Dany's Latest Adventues in Chemistry

Today has been an exciting day with Dr. Zheng and Dr. Corrales (a computational chemist I may have mentioned in an earlier post). Because Dr. Zheng was sick on both Monday and Tuesday, I unfortunately did not get the opportunity to begin lab work. However, we did discuss more specifically what my job will entail.

Before I get into details on what that job is, I should quickly provide a summary of how luminescence, or the chemical creation of light, works in the case of organic molecules. Light emission here starts with the idea of coordination complexes -- ie, molecules that form together to make bigger molecules. The coordination complexes Dr. Zheng and I are dealing with have one central ion and three outer ligands. What metal ion exists at the center of the coordination complex determines what wavelength of light is emitted upon excitation, regardless of when and how that excitation occurs.

The ligands, however, are a much more complicated matter. Their function is twofold. The first is to receive energy; this could be anything from passing a current through them to shining a light upon them. Ligands, here, are very much like the antennae that capture light and transfer it to the center of a photosystem in photosynthesis. The second function of ligands is to transfer energy to the central ion for light emission -- and this is where things become a little more complicated. Energy that wishes to leave the domain of the ligands may do so in a number of stages, known as 'singlet' or 'triplet' states. Energy could travel through many singlet states -- or none at all -- before getting to a single triplet state. If an electron does so happen to make it to a triplet state, it must then still transfer itself to the central ion of the coordination complex. The bad news? Across every "interstate" transition, energy loss occurs. This means that by the time an electron might make it to the central ion, there might be so little energy left that any feasible emission would be weak at best.

Currently, the focus of my research in the Zheng lab is to figure out what combination of ligands should be used for electron transfer. Indeed, the ligands are currently the foremost deterrent to achieving high energy transfer efficiency and thus luminescent efficiency at the moment -- experimenting with ligands of different characteristics (such as its electron donating/accepting ability) and putting together a trend of efficiency based on those characteristics would allow us to determine what is the most efficient luminescent compound.

So, this is where my work begins! In determining what kind of ligand best suits energy transfer, my first two "data points" will include the study of two compounds that are the same, but differ only by ligand. Next week, if all goes well, I will begin work on synthesizing these compounds and eventually comparing them as to whether electron "donating" ligands are more conducive to luminescence than are electron "withdrawing" ligands. Based on what conclusion I come up with, we will decide on what the third "data point" (compound) should be, and test to see whether this new compound fits the trend predicted by my first two data points.

This isn't even beginning to discuss the work I will be doing in the interim with Dr. Corrales. While I am creating these compounds, I will be learning how to model chemical compounds with a piece of software called NWChem. It's very easy to get overambitious with the use of this software, as it is terribly complicated, so I will need to start now learning how to model something as simple as a water molecule and increase in complexity from there. The eventual goal is to be able to create a modular setup that reflects the data points that I've found experimentally. That way, future chemists working in this field of study need not continue "stabbing in the dark" experimentally, so to speak, with various ligands and can determine a general idea of what the ideal coordinating complex ligand should be.

Hopefully, with all setbacks taken care of, I might finally proceed with beginning lab work and computational work next week. My third meeting with Dr. Corrales is on Tuesday; additionally, I will be meeting with another advisor who is experienced setting up computational calculations. In the interim, then, I will be studying lab recipes relevant to the creation of my first two compounds. The recipes themselves are embedded in a publication Dr. Zheng and his student collaborated on, so you can how good it feels to finally be able to understand a scientific publication (to an extent, of course!)