Browsing by Author "Srinivasadesikan, Venkatesan"

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A dihydrogen phosphate selective anion receptor based on acylhydrazone and pyrazole
(2015-01-01)
Pandian, Thiravidamani Senthil
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Choi, Yusun
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Srinivasadesikan, Venkatesan
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Lin, Ming-Chang
;
Kang, Jongmin
A novel chromogenic anion receptor 1 based on acylhydrazone and pyrazole has been designed and synthesized. Chromogenic anion receptor 1 forms stable 1:1 complexes with dihydrogen phosphate (H2PO4-) and other halide (Cl-, Br-) anions in DMSO solution, as shown by UV-vis, fluorescence and H-1 NMR spectroscopic experiments. The pyrazole containing host 1 in the optimized geometry of the complex has been noted as planar. The planarity of the host with the H2PO4- anion resulted from four strong N-H center dot center dot center dot O and two weak C-H center dot center dot center dot O types of H-bonding. In total six H-bonding and the planarity of the host in the complex are responsible for the high binding energy. The addition of an excess of more basic anions (F- and CH3COO-) induces stepwise deprotonation, an event signalled by the appearance of a bright yellow color. The intensity of the fluorescence spectrum increases when hydrogen bonding occurs and decreases when deprotonation occurs, which is evidenced by fluorescence titrations.
A Hydrogen Pyrophosphate Selective Anion Receptor Based on Thiosemicarbazone
(2017-12-01)
Pandian, Thiravidamani Senthil
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Srinivasadesikan, Venkatesan
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Lin, Ming-Chang
;
Park, Jong I. L.
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Kang, Jongmin
A novel rigid anion receptor 1 containing thiosemicarbazone groups were synthesized. Receptor 1 displayed competitive turn-off fluorescence and colorimetric response for hydrogen pyrophosphate. This recognition process was confirmed by UV-vis, fluorescence titrations. A detailed analysis of the TD-density functional theory calculations was consistent with the observed colorimetric experiments. These experiments revealed that the colorimetric and fluorescent response is triggered by thiourea/ HP2O73- hydrogen bonding.
A selective acetate anion binding receptor: participation via cationic CH3 donors
(2015-10-28)
Pandian, Thiravidamani Senthil
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Srinivasadesikan, Venkatesan
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Lin, M. C.
;
Kang, Jongmin
;
應用化學系
A novel receptor 1, which has only C-H hydrogen bonds as recognition element has been designed and synthesized. The receptor 1 utilizes cationic CH3 in 2-methyl benzimidazole and naphthalene benzylic C-H as hydrogen bonding donor. The binding cavity formed in receptor 1 prefers to accommodate small negatively charged atom such as oxygen. Therefore, acetate and nitrite show strong affinity for receptor 1 in acetonitrile due to negatively charged oxygen in them. In addition, the order of binding affinity for halides are Br->Cl->I-. These results reflect the size and basicities of halides. Further, H-1 NMR titration of halide clearly indicates the anion-pi interaction. The experimental data from UV-vis, fluorescence and 1H NMR titration are consistent with DFT results. (C) 2015 Elsevier Ltd. All rights reserved.
A simple pyrene based AIEE active schiff base probe for selective naked eye and fluoresence off-on detection of trivalent cations with live cell application
(2016-08)
Simon, Turibius
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Shellaiah, Muthaiah
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Srinivasadesikan, Venkatesan
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Lin, Ching-Chang
;
Ko, Fu-Hsiang
A simple pyrene based schiff base derivative 2-((pyren-1-ylmethylene)amino)ethanol (PE) has been synthesized via one-pot reaction and its nano-aggregation induced emission enhancement (AIEE) was reported through UV/PL, TEM and DLS studies. Interestingly, PE in CH3CN revealed the naked eye and fluorescence turn-on sensing responses towards Fe3+, Cr3+ and Al3+ ions, by means of PET and PE-PE* excimer formation. The 2:1 stoichiometry of sensor complexes PE-M3+ (M=Fe/Cr/Al) were calculated from Job\'s plots based on UV-vis absorption titrations and supported by FTIR and ESI (+Ve) mass analysis. In addition, the binding site of PE-M3+ sensor complexes was well established by H-1 NMR titrations and its sensor reversibility was recognized during subsequent addition of M3+ ions and PMDTA, respectively. The detection limits (LODs) and the association constant (K-a) values of PE-M3+ complexes were calculated by standard deviation and linear fittings. Likewise, quantum yield (Phi(f)) calculations, TEM analysis, pH effect and density functional theory (DFT) studies were executed for the PE-M3+ sensor complexes. More importantly, confocal fluorescence microscopy imaging in Raw264.7 cells showed that PE could be used as an effective fluorescent probe for detecting Fe3+, Cr3+ and Al3+ ions in living cells. (C) 2016 Elsevier B.V. All rights reserved.
Acid/Base and H2PO4- Controllable High-Contrast Optical Molecular Switches with a Novel BODIPY Functionalized [2]Rotaxane
(2015-12-09)
Arumugaperumal, Reguram
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Srinivasadesikan, Venkatesan
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Raju, Mandapati V. Ramakrishnam
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Lin, Ming-Chang
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Shukla, Tarun
A novel multifunctional mechanically interlocked switchable [2]rotaxane R4 containing two molecular stations and rotaxane arms terminated with boron-dipyrromethene (BODIPY) fluorophores and its derivatives were synthesized for the first time by CuAAC click reaction. The shuttling motion of macrocyde between the dibenzylammonium and triazolium recognition sites and the distance dependent photoinduced electron transfer process of R4 is demonstrated by utilizing external chemical stimuli (acid/base). Interestingly, the reversible self-assembly process of R4 was recognized by the acid-base molecular switch strategy. Notably, two symmetrical triazolium groups acted as molecular stations, H2PO4- receptors, and H-bonded donors. Both [2]rotaxane R4 and thread R2 demonstrated excellent optical responses and high selectivity toward H2PO4- ion. The specific motion and guest-host interactions of mechanically interlocked machines (MIMs) were also further explored by quantum mechanical calculations. The thread R2 also demonstrated to enable the detection of H2PO4- in RAW 264.7 cells successfully.
Facile rhodamine-based colorimetric sensors for sequential detections of Cu(II) ions and pyrophosphate (P2O74-) anions
(2016-01-01)
Arumugaperumal, Reguram
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Srinivasadesikan, Venkatesan
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Lin, Ming-Chang
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Shellaiah, Muthaiah
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Shukla, Tarun
Two rhodamine hydrazine derivatives Rh1 and Rh2 with catechol and ether functionalities have been synthesized and utilized towards sequential colorimetric detections of Cu(II) and pyrophosphate (PPi) ions in CH3CN-H2O (v/v = 9 : 1, 5 mM Tris-HCl, pH 7.4) semi-aqueous medium. Notably, Rh1 and Rh2 are the first example of colorimetric rhodamine-based probes for the sequential detections of Cu2+ ion and PPi anion. Based on the significant colorimetric responses (from colorless to pink) of Rh1 and Rh2 to Cu2+ ions, the detection limits were estimated as low as 1.22 x 10(-8) M and 8.0 x 10(-7) M, respectively, which signified the utilities of designed probes towards facile detections of Cu2+ ions. Furthermore, upon the successive addition of PPi ion to Rh1-Cu2+ and Rh2-Cu2+ complexes, it has been altered and restored to its origin of Rh1 and Rh2 via re-coordination of PPi to Cu2+ ion, which was confirmed by color changes from pink to colorless. Moreover, computational DFT calculations provided more insights into HOMO-LUMO structures of rhodamine derivatives and their copper complexes. Additionally, the solid state strip-based colorimetric detections of Cu2+ ion were supplemented as a real time application.
KSCN-activation of hydrogenated NiO/TiO2 for enhanced photocatalytic hydrogen evolution
(2020-05-01)
Wang, Tsai-Te
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Chiang, Chao-Lung
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Lin, Yu-Chang
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Srinivasadesikan, Venkatesan
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Lin, Ming-Chang
It was investigated the efficiency of hydrogen production from NiO-loaded TiO2 treated by methanol hydrogenation and functionalized by SCN ligand (SCN-M:(NiO/TiO2)). The effects of a p-n junction created between NiO and TiO2 were demonstrated to enhance significantly the overall photocatalytic performance. The optical and microstructural properties of SCN-M:(NiO/TiO2) were studied with ultraviolet-visible spectra (UV-Vis), photoluminescence (PL), Raman spectra, X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS). The atomic and electronic configurations of SCN-M:(NiO/TiO2) were investigated with analysis of the X-ray absorption near-edge structure (XAS) in situ under irradiation with Xe lamp incorporating a filter (AM 1.5G). An effective quantum yield of 1.34% for hydrogen production was attained with SCN-M:(NiO/TiO2). Quantum-chemical calculations revealed a synergistic decrease of the band gap upon loading Ni, Ni-linked O-2 and anionic SCN-ligand binding. The optimal energy bandgap was decreased to 2.70 eV for (SCN/O-2)-3Ni@TiO2, which reasonably supported the enhancement of H-2 evolution.
Nitrite selective anion receptor based on 1-methyl-1H-perimidine
(2015-10-07)
Pandian, Thiravidamani Senthil
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Srinivasadesikan, Venkatesan
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Lin, M. C.
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Kang, Jongmin
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應用化學系
A new anion receptor 1, which utilizes only C-H hydrogen bonding have been designed and synthesized. This receptor utilizes both aromatic C-H (two perimidine C2-H, anthracene 9-H) and aliphatic C-H (two perimidine 1-methyl C-H, two benzylic C-H) as hydrogen bonding moieties. The receptor 1 is found to have considerable binding affinity for weakly basic anions even in polar solvent such as DMSO. In addition, receptor 1 is selective for nitrite. The experimental data from UV-vis, fluorescence and H-1 NMR titration are consistent with theoretical studies. The order of the interaction of the C-H groups of perimidine containing receptor with NO2- anion is found to be perimidine (C-H)>methylene (C-H)>methyl (C-H)>anthracene (C-H). 0 2015 Elsevier Ltd. All rights reserved.
Novel anthracene- and pyridine-containing Schiff base probe for selective "off-on\'\' fluorescent determination of Cu2+ ions towards live cell application
(2016-07-01)
Simon, Turibius
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Shellaiah, Muthaiah
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Srinivasadesikan, Venkatesan
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Lin, Ching-Chang
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Ko, Fu-Hsiang
The novel anthracene- and pyridine-containing Schiff base derivative 2-(2-(anthracen-9-ylmethylene)-hydrazinyl) pyridine (AP) has been synthesized via one-pot reaction and its fluorescent "off-on\'\' detection of Cu2+ ions, via PET-based mechanism, is reported. The 1 : 1 stoichiometry of AP center dot center dot center dot Cu2+ sensor complex was calculated from Job\'s plot based on PL titrations and supported by ESI (+Ve) mass spectral analysis. In addition, the binding sites of AP center dot center dot center dot Cu2+ sensor conjugate were supported by H-1 NMR titration. The detection limit (LOD) and association constant (Ka) of AP center dot center dot center dot Cu2+ complex were obtained by standard deviation and linear fittings. Furthermore, quantum yield (Ff), SEM analysis, pH effect, FTIR interpretation and density functional theory (DFT) studies were conducted for the AP center dot center dot center dot Cu2+ sensing conjugate. More decisively, confocal fluorescence microscopy imaging from Raw264.7 cells indicated that AP could be used as an effective fluorescent probe for the analysis of Cu2+ ions in living cells.
Novel pyrene containing monomeric and dimeric supramolecular AIEE active nano-probes utilized in selective "off-on" trivalent metal and highly acidic pH sensing with live cell applications
(2016)
Shellaiah, Muthaiah
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Simon, Turibius
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Srinivasadesikan, Venkatesan
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Lin, Chein-Ming
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Sun, Kien Wen
Two novel pyrene containing monomeric and dimeric Schiff base derivatives PCS1 and PCS2 have been synthesized via one-pot reaction and their nano-J-type aggregation induced emission enhancement (AIEE) was well demonstrated using UV-Vis/PL, transmission electron microscopy (TEM), dynamic light scattering (DLS), time resolved photoluminescence (TRPL), and live cell imaging studies. In contrast to PCS2, PCS1 in CH3CN exhibits fluorescence "off-on" sensor selectivity towards transition trivalent metal ions (Fe3+, Cr3+ and Al3+) among other metals, via PET inhibition with excimer PCS1-PCS1(star) formation. The 2 : 1 stoichiometry of PCS1 center dot center dot center dot M3+ (M = Fe/Cr/Al) sensor complexes was calculated from Job\'s plots based on their PL titrations. In addition, the binding sites of PCS1 center dot center dot center dot M3+ sensor complexes were well recognised from the H-1 NMR titrations and supported by ESI(+ve) mass and FTIR analysis. Additionally, fluorescence reversibilities of PCS1 center dot center dot center dot M3+ were observed via consequent addition of M3+ ions and PMDTA, respectively. Furthermore, the detection limits (LODs) and the association constant (K-a) values of PCS1 center dot center dot center dot M3+ complexes were calculated using standard deviation and linear fittings. Likewise, quantum yield (Phi) measurements, TEM analysis, determination of the effect of pH, density functional theory (DFT) and time resolved photoluminescence (TRPL) studies were performed for the PCS1 center dot center dot center dot M3+ sensor complexes. More importantly, confocal fluorescence microscopy imaging of Raw264.7 cells showed that PCS1 could be used as an effective fluorescent probe for detecting transition trivalent metal ions (Fe3+, Cr3+, and Al3+) in living cells. Impressively, both PCS1 and PCS2 showed "off-on" sensing at highly acidic pH values (1-3) with live cell applications.
Quantum mechanistic insights on aryl propargyl ether Claisen rearrangement
(2014)
Srinivasadesikan, Venkatesan
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Dai, Jiun-Kuang
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Lee, Shyi-Long
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應用化學系
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Department of Applied Chemistry
The mechanism of aryl propargyl ether Claisen rearrangement in gas and solvent phase was investigated using DFT methods. Solvent phase calculations are carried out using N,N-diethylaniline as a solvent in the PCM model. The most favorable pathways involve a [3,3]-sigmatropic reaction followed by proton transfer in the first two steps and then deprotonation or [1,5]-sigmatropic reaction. Finally, cyclization yields benzopyran or benzofuran derivatives. The [3,3]-sigmatropic reaction is the rate-determining step for benzopyran and benzofuran with Delta G(double dagger) value of 38.4 and 37.9 kcal mol(-1) at M06/6-31+G**//B3LYP/6-31+G* level in gas and solvent phase, respectively. The computed results are in good agreement with the experimental results. Moreover, it is found that the derivatives of aryl propargyl ether proceeded Claisen rearrangement and the rate-determining step may be shifted from the [3,3]-sigmatropic reaction to the tautomerization step. The NBO analysis revealed that substitution of the methyl groups on the aliphatic segment has decreased the stabilization energy E(2) and favors the aryl propargyl ether Claisen rearrangement.
The role of cesium fluoride in aryl propargyl ether Claisen rearrangement and its mechanistic elucidation: a theoretical study
(2016-10)
Menkir, Mengistu Gemech
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Srinivasadesikan, Venkatesan
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Lee, Shyi-Long
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應用化學系
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Department of Applied Chemistry
The role of cesium fluoride (CsF) in aryl propargyl ether Claisen rearrangement and its mechanistic pathway have been investigated in gas and solvent phase using the density functional theory implemented in Gaussian 09. Our results indicate that the [3,3]-sigmatropic rearrangement is the rate-limiting step with Delta G (aEuro) value of 37.1 kcal/mol in solvent phase. Furthermore, the results show that the enolization of alpha-allenylketone intermediate (Int1-CsF) has a higher free energy barrier, which implies that the formation of benzopyran is not favored in the presence of CsF. However, the abstraction of the alpha-hydrogen atom in Int1-CsF with CsF shows a very low free energy barrier and is the most favored pathway for aryl propargyl ether Claisen rearrangement in the presence of CsF to form benzofuran. In the case of substituted aryl propargyl ethers, a methoxy group on the benzene ring lowers the activation barrier. The HOMO-LUMO, conformational and NBO analysis indicate that increasing methyl substitution on the propargyl residue enhances the rearrangement reaction.