Oxidation states from LOBA calculations

Oxidation states of atoms in compounds can be obtained using the IUPAC definition - "The oxidation state of an atom is the charge of this atom after ionic approximation of its heteronuclear bonds."(DOI or by calculation. The problem with calculations is that the result depends on the calculation used. LOBA calculations work quite well for a range of examples. For a recent comparison of different calculations see

Here the examples used are [Fe(CN)₆]^3- and [Fe(CN)₅NO]^2-. These anions are called ferricyanide and nitroprusside respectively. The first is low spin Fe(III) and the latter is low spin Fe(II).

They are in the Moilin Library in the Inorganics folder and are called fe(cn)6m3 and fe(cn)5nom2.

Start Oscail and use File/Ptest/moilin/scratch to set the job to Ptest. Run Moilin. If the screen does not start up blank then use Bu/Purge to clear the current job.
Click the screen in Bu mode and check Load a Molecule from the Library and OK. Find fe(cn)5nom2 in the Inorganics folder and load it.



Click the Orca button and then NewInput



Make sure the charge is set to -2 and the multiplicity to 1
Click Run

When the message structure converged appears Click EndOrca.

Click the MultiWFN button and select Oxid.States from LOBA you can change the default threshold of 50

Click OK. When the calculation is complete Notepad++ opens



Notice that Fe is +2 and the NO nitrogen is +3. Two of the possible oxidation states are Fe(III) and NO or Fe(II) and (NO)⁺. The latter is supported by this calculation and by experiment e.q. the NO IR peak position.

If you repeat this calculation for [Fe(CN)₆]^3- you will need to check that the charge and multiplicity are set to -3 and 2.

You should get

When a LOBA calculation is requested Moilin writes the files rloba.bat and rloba.txt
rloba.txt contains the commands used to run the calculation. In this case it contains

19
1
8
100
50
0
-10
q

If you click the DOS button on the Moilin toolbar and type rloba at the DOS prompt
the calculation will run again and notepad++ will open with the results.

If you edit the rloba.txt file and add the fragment instruction (-1 etc.)

 19
1
8
100
-1
2,8
50
0
-10
q

and then run rloba again you should see the oxidation state of the first CN