Hi Jubyeong,

I really doubt if you would find a recent paper focusing mainly on the effect of metal-ligand ratio simply because this is one of the generally accepted concepts if you ask me. However, people might discuss this while looking at other effects or properties which is probably why your search is quite difficult. The easiest way I would suggest is to find a book (maybe an inorganic chemistry textbook), find the section where this effect is discussed, get the references used in that section and those references should lead you to many other articles discussing this topic. You can do the same with the articles that Yahia suggested.

But if I were to give an advice here, don't see this as increasing the metal concentration or increasing the ligand concentration and so forth. It is simply a matter of stoichiometry no matter how you look at it (see section 3.1. in the attached document, never mind the stereochemistry but just the susbtitution). If you have 1 metal capable of coordinating to 2 ligands but you only give it 1 ligand (1:1 ratio), you will have a mono-coordinate complex. If you give it 2 ligands, you will have a bis-coordinate complex. Now, what you did is exactly this but in reverse. You took 1 ligand and gave it 0.5 metal (i.e. that is capable of coorinating to 2 ligands, note that 0.5 is assumed as representative of a low metal concentration) thus you got a bis-coordinate complex because the ratio is 2:1 still. At higher metal concentration you achieve a 1:1 ratio and thus you end up with a mono-coordinate complex.

I hope this helps.

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