This paper investigates the Jahn-Teller effect in the icosahedral cation B(80)(+) and compares the descent in symmetry with that in C(60)(+). For both cations the icosahedral ground state is a (2)H(u) state, which exhibits a H ⊗ (g ⊕ 2h) Jahn-Teller instability. A detailed construction of the potential energy surface of B(80)(+) using different DFT methods including B3LYP/6-31G(d), VWN/6-31G(d)...

One of the fastest steps in the initial decomposition of HFCs under combustion conditions is hydrogen atom abstraction by hydroxyl radicals. We have utilized ab initio quantum mechanics and transition-state theory (TST) to calculate the temperature dependence of rate constants for the reactions of OH with CH4, CH3F, CH2F2, and CHF3. Rate constants calculated using HF/6-31G(d) frequencies and MP...

We assess the performance of six density functionals, each paired with one of five basis sets (a total of 30 model chemistries) for the prediction of geometrical parameters in the coordination sphere of nine vanadium complexes (for a total of 270 structural analyses). We find that results are generally consistent over the range of functionals tested and that none fail drastically. For bond leng...

The energy storage and the molecular rearrangements due to the primary photochemical event in rhodopsin are investigated by using quantum mechanics/molecular mechanics hybrid methods in conjunction with high-resolution structural data of bovine visual rhodopsin. The analysis of the reactant and product molecular structures reveals the energy storage mechanism as determined by the detailed molec...

A series of three donor molecules (DPP-B, DPP-N and DPP-P) based on diketopyrrolopyrrole (DPP) sharing the similar backbone D-π-A-π-D have been investigated. In these molecules, substituents such as pyrene, naphthalene benzene act electron donating end groups, DPP central core unit thiophene has used a bridge between acceptor fragments. Theoretical calculations carried out with help density fun...

Cálculos teóricos da reação do cátion formila (CHO) com tolueno, cumeno e p-cresol mostraram que a transferência de próton é termodinamicamente preferida em relação a acilação. No caso do tolueneo, a acilação do anel aromático, para formação do complexo de Wheland, é 11,7 kcal mol mais alta em energia ( H) que a protonação, em nível de cálculo MP4(SDTQ)/ 6-31++G(d,p)//MP2(full)/6-31G(d,p). Esta...

The syntheses of new tetraaza macrocyclic compounds of variable ring sizes by non-template methods and their characterization with the help of elemental analysis and spectroscopic techniques (FT-IR, 1 H-NMR, and 13 C-NMR) have been reported in detail. The vibrational frequencies determined experimentally are compared with those obtained theoretically from density functional theory (DFT) and Har...

We have studied the Fourier Transform Infrared (FT-IR) and the Fourier transform Raman (FT-Raman) spectra of stanozolol and oxandrolone, and we have performed quantum chemical calculations based on the density functional theory (DFT) with a B3LYP/6-31G (d, p) level of theory. The FT-IR and FT-Raman spectra were collected in a solid phase. The consistency between the calculated and experimental ...

The FTIR and FT-Raman spectra of metronidazolewere recorded in the regions 4000-400cm and 4000-400cmrespectively. The spectroscopic data of the molecule in the ground state were calculated using Hartee-Fock and Density Functional Method (B3LYP) with 6-31G(d,p) basis set. With the observed FTIR and FT-Raman data, a complete vibrational band assignment and analysis of the fundamental modes of the...

The mechanism of the cycloaddition reaction between singlet state dichlorosilylene germylidene (Cl2Si=Ge:) and acetone has been investigated with B3LYP/6-31G* and B3LYP/6-31G** method, from the potential energy profile, we predict that the reaction has one dominant reaction pathway. The presented rule of the reaction is that the two reactants firstly form a Si-heterocyclic four-membered ring ge...