Density functional theory, DFT B3LYP

Density Functional Theory, DFT (B3LYP), CASSCF (Complete Active-State Self-Consistent Field) and MRSD-CI (Multi-Reference Single-Double Correlation Interaction) calculations on the diatomic units AuO, AuO", AuO " and AuO " clearly show that stability of Au-0 bond reduces in this order. This trend is consistent with the molecular orbital diagram of AuO molecule presented in Fig. 10. 

In 1997, Jemmis, Schleyer and coworkers studied the structure and energetics of lithi-ated cyclopropenyl cation and their acyclic isomers using ab initio MO (HF/6-31G ) and density functional theory (DFT, B3LYP/6-31G ) methods . Successive lithiation results in... 

A few theoretical studies of oxetanes and oxetanones have been reported since CHEC-II(1996). Building upon a study of the oxetane- -HCl complex studied by rotational spectroscopy, MP2 calculations were used to investigate the axial and equatorial HCl arrangement, and to try and explain why for oxetane- -HCl only one conformer was observed <2001CPL250, 2002CPL123>. The amine-catalyzed aldol reaction via enamine intermediates has been explored using density functional theory (DFT) (B3LYP/6-31G ) and conductor-like polarizable continuum model... 

The homo- and heterochiral self-association of lH-l,6a-dihydropirrolo[2,3-b] pyrrole derivatives has been studied using density functional theory (DFT) (B3LYP/ 6-31+G ) and ab initio (MP2/6-311+G ) methods [26]. The selected pyrrolo-pyrrole structure (Scheme 3.16) has a unique disposition of theNH group situated in cis to the substituent in position 6a. This simplifies the study, reducing the potential number of conformations, and also maximizes the interaction of the 6a position X groups in the homochiral complexes, as they are forced to point each other. 

The enantiomerization of 6,7-dihydro-dibenzo[///][l,2]diazocine-5,8-dione 2 was investigated using quantum-mechanical methods. At the density functional theory (DFT) B3LYP/6-31G(d,p) level, two enantiomeric -symmetric transition states (TSs) and two enantiomeric pathways were found with a calculated barrier of 155.6 kj mol-1. The pathways can be divided into two steps one involving primarily inversion of the amidic bridge and the other movement of the aromatic rings <2004TA537>. 

From a more quantitative point of view, it is more difficult to achieve accurate computations for DPEs than for PAs of neutral substrates, because molecular anions are involved in the former case. However, when using second-order perturbation theory (MP2), a coupled-cluster theory (CCSD(T)) or a density functional theory (DFT/B3LYP), in conjunction with a moderate atomic basis set including a set of diffuse and polarization functions, such as the 6-3114—FG(d,p) or cc-aug-pVDZ sets, the resulting DPE errors appear to be fairly systematic. To some extent, the accuracy rests on a partial but uniform cancellation of errors between the acid and its conjugate base. Therefore, use of appropriate linear regressions between experimental and calculated values allows the DPEs for new members of the series to be evaluated within the chemical accuracy of 4=0.1 eV or 4=10 kJmoD. ... 

Also of interest is the density functional theory (DFT) (B3LYP/3-21G level) study of the 1,3,5-dithiazine bicyclic derivative 8, whose optimized geometry shows interproton distances that are in good agreement with observed nuclear magnetic resonance (NMR) nuclear Overhauser effect (NOE) values <2003SL1731>. 

HF, MP2, and CCSD(T) ab initio molecular orbital (MO) theory and hybrid density functional theory (DFT) B3LYP calculations were applied to diarsinines 51-53 to determine the reaction energies of the homodesmic equations, structure properties, stabilities, reactivities, and heteroaromaticity (Scheme 18) <2002JOC271, 2003IAS49, 2003JMT(663)145, 2005JOM(690)4761>. 

Fig. 7. Distance-dependent potential energy curves for the anunonia adduct to the silyl cation, H3N"-SiH3 at different levels of correlated wavefunctions density functional theory (DFT-B3LYP) with a basis set of triple-zeta quality (aug-cc-pVTZ), MP2 as well as MP4 perturbation, and coupled cluster CCSD(T) calculations with double-zeta basis sets (aug-cc-pVDZ).

These reactions employ microwave heating and water as the reaction medium at 100 °C for 7-9 min. The mechanism for diastereoselectivity was confirmed by density functional theory (DFT) (B3LYP) calculations. Subsequently, new multicomponent domino reactions of Meldrum s acid 159, aromatic aldehydes 69, and electron-rich heteroaryl-amines 80 have been established for the synthesis of spiro pyrazolo[l,3]dioxanes-pyridine -4,6-diones and spirojisoxazolo [l,3]dioxanes-pyridine -4,6-diones 160 in aqueous solution under microwave irradiation (Scheme 12.64) [88]. A total of 26 examples were examined to show the broad substrate scope and high overall yields (76-93%). A new mechanism was proposed to explain the reaction process and the resulting chemo-, regio-, and stereoselectivity. 

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