Browsing by Author "Chung, Wen-Sheng"

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1,3-Alternate Calix[4]arene as a Homobinuclear Ditopic Fluorescent Chemosensor for Ag(+) Ions
(2011-10-04)
Ho, I-Ting
;
Haung, Kuan-Chang
;
Chung, Wen-Sheng
;
應用化學系
;
Department of Applied Chemistry
A novel 1,3-alternate calix[4]arene L, containing two different cationic binding sites of bis-triazoles and bis-enaminone groups, was synthesized and shown to be a homobinuclear ditopic fluorescent chemosensor for Ag(+) ions. The fluorescence intensity of L was selectively enhanced by binding with Ag(+) ions in methanol/chloroform (49:1, v/v) cosolvent. In the presence of most competing metal ions, L retains its selectivity toward Ag(+) ion. The binding constants K(1) and K(2) of the successive complexation of L with the first and second Ag(+) ions were calculated to be 4.46 x 10(3) and 9.20 x 10(4)M(-1), respectively. The higher K(2) value revealed that a positive allosteric effect participated in the complexation of L with the second equivalent of Ag(+). Based on (1)H NMR titration results, we inferred that the two distal bis-enaminone and bis-triazole groups on L cooperatively coordinated to Ag(+) ions with the help of cation-pi interactions from the phenoxy rings. Furthermore, the ESI-MS spectrometry clearly proved the formation of the homobinuclear complex L center dot(Ag(+))(2), because a base peak at m/z of 750.1701 was detected and its isotope pattern was in excellent agreement with the calculated one.
1,3-Alternate Calix[4]arene as a Homobinuclear Ditopic Fluorescent Chemosensor for Ag+ Ions
(2011-10-04)
Ho, I-Ting
;
Haung, Kuan-Chang
;
Chung, Wen-Sheng
;
應用化學系
;
Department of Applied Chemistry
A novel 1,3-alternate calix[4]arene L, containing two different cationic binding sites of bis-triazoles and bis-enaminone groups, was synthesized and shown to be a homobinuclear ditopic fluorescent chemosensor for Ag+ ions. The fluorescence intensity of L was selectively enhanced by binding with Ag+ ions in methanol/chloroform (49:1, v/v) cosolvent. In the presence of most competing metal ions, L retains its selectivity toward Ag+ ion. The binding constants K-1 and K-2 of the successive complexation of L with the first and second Ag+ ions were calculated to be 4.46 x 10(3) and 9.20 x 10(4)M(-1), respectively. The higher K-2 value revealed that a positive allosteric effect participated in the complexation of L with the second equivalent of Ag+. Based on H-1 NMR titration results, we inferred that the two distal bis-enaminone and bis-triazole groups on L cooperatively coordinated to Ag+ ions with the help of cation-pi interactions from the phenoxy rings. Furthermore, the ESI-MS spectrometry clearly proved the formation of the homobinuclear complex L center dot(Ag+)(2), because a base peak at m/z of 750.1701 was detected and its isotope pattern was in excellent agreement with the calculated one.
A Bifunctional Chromogenic Calix[4]arene Chemosensor for Both Cations and Anions: A Potential Ca(2+) and F(-) Switched INHIBIT Logic Gate with a YES Logic Function
(2010-08-01)
Chang, Kai-Chi
;
Su, In-Hao
;
Wang, Yu-Yun
;
Chung, Wen-Sheng
;
應用化學系
A bifunctional chromogenic calix[4]arene 3, which contains both triazoles and hydroxy azophenols as both cationic and anionic recognition sites and the azophenol moiety as a coloration unit, was designed and synthesized. The recognition of Ca(2+) by 3 gave rise to a marked colour change from greenish to bright yellow, whereas the recognition of F(-) by 3 showed a colour change from light green to bluish. The colour changes of 3 by the inputs of Ca(2+) and F- have been implemented to construct a combinational logic circuit at the molecular level.
A Bifunctional Chromogenic Calix[4]arene Chemosensor for Both Cations and Anions: A Potential Ca2+ and F- Switched INHIBIT Logic Gate with a YES Logic Function
(2010-08-01)
Chang, Kai-Chi
;
Su, In-Hao
;
Wang, Yu-Yun
;
Chung, Wen-Sheng
;
應用化學系
A bifunctional chromogenic calix[4]arene 3, which contains both triazoles and hydroxy azophenols as both cationic and anionic recognition sites and the azophenol moiety as a coloration unit, was designed and synthesized. The recognition of Ca2+ by 3 gave rise to a marked colour change from greenish to bright yellow, whereas the recognition of F- by 3 showed a colour change from light green to bluish. The colour changes of 3 by the inputs of Ca2+ and F- have been implemented to construct a combinational logic circuit at the molecular level.
A highly selective fluorescent chemosensor for Ag+ based on calix[4]arene with lower-rim proximal triazolylpyrenes
(2012-08-01)
Wang, Nae-Jen
;
Sun, Chung-Ming
;
Chung, Wen-Sheng
;
應用化學系
;
Department of Applied Chemistry
Ligand 3, a calix[4]arene with lower-rim proximal triazolylpyrenes, is a ratiometric fluorescent chemosensor for Ag+ with higher sensitivity compared to ligand 5, a calix[4]arene with lower-rim distal triazolylpyrenes, and the conventional fluoroionophore with non-conjugated triazole and pyrene. In a polar protic solvent, the binding ratios for 3 center dot Ag+ was determined to be 1:1 and the association constant was found to be 7.0 x 10(3) M-1. The detection of Ag+ by ligand 3 even works in aqueous methanol solution. (C) 2012 Elsevier B.V. All rights reserved.
A novel photoinduced ring opening and isomerization of adamantane-2-spiro isoxazolines using MO(CO)(6)
(2006-10-02)
Senthilvelan, Annamalai
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Lee, Gene-Hsiang
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Chung, Wen-Sheng
;
應用化學系
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Department of Applied Chemistry
The MO(Co)(6)-mediated photoinduced ring-opening reactions of adamantane isoxazolines involve novel rearrangement that provide enaminoketones as major products and beta-hydroxy ketones as minor ones; in contrast, only beta-hydroxy ketones and alpha,beta-unsaturated ketones were obtained under thermal condition. (c) 2006 Elsevier Ltd. All rights reserved.
A specific and ratiometric chemosensor for Hg(2+) based on triazole coupled ortho-methoxyphenylazocalix[4]arene
(2011-10-21)
Wang, Nae-Jen
;
Sun, Chung-Ming
;
Chung, Wen-Sheng
;
應用化學系
;
Department of Applied Chemistry
Calix[4]arene 3, which contains two distal triazole groups on the lower rim and two distal o-methoxyphenylazo groups on the upper rim, was synthesized and found to be a specific and ratiometric sensor for Hg(2+) in a polar protic solvent. A series of o-methoxyphenylazo derivatives (3, 4, 5, 7, and 9) were synthesized, which proved that the lower-rim triazoles and the hydroxyl azophenol(s) were the major ligands for metal ion binding. Though analogues 4 and 10 showed some sensitivity for Hg(2+), compound 3 was the only ratiometric chemosensor for Hg(2+) among the series of azocalix[4]arenes synthesized in this work. The formation of 3. Hg(2+) complex was supported by UV/vis and NMR titration studies and Mass spectrometry. Based on the symmetrical features of NMR spectra of 3 center dot Hg(2+), the complex is believed to be symmetrical with respect to the calix[4]arene cavity. Furthermore, the complex was determined to be 1:1 binding stoichiometry by Job's plot, and the association constant was determined to be 4.02 x 10(3) M(-1) using Benesi-Hildebrand plot. (C) 2011 Elsevier Ltd. All rights reserved.
A specific and ratiometric chemosensor for Hg2+ based on triazole coupled ortho-methoxyphenylazocalix[4]arene
(2011-10-21)
Wang, Nae-Jen
;
Sun, Chung-Ming
;
Chung, Wen-Sheng
;
應用化學系
;
Department of Applied Chemistry
Calix[4]arene 3, which contains two distal triazole groups on the lower rim and two distal o-methoxyphenylazo groups on the upper rim, was synthesized and found to be a specific and ratiometric sensor for Hg2+ in a polar protic solvent. A series of o-methoxyphenylazo derivatives (3, 4, 5, 7, and 9) were synthesized, which proved that the lower-rim triazoles and the hydroxyl azophenol(s) were the major ligands for metal ion binding. Though analogues 4 and 10 showed some sensitivity for Hg2+, compound 3 was the only ratiometric chemosensor for Hg2+ among the series of azocalix[4]arenes synthesized in this work. The formation of 3. Hg2+ complex was supported by UV/vis and NMR titration studies and Mass spectrometry. Based on the symmetrical features of NMR spectra of 3 center dot Hg2+, the complex is believed to be symmetrical with respect to the calix[4]arene cavity. Furthermore, the complex was determined to be 1:1 binding stoichiometry by Job's plot, and the association constant was determined to be 4.02 x 10(3) M-1 using Benesi-Hildebrand plot. (C) 2011 Elsevier Ltd. All rights reserved.
Analysis of Calix[4]arenes Using Nonaqueous Capillary Electrophoresis
(2013-01-01)
Su, Hsiu-Li
;
Lee, Yi-Ping
;
Hung, Huan-Yi
;
Lee, Cheng-Yu
;
Chung, Wen-Sheng
In nonaqueous capillary electrophoresis (NACE), an organic solvent is used in place of an aqueous medium as the background solution to improve the solubility and selectivity for hydrophobic analytes. In this study, we employed NACE with UV detection for the analysis of eight calix[4]arenes. We examined the influence of several parameters-the buffer composition, the nonaqueous solvent's composition and proportion, and the concentration of the electrolyte of the nonaqueous buffer-on the efficiency of the electrophoretic separation. The separation was achieved through the analyte's different effective mobility via different degrees of deprotonation on the phenolic OH groups of the calix[4]arene. This deprotonation can further affect the analyte's ability to form a complex with the metal ion. The optimized background electrolyte (BGE), comprising a mixture of N-methylformamide/acetonitrile (30:70, v/v) and 100 mM AcOH/20 mM NH4OAc, provided rapid (<11 min) separation of the calix[4]arenes with good resolution. The relative standard deviations of the migration times for the eight analytes were all less than 1%. Within the calibration concentration range, the coefficients of determination (R-2) were all greater than 0.9914. Thus, the present study demonstrated NACE can provide adequate separation for the analysis of calix[4]arenes.
Anthryl-1,2,4-oxadiazole-Substituted Calix[4]arenes as Highly Selective Fluorescent Chemodosimeters for Fe3+
(2015-04-01)
Chen, Ying-Jung
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Yang, Shun-Chieh
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Tsai, Chia-Chen
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Chang, Kai-Chi
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Chuang, Wen-Han
Fluorescent chemosensors 1 and 2, with 1,2,4-oxadiazoles as the binding ligands and anthracene as the fluorophore, were synthesized through sequential 1,3-dipolar cycloaddition reactions of 25,27-dioxyacetonitrilecalix[4]arenes 8 and 11. The fluorescence of 1 was severely quenched by both Fe3+ and Cu2+, whereas that of 2 was selectively quenched only by Fe3+. Control compound 4 was also selectively quenched by Fe3+, which implied the importance of anthryl-1,2,4-oxadiazole core; furthermore, it was shown to give various oxidation products such as oxanthrone 13, anthraquinone 14, and imidazolyl oxanthrone 15. In addition to product separation and identification, the fluorescent quenching mechanism of these 9-anthryl-1,2,4-oxadiazolyl derivatives by Fe3+ is also discussed. Furthermore, it should be noted that the oxadiazole-substituted anthracene 4 and calix[4]arene 2 are Fe3+-selective fluorescent chemodosimeters without the interference by Cu2+.
Biscalix[4]arene Derivative As a Very Efficient Phase Selective Gelator for Oil Spill Recovery
(2013-11-15)
Tsai, Chia-Chen
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Cheng, Ying-Tsai
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Shen, Li-Ching
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Chang, Kai-Chi
;
Ho, I-Ting
A biscalixarene framework, without long alkyl chains, has been readily synthesized in three steps starting from the parent calix[4]arene. The biscalix[4]arene 1 was able to form organogels in various alcoholic solvents; furthermore, it exhibited an excellent phase selective gelation property that is potentially useful in oil spill recovery.
Calix[4]arene with Lower-Rim beta-Amino alpha,beta-Unsaturated Ketones Containing Bis-Chelating Sites as a Highly Selective Fluorescence Turn-On Chemosensor for Two Copper(II) Ions
(2011-03-01)
Ho, I-Ting
;
Chu, Jean-Ho
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Chung, Wen-Sheng
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應用化學系
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Department of Applied Chemistry
We report herein the synthesis of a fluorescence turn-on chemosensor, 25,27-bis{N-[1-(4-{[4-amino-4-(1-naphthyl)-2oxo- 3-butenyl]oxy}phenyl)aminocarbonyl]methoxy}-26,28-dihydroxycalix[4]arene (3b), which is highly selective toward Cu(2+). The fluorescence intensity of 3b was enhanced upon adding [Cu(ClO(4))(2)], which reached a maximum with approximately 4 equiv. of Cu(2+) but then started to decrease in intensity at higher Cu(2+) concentrations. Job plot experiments revealed a 1:2 binding stoichiometry of 3b with Cu(2+). Based on (1)H NMR titration results, we infer that there are two possible binding sites for Cu(2+) in 3b: one at the lower-rim phenolic-OH and amide groups, and the second at the beta-amino alpha,beta-unsaturated ketone groups. It is important to note that during the complexation of 3b with [Cu(ClO(4))(2)], the Cu(2+) ions were reduced to Cu(+) by both the phenolic OH and the amines of the beta-amino alpha,beta-unsaturated ketones. Furthermore, control compounds 6 and 9b were synthesized to clarify the possible binding sites of Cu(2+) in 3b. By comparing the binding constants of 3b, 6, and 9b with Cu(2+), we found that 3b exhibited a positive allosteric behavior toward the coordination of two Cu(2+) ions.
Calix[4]arenes with Combined Axial Chirality and Inherent Chirality: Synthesis, Absolute Configuration and Chiral Recognition
(2016-07-01)
Zhang, Wen-Zhen
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Ma, Hui
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Xiang, Guang-Ya
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Luo, Jun
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Chung, Wen-Sheng
Calix[4]arene diastereomeric pairs with combined axial chirality and inherent chirality were readily synthesized via monoalkylation of 1,2-substituted calix[4]arene crown-4 incorporating an axially chiral binaphthyl moiety with different electrophiles as a key step. The reaction showed high generality and distinct diastereoselectivity. The easy separation of the diaster-eomers, the good diastereoselectivity of the reaction, and the poor stereoselectivity of the chiral recognition of diastereomeric pairs were attributed to the remarkable steric effect of the axially chiral binaphthyl moiety. Absolute configurations were determined by X-ray crystallography.
Calix[4]arenes with Combined Axial Chirality and Inherent Chirality: Synthesis, Absolute Configuration and Chiral Recognition
(2016-07-01)
Zhang, Wen-Zhen
;
Ma, Hui
;
Xiang, Guang-Ya
;
Luo, Jun
;
Chung, Wen-Sheng
Calix[4]arene diastereomeric pairs with combined axial chirality and inherent chirality were readily synthesized via monoalkylation of 1,2-substituted calix[4]arene crown-4 incorporating an axially chiral binaphthyl moiety with different electrophiles as a key step. The reaction showed high generality and distinct diastereoselectivity. The easy separation of the diaster-eomers, the good diastereoselectivity of the reaction, and the poor stereoselectivity of the chiral recognition of diastereomeric pairs were attributed to the remarkable steric effect of the axially chiral binaphthyl moiety. Absolute configurations were determined by X-ray crystallography.
Capping the upper and lower rims of calix[4]arenes by aryl dinitrile oxide reactions
(2006-11-20)
Shiao, Ya-Jiun
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Chiang, Pei-Chen
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Senthilvelan, Annamalai
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Tsai, Ming-Tsung
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Lee, Gene-Hsiang
1, 3-Dipolar cycloadditions of upper- and lower-rim diallylcalix[4]arenes (1 and 3) with aryl dinitrile oxides provide a unique and efficient way of capping the calix[4]arenes. When dinitrile oxides reacted with 5-allylcalix[4]arene 7, they underwent a 1,3-dipolar cycloaddition on one side and an electrophilic substitution on the other side, which led to a novel type of asymmetric calix[4]arenes (9 and 12). (c) 2006 Elsevier Ltd. All rights reserved.
Constructing bridged multifunctional calixarenes by intramolecular indole coupling
(2019-10-07)
Bolshchikov, Boris
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Volkov, Sergey
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Sokolova, Dania
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Gorbunov, Alexander
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Serebryannikova, Alina
2,2 '-Bisindole units are suggested as new bridging motifs which can be easily created at calixarene cores. In TFA solutions, calix[4]arenes having pairs of indole groups originating from tryptamine or tryptophan residues are converted selectively into macrocycles bridged by indolylindoline moieties. The latter are easily transformed into fluorescent 2,2 '-bisindole bridges upon oxidation. The coupling/oxidation sequence works fine at bridging the cavities of the cone and 1,3-alternate (thia)calix[4]arenes in their distal positions. Ester groups, triazole units and crown ether loops, which are practically important functionalities in calixarene chemistry, are compatible with the bridging strategy thus making available diverse calixarene-based hosts comprising novel features provided by the 2,2 '-bisindole bridges. Of them the abilities to self-assembly and to bind anions through multiple hydrogen bonds were observed by X-ray crystallography, fluorescence measurements, and NMR experiments. When combined with a cation-binding site, the 2,2 '-bisindole units can turn the calixarene molecules into heteroditopic receptors being able to stabilize the anionic parts of the ion pairs. This feature was assessed by using the 1,3-alternate calix[4]arene having the 2,2 '-bisindole bridge and the crown-5-ether loop which was found to form neutral complexes with potassium acetate or potassium benzoate.
Controlled Sol-Gel and Diversiform Nanostructure Transitions by Photoresponsive Molecular Switching of Tetraphenylethene- and Azobenzene-Functionalized Organogelators
(2020-07-01)
Arumugaperumal, Reguram
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Hua, Wei-Ling
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Raghunath, Putikam
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Lin, Ming-Chang
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Chung, Wen-Sheng
The implementation of stimuli-responsive materials with dynamically controllable features has long been an important objective that challenges chemists in the materials science field. We report here the synthesis and characterization of [2]rotaxanes (R1 and R1-b) with a molecular shuttle and photoresponsive properties. Axles T1 and T1-b were found to be highly efficient and versatile organogelators toward various nonpolar organic solvents, especially p-xylene, with critical gelation concentrations as low as 0.67 and 0.38 w/v %, respectively. The two molecular stations of switchable [2]rotaxanes (R1 and R1-b) can be revealed or concealed by t-butylcalix[4]arene macrocycle, thus inhibiting the gelation processes of the respective axles T1 and T1-b through the control of intermolecular hydrogen-bonding interactions. The sol-gel transition of axles T1 and T1-b could be achieved by the irradiation of UV-visible light, which interconverted between the extended and contracted forms. Interestingly, the morphologies of organogels in p-xylene, including flakes, nanobelts, fibers, and vesicles depending on the molecular structures of axles T1 and T1-b, were induced by UV-visible light irradiation. Further studies revealed that acid-base-controllable and reversible self-assembled nanostructures of these axle molecules were mainly constructed by the interplay of multi-noncovalent interactions, such as intermolecular pi-pi stacking, CH-pi, and intermolecular hydrogen-bonding interactions. Surprisingly, our TPE molecular systems (R1, R1-b, T1, and T1-b) are nonemissive in their aggregated states, suggesting that not only fluorescence resonance energy transfer but also aggregation-caused quenching may have been functioning. Finally, the mechanical strength of these organogels in various solvents was monitored by rheological experiments.
Convergent Synthesis of Macrocyclic and Linear Desferrioxamines
(1970-01-01)
Chiu, Cheng-Hsin
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Jheng, Ting-Cian
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Peng, Bo-Chun
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Chung, Wen-Sheng
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Mong, Kwok-kong Tony
Polyhydroxamate desferrioxamines (DFO) are nontoxic siderophores endowed with high potential for development of therapeutic chelating agents. Herein, we report a modular and convergent strategy for diverse synthesis of macrocyclic and linear DFOs. The strategy employed orthogonally protected N-hydroxy-N-succinylcadaverine building blocks, which allowed bidirectional extension of the DFO structure. The efficiency of the new strategy was demonstrated by the total synthesis of 44-membered macrocyclic DFO-T-1, as well as four related DFO compounds in 11-13 linear steps and 2.1 %-10 % overall yields. Comparison of the iron binding affinity of the DFOs revealed DFO-E as the best chelator.
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
;
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.
Deformative Transition of the Menschutkin Reaction and Helical Atropisomers in a Congested Polyheterocyclic System
(2014-11-07)
Chang, Yung-Yu
;
Ho, Tse-Lok
;
Chung, Wen-Sheng
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應用化學系
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Department of Applied Chemistry
A 4,7-phenanthroline polycyclic 1A designed for probing the limits of the Menschutkin reaction was synthesized in a six-step sequence. The rotational barrier of the phenyl ring nearby the N-methyl group in rac-2A was estimated to be >= 18.1 kcal/mol from VT-NMR experiments, making them a new type of helical atropisomer. The methylation rate constants of 9 and 1A with MeI was found to be 2.22 x 10 (4) and 9.62 x 10 (6) s(1) mol(1) L, respectively; thus, the formation rate of (P/M)-2A is one of the slowest rates ever reported for a Menschutkin reaction. The N-methyl protons in (P/M)-2A exhibit a significant upfield shift (Delta delta 1.0 ppm) in its H-1 NMR, compared to those without a nearby phenyl, indicating a strong CH-pi interaction is involved. Conformational flexibility in dipyridylethene 9 is clearly shown by its complexation with BH3 to form helical atropisomers (P,P/M,M)-10. The pKa values of the conjugate acids of 1A and 9 in acetonitrile were determined to be 4.65 and 5.07, respectively, which are much smaller compared to that of pyridine 14a (pK(a) = 12.33), implying that the basicity, nucleophilicity, and amine alkylation rates of 1A and 9 are markedly decreased by the severe steric hindrance of the flanking phenyl rings in the polyheterocycles.