October 28, 2020, 05:01:25 PM
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Topic: Large metal ion template reaction  (Read 269 times)

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Offline tbmcd

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Large metal ion template reaction
« on: May 06, 2020, 08:37:02 AM »
I have a slight problem with an undergrad question relating to a supramolecular template reaction.
It states that when phthalonitrile is reacted with uranyl acetate it forms a macrocyclic complex with an intense peak in the mass spectrum at m/z 1322.4.
Learning about metal phthalocyanines in the past it seems like phthalonitrile can polymerise to form a macrocycle with a suitable hole size to accommodate whatever metal ion occupies it (like this https://imgur.com/a/pwPN4V9). However, in this case, I've been having a lot of trouble finding the possible structure of this complex.
Assuming that the molar mass is given by the mass spectrum I thought that you might be able to find the molar mass of the macrocycle by doing this...
1322.4 g mol-1 = M(uranyl) - n*M(phthalonitrile)
1322.4 g mol-1 = 270.03 g mol-1 - n*128.13 g mol-1
∴n = 8.21
However n should be an interger as it is stoichiometric no?
This made me think there could be a possibility of a dinuclear uranyl bridge via acetate/hydroxide somehow.
However, after doing a lot of similar calculations including those I never really got quite spot on the reported m/z value of 1322.4...
eg. One structure I attempted to draw up to try and achieve the m/z value but I was slightly off:
270*2+6*128.13+17=1325.78 g mol-1
(I probably haven't drawn it correctly sorry, I think all the macrocycle bonds to the uranyl ion should be in the same equatorial plane - no clue if the conjugation makes sense or even the charge now I think of it, or if single hydroxyl bridging is even possible for dinuclear complexes ???)

I'm batting to figure out a plausible structure and was wondering if I was possibly missing something blatantly obvious, or if anyone had any suggestions regarding the structure?
Many thanks!

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