with the perturbation parameters γ Z and ξ Z . It has to be noted that these parameters are usually regarded as fitting constants for numerical data with regard to the fact that detailed analytic expressions are hard to derive . The individual and combined consideration of such perturbations can be applied for parabolic and cubic charge transfer approaches and thus results in modified expressions for the HSPs as presented in the supporting information (SI Models 1 -3 and SI Models 6 -11 (Eqns. ( ) -( ) and ( ) -( ) in the SI). In combination with cubic and parabolic charge transfer descriptions, the individual consideration of such extensions results in the fitting expressions SI Models 1 -11 for the HSPs in the supporting information. We will fit the corresponding models to experimental and computed values of the HSPs and compare their accuracy to our previous simple expression (Eqn. ( )) in order to evaluate the influence of more advanced higher order contributions and perturbation approaches. A reasonable hypothesis would be that these more sophisticated approaches provide a more accurate description of dipolar and hydrogen bonding effects which thus enables a higher predictive accuracy for the HSPs and vice versa a broader application.