Figure 2.

Solvatochromic behavior of “push–pull” chromophores (large ellipses) is shown using a Jablonski³⁴ diagram. Because of the rapidity of electronic transitions in comparison to nuclear motions, the initial high energy excited state (S₁) is surrounded by a ground state solvent sphere (small ellipses),^35,36 but because the excited state is long-lived relative to the time scale of solvent reorganization, the solvent sphere is able to reorganize and stabilize the excited state to an extent determined by the solvent sphere polarity. Adapted from Loving et al.³⁷ and showing the solvatochromic behavior of dapoxyl³⁸ (see later).