Post 3: Cyanopyridine Study part 2

Cyanopyridine Study part 2

2NCPy CuI Products

Thus far I have characterized what I think to be 5 different compounds from 2NCPy. Since none of the compounds have had their formulas confirmed, they will be known by the color they luminesce under blacklight. These compounds are orange, yellow, green, and brown.

The most troublesome of them has been the black, it has formed in almost every synthesis I’ve tried and is especially prevalent when an excess of 2NCPy. It has no noticeable luminescence and it is theorized to be the cyclotrimerization of 2NCPy coordinated with CuI. Below are results of CHN analysis and AA which show results consistent with the cyclotrimerization hypothesis which would have a formula of (CuI)3L1 where L is the 2NCPy taken 3 times.

Cu % mass C % mass H % mass N % mass
Empirical 21.1 25.9 1.6 9.8
Theoretical 21.6 24.5 1.4 9.5

 

The brown compound was made using the same method described above for the 4NCPy. Using the KI method with a slight exess of ligand, a compound with a very faint brown luminescence was isolated. It is also suspected that the green yellow and orange product may transition to this brown product upon exposure to ether.

Not much is yet known about these more luminescent green, yellow and orange compounds. It is known that they can be rather unstable in common solvents like ether and methylene chloride which has caused some challenges. The one method we have devised to make these allotropes has been to dissolve 2mmol amounts of CuI and 2NCPy in 25ml acetonitrile. This is done by first dissolving the 2NCPy into 5mL acetonitrile then adding it dropwise to the larger 20 mL solution of CuI with continuous stirring. This prevents too much formation of the dreaded black product. After this point, the acetonitrile taken off either through vacuum or heating and the solution is either run to dryness, or saturation at which point it is filtered then put in the freezer. We have had quite a bit of trouble isolating these 3 luminescent compounds from one another. It seems that they all have the same stoichiometry with respect to the ligand and they often all form rather readily in the same reaction flask. Thus far we have been able to theorize that the orange product is stable under high heat and the other two products will transition to this product under said heat. The green and yellow product are theorized to be better suited to cold conditions. We have made a relatively pure bulk sample of the green one through crystallization of a saturated acetonitrile solution of our compound in the freezer. The yellow has been the most troublesome and we think it may contain some acetonitrile within its lattice because it is very unstable even under air and rather readily converts to the green or orange product. We think it would best be stored in a cold sealed environment without excess acetonitrile which could facilitate the transition
Thus far, only one consistent crystal structure has been found which was gathered using a crystallization dish with the acetonitrile solution described above. That crystal structure is a stairstep ladder shown below. Thus far our best estimates are that this is the crystal structure of the yellow allotrope of the compound

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Comparisons of the theoretical powder pattern of this crystal to the powder pattern of the authentic samples of the brown, green, and orange product has given very unconvincing results which appear not to match. But it is quite interesting to note that the green and brown compounds have very similar powder patterns which may suggest that they are actually the same compound but of varying purity. These comparisons are shown in the graph bellow:

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