Spectroscopy - Electrochemistry - Solar Energy Conversion

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October in the Dempsey Group

The fall semester is well underway here in Chapel Hill! We’ve slowly been watching the construction on the 4th floor of Kenan move along, and are looking forward to having a safer (sprinklers!) and more accessible (new bathrooms!) work space!

Last month, Melody and Hannah’s paper Exchange equilibria of carboxylate-terminated ligands at PbS nanocrystal surfaces was published in Physical Chemistry Chemical Physics!

We all had a busy summer, and almost everyone traveled to a conference to present their research. Debanjan, Tao, Katherine, Dan, Chris, Tayliz, and Jillian all attended the 3rd International Conference on PCET in Blowing Rock. Kunal and Cole came out for 2 days to catch some of the presentations. Jillian organized the meeting, and Dan and Katherine served on the local host committee. Katherine’s summary of PCET2018 was  recently published in ACS Energy Letters.

Carolyn and Melody attended the Nanocrystals Gordon Research Conference and Dan attended the Electron Donor-Acceptor Interactions Gordon Research Conference. Jillian traveled like a crazy person, attending AFOSR and DOE program meetings, a PCET workshop in Gottingen, the Organometallics GRC, the CCI Solar Fuels Capstone Meeting, the International Conference on Coordination Conference, the Electron Donor-Acceptor Interactions Gordon Research Conference, the ACS meeting, and a Packard Fellows Meeting. And a few weeks ago, most of the lab presented their work at the Triangle Student Research Competition.

September was a busy month for everyone, and we ended the month with a fun evening at Tru!

Spring 2018 Dempsey Group News Update

Lots of exciting things have been going on this spring in the Dempsey Group– and we’ve been too busy to keep our news page updated! If you’ve been following our twitter page though, you’re probably more up to date!

First, our three second year students– Carolyn, Melody, and Michael– all successfully passed their second year candidacy exams! Third year Katherine passed her proposal exam, and Dan presented his 4th year talk!

Debanjan Dhar, joined our lab as a postdoc in March. Debanjan received his Ph.D. with Bill Tolman at the University of Minnesota and he’ll be working on molecular electrocatalysis in our lab.

We said goodbye to Postdoc Dylan Gary, who headed off to anew position at Nanosys in California.

First year Tayliz Rodriguez and former undergraduate Hannah Starr were both awarded NSF Graduate Research Fellowships!

Dan, Hui Min, and Kevin’s paper, Bathochromic Shifts in Rhenium Carbonyl Dyes Induced through Destabilization of Occupied Orbitals, was accepted and published in Inorganic Chemistry. This work is the result of a successful adn exciting collaboration with Kelsey Brereton (UNC),  Alex Miller (UNC), and Greg Felton (Eckerd College). This paper expands on an underexplored method of tuning the absorption profiles of a series of rhenium(I)-based chromophores. Axial ligand substitutions are used to destabilize metal-based molecular orbitals on the molecules, resulting in dramatically increased visible light absorption. Time-dependent DFT is used to understand the influence the ligands’ effect on electronic structure and photophysical properties.

Michael helped launch a Course-Based Undergraduate Research Experience in the General Chemistry labs (Chem 102L) as a Graduate Research Consultant. The undergraduates worked to identify new oxygen-evolving materials as part of the HARPOON (Heterogeneous Anodes Rapidly Perused for Oxygen Overpotential Neutralization) Project. The whole lab helped run a booth at the NC Science Festival in April, and we welcomed visitors from the ADMIRES program to our lab in February!

Jillian gave the Dalton Transactions Lectureship at UC Berkeley, and presented work from the lab at the ACS Meeting in New Orleans (and co-organized an symposium on PCET PhotoCatalysis with Inorganic Molecules & Materials), the Solar Fuels GRC, the Inter-American Photochemical Society meeting, the Argonne-Northwestern Solar Energy Research (ANSER) Center Symposium, the NY local section meeting of the ACS, and visited UT El Paso as a student-invited seminar speaker.

And lastly, Jillian learned her promotion to Associate Professor with Tenure was approved by the Board of Trustees, effective 7/1/18!

Chris’s paper accepted to J. Phys. Chem. B

Chris’s paper, titled ‘Influence of Proton Acceptors on the Proton-Coupled Electron Transfer Reaction Kinetics of a Ruthenium-Tyrosine Complex’ was accepted to The Journal of Physical Chemistry B. In this paper, we report a polypyridyl ruthenium complex with fluorinated bipyridine ligands and a covalently bound tyrosine moiety and discuss its photo-induced proton-coupled electron transfer (PCET) reactivity in acetonitrile. PCET reactivity was found to proceed through an equilibrium ET-PT pathway in which irreversible deprotonation of the tyrosine radical cation shifts the ET equilibrium, conferring a base dependence on the reaction. Across the five pyridine bases explored, spanning a range of 4.2 pKa units, a linear free energy relationship was found for the proton transfer rate constant with a slope of 0.32. These findings highlight the influence that proton transfer driving force exerts on PCET reaction kinetics.

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