In chemistry, a compound is formed when atoms from two or more different elements form a chemical bond.
An ionic bond, for instance, involves the transfer of an electron from one atom to another. Essentially, one atom is gaining an electron while another atom is losing an electron.
Another type of bond- covalent- occurs when atoms share electrons.
In our daily lives, chemical bonds occur around us constantly. The rain (H2O) falling outside your window, the sugar (C12H22O11)in your coffee, and the carbon dioxide (CO2) you exhale are all examples of chemical bonds.
Hunter Hickox, a May 2018 PhD graduate in the Department of Chemistry, works at the fundamental chemical level to discover both unidentified compounds and unknown ways these compounds can form bonds.
Part of the Robinson research group led by Dr. Gregory Robinson, Hickox investigates the chemistry of main group elements. The most abundant elements on Earth, the group includes: Sodium (Na), Potassium (K), Calcium (Ca), Aluminum (Al), Carbon (C), Nitrogen (N), Oxygen (O), Sulfur (S), and Silicon (Si).
Most elements have a favored oxidation state that is primarily what exists in nature.
Generally, elements from the main group are in a positive formal oxidation state, which means they lack electrons. For example, in silicon tetrachloride, SiCl4, the silicon atom is in the plus four oxidation state, and each chlorine atom is in the negative one oxidation state.
The research group primarily focuses on synthesizing new compounds with low-oxidation state main group elements.
To create these low-oxidation state main group elements, Hickox works to perform reductions, or a lowering of the oxidation state.
In 2008, Hickox’s research group made a silicon compound with a lowered oxidation state (from plus four to zero).
“Since silicon usually exists in the plus four oxidation state, it usually contains four bonds of some type. However, you can isolate silicon that has fewer than four bonds, and has a lower oxidation state,” Hickox explains.
The second-most abundant element on the planet, silicon is used for all sorts of applications like semiconductors, polymers, concrete, etc.
Because of its many uses, understanding how silicon works is essential.
Hickox and his research group look into the fundamentals of silicon reactivity and bonding to investigate any new potential reactivity it may have.
“Dr. Robinson’s group is at the forefront of this type of low-oxidation state main group chemistry, and it was an area that really interested me, says. Hickox.
“It’s extremely difficult chemistry to do, because all of the compounds are highly air- and moisture-sensitive.”
This added amount of synthetic difficulty for every step in every reaction is what first drew him to the research.
“A lot of my work has been synthesizing silicon compounds with silicon in the plus twooxidation state, and only covalently bonded to two other elements, instead of the usual four. These compounds are highly reactive, and very difficult to stabilize, so we have to keep them in strict air- and moisture-free environments.”
Many of these low-oxidation-state main group species are important intermediaries in synthesis and catalysis.
“We suspect there are many applications in areas such as catalysis- or the acceleration of a chemical reaction- but we don’t know because none of these compounds have been made yet.”
Most of Hickox’s work has involved the synthesis of what are called silylenes.
A silylene is a silicon atom that is only covalently bonded to two other elements, and has a silicon-based lone pair of electrons.
The silicon atom in a silylene is in the plus two oxidation state, which is lower than what silicon is normally in. The lone pair of electrons on the silylene makes it extremely reactive.
“The first project I completed at UGA in 2015 involved the breaking of a silicon-silicon double bond, and the formation of two silylenes. I used a transition metal compound to break this bond, which was actually the first example of direct cleavage of a silicon-silicon double bond by a transition metal.”
Hickox explains that this was a surprising result, and led him to continue to investigate the formation of silylenes.
Hickox completed his second project in 2016- becoming the first to create a previously unknown silylene species Si(H)Cl, where the silicon atom was only bonded to one hydrogen atom and one chlorine atom.
Hickox graduates in May 2018 and plans to go into the industry to continue his research.
“I would love to continue to synthesize air-sensitive compounds. These types of compounds are highly reactive, and can be exceedingly interesting. I’m a very hands-on type of person, so I would like to continue to perform research, either for the government or private sector.”