Complex sentence: Multipoles could account for attraction between molecules having permanent multipole moments that participate in electrostatic interaction, but unfortunately, experimental data showed that many of the compounds observed to experience van der Waals forces had no multipoles at all.
Split into simpler sentences: Multipoles could account for attraction between molecules having permanent multipole moments that participate in electrostatic interaction. However, experimental data showed that many of the compounds observed to experience van der Waals forces had no multipoles at all.