Density functional theory (DFT) studies at B3LYP/6-31G (d) (Becke, 3-parameter, Lee-Yang-Parr) level were performed to evaluate adsorption interactions between ethylene oxide (EO) molecule, and pristine and transition metals (TM) (i.e., Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) doped ZnO nanocluster (TM-doped Zn12O12). The adsorption energy (Ead), band gap energy (Eg), Mulliken charge transfer (QT) and molecular electrostatic potential (MEP) were calculated to examine the sensitivity of the Zn12O12 and its TM-doped forms toward EO detection. It was found that in contrast to the pristine Zn12O12, the electronic properties of TM-doped Zn12O12 were sharply sensitive to the presence of EO gas molecules. The results revealed that among the studied TM-doped Zn12O12, Cr- and V-doped Zn12O12 have great potential applicability as EO sensor, due to their highest Eg change (ΔEg) values, after the EO adsorption. Moreover, the density of state (DOS) calculations confirmed that strong electronic interaction between Cr- and V-doped Zn12O12 and EO molecules can makes them interesting empirical candidate for detection and adsorptive removal of EO gas molecules.
The Diels‐Alder reaction between Danishefsky's diene (DD 4) and (2E)‐3‐phenyl‐2‐(trifluoromethyl) acrylonitrile (EPTA 5) at 393 K in the presence of toluene has been studied using the molecular electron density theory at the M06‐2X/6‐31G(d,p) computational level. The calculated relative Gibbs free energies indicated that the studied reaction takes place in a complete regioselective and stereoselective manner in which the most nucleophilic center of DD 4 is attacked by the most electrophilic center of EPTA 5 passing through the stationary point of TS2n. It was shown that the TS2n affords the corresponding cycloadduct of CA2n as the unique product in excellent agreement with the experimental outcomes. On the other hand, a great destabilizing steric repulsion between methoxy moiety of DD 4 and the trifluoromethyl moiety of EPTA 5 along the exo stereoselective approach is responsible for the predominance of the endo approach over the exo one. The nucleophilic and electrophilic Parr functions at the reactive sites of the DD 4 and EPTA 5 have been used to explain the regioselectivity of the Diels‐Alder reaction. According to the electron localization function analysis of the intrinsic reaction coordinate profile of the energetically most preferred TS2n, a nonconcerted two‐stage one‐step molecular mechanism has been proposed. The mechanism indicated the formation of C1C6 single bond through coupling of C1 to C6 and subsequent C4C5 single bond through coupling of C4 to C5 at cycloadduct CA2n.
The adsorption interactions between ethylene oxide (EO) molecule and pristine and aluminum-doped coronene (Al-coronene) were studied in the presence and absence of perpendicular external electric fields (EFs) with strengths [Formula: see text], [Formula: see text] and [Formula: see text] a.u. using density functional theory (DFT) calculations. The geometry optimizations and adsorption calculations were carried out by employing 6-31[Formula: see text]G** basis set. The changes in geometric and electronic structures after the adsorption were investigated to characterize the sensitivity of pristine and Al-coronene toward EO molecules. For all the studied systems, adsorption energies ([Formula: see text], band gap energy ([Formula: see text], Mulliken charge transfer, molecular electrostatic potential (MEP) and density of electron state (DOS) were calculated and discussed. According to the obtained results, the high impact of the applied EFs on the adsorption characteristics of EO molecules on the pristine and Al-doped coronenes showed that applying EF is a good strategy for enhancing the EO adsorption capability of the pristine and Al-doped coronenes, improving the potential application of coronene-based sensors for detection of EO in trace amounts.
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