Singlet ground state interaction

In summary, independently of the second carbene substituent, phosphinocarbenes have a singlet ground state, with a small singlet-triplet gap. They have a planar geometry at phosphorus and a short phosphorus-carbon bond, indicating an interaction between the phosphorus lone pair and the carbene vacant orbital. In the case of silyl- and phosphoniophosphinocar-benes, there is an additional interaction between the carbene lone pair and lowlying [Pg.179]

Introducing another contact pair, 1X, which arises from interaction of the singlet ground-state light absorber, 1S0, with either +02 or we get what we may call an extended Tsubomura-Mulliken diagram (Fig. 3). 

Therefore, under spin-orbital coupling interaction the transition moment M for transition from singlet ground state to a mixed e r t H state is given as... 

Snaathorst et al h 12 have investigated the acetone solvate of the salt [Cu(mnt)2]2 [MB+]2 (where MB = methylene blue) by single-crystal ESR techniques. They found that the complex consisted of dimerized aniens each with a singlet ground state and a thermally accessible triplet state. At 4.2 K, triplet-triplet interactions between dimers along the a axis were responsible for satellite lines in the ESR spectrum. 

Finally, the orbital interaction is divided into two terms. One is an orbital contribution involving a matrix element of H which concerns only the singlet ground state and the other is an orbital contribution involving a matrix element of H, which mixes a singlet ground state with triplet excited states ... 

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