The observed peak shift of FA was —0.56 eV, while the theoretical values by the LR-PCM-TD-DFT and the dimer model were —0.35 and —0.22 eV, respectively. This means that the effects of hydrogen bonding and polarization of the solute are both important. In the case of NMF and NMA, the calculated peak shifts with dimer model, —0.50 and —0.12 eV, well reproduced the experimental values, —0.64 and —0.10 eV, respectively. These values are better than those by LR-PCM (—0.02 and -1-0.02 eV). Therefore, in the liquid phase of NMF and NMA, the [Pg.43]

DFT was employed to study the mechanism of ammonolysis of phenyl formate in the gas phase, and the effect of various solvents on the title reaction was assessed by the polarizable continuum model (PCM). The calculated results show that the neutral concerted pathway is the most favourable one in the gas phase and in solution.24 The structure and stability of putative zwitterionic complexes in the ammonolysis of phenyl acetate were examined using DFT and ab initio methods by applying the explicit, up to 7H20, and implicit PCM solvation models. The stability of the zwitterionic tetrahedral intermediate required an explicit solvation by at least five water molecules with stabilization energy of approximately 35 kcalmol-1 25 [Pg.58]

Formation of the reaction products, in the case of the methylene linker, was rationalized by means of density functional theory (DFT) calculations with the inclusion of a solvent effects polarized continuous model (PCM). The calculations [Pg.48]

The Onsager model describes the system as a molecule with a multipole moment inside of a spherical cavity surrounded by a continuum dielectric. In some programs, only a dipole moment is used so the calculation fails for molecules with a zero dipole moment. Results with the Onsager model and HF calculations are usually qualitatively correct. The accuracy increases significantly with the use of MP2 or hybrid DFT functionals. This is not the most accurate method available, but it is stable and fast. This makes the Onsager model a viable alternative when PCM calculations fail. [Pg.209]

Figure 2 Correlations between the global HOMED indices and the relative energies (A in kcal/mol) estimated for neutral isomers of adenine and its building blocks in the gas phase (a) and in water solution (b). HOMED, harmonic oscillator model of electron delocalization DFT, density functional theory PCM, polarizable continuum model. Reprinted with permission from Raczyhska et al. (2015RSCA36587) with permission from The Royal Society of Chemistry. |

In any case, it is clear that proper treatment of the solvent effect, both static and dynamical, is fundamental for reliable evaluation of the CT transition s stability in the condensed phase. When using continuum solvation models, a state-specific approach combined with an accurate description of the excited-state electron density (averaging procedures of the excited-state density such as those usually employed in CASPT2 should be avoided) is mandatory, since LR-PCM/TD-DFT strongly underestimates the stability of transition with even partial CT character. [Pg.69]

Both J(C-3,C-6) and j(C-5,C-6) were used successfully as probes to examine the keto-enol tautomerism in derivatives of 2-OH-pyridine 52 in solution, which is strongly dependent on the solvent s dielectric constant and type/position of the substitution [96], Experimental J values of the pyridine-pyridone tautomers were measured in natural abundance with the INADEQUATE technique, and theoretical values were computed at DFT level of theory considering the solvent by the SCRF-PCM model [96], [Pg.127]

The NEQ limit is the most suitable to the treatment of the absorption process. The study of the fluorescence process is instead more complex, since in this case dynamical solvent effects cannot be rigorously decoupled from the intramolecular effects due to the motion of the wave-packet (WP) on the excited-state surface. However, it is possible to define some limit reference models, and intuitive consideration of the properties of the solvent and/or the excited potential energy surface is often sufficient to define what is the most suitable to the treat the case under study (see next sections). PCM can be used in conjunction with all the most important excited-state electronic methods. Since we selected TD-DFT as our reference electronic method, we shall treat PCM/TD-DFT in more detail in the next sections. [Pg.49]

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