(Note:Author for Correspondence: Neeraj Misra, B-981, sector-A, Mahanagar, Lucknow 226006, India) This work deals with a theoretical study of the molecular structure of colchicine. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities were calculated by the ab initio Hartree-Fock method and the Density Functional B3LYP method employing 6-31G(d) as the basis set, and the vibrational studies were interpreted in terms of the potential energy distribution (P.E.D.). The internal coordinates were optimized repeatedly to maximize the P.E.D. contributions. A detailed interpretation of the infrared and Raman spectra of colchicine is reported. The scaled theoretical wave numbers are in perfect agreement with the experimental values. The FT-IR spectra of colchicine was recorded in solid phase, and the FT-Raman spectra of colchicine have been taken from the literature.
To analyze the mechanism of the β-hydrogen elimination process of η3-1,1-dimethylallylpalladium compounds, we assumed the plausible intermediates and transition states for composing the possible pathways. Their geometry optimization, and vibrational frequencies and energy calculations were carried out with density functional theory (DFT) at the B3LYP level. The most suitable pathway was that in which the allylic ligand transformed from η3- to η1-allyl form having agnostic interaction between β-hydrogen and palladium atoms, and succeeding elimination of β-hydrogen gave 2-methyl-1,3-butadiene moiety with low activation energy (9.76 kcal/mol).
The molecular structure of a dinuclear nickel(II) complex was optimized by several computational methods, including ab initio, DFT, and semi-empirical methods. The computed structures were compared with crystallographically obtained structures. All the DFT methods reproduced the crystal structures well, and the B3LYP and LC-BLYP methods were better than the others. None of the semi-empirical methods gave a reasonable structure. All the reasonable structures were obtained by assuming the quintet state, which was consistent with the ferromagnetic exchange interaction.
This study investigates the importance of visualization resources to help students for mental preparation and laboratory-time utilization. The results of experimental and control groups showed that students' understanding of the concepts and experimental procedures improves after reviewing the visualization resources (t=8.52 for quizzes and 4.31 for reports, p<0.001, effect size=1.2). The results of the study suggested that the resources could serve as a mental preparation tool.