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1.
Spectrochim Acta A Mol Biomol Spectrosc ; 228: 117835, 2020 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-31780309

RESUMO

Hydrogen sulfide shows great importance in various physiological and biochemical processes. The development of fluorescence probes for facile and efficient detection of H2S has attracted increasing attention of researchers. Herein, we synthesized two fluorescence probes based on simple naphthalene structure for detection of H2S. Upon reaction with H2S, the probe DN-DM exhibited a red fluorescence emission with large Stokes shift. The probe showed high sensitivity, pH insensitivity and good selectivity for H2S over other analytes including common biothiols. The detection mechanism was based on the thiolysis of the dinitrophenyl ether moiety, which was confirmed by 1H NMR spectral analysis. The DFT calculation was also performed for a deeper understanding of the photophysical properties. In addition, these probes showed good cell-membrane permeability and could be utilized for detection of H2S in living cells.

2.
Chem Asian J ; 14(9): 1462-1466, 2019 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-30883030

RESUMO

A general and efficient synthetic methodology for the preparation of enantio- and diastereopure [6]-, and [7]helicenes is developed. Commercially available chiral binaphthanols are utilized to generate the arylene-vinylene precursors, which undergo helical folding via photocyclization to give enantio- and diastereopure [6]-, and [7]helicenes. These optically pure helicenes could be easily obtained via silica gel column chromatography without the use of expensive HPLC or chiral resolution reagents. The configurations and structures of these helicenes are confirmed by CD spectra and X-ray crystallographic analysis. This work provides a new method for preparation of enantiopure helicenes.

3.
Phys Chem Chem Phys ; 21(16): 8197-8200, 2019 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-30816387

RESUMO

The ordering of endohedral clusterfullerenes Sc3N@C80 and YSc2N@C80 co-crystallized with Ni(OEP) and isolated complexes with Ni(OEP) have been investigated theoretically. Having used multiple orientations of M3N clusters inside the cages with Fibonacci sampling, we describe the effect of intermolecular interactions on the orientation of the endohedral cluster.

4.
J Comput Chem ; 38(3): 144-151, 2017 01 30.
Artigo em Inglês | MEDLINE | ID: mdl-27813179

RESUMO

An increasing number of observations show that non-classical isomers may play an important role in the formation of fullerenes and their exo- and endo-derivatives. A quantum-mechanical study of all classical isomers of C58 , C60 , and C62 , and all non-classical isomers with at most one square or heptagonal face, was carried out. Calculations at the B3LYP/6-31G* level show that the favored isomers of C58 , C60 , and C62 have closely related structures and suggest plausible inter-conversion and growth pathways among low-energy isomers. Similarity of the favored structures is reinforced by comparison of calculated ring currents induced on faces of these polyhedral cages by radial external magnetic fields, implying patterns of magnetic response similar to those of the stable, isolated-pentagon C60 molecule. © 2016 Wiley Periodicals, Inc.

5.
Phys Chem Chem Phys ; 19(1): 419-425, 2016 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-27905601

RESUMO

Structural identification is a difficult task in the study of metallofullerenes, but understanding of the mechanism of formation of these structures is a pre-requisite for new high-yield synthetic methods. Here, systematic density functional theory calculations demonstrate that metal sulfide fullerenes Sc2S@Cn have similar cage geometries from C70 to C84 and form a close-knit family of structures related by Endo-Kroto insertion/extrusion of C2 units and Stone-Wales isomerization transformations. The stabilities predicted for favoured isomers by DFT calculations are in good agreement with available experimental observations, have implications for the formation of metallofullerenes, and will aid structural identification from within the combinatorially vast pool of conceivable isomers.

6.
J Comput Chem ; 37(20): 1907-13, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-27282122

RESUMO

Recent experiments indicate that fullerene isomers outside the classical definition can also encapsulate metallic atoms or clusters to form endohedral metallofullerenes. Our systematic study using DFT calculations, suggests that many heptagon-including nonclassical trimetallic nitride template fullerenes are similar in stability to their classical counterparts, and that conversion between low-energy nonclassical and classical parent cages via Endo-Kroto insertion/extrusion of C2 units and Stone-Wales isomerization may facilitate the formation of endohedral trimetallic nitride fullerenes. Close structural connections are found between favored isomers of trimetallic nitride template fullerenes from C78 to C82 . It appears that the lower symmetry and local deformations associated with introduction of a heptagonal ring favor encapsulation of intrinsically less symmetrical mixed metal nitride clusters. © 2016 Wiley Periodicals, Inc.

7.
Chemphyschem ; 15(13): 2780-4, 2014 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-25045089

RESUMO

Sc(2)S@C(84) has recently been detected but not structurally characterized.1 Density functional theory calculations on C(84) and Sc(2)S@C(84) show that the favored isomer of Sc(2)S@C84 shares the same parent cage as Sc(2)C2@C(84), whereas Sc(2)S@C(84):51383, which violates the isolated-pentagon rule, is the second lowest energy isomer with the widest HOMO-LUMO gap and shows high kinetic stability. The analysis shows that Sc(2)S@C(84):51575 is favored when the temperature exceeds 2,800 K and it can transform into the most favorable isomer Sc(2)S@C(84):51591. Molecular orbital analysis indicates that both Sc(2)S and Sc(2)C(2) formally transfer four electrons to the cage, and quantum theory of atoms in molecules analysis demonstrates that there is a covalent interaction between Sc(2)S and C(84):51591. The IR spectra of Sc(2)S@C(84) are provided to aid future structural identification.

8.
Chem Asian J ; 9(5): 1265-9, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24596336

RESUMO

Nanometer-sized flakes of MnV2O6 were synthesized by a hydrothermal method. No surfactant, expensive metal salt, or alkali reagent was used. These MnV2O6 nanoflakes present a high discharge capacity of 768 mA h g(-1) at 200 mA g(-1), good rate capacity, and excellent cycling stability. Further investigation demonstrates that the nanoflake structure and the specific crystal structure make the prepared MnV2O6 a suitable material for lithium-ion batteries.

9.
J Am Chem Soc ; 136(8): 3184-91, 2014 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-24483295

RESUMO

The electron donor-acceptor dyads are an emerging class of materials showing important applications in nonlinear optics, dye-sensitized solar cells, and molecular electronics. Investigation of their structure and electron transfer at the molecular level provides insights into the structure-property relationship and can benefit the design and preparation of electron donor-acceptor dyad materials. Herein, the interface adstructure and electron transfer of buckyferrocene Fe(C60Me5)Cp, a typical electron donor-acceptor dyad, is directly probed using in situ electrochemical scanning tunneling microscopy (STM) combined with theoretical simulations. It is found that the adsorption geometry and assembled structure of Fe(C60Me5)Cp is significantly affected by the electrochemical environments. In 0.1 M HClO4 solution, Fe(C60Me5)Cp forms well-ordered monolayers and multilayers on Au(111) surfaces with molecular dimer as the building block. In 0.1 M NaClO4 solution, typical six-fold symmetric close-packed monolayer with vertically adsorbed Fe(C60Me5)Cp is formed. Upon electrochemical oxidation, the oxidized Fe(C60Me5)Cp shows higher brightness in an STM image, which facilitates the direct visualization of the interfacial electrochemical electron transfer process. Theoretical simulation indicates that the electrode potential-activated, one-electron transfer from Fe(C60Me5)Cp to the electrode leads to the change of the delocalization character of the frontier orbital in the molecule, which is responsible for the STM image contrast change. This result is beneficial for understanding the structure and property of single electron donor-acceptor dyads. It also provides a direct approach to study the electron transfer of electron donor-acceptor compounds at the molecular level.

10.
Phys Chem Chem Phys ; 15(30): 12475-9, 2013 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-23632563

RESUMO

2D porous networks have attracted great attention as they can be used to immobilize functional units as guest molecules in a spatially ordered arrangement. In this work, a novel molecular hybrid network with two kinds of cavities was fabricated. Several kinds of guest molecules, such as coronene, copper(II) phthalocyanine (CuPc), triphenylene, heptanoic acid and fullerene molecules, can be immobilized into this template. Site- and size-selective effects can be observed. Furthermore, we have also fabricated interesting 2D crystal architecture with complex four-component structure at the liquid-solid interface, following investigation by scanning tunnelling microscopy (STM). The current findings provide a convenient approach towards the formation of more complex and functionalized surface nanopatterns, which can benefit the study of host-guest assembly behaviour within a monolayer composed by several components at interfaces.

11.
Org Biomol Chem ; 10(33): 6732-9, 2012 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-22806075

RESUMO

The roles of benzoic acid and water on the Michael reaction of pentanal and nitrostyrene catalyzed by diarylprolinol silyl ether are revealed by density functional theory calculations. The calculations demonstrate that the benzoic acid is ready to attack the catalysts and form a hydrogen bond between the hydrogen atom of the COOH of benzoic acid and one of the N atoms of the catalyst. The complex formed from pentanal, catalyst and benzoic acid attacks nitroalkene and forms transition states. Finally, the transition states hydrolyze and the products are formed. The calculations demonstrate that the stereoselectivity is dominated by the steric hindrance of the 2-substituent groups, and the benzoic acid can increase the reaction rate evidently by decreasing the activation energies; however, H(3)O(+) or strong acid may prevent the formation of the transition states between enamines and nitroalkenes. The employed solvent can decrease the activation energies and promote the proton transfer from benzoic acid onto the catalyst 2. The calculated enantiomeric excess values are in good agreement with the experimental results. These calculations also reveal that the role of benzoic acid is dependent on the sophisticated structures of the catalysts and provide a valuable index for the structural design of new catalysts and selection of additives or co-catalysts.

12.
J Nanosci Nanotechnol ; 11(9): 7682-6, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22097473

RESUMO

Chiral Zn(II)/D-,L-phenylalanine (Phe) bio-coordination polymer nanofibers with fluorescence were prepared by fast coordination-assisted assembly. The synthetic strategy is based on the fact that the Zn2+ ions were linked to oxygen atoms from carboxylate groups of the D- or L-amino acid by coordination interactions to form the chiral polymers. The Zn(II)/D-,L-Phe nanofibers had homogeneous diameters in the range of 700-900 nm and ultra-long length in several hundred micrometers, and the surface of the fiber was extremely smooth. In addition, the enantiomers of Zn(II)/Phe nanofibers exhibited both optical activity and fluorescent property in the solid state, which has great potential for application in the field of biomimetic nanofabrication and micro-/nano-optoelectronics.

13.
Acta Crystallogr Sect E Struct Rep Online ; 67(Pt 7): m836, 2011 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-21836843

RESUMO

In the title complex, {(C(2)H(8)N)[Sm(C(2)O(4))(2)(H(2)O)]·3H(2)O}(n), the Sm(III) atom is chelated by four oxalate ligands and one water mol-ecule forming a distorted tricapped trigonal-prismatic geometry. Each oxalate ligand chelates to two Sm(III) atoms, generating a three-dimensional anionic network with cavities in which the ammonium cations and lattice water mol-ecules reside. Various O-H⋯O, N-H⋯O and C-H⋯O hydrogen-bonding inter-actions further stablize the crystal structure.

14.
Acta Crystallogr Sect E Struct Rep Online ; 67(Pt 7): m837-8, 2011 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-21836844

RESUMO

The title complex, {(C(2)H(8)N)[Y(C(2)O(4))(2)(H(2)O)]·3H(2)O}(n), was obtained accidentally under hydro-thermal conditions. The Y(III) atom is chelated by four oxalate ligands and one water mol-ecule resulting in a distorted tricapped trigonal-prismatic geometry. Each oxalate ligand bridges two Y(III) atoms, thus generating a three-dimensional network with cavities in which the ammonium cations and lattice water mol-ecules reside. Various O-H⋯O and N-H⋯O hydrogen-bonding inter-actions stabilize the crystal structure. The title complex is isotypic with the Eu and Dy analogues.

15.
Chem Asian J ; 6(6): 1304-14, 2011 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-21480535

RESUMO

The discovery of buckminsterfullerene C(60) opened up a new scientific area and stimulated the development of nanoscience and nanotechnology directly. Fullerene science has since emerged to include fullerenes, endohedral fullerenes (mainly metallofullerenes), exofullerenes, and carbon nanotubes as well. Herein, we look back at the development of fullerene science from the perspective of epistemology by highlighting the proposed main rules or criteria for understanding and predicting the structures and stability of fullerene-based compounds. We also point out that a rule or criterion may contribute significantly to the corresponding discipline and suggest that two unsolved issues in fullerene science are the addition patterns of fullerene derivatives and the structures and stability of nonclassical fullerenes.

16.
J Chem Phys ; 132(15): 154304, 2010 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-20423178

RESUMO

The complete set of 2333 isomers of C(26) fullerene composed of square, pentagonal, hexagonal, and heptagonal faces together with some noncage structures is investigated at the Hartree-Fock and density functional theory (DFT) levels. For the singlet states, a nonclassical isomer C(26)-10-01 with a square embedded is predicted by the DFT method as the lowest energy isomer, followed by the sole classical isomer C(26)-00-01. Further explorations reveal that the electronic ground state of C(26)-10-01 is triplet state in C(s) symmetry, while that of C(26)-00-01 corresponds to its quintet in D(3h) symmetry. Both the total energies and nucleus independent chemical shift values at DFT level favor the classical isomer. It is found that both C(26)-00-01 and C(26)-10-01 possess high vertical electron affinity. The addition of electron(s) to C(26)-10-01 increases its aromatic character and encapsulation of Li atom into this cage is highly exothermic, indicating that it may be captured in the form of derivatives. To clarify the relative stabilities at elevated temperatures, the entropy contributions are taken into account based on the Gibbs free energy at the B3LYP/6-311+G( *) level. C(26)-10-01 behaves thermodynamically more stable than the classical isomer over a wide range of temperatures related to fullerene formation. The IR spectra of these two lowest energy isomers are simulated to facilitate their experimental identification.

17.
J Comput Chem ; 31(8): 1715-21, 2010 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-20082391

RESUMO

Nonclassical fullerenes with heptagon(s) and their derivatives have attracted increasing attention, and the studies on them are performing to enrich the chemistry of carbon. Density functional theory calculations are performed on nonclassical fullerenes C(n) (n = 46, 48, 50, and 52) to give insight into their structures and stability. The calculated results demonstrate that the classical isomers generally satisfy the pentagon adjacency penalty rule. However, the nonclassical isomers with a heptagon are more energetically favorable than the classical ones with the same number of pentagon-pentagon bonds (B(55) bonds), and many of them are even more stable than some classical isomers with fewer B(55) bonds. The nonclassical isomers with the lowest energy are higher in energy than the classical ones with the lowest energy, because they have more B(55) bonds. Generally, the HOMO-LUMO gaps of the former are larger than those of the latter. The sphericity and asphericity are unable to rationalize the unique stability of the nonclassical fullerenes with a heptagon. The pyramidization angles of the vertices shared by two pentagons and one heptagon are smaller than those of the vertices shared by two pentagons and one hexagon. It is concluded that the strain in the fused pentagons can be released by the adjacent heptagons partly, and consequently, it is a common phenomenon for nonclassical fullerenes to violate the pentagon adjacent penalty rule. These findings are heuristic and conducive to search energetically favorable isomers of C(n), especially as n is 62, 64, 66, and 68, respectively.

18.
Acta Crystallogr Sect E Struct Rep Online ; 66(Pt 11): m1440, 2010 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-21588863

RESUMO

In the title complex, [Cd(C(2)O(4))(C(12)H(8)N(2))](n), the Cd(II) atom has a distorted octa-hedral coordination, defined by four O atoms from two symmetry-related oxalate ligands and by two N atoms from a bidentate 1,10-phenanthroline ligand. Each oxalate ligand bridges two Cd(II) atoms, generating a zigzag chain structure propagating along [100]. The packing of the structure is consolidated by non-classical C-H⋯O hydrogen-bonding inter-actions.

19.
J Chem Crystallogr ; 40(3): 266-271, 2009 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-20526459

RESUMO

Nine metal compounds of Mn(II), Zn(II) and Cd(II) derived from dinitropyridone ligands (3,5-dinitro-pyrid-2-one, 2HDNP; 3,5-dinitropyrid-4-one, 4HDNP and 3,5-dinitropyrid-4-one-N- hydroxide, 4HDNPO) were characterized by elemental analysis, FT-IR and partly by TG-DSC. Three of which were further structurally characterized by X-ray single-crystal diffraction analysis. The structures of the three compounds, Mn(4DNP)(2)(H(2)O)(4), 4, Zn(4DNPO)(2)(H(2)O)(4), 8, and Cd(4DNPO)(2)(H(2)O)(4), 9, crystallize in the monoclinic space group P2(1)/n and Z = 2, with a = 8.9281(9), b = 9.1053(9), c = 10.6881(11) A, beta = 97.9840(10) degrees for 4; a = 8.4154(7), b = 9.9806(8), c = 10.5695(8) A, beta = 97.3500(10) degrees for 8; a = 8.5072(7), b = 10.2254(8), c = 10.5075(8) A, beta 96.6500(10) degrees for 9. All three complexes are octahedral consisting of four equatorial water molecules, and two nitrogen or oxygen donor ligands (DNP or DNPO). The abundant hydrogen-bonding and pi-pi stacking interactions seem to contribute to stabilization of the crystal structures of the compounds. The TG-DTG results revealed that the complexes showed a weight loss sequence corresponding to all coordinated water molecules, nitro groups, the breaking of the pyridine rings and finally the formation of metal oxides.

20.
Guang Pu Xue Yu Guang Pu Fen Xi ; 28(11): 2695-8, 2008 Nov.
Artigo em Chinês | MEDLINE | ID: mdl-19271520

RESUMO

A simple, environmentally friendly, cost-effective, and sensitive method was developed for the determination of trace lead in tap water by flow injection (FI) on-line unequal flow complexation preconcentration procedure coupled with flame atomic absorption spectrometry (FAAS). Compared with conventional preconcentration method, the unequal flow complexation preconcentration procedure, increased the flow rate of sample while decreased the flow rate of complexing agent. The new method decreased the dilution effect of sample caused by the chelating agent, increased the sorption preconcentration effect, and increased the enhancement factor. The decrease in the flow rate of chelating agent will not result in a deficient complex formation because the concentration of APDC is much higher than that of the sample's. Compared with other sorption preconcentration methods, such as, multiplexed sorption preconcentration procedure, the unequal flow complexation preconcentration procedure need not to prolong the preconcentration time, but received even better results. Taking lead as a model element, ammonium pyrrolidine dithiocarbamate (APDC) as the chelating agent, and ethanol as the eluent, the proposed FI on-line KR unequal flow complexation preconcentration procedure was coupled with FAAS for the determination of trace lead in tap water. With a sample loading flow rate of 10. 4 mL x min(-1) and preconcentration time of 60 s, the enhancement factor increased from 30 (conventional equal flow complexation preconcentration procedure) to 59 (unequal flow complexation preconcentration procedure), the detection limit (3sigma) of 5.6 microg x g L(-1) was obtained at a sampling frequency of 40 samples x h(-1). The relative standard deviations (n = 11) were found to be 2.1% at the level of 0.5 mg x L(-1). The recovery ranged from 98.5% to 102%. The proposed method has been successfully applied to the determination of lead in tap water samples.

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