CMDITR Review of Undergraduate Research - Pluto - University of ...

suggests that any effects of
these on β are negligibly
small.
Dr. Bruce Eichinger
provided density functional
theory (DFT) calculations of β
for each of the new
chromophores. Experimental
β values for the new YNA
chromophores and their
analogs, along with the
theoretical calculations of β
for the YNA chromophores
are given in Table 1. It
should be noted that the
experimental and theoretical β
values are in different units, so
no quantitative conversion is
available. However, the
relative values can be used to
identify trends of the
molecules relative to each
other.
Figure 1.
YLII-18
YLII-37
YLII-39
TCF-1 or SHJ-1
EZ-FTC
CLD-5
Analysis and Aftermath
In the cases of YLII-18 and 39, the
experimental results were promising. As can be
seen in Table 1, the experimental β values for the
TCHP chromophores were somewhat higher in
both cases than those of their analogs. The
percent increase relative to the benchmark is
different for each chromophore, but taking
extremes, the results are within experimental
error.
Additionally, theory predicted that the ratio
of the β values for YLII-18 and YLII-39 would
be about 5.1, which is well within experimental
error. In fact, the error between the experimental
and theoretical relative β s (taking experimental
values as the accepted answer, which yields the
larger error) is less than 4%. In short, 1) the
TCHP had roughly the same effect on
experimental values relative to the benchmark
chromophores, and 2) the experimental β values
were in almost exactly the same proportion as
the theoretical values.
Taken together, these experimental and
theoretical data suggest that TCHP is a slightly
stronger acceptor than TCF.
However, YLII-37 breaks from this trend.
The experimental/theoretical ratio is roughly half
that of the other chromophores, and the
experimental β was much lower than that of the
benchmark. Furthermore, the acceptor is the only
difference between YLII-37 and its
corresponding chromophore, eliminating the
possibility that the discrepancy was caused by
another structural difference.
When these results were presented, they
prompted a new look at the NMR spectrum of
the YLII-37 sample. This revealed a likelihood
of significant levels of contaminants, which
could have yielded a lower concentration of
chromophore in the tested solution than was
factored into the calculations, attenuating the β
value.
Table 1.
β values
TCHP
Chromophore
experimental
Benchmark
Chromophore
experimental
YLII-18 / SHJ-1 2178 +- 297 1993 +- 62 32.7
YLII-37 / EZ-FTC 5615 +- 568 9834 +- 637 162.7
YLII-39 / CLD5 10713 +- 1212 7325 +- 644 166.9
YNA
Chromophores
theoretical
CMDITR Review of Undergraduate Research Vol. 1 No. 1 Summer 2004 23