[Maleficus187]

I'm having trouble with a charge transfer complex of iodine and imidazole. I have tried probably a dozen times to add an imidazole solution to and iodine solution (both in chloroform, but I have tried in cyclohexane, n-pentane, and dichloromethane as well) and I have only gotten good results my first or second time. When I first began I did a quick addition just to see if I got a reaction. I got a very small amount of precipitate so I tried a dropwise addition with stirring to help facilitate particle growth from there on out. My first quantitative attempt and ended up getting about 25% mass yield back and after a few more days I got another 25% of the mass upon a second filtration. From this point on, I have not gotten more than 1-2% mass yield if any out of any of my attempts. Every time in chloroform and dichloromethane I got a strong color change from violet to brown upon addition of the imidazole solution, but many of them I do not get any precipitate. I have done XPS on my first trial where I got about 50% yield and elemental analysis on that same product, as well as another attempt to form the complex in a 1:2 ratio (just for good measure to ensure that the product does not form a 1:2 complex) where I got about 2% yield. XPS results looked fairly good in my nitrogen to iodine ratio, and elemental analysis was spot on for my first product and just slightly off for my 1:2 ratio attempt. I have tried increasing the concentrations of both reactants, one reactant, checked the pH of my solutions, and I just cannot get the same results as my first trial. I have also tried using ABCO in chloroform with iodine and got the same results of a color change but no precipitate. I have tried doing the addition in the dark to prevent a further reaction of the CT complex from light. My first trial was using iodine left over in my professors lab from about 10 years ago, and most of my trials after that were performed with the same iodine, but today I even tried a fresh solution with new iodine I just got last week. My next attempt is to try degassing the solutions. Does anyone have any other ideas of what my problem could be?

[malcolmb]

Hi Jeherr,

I must say from the start that I don't really have much experience with CT compounds, but it sounds like you're making it each time if the colour's changing. If you're using a solvent like DCM, then why don't you just leave it to evaporate a bit in the dark to prevent decomposition. Perhaps the solution is just not concentrated enough? Or vacuum off your solvent while keeping your flask cold (you'll need a very strong pump for that though). You've probably thought of all this, but I thought I'd share it anyway. Good luck with your research!