I need comparative data about pi-electron distribution over benzimidazole and bipyridine groups. Is there any simple way to calculate it?
Furthermore, if the above character will change when we consider them as the ligands in coordination complex?
Hi,
This is a tough problem for the complexes. Initially you should just look at the energy levels of the HOMO and LUMO. The more electron deficient ring system will have a lower HOMO and LUMO level.
Second you could calculate the redox potentials or see if they have been measured. To calculate you must follow the thermodynamic cycle which you could find online. It will involve calculated the energy of various oxidation states of your molecules and frequencies in solvent and in the gas phase. At the end there are correction factors for a given level of theory that are needed. Afterward you could do the same for the complex and hope that you can identify the ligand centered redox process.
You could look at the orbital coeficients (choose 2p and 3p for example) that can be found in the output. Square the values and you have the densities. You could compare these in free ligand and complex.
Dear Professor Jarowski,
thanks so much for you complete and instructive discussion.
Bests
I would expect that bipyridine is more electron defficient with respect to benzimidazole
because it is well known that heteroatom in six membered rings act as electron withdrawing group so decreasing the electron denisty on the ring
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