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ION-DIPOLE INTERACTIONS

Ion-dipole interactions belong to weak, nonvalent bonds. They are of non-chemical nature. They are interactions between ions and polar groups of molecules. Ion-dipole interactions play the important role in mane biological systems.
The potential attraction energy between an ion and a static constant dipole is inversely proportional to the squared distance between them:
       , where
      p - is the dipole moment of the static dipole,
      q - is the ion charge,
      θ - is the angle between the field vector and the dipolar moment,
      ε - is the electric permittivity of medium,
      ε0 - is the electric permittivity of vacuum,
      r - is the distance between the ion and the dipole.

The potential attraction energy between an ion and a movable constant dipole is inversely proportional to the biquadratic distance between them:
      ,where
k - is the Boltzmann constant, T - is the absolute temperature .

The attraction energy between an ion and an induced dipole is inversely proportional to the biquadratic distance, that is why it decreases much faster while the distance is decreasing:
      .