His primary area of research is applied theoretical chemistry with emphasis on structure, bonding and reactivity, across the periodic table of the elements.

In 2005 he accepted an invitation from the Indian Institute of Science (IISc), Bangalore, and joined the Department of Inorganic and Physical Chemistry.

In 2008 Dr. Jemmis moved again, this time on a five-year deputation, accepting the responsibility to start the Indian Institute of Science Education and Research, Thiruvananthapuram and served there till 2013.

Significant results have been obtained in understanding the reactions of transition metal organometallics, week H-bond,[7] electronic structure of three-dimensional aromatic compounds,[1][8] polyhedral boranes, carboranes, silaboranes, electron counting rules for polycondensation, and structure of boron allotropes.

The Jemmis mno rules for polyhedral boranes have found a place in textbooks [14][15][16][17][18][19][20] and are being taught in Inorganic Chemistry Courses in leading educational institutions around the world.