Title: Synthesis and Analysis of 2,2Dimethyl4,4Bipyridine Crystal Complexes
1Synthesis and Analysis of 2,2-Dimethyl-4,4-Bipyr
idine Crystal Complexes
- David Carnevale 09 (sponsor Professor M. M.
Turnbull)
Results
Abstract
Recent work done by the Turnbull research
group has produced ladder complexes of
2,3-dimethylpyrazine, which delivered intriguing
magnetic exchanges along the rail of the ladder.
My research was to attempt to create ladder
complexes of 2,2-dimethyl-4,4-bipyridine
(2,2-Dm-4,4-bpy), in order to analyze the
effect of separating the methyl groups while
keeping the same structure around the metal
halide. By putting the molecule in this
orientation, the magnetic exchange along the rung
should remain the same, while the exchange along
the rail should differ from the pyrazine complex.
IR spectra, X-Ray diffraction, and SQUID data
will be taken on the compounds as part of the
analysis.
From the IR data, it was observed that the
products were different from the starting
materials, but similar in nature, due to peak
shifts at 1596, 1534, 822, and 633. Due to
the products particle nature, an X-Ray
diffraction scan was initially impossible,
producing noisy and illegible scans. However,
once they were recrystallized, a proper X-ray
scan was possible. However, the SQUID data showed
that the the compounds were not ladder complexes,
due to the lack of a ?max on the M vs. T graph.
Something of interest occurred when the LogT vs.
LogM of both compounds was looked at, which
showed change in slope, meaning there is some
sort of phase change which occurs within the
compound.
These two pictures are the X-Rays scans of the
Cl2 product (left) and the Br2 product (right),
before recrystallization. The peaks are roughly 5
degrees wide, which makes them unusable.
Due to the issues with the compounds we
determined that recrystallization was necessary
in order to proceed. It was possible to
recrystallize the Br2 product by dissolving the
compound in a minimal amount of DMSO and layering
ethanol on top. The same method didnt work with
the Cl2 product, however the clumping factor was
improved by running a diffusion system, so that
the product formed slowly. By doing this, a solid
was produced, which took on a more crystalline
form.
Introduction
lt The picture to the left shows the Chi vs. T
graph, were the solids ladder compounds, you
would expect to see a maximum in the graph rather
than the exponential curve which is present.
The goal was to synthesize ladder complexes
based on the basic equation of Cu(2,2-Dimethyl-4,
4-Bipyridine)X2 where X2 is either Br2 or Cl2.
One issue that arises with the synthesis of the
compounds is the severe difficulty in making
2,2-Dm-4,4-Bpy. This issue was remedied by
buying one of the seven grams of commercially
available product. Since there was such a small
amount of starting material, the compounds were
made in very small quantities and yields. The
compounds appeared to form according to the
planned formula, however the orientation of the
crystal complexes do not appear to be ladders.
These two pictures are the X-Rays scans of the
Cl2 product (left) and the Br2 product (right),
after recrystallization. These pictures are much
clearer and are usable for data.
Experimental
It was initially determined that 1,4-Dioxane
was a good solvent to use with 2,2-Dm-4,4-bpy,
however due to the low solubility of CuCl2 and
the later finding that our Dioxane was
contaminated, it was later decided that
Nitromethane would be a better solvent. The
compounds were prepared by combining CuX2
2,2-Dm-4,4-Bpy in equimolar parts, using
Nitromethane as the solvent. The two solids were
dissolved separately and then 2,2-Dm-4,4-Bpy
solution was added to the CuX2 solution. Upon
addition, in both cases, a solid immediately
precipitated out, the Cl2 product being blue,
while the Br2 product was an army green. When
the solutions were filtered, almost all of the
solid went through the filter paper, meaning the
particles were very fine, for both the Cl2 and
Br2 products. At first the solutions were
filtered through the same filter paper repeatedly
in order to recover the solid. Later, a fritted
disc filter was used to filter the solution,
which recovered almost all of the solid from the
solution. An issue that arose from the small
particle size was an inability to run a decent
X-Ray scatter on the solid.
Above are the graphs of the ChiT vs T (left )
and the 1/Chi vs T (right) from the first batch
of the Cl2 product that was made. The key issue
is that the two slopes are opposite of what they
should be (the left should look like the right
and vice versa). The two charts below show the
same charts, respectively, of a second batch of
the Cl2 product., which shows some improvement on
appearance, but still arent ideal.
The chart above shows the IR of the
2,2-dimethyl-4,4-bipyridine. The two charts
below show the IR of the Cl2 and the Br2
products, which show the peak shifts that occur
throughout the plot.
Conclusion
At present, a ladder complex of
2,2-dimethyl-4,4-bipyridine has yet to be
synthesized. The produced complexes need to be
studied further in order to determine the
orientation of the complexes as well as
determining the cause of the phase change that
occurs in the solid.