B3LYP computational method

Further details of the underlying computational methods and basis sets to determine the wavefunction and density are described in Appendix A. Unless otherwise noted, all numerical examples of this book employ the B3LYP/6-311++G level of theory. 

In an effort to prepare bidentate boranes as colorimetric anion sensors, the incorporation of chromophoric boron moieties has also received attention. Reaction of lO-bromo-9-thia-lO-boranthracene 33 with dimesityl-1,8-naphthalenediylborate 26 affords diborane 34 (Scheme 14). This bright yellow diborane is soluble in chloroform, THF and pyridine. It has been fully characterized but its X-ray crystal structure could not be determined experimentally. Its structure was computationally optimized using DFT methods (B3LYP, 6-31 + G for the boron and sulfur... 

Subsequently, DFT methods (B3LYP functional ) were employed to compute (1) natural charges from which changes in charges are mapped out for comparison with the NMR-based conclusions, (2) GIAO-NMR to predict the chemical shifts for comparison with the experimental results, and (3) nuclear-independent chemical shift (NICS) in order to evaluate relative aromaticity in different rings. Finally, solvent effects were estimated by the polarized continuum model (PCM). In selected cases, parallel DNA-binding studies (with MCF-7 human mammary... 

It has been shown that different methods may ascribe different bond lengths to the 0-0 and C—O bonds and that the medium and substituents affect the electronic behaviors of carbonyl oxides." For example, recent computational studies (B3LYP/6-31 + G (d, p)) of carbonyl oxides, syn- and awri-methyl carbonyl oxides and dimethylcarbonyl oxides in gas and solution reveal that dipolar character increases with the number of methyl groups, and the ionic configuration is stabilized in a polar medium. These effects result in a weakened 0 0 bond and an increased double-bond character in the CO bond. ... 

The protonated methyl halides have also been studied by ab initio computational methods.443 Whereas initial protonation occurs on the halogen atom, the second protonation occurs primarily on the C-H bonds. The B3LYP/6-31G potential energy surfaces (PES) for CEEXTE2"1" (X=F, Cl, Br, I) are found to be repulsive. 

In addition to the above kinetics studies, the fluorene cyclization was studied using ab initio computational methods.323 It was found that the theoretically predicted barriers to the cyclizations for the dicationic intermediates agree well with the values obtained from the kinetic experiments. For example, geometry optimization and energy calculations at the B3LYP/6-31 level estimated that the activation energy (Ea) is 14.0 kcal/mol for the 4jt-electron conrotatory electrocyclization reaction involving compound 57 and the diprotonated intermediate (46, eq 13). 

Table 7.8 Some calculated dipole moments (Debyes) compared to experiment. For each method is given the number of positive, negative, and formal (to one decimal place) zero deviations from experiment, and the unsigned arithmetic mean of the absolute values of the deviations. The basis set for the B3LYP, M06 and MP2 calculations is 6-31G. Experimental values are taken from [67, 69] calculations are by the author Computational method...

Investigations into the ability of computational methods to accurately predict Amax for coumarins have shown that density functional theory (DFT) calculations using the B3LYP functional and the 6-311+G(2d,2p) basis set provide accurate Amax when solvent effects are included <2005CPL(415)20>. 

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