Duong Tuan Quang

Rhodamine-derived Schiff base for the selective determination of mercuric ions in water media

A new rhodamine-derived Schiff base (RS) was synthesized and its sensing property to metal ions was investigated by UV/vis and fluorescence spectroscopies. Addition of Hg2+ ions to the aqueous solution of RS gave a visual color change as well as significantly fluorescent enhancement, while other ions including Pb2+, Cd2+, Cr3+, Zn2+, Cu2+, Fe2+, Co3+, Ni2+, Ca2+, Mg2+, K+ and Na+ ions did not induce any distinct color/spectral changes, which constituted a Hg2+-selective fluorescent OFF-ON chemosensor. The Hg2+-induced ring-opening of spirolactam of rhodamine in RS resulted in the dual chromo- and fluorogenic observation.

A new fluorescent chemosensor for Hg2+ in aqueous solution

We prepared an aminothiourea-derived Schiff base (DA) as a fluorescent chemosensor for Hg(2+) ions. Addition of 1 equiv of Hg(2+) ions to the aqueous solution of DA gave rise to an obvious fluorescence enhancement and the subsequent addition of more Hg(2+) induced gradual fluorescence quenching. Other competing ions, including Pb(2+), Cd(2+), Cr(3+), Zn(2+), Fe(2+), Co(3+), Ni(2+), Ca(2+), Mg(2+), K(+) and Na(+) , did not induce any distinct fluorescence changes, indicating that DA can selectively detect Hg(2+) ions in aqueous solution.

A new rhodamine-based fluorescent chemodosimeter for mercuric ions in water media

A new rhodamine-ethylenediamine-nitrothiourea conjugate (RT) was synthesized and its sensing property as a fluorescent chemodosimeter toward metal ions was explored in water media. Analytical results from absorption and fluorescence spectra revealed that the addition of Hg(2+) ions to the aqueous solution of the chemodosimeter RT caused a distinct fluorescence OFF-ON response with a remarkable visual color change from colorless to pink; however, no clear spectral and color changes were observed from other metal ions including: Zn(2+) , Cu(2+) , Cd(2+) , Pb(2+) , Ag(+) , Fe(2+) , Cr(3+) , Co(3+) , Ni(2+) , Ca(2+) , Mg(2+) , K(+) and Na(+) . The sensing results and the molecular structure suggested that a Hg(2+) -induced a desulfurization reaction and cyclic guanylation of the thiourea moiety followed by ring-opening of the rhodamine spirolactam in RT are responsible for a distinct fluorescence turn-on signal, indicating that RT is a remarkably sensitive and selective chemodosimeter for Hg(2+) ions in aqueous solution. Hg(2+) within a concentration range from 0.1 to 25 μM can be determined using RT as a chemodosimeter and a detection limit of 0.04 μM is achieved.

Complexes of carbon dioxide with dihalogenated ethylenes: structure, stability and interaction

Interactions of ethylene and its 1,2-dihalogenated derivatives with CO2 induce the formation of twenty four molecular complexes with stabilization energies in the range of 1.1 to 7.5 kJ mol−1 as computed at the CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVDZ level. The stability of the parent C2H4⋯CO2 complex is due to a π⋯π* interaction which has not yet been reported in the complexes of CO2-philic compounds and CO2. The cis-XCHCHX⋯CO2 complexes are found to be slightly more stable than the trans-XCHCHX⋯CO2, with X = F, Cl and Br. Generally, the overall stabilization energy of each complex is determined by the C–H⋯O hydrogen bond and the C–X⋯C Lewis acid–base interaction, in which the latter plays a larger role. Substitution of two H atoms in CH2CH2 by the same halogen atoms stabilizes the complexes XCHCHX⋯CO2, and for the same dihalogenated derivatives, the stability of XCHCHX⋯CO2 tends to increase from X = F via Cl and to Br. The obtained results suggest that the contraction of the C–H bond involved in the C–H⋯O hydrogen bond and the blue-shift of its stretching frequency depend not only on a polarization of the C–H bond in the isolated monomer but also on the geometric shape of the complex formed.

A novel approach for synthesis of hierarchical mesoporous Nd 2 O 3 nanomaterials

Abstract A novel route to the fabrication of hierarchical mesoporous Nd 2 O 3 nanostructures including nanospheres and nanoporous network was described. Their structure and morphology evolution of the as-synthesized materials were determined by various techniques such as scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, Fourier transforminfrared spectra, nitrogen adsorption/desorption isotherm, and a formation mechanism was proposed. The results revealed that the Nd 2 O 3 nanospheres had the diameter of 300 nm, which were composed of small primary nanoparticles (NPs) with the size of 10 nm. The nanoporous structure also formed the NPs of ca . 10 nm which were connected with each other to form a three-dimensional (3D) texture. This simple and mild approach to fabricate hierarchical mesoporous Nd 2 O 3 nanostructures could be easily scaled up and potentially extended to synthesize other oxide hierarchical structures.

Structure, stability and interactions in the complexes of carbonyls with cyanides

Our theoretical study at the CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVDZ level for twenty-two stable structures of the interactions between aldehyde RCHO (R=H, CH3, NH2, F, Cl, Br) and cyanides XCN (X=H, F) found that the strength of these complexes is contributed by the C–H···O(N) and/or N–H···N hydrogen bonds and/or >C=O···C Lewis acid–base interaction. The stability of the RCHO···FCN complexes is mainly determined by the >C=O···C Lewis acid–base interaction, while the Csp–H···O hydrogen bond plays a decisive role in the RCHO···HCN complexes. For each complex of RCHO with either HCN or FCN, the substitution of R by CH3 or NH2 strengthens the complex, while the halogen substitution negligibly affects the complex’s stability, as compared to the non-substituted HCHO···XCN complexes. The decomposition analysis using SAPT2+ approach showed that the attractive electrostatic term plays the predominating role of up to 50% overcoming the induction and dispersion terms in stabilizing these complexes. Remarkably, the obtained results give further support to the observation that the change in C–H bond involved in the hydrogen bond and its stretching vibrational frequency depend both on the polarity of the C–H bond in the proton donor and on the gas-phase basicity of the proton acceptor.

A highly sensitive fluorescent chemosensor for simultaneous determination of Ag(I), Hg(II), and Cu(II) ions

Simultaneous determination of the heavy metal ions at the µg/L level in an aqueous solution has always been attractive to scientists. Here, we present a simple, rapid and highly sensitive fluorescent chemosensor for simultaneous determination of mercury, copper, and silver ions in an aqueous solution in the presence of various competitive metal ions, including Na + , K + , Ca 2+ , Ba 2+ , Mg 2+ , Pb 2+ , Cd 2+ , Co 2+ , Zn 2+ , Fe 2+ , Ni 2+ , Al 3+ , and Cr 3+ ions. The detection limits of the sensor for Hg 2+ , Cu 2+ , and Ag + ions are 2.8, 0.8, and 1.0µg/L, respectively. This sensor is potentially suitable for detecting and monitoring these metal ions in drinking water samples according to the regulations of the World Health Organization.

A theoretical study for quantum chemical calculations of tungsten tetracarbonyl complexes with tetrylone ligands E(PH3)2 (E = C − Pb): a quest for understanding

Quantum chemical calculations at the BP86 level with various basis sets (SVP, TZVPP) have been carried out for transition metal complexes of carbodiphosphorane analogues (called tetrylones) E(PH 3 ) 2 with E = C, Si, Ge, Sn, Pb. The nature of the [W(CO) 4 -E(PH 3 ) 2 ] ( W4-EP 2 ) bonds was analyzed with charge method. The equilibrium structures of the tetrylone complexes W(CO) 4 -E(PH 3 ) 2 exhibit an interesting trend which possess for E = C, Si a trigonal bipyramidal coordination at tungsten where the tetrylone ligand occupies an equatorial position. The heavier homologues with E = Ge, Sn, Pb exhibit a square pyramidal coordination at tungsten where the tetrylone ligand is at a basal position while one phenyl group is found trans to the apical CO group which yields a hexacoordinated tungsten complex. The calculated equilibrium structures of the complexes [(CO) 4 W-{E(PH 3 ) 2 }] show that only the carbone ligand C(PH 3 ) 2 is bonded head-on to the metal fragment in the adduct W4-CP 2 which the bending angle, α, is 180.0° and the heavier homologues W4-SiP 2 to W4-PbP 2 have side-on bonded ligands E(PH 3 ) 2 which the bending angle, α become more acute. The theoretically predicted bond dissociation energies (BDEs) of W4-EP 2 system slightly increase from W4-GeP 2 (D e = 46.1 kcal/mol) to W4-PbP 2 (D e = 48.5 kcal/mol). The strange trend has been observed for the slighter homologues with E = C, Si which exhibits the largest value BDE 54.1 kcal/mol for W4-CP 2 and 50.1 kcal/mol for W4-SiP 2 . Analysis of the bonding situation shows that the W-E bonds have a significant contribution from (CO) 4 W←E(PH 3 ) 2 π-donation. This is because the energy levels of the π-type donor orbitals of W4-CP 2 – W4-SnP 2 are higher lying than the σ-type donor orbitals except for W4-PbP 2 where the σ donor HOMO is higher in energy than the π-type donor HOMO-2. All complexes [W(CO) 4 -E(PH 3 ) 2 ] are suitable targets for synthesis which would open up completely new perspectives for experimental researchers.

A fluorescent sensor based on dansyl-diethylenetriamine-thiourea conjugate: a through theoretical investigation

A new dansyl-diethylenetriamine-thiourea conjugate (DT) for detection of Hg 2+ ions in aqueous solution has been theoretically designed and compared to our previously published results. The synthetic path, the optimized geometric structure and the characteristics of the DT were found by the theoretical calculations at the B3LYP/LanL2DZ level. Accordingly, the DT can react with Hg 2+ ion to form a product with quenched fluorescence. It is remarkable that the experimental results are in an excellent agreement with the theoretically evaluated data. Keywords. Fluorescence, chemodosimeter, dansyl, diethylenetriamine, thiourea, Mercury, TD-DFT, PET.