“…These geometric distortions upon excitation should lead to modifications in the dipole moment of the molecule. The Lippert–Mataga equation − was employed to study the influence of solvent on the emission spectra and the change in the dipole moment upon excitation: Here Δν is the Stokes shift (in cm –1 ); ν ab and ν em are the wavenumbers corresponding to spectral maxima in absorption and fluorescence spectra, respectively (in cm –1 ); μ E and μ G are the dipole moments of the compound in solution in excited and ground states, respectively (in D = 1 × 10 –18 cm 5/2 g 1/2 s –1 ); h is the Planck constant ( h = 6.626 × 10 –27 erg s); c is the speed of light in vacuum ( c = 2.998 × 10 10 cm s –1 ); a is the effective radius of Onsager cavity (in cm); and Δ f is the Lippert–Mataga solvent polarity parameter. , Figure shows the dependence of the Stokes shift versus Δf and Table collects the value of the parameters employed for the fitting of the Lippert–Mataga equation. The change in the dipole moment upon the excitation, Δμ = μ E – μ G , is comparable to other compounds in which ITC processes have been reported such as 4-styryl-1,8-naphthalimides, 2,4,6-tri(5-aryl-2-thienyl)pyrimidines and boradiazaindacenes, among others. − As expected, Δμ is especially high in compound 2 , and it can be associated with a strong deformation of the excited state.…”