higher than that of the commercially available quantum dots. To help understand why the monomer conformations could greatly affect the optical properties of Pdots, molecular dynamics simulations were performed for the first time in such complicated Pdot systems. To demonstrate applications for in vivo fluorescence imaging, both microangiography imaging on living zebrafish embryos and specific tumor targeting on mice were performed. We anticipate that these studies will pave the way for the design of new highly fluorescent Pdot systems.
One-Pot Tandem Photoredox and Cross-Coupling Catalysis with a Single Palladium Carbodicarbene Complex
(2018-04-16)
Hsu, Yu-Cheng
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Wang, Vincent C. -C.
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Au-Yeung, Ka-Chun
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Tsai, Chung-Yu
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Chang, Chun-Chi
The combination of conventional transition-metal-catalyzed coupling (2e(-) process) and photoredox catalysis (1e(-) process) has emerged as a powerful approach to catalyze difficult cross-coupling reactions under mild reaction conditions. Reported is a palladium carbodicarbene (CDC) complex that mediates both a Suzuki-Miyaura coupling and photoredox catalysis for C-N bond formation upon visible-light irradiation. These two catalytic pathways can be combined to promote both conventional transition-metal-catalyzed coupling and photoredox catalysis to mediate C-H arylation under ambient conditions with a single catalyst in an efficient one-pot process.
Synthesis and Isolation of an Acyclic Tridentate Bis(pyridine)carbodicarbene and Studies on Its Structural Implications and Reactivities
(2015-02-16)
Hsu, Yu-Chen
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Shen, Jiun-Shian
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Lin, Bo-Chao
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Chen, Wen-Ching
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Chan, Yi-Tsu
The simple synthetic development of acyclic pincer bis(pyridine)carbodicarbene is depicted herein. Presented is the first isolated structural pincer carbodicarbene with a C-C-C angle of 143 degrees, larger than the monodentate framework. More importantly, theoretical analysis showed that this carbodicarbene embodies a more allene-like character. Palladium complexes supported by this pincer ligand are active catalysts for Heck-Mizoroki and Suzuki-Miyaura coupling reactions.
The Elusive Three-Coordinate Dicationic Hydrido Boron Complex
(2014-01-22)
Chen, Wen-Ching
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Lee, Ching-Yu
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Lin, Bo-Chao
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Hsu, Yu-Chen
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Shen, Jiun-Shian
The formation of a hitherto unknown three-coordinate dicationic hydrido boron complex is described. Interestingly, supporting ligand carbodicarbene gave unprecedented reaction with BH3 without using more highly electrophilic Lewis acid precursors. Spectroscopic, crystallographic, and computational analysis was performed to understand the electronic features of these species.