A Mossbauer Spectroscopy problem

I believe this is the second post about Mossbauer Spectroscopy. The first one is here. So here is the problem that I saw in the book:

Some iron complexes in the form of FeX2(py)2 can be monomeric or polymeric as shown below (X=Cl, I).

Using the Mossbauer data given in the table below, determine which complex is polymeric.

Complex	IS	QS
FeCl2(py)2	1.21	1.25
FeI2(py)2	0.86	1.33

Solution:

First of all, for Iron we should know that the increased electron density at the nucleus will cause the isomer shift (IS) to decrease. Lower coordination number will also have a decreasing effect on IS. All these tell us that iodide complex will have the pseudo tetrahedral geometry like the one on left. 

I also know that complexes with lower symmetries have higher QS. This might explain the QS value for the iodide complex.

This problem was adapted from a publication:

http://pubs.acs.org/doi/pdf/10.1021/ic50190a021

If you read the paper, you will see that the authors did not have a crystal structure for the iodide complex. So, this problem is another example how useful Mossbauer Spectroscopy is. You can also read their discussion. To be correct, I read the paper first and then wrote my post.