Thursday, June 17, 2010

An unexpected twist

Lately I have become somewhat obsessed with trying to find concrete examples of conical intersections between potential energy surfaces of excited states of organometallic complexes. One example is here.

This led to reading a nice paper in Journal of Physical Chemistry Letters by Zurek and Paterson. They consider a platinum complex which undergoes a significant structural change upon photoexcitation (photoisomerisation).

However, contrary to what was thought originally the metal is just a spectator. In particular, the relevant excited states are not MLCT (metal-to-ligand charge transfer) states but rather pi-pi* states localised on the organic ligand.

Radiationless deactivation does occur through a conical intersection, but this intersection is also present in just the ligand. The key motion is associated with the C-N-C bond which links the two quinolone parts of the ligand. The intersection occurs when the CNC angle is 120 degrees and the two quinoline groups are twisted almost 90 degrees.

One question I have is what is the simplest possible effective Hamiltonian which could capture this photophysics.


  1. Are you sure that's not "quinoline"? I'll be stuffed if that doesn't look a lot like a bulky Bindschedler's Green to me...

  2. I stand corrected. It is quinoline.
    such details are lost on physicists....