This is Jonathon Vandezande, the Director of Computational Chemistry here at Rowan.
Today I will be introducing the spin states workflow for predicting the lowest energy spin state of a molecule or system.
First, log into labs.rowansci.com and select the new spin states workflow. Here we can upload our molecule, input it via SMILES, or draw the 3D structure.
Today we will be working with a Mn(Cl)₆⁺⁴ complex. We can add the manganese first and then add the chlorine in each of the octahedral positions. We can then go ahead and save our molecule and update the name.
We should then make sure to have the correct charge and multiplicity, and go over to the tasks area to select which spin states we would like. Here we will be looking at the doublet, quartet, and sextet state of this molecule. We can then select the mode, which is consistent with the modes that you can see in multistage optimization. You can learn more about these modes in the multistage optimization workflow overview, or look at the mode info box. We will be using RAPID mode today. We will go ahead and submit this and we can let it run.
I'll jump over here to an already completed version of this where we can see our Mn(Cl)₆⁺⁴. This job took about one minute to run and was able to quickly predict our preferred multiplicity. In this case, since chlorine is a weak field ligand, we see the sextet state being the lowest in energy. We can also observe that as we go to a higher and higher multiplicity, that the manganese chloride bond slightly stretches. We can compare this to a Mn(H₂O)₆⁺² system, where water is a slightly stronger field ligand, we expect to see a slightly smaller difference between the highest and lowest spin state.
We can also look at the manganese carbonyl system where a carbonyl is a strong field ligand and suddenly the energy difference between the lowest spin state and the highest spin state completely flips where now the doublet is the favored spin state.