The role of the natural transition orbital density in the S0 → S1 and S0 → S2 transitions of fulvene with next generation QTAIM.

Variations of the bond-path ellipticity ε profiles of the bond-path ( r ) of the torsional C2-C6 BCP corresponding to the (S 0 , S 1 , S 01) (left panel) (S 0 , S 2 , S 02) (right panel) electronic states at values of the torsion θ = 64.3° corresponding to the conical intersection (CI). The vertical dashed lines indicate the position of the BCP for each electronic state. • Present the S 0 → S 1 and S 0 → S 2 NTO densities for fulvene with 3-D next generation QTAIM. • Symmetrization of the S 0 → S 1 torsional BCP along bond-path found for the presence of a CI. • Corresponding NTO transition density S 0 → S 1 displays hindered BCP motion. • NTO density for S 0 → S 1 of the torsional BCP undergoes a large rearrangement at the CI. • Symmetrization effect absent for the S 0 → S 2 torsional BCP that lacks a CI. We present, for the first time, the S 0 → S 1 (S 01) and S 0 → S 2 (S 02) natural transition orbital (NTO) densities for fulvene, using the 3-D next generation QTAIM that can visualize and quantify the rearrangement of the charge density that occurs in response to the applied torsion and as a consequence of the preferred direction of electron density accumulation. A symmetrization of the position of the bond critical point (BCP) of the torsional C2-C6 BCP along the containing bond-path was determined to be characteristic of the presence of a conical intersection (CI) for the S 0 → S 1 (S 01) transition. [ABSTRACT FROM AUTHOR]