He is very well known for his work and development of Molecular Orbital Theory. Anybody who has taken a course on Symmetry and Group Theory will also remember his name from Mulliken Symbols (A, B, E, T).
For his work on molecular orbital theory in particular he was awarded a Nobel Prize in Chemistry.
I know today's paper is not one of those journal papers, but hey that's what I read and it IS about chemistry. So, I guess it counts.