Singlet triplet splitting

Study singlet-triplet splittings more accurately... 

CNDO/2 for predicting molecular geometries, it gave a vastly superior treatment of singlet-triplet splittings and spin densities. 

Finally, we mention the very encouraging successes combining atomic natural orbitals and full Cl calculations for small molecules (Almlof, Bauschllcher, and Taylor). With this method the singlet-triplet splittings... 

Electronic Excitation Energies and the Singlet/Triplet Splitting in Carbenes... 

Where the + — terms refer to / an type excitations and the to a n - v type transition. These absorptions occur at longer wavelengths than the related model compounds (benzene and dimethylamine for Michler s ketone), have a high intensity, emax 104 liter/mole-cm, a small singlet-triplet splitting, and undergo a red shift of the absorption on going to a more polar solvent. 

From the point of view of ESR spectroscopy, the distinction between molecules with one unpaired electron and those with more than one lies in the fact that electrons interact with one another these interactions lead to additional terms in the spin Hamiltonian and additional features in the ESR spectrum. The most important electron electron interaction is coulombic repulsion with two unpaired electrons, repulsion leads to the singlet-triplet splitting. As we will see, this effect can be modeled by adding a term, JS St, to the spin Hamiltonian,... 

Singlet-triplet splittings (AEst) for carbenes are notoriously difficult to... 

Table 1 Singlet-triplet Splittings (AEsr, kcal/mol) of Diradicals (4, 5, 6, and 7) at Various Levels of Theory ...

The singlet-triplet splitting of NH was determined experimentally by spectroscopy of neutral NH and by negative ion photoelectron spectroscopy (PES) of the NH anion. In the latter experiment, the anion NH is prepared in the gas phase and exposed to monochromatic ultraviolet (UV)-laser hght. This photolysis leads to ejection of photoelectrons whose kinetic energies ( k) are analyzed. As the energy... 

The imidogen anion (NH ) can ionize to form either the singlet or triplet nitrene, thus, the difference in the kinetic energies of the photoelectrons leading to NH and NH is just the singlet-triplet splitting of NH. 

Analogous negative ion PES experiments reveal that the singlet-triplet splitting of methylene (CH2) is only 9.05 kcal/mol.This difference is easily understood on the basis of a simple molecular orbital (MO) diagram. 

As the singlet-triplet splitting of phenylnitrene is 18 kcal/mol, one can deduce that singlet phenylnitrene is 11.4—13.4 kcal/mol more stable than singlet pyridyl-carbene. However, the corresponding radicals, anilines, and substituted pyridines... 

---