Triplet ground state geometry

The total 7t-eIectron energy of benzene is 6a -I- 8)3, corresponding to a DE of 2)3. Cyclobutadiene is predicted to have a triplet ground state (for a square geometry) and zero... 

Figure 1.1 Schematic picture of the simulation approach. Numbers denote the sequence of steps involved. (1) MD simulation on the ground state. (2) Vertical excitation of selected geometries and dynamics on the singlet excited state. (3) Assumption of intersystem crossing at the smallest singlet-triplet gap. (4) Dynamics on the triplet ground state. Reproduced with permission from Ref. [31]. Copyright 2013 American Chemical Society.

Harrison and Shalhoub131 have recently investigated the related carbonylnitrenes HCON, FCON, MeCON, and MeOCON, finding a triplet ground state in all cases. Geometry optimizations were carried out using an STO-3G basis set. 

Table 7 Calculated S-T transition moments from the ground state (So) to the three lowest triplet states (Tn) at the ground state geometry, oscillator strengths (/), radiative lifetimes (rn), and vertical transition energy (En). From Ref. [70].

FIGURE 20. Aspects of the electronic distribution in the vertical triplet aniline (triplet state at the singlet ground-state geometry) (a) Differential density Pink represents the Ap(r) = 0.005 an, and blue represents the Ap(r) = —0.005 an isosurface of the differential density, (b) ELF = 0.87 isosurfaces of the electron localization function. Values correspond to basin populations and integrated spin densities (s values)... 

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