With the current rate at which we’re using oil, we’re setting ourselves up to run out of the resource in the next 60 years.

It’s no question that our world depends on the black liquid. In 2017 alone, the United States consumed approximately 7.28 billion barrels of petroleum, equating to about 19.96 million barrels consumed daily. Our dependence on oil is undoubtedly unsustainable, especially considering its detrimental effects on climate change. We’ve already explored solar panels, wind turbines, and nuclear reactions - but what about water splitting?

Source: World Economic Forum

More Than Just a Drink

Water consists of two bonded elements: hydrogen and water. Oxygen has no use for energy purposes, but the combustion of hydrogen can actually create large amounts of energy. However, the hydrogen in water is bonded to oxygen, the bond must be split to get the hydrogen. An efficient method to obtain hydrogen involves using a catalyst to help harness the energy from sunlight to split the water into hydrogen and oxygen, a method referred to as “artificial photosynthesis”. Thus, the purpose of the research project was to synthesize a ligand that serves as the catalyst for the artificial photosynthesis process.

Previous research conducted by Dr. Randolph Thummel and his research group indicated that a certain cyclic structure of a ligand is ideal for artificial photosynthesis catalysts. Various ligands were reported by the group to bind with metal ions to form a catalyst, each with different cavity sizes and rigidities. After discerning patterns between cavity size/rigidity and catalytic activity of many different ligands, the group and I determined that the complex E (seen below) should be an efficient water splitting catalyst.

Various ligands and complexes investigated by the Thummel group for catalytic activity

Organic Synthesis

the overall reaction scheme of ligands (1-4) and desired complex (E)

Combination

Different chemicals and organic materials were prepared in appropriate environments (such as oil baths and vacuum ovens) in order to synthesize our catalyst. We initiated our experiment with a compound called 3-bromo-2-nitrotoluene, and through a complex reaction scheme, synthesized 8,8’-diacetyl-3,3’-dimethylene-2,2’-biquinoline.

Purification

Two processes called column chromatography and thin-layer chromatography (TLC) were the processes for purification. These chromatography methods help separate different compounds according to their specific polarities. Thus, we identified the end product by collecting a sample that had a matching polarity with the desired product.

identification

Nuclear magnetic resonance (NMR) was used to identify the products that were collected through chromatography. The NMR machine alters the spin of hydrogen protons in order to observe their local magnetic fields. Different peaks show up on NMR graphs according to the relative position of hydrogen and other neighboring protons, distinguishing different organic compounds from each other.

Conclusion

In the end, the project, while unfinished, was still successful. The mass yield of the final ligand (4 in the diagram above) was too low, so the complex (E) was not fully synthesized. The low percent yield could have been attributed to many factors, including the heating time of the final ligand as well as the contamination of certain reagents. Next steps in the project include setting up smaller scale conversions of 3 to 4 so that we can determine the ideal heating time that produces the highest yield of 4. Once enough of 4 is made, we can integrate cobalt to make a complex that will serve as our final catalyst.

Want More Information?

You can click here for the official lab report or view below for the official poster.