Periodic Table still influencing today's research

  • Feb 6, 2019
  • James McCusker

This year marks the 150th anniversary of the Periodic Table. The principles that drove Dmitri Mendeleev to construct his periodic table are still influencing today’s research advances.

In a review published in a special issue of Science, which celebrates this sesquicentennial anniversary, Michigan State University chemistry Professor James K. McCusker highlights some of the current research around the globe driven by Mendeleev’s influence.

“Our goal was to showcase contemporary research being pursued around the world, including DOE-supported research at MSU, that’s working to realize new approaches to photoinduced chemical processes,” said Prof. McCusker.

Structure of [Ru(bpy)3]2+ and [Fe(bpy)3]2+ �where M is either ruthenium (Ru) or iron (Fe).
Structure of [Ru(bpy)3]2+ and [Fe(bpy)3]2+
where M is either ruthenium (Ru) or iron (Fe).

Prof. McCusker’s contribution focused on the process of light absorption by that incorporates elements from the so-called “transition block” of the Periodic Table. Compounds from this class are involved in everything from solar energy conversation to organic synthesis.

“The effective capture and use of sunlight – an inexhaustible, globally accessible and pollution-free energy source – is critical for replacing fossil fuels and in mitigating climate change,” Prof. McCusker said. “In order to realize this goal, one of the key processes that must occur following the absorption of light is the transfer of electrons, similar to what plants do in photosynthesis.”

“Although much remains to be done, an understanding of the periodic nature of the problem coupled with the creative work by a growing number of research groups around the world portends that the prospect for a seismic shift in how we interface molecular inorganic chemistry to the science of light capture and conversion is bright indeed,” Prof. McCusker said.

Comparison of electronic structures.
Comparison of electronic structures.
Schematic potential energy surface diagrams appropriate for compounds such as [Ru(bpy)3]2+ (left) and [Fe(bpy)3]2+ (right). Each parabola represents an electronic state corresponding to some molecular energy levels; only the two lowest-energy excited ligand-field states (3T1 and 5T2) are included for clarity. The inversion in the relative energies of the MLCT and ligand-field excited states on going from Ru(II) to Fe(II) is the primary reason for the difference in photophysical behavior between the two classes of compounds.