Non-bonding MO

Fig. 6 The Huckel MOs of the three isomeric benzoquinodimethanes [8]. The bonding MOs of the ortho- and para-isomers are filled according to the Pauli exclusion principle. The electron configuration of the non-bonding MOs of the metaisomer is dictated by Hund s rule.

Figure 6.6 A MO diagram for BF3 with the five non-bonding MOs placed on one level...

There is no metal orbital of T2 symmetry, so eq. (41) represents a non-bonding MO, l2u,z-By inspection, the three degenerate MOs of T2 symmetry are... 

Figure 41. Qualitative MO energy diagram for [MoO(bdt)2]1. Here, (b) represents a bonding MO and (nb) represents a non-bonding MO. [Adapted from (106).]...

In the triarylallyl carbanion study and in the absence of accepting stilbene, EjZ photoisomerization of the irradiated carbanion was observed and the effect of changing the substituent at position 2 was examined. Starting from the zero coefficient at carbon-2 in the non bonding MO of the allyllic system, Tolbert considers that the substituent at the 2 position does not affect the energy of the MO. If an electron transfer mechanism governs the reactivity, the substituent on this position will not modify the process in a significant way. The experimental results were very dependent on the C-2 substitution and this reaction was therefore considered as relevant of the intrinsic photochemistry of the anion [145]. This view has been confirmed in other studies on 1,3-diphenylallyl carbanion the kinetic parameters of the photoisomerizations were found to be inconsistent with an electron transfer mechanism [146, 147]. 

Fig. 3.14 Generalized molecular orbital diagram possible electronic transitions in organic molecules, associated absorption regions and examples of common chromophores (modified according to Bottcher, 1991) n, non-bonding MO antibonding MOs are indicated by. ...

From this perspective, it emerges that the kinetic driving force for the cation radical cycloaddition relative to the corresponding neutral one can be expressed as the difference in the ionizabilities of the reactant and the transition state. As a specific example, we may consider a highly non-synchronous TS for cation radical Diels-Alder cycloaddition—which is supported by theoretical calculations (vide infra). This transition state is essentially a distonic cation radical, the radical site of which is easily ionized because the odd electron is in a non-bonding MO. In contrast, the... 

Selected intermediate radical anion species could be prepared and studied, primarily in solution (Fig. 22).88 Of particular interest were diradical anions 2521 -282 1- and diradical dianions 332 2 -352 2, i.e., diradicals related to the corresponding high-spin polyradicals by different occupancy of their non-bonding MOs (Fig. 22). 

Fig. 22 Diradical anions and diradical dianions and their occupation of non-bonding MOs.88...

Figure 6 MO diagram of the charge-compensated PF4 complex5 (the low-lying non-bonding MOs from 2s...

---