虚拟技术在实验教学中的应用

介绍了虚拟技术在实验教学改革中的作用与意义，探讨了电子信息系统实验教学改革的新思路与实现措施，并总结了实验教学改革的初步成果．     

A hybrid approach combining energy density analysis with the interaction energy decomposition method

We propose a new analysis technique for characterizing molecular interactions that combines an energy decomposition scheme, such as the Kitaura-Morokuma decomposition method, with energy density analysis, which partitions the total energy of the system into atomic contributions. The combined scheme, termed Interaction-EDA, enables us to estimate the local contribution of interaction energy components, such as electrostatic, exchange, polarization, and charge transfer. The evaluation of the local interaction energy is rather important in large systems. For a numerical assessment, the Interaction-EDA method is applied to the process of CO adsorption on Si(100) - (2 x 1) surface.     

Synthesis and characterization of thiophene‐substituted N‐phenyl maleimide polymers by photoinduced radical polymerization

Two types of novel functionalized N‐[4‐(4′‐hydroxyphenyloxycarbonyl)phenyl]maleimide and N‐(4‐{[2‐(3‐thienyl)acetyl]oxyphenyl}oxycarbonylphenyl)maleimide (MIThi) were synthesized starting from 4‐maleimido benzoic acid. Photoinduced radical homopolymerization of MIThi and its copolymerization with styrene were performed at room temperature to give linear polymers containing pendant thienyl moieties using ω,ω‐dimethoxy‐ω‐phenylacetophenone as an initiator. Copolymers' compositions and the equilibrium constant (K) for electron donor–acceptor complex formation suggest an alternating nature of the copolymerization. The monomer reactivity ratios and Alfrey–Price Q,e values were also determined. The thermal behavior of the new synthesized monomers and polymers was investigated by differential scanning calorimetry and thermogravimetric analysis. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 995–1004, 2002     

Theoretical Study on the Hydrogen Bonding Interactions in Complexes of 5‐Hydroxytryptamine with Water

The energies, geometries and harmonic vibrational frequencies of 1:1 5‐hydroxytryptamine‐water (5‐HT‐H₂O) complexes are studied at the MP2/6‐311++G(d,p) level. Natural bond orbital (NBO), quantum theory of atoms in molecules (QTAIM) analyses and the localized molecular orbital energy decomposition analysis (LMO‐EDA) were performed to explore the nature of the hydrogen‐bonding interactions in these complexes. Various types of hydrogen bonds (H‐bonds) are formed in these 5‐HT‐H₂O complexes. The intermolecular C4H5^5‐HT···O^w H‐bond in HTW3 is strengthened due to the cooperativity, whereas no such cooperativity is found in the other 5‐HT‐H₂O complexes. H‐bond in which nitrogen atom of amino in 5‐HT acted as proton donors was stronger than other H‐bonds. Our researches show that the hydrogen bonding interaction plays a vital role on the relative stabilities of 5‐HT‐H₂O complexes.     

Density functional theory investigation of the binding interactions between phosphoryl,carbonyl, imino,and thiocarbonyl ligands and the pentaaqua nickel(II) complex: Coordination affinity and associated parameters

Density Functional Theory (UB3LYP/6‐311++G(d,p)) calculations of the affinity of the pentaaqua nickel(II) complex for a set of phosphoryl [O?P(H)(CH₃)(PhR)], imino [HN?C(CH₃)(PhR)], thiocarbonyl [S?C(CH₃)(PhR)] and carbonyl [O?C(CH₃)(PhR)] ligands were performed, where R?NH₂, OCH₃, OH, CH₃, H, Cl, CN, and NO₂ is a substituent at the para‐position of a phenyl ring.The affinity of the pentaaqua nickel(II) complex for these ligands was analized and quantified in terms of interaction enthalpy (ΔH), Gibbs free energy (ΔG²⁹⁸), geometric and electronic parameters of the resultant octahedral complexes. The ΔH and ΔG²⁹⁸ results show that the ligand coordination strength increases in the following order: carbonyl < thiocarbonyl < imino < phosphoryl. This coordination strength order is also observed in the analysis of the metal‐ligand distances and charges on the ligand atom that interacts with the Ni(II) cation. The electronic character of the substituent R is the main parameter that affects the strength of the metal‐ligand coordination. Ligands containing electron‐donating groups (NH₂, OCH₃, OH) have more exothermic ΔH and ΔG²⁹⁸ than ligands with electron‐withdrawing groups (Cl, CN, NO₂). The metal‐ligand interaction decomposed by means of the energy decomposition analysis (EDA) method shows that the electronic character of the ligand modulates all the components of the metal‐ligand interaction. The absolute softness of the free ligands is correlated with the covalent contribution to the instantaneous interaction energy calculated using the EDA method. © 2013 Wiley Periodicals, Inc.     

Hammett and Brown correlations in the structure and electronic properties of H2Si=SiHAr (Ar = p-C6H4X; X = NH2, OH,Me, H,F, Cl,CHO, COOH,CN, NO2) molecules

Substituent effect on the structure and electronic properties of H₂Si=SiHAr (Ar = p-C₆H₄X; X = NH₂, OH, Me, H, F, Cl, CHO, COOH, CN, NO₂) molecules are studied at the CAM-B3LYP/6-311G(d,p) level of theory. Energy decomposition analysis (EDA) is used as a useful tool for illustrating the interaction between H₂Si and SiHAr fragments in HArSi=SiH₂ molecules. Energetic analysis reveals that the singlet state of the fragments is more stable than triplet state. Also, interactions are stronger in the presence of electron-withdrawing groups (EWGs) in comparison to electron donating groups (EDGs). EDG and EDG effects are investigated on the stability of fragments, frontier orbital energy, distortion, HOMO–LUMO gap, electron-donating (ω⁻) and electron-accepting (ω⁺) powers of the studied molecules. Then, the correlations between these calculated parameters with the Hammett and Brown constants (σ_p and σ_p⁺, respectively) are provided. Also, time-dependent density functional theory method (TD-DFT) is employed for the determination of the strongest absorption band values (λ_max,el) of these molecules. This absorption band is attributed to the HOMO →LUMO transition.     

Azolium/Hydroquinone Organo-Radical Co-Catalysis: Aerobic C−C-Bond Cleavage in Ketones

Organo-radical catalysts have recently attracted great interest, and the development of this field can be expected to broaden the applications of organocatalysis. Herein, the first example of a radical-generating system is reported that does not require any photoirradiation, radical initiators, or preactivated substrates. The oxidative C−C-bond cleavage of 2-substituted cyclohexanones was achieved using an azolium salt and a hydroquinone as co-catalysts. A catalytic mechanism was proposed based on the results of diffusion-ordered spectroscopy and cyclic voltammetry measurements, as well as computational studies.     

Substituent Effect on the Electronic Properties and Nature of the W≡C Bond in trans‐Cl(OC)(H3P)3W(≡C‐para‐C6H4X) (X = H,F, SiH3, CN,NO2, SiMe3, CMe3, NH2, NMe2) Complexes: A Computational Quantum Chemistry Study

In this investigation, we describe substituent effect on the dipole moment, ionization potential, electron affinity, structure, frontier orbitals energy, in the trans‐Cl(OC)(H₃P)₃W(≡C‐para‐C₆H₄X) (X = H, F, SiH₃, CN, NO₂, SiMe₃, CMe₃, NH₂, NMe₂) complexes using MPW1PW91 quantum chemical calculations. The nature of chemical bond between the [Cl(OC)(H₃P)₃W]⁻ and [C‐para‐C₆H₄X]⁺ fragments was illustrated with energy decomposition analysis (EDA). Percentage composition in terms of the defined groups of frontier orbitals for these complexes was inspected to investigate the character in metal–ligand bonds. Quantum theory of atoms in molecules (QTAIM) was used for illustration of metal–ligand bonds in these complexes.     

Facile synthesis of nitrogen-doped carbon dots for Fe sensing and cellular imaging

A fast and facile approach to synthesize highly nitrogen (N)-doped carbon dots (N-CDs) by microwave-assisted pyrolysis of chitosan, acetic acid and 1,2-ethylenediamine as the carbon source, condensation agent and N-dopant, respectively, is reported. The obtained N-CDs are fully characterized by elemental analysis, transmission electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction pattern, X-ray photoelectron spectroscopy, UV–vis absorption, and photoluminescence spectroscopy. Doping N heteroatoms benefits the generation of N-CDs with stronger fluorescence emission. As the emission of N-CDs is efficiently quenched by Fe³⁺, the as-prepared N-CDs are employed as a highly sensitive and selective probe for Fe³⁺ detection. The detection limit can reach as low as 10 ppb, and the linear range is 0.010–1.8 ppm Fe³⁺. The as-synthesized N-CDs have been successfully applied for cell imaging and detecting Fe³⁺ in biosystem.