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Structure, Reactivity, Nonlinear Optical Properties and Vibrational Study of 5-Thioxo-1,4-thiazaolidin-3-one and 5-thioxo-1,4,2-thiazasilolidin-3-one (Silicon vs. Carbon). A DFT Study
摘要： The structures and nonlinear optical properties (NLO) of 5-thioxo-1,4-thiazaolidin-3-one(Rhodanine) and 5-thioxo-1,4,2-thiazasilolidin-3-one (silarhodanine) tautomers were studied in gas phase and in solutions using the B3LYP density functional theory and composite CBS-QB3 method. The global minimum at the B3LYP/6-31++G(d,p) and CBS-QB3 levels of theory is tautomer 5 in the gas phase and in solvents for rhodanine, and simiarly, tautomer 13 is the global minimum for silarhodanine. The interconversion among the tautomers is proceeded by an intramolecular proton transfer reaction. An identical solvent effects can be noted for rhodanine and silarhodanine tautomers. The activation barrier towards ring-opening processes (1→2, 9→10) decreases with the increasing dielectric constant of the solvent; on the other hand, the barrier of the ring-closure processes (2→3, 10→11) increases with the increasing dielectric constant. The tautomers are predicted to show significant NLO properties. Also, a number of correlations between the dipole moment and electron densities in bond critical points of the S3-C4 bond and interaction energy as well as vibrational frequencies at the transition states (TS2–3,TS10–11) were examined under different solvents. Finally, the investigation of the heavy atom substitution effects on the properties of silarhodanine is proven to be very weak under these conditions.
关键词： Vibrational assignments,Silarhodanine,Reactivity,Rhodanine,NLO,Ring-opening,Solvent effects
更新于2025-09-23 15:23:52
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[Springer Theses] The Electronic Transitions of Molecular Oxygen || Solvent Effects on the O2(a1?g) → O2(b1$$\Sigma_{\text{g}}^{ + }$$) Transition
摘要： In this chapter, we have presented O2(a1Δg) → O2(b1Σ+g) absorption spectra and extinction coefficients for oxygen in 16 solvents. Through the Strickler-Berg equation, these data were converted into the corresponding O2(b1Σ+g) → O2(a1Δg) radiative rate constants to give the first comprehensive set of data on the probability of the O2(b1Σ+g) → O2(a1Δg) transition in solution. With these data in hand, energies and transition probabilities of all three electronic transitions in oxygen have been quantified in a wide range of solvents. We find that our data is consistent with the theoretical framework put forth by Minaev. Nevertheless, our data also suggest that the interaction between oxygen and the solvent takes place through different mechanisms that are simultaneously acting to perturb each of the electronic transitions in oxygen in different ways. In our mind, the system must now be subjected to more systematic and extensive theoretical investigations, in order to quantitatively rationalize these experimental observations.
关键词： Minaev’s theory,radiative rate constants,O2(a1Δg) → O2(b1Σ+g) transition,Strickler-Berg equation,solvent effects
更新于2025-09-23 15:19:57
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Carbon Dioxide Precipitation Method to Prepare Zinc Oxide
摘要： Carbon dioxide (CO2) was firstly used to precipitate Zn ions with urea to prepare zinc oxide (ZnO). The advantages of this method were small particle size, high yield and low sensitivity to conditions, such as temperature and time, and the decrease of solvent consumption. Further, the influence of carbon dioxide pressure, reaction time and temperature were studied and optimized.
关键词： Particle Size,Nanoparticles,Solvent Effects,Carbon Dioxide Utilization,Precipitation Method
更新于2025-09-10 09:29:36