Room 101

Room 101 | 8:45 a.m.

SPECTROSCOPIC AND COMPUTATIONAL CHARACTERIZATION OF ETHYLFLUOROSULFATE AND ETHYLCHLOROSULFATE: A GAS PHASE MICROWAVE STUDY

Presented by: Luis R. Padilla Jr.

Luis R. Padilla Jr., Victor Drewanz, Aaron J. Reynolds, Samuel A. Kenney, Kenneth R. Leopold*

padil123@umn.edu and kleopold@umn.edu 

Upon studying the gas phase chemistry of the superacid fluorosulfonic acid (FSO2OH) via rotational spectroscopy, numerous unexpected, strong transitions appeared. Further analysis led to the assignment of the first rotational spectrum of ethylfluorosulfate (CH3CH2OSO2F) formed by sample contamination with ethanol. While the reaction between fluorosulfonic acid and ethanol is known in the condensed phase, its observation by gas phase microwave spectroscopy was unexpected. A computational and experimental investigation into the halosulfonic acid-alcohol product was further pursued to gain detailed knowledge of their lowest energy conformation. Replicating the conditions with propanol, methanol, ethanethiol, and 1-propanethiol all failed to yield any observable halosulfate product. However, when using chlorosulfonic acid (ClSO2OH) instead of FSO2OH, ethylchlorosulfate (CH3CH2OSO2Cl) was detected, and its rotational spectrum was assigned. Only the lowest energy conformers were observed because the molecules were cooled to ~2K in the spectrometer by adiabatic supersonic expansion. Experimental isotopic analysis and quantum chemical calculations support that these halosulfates are asymmetric in their lowest energy conformation. At high J quantum numbers, internal rotation line splitting was observed for the fluorinated species but not the chlorinated species. The line splitting is a result of quantum tunneling in the methyl rotor of CH3CH2OSO2F, yielding a V3 barrier of 1100 cm-1 ± 29 cm-1 consistent with theoretical calculations. Chlorine’s nuclear spin of 3/2 couples its nuclear angular momentum with the molecule’s rotational angular momentum, causing hyperfine line splitting. The nuclear hyperfine structure was resolved for both 35Cl and 37Cl isotopologues, which aided in assigning the ground state geometry.

Room 101 | 9:10 a.m.

PROBING NON-THERMAL PLASMA-LIQUID ELECTRIC FIELD MAGNITUDES IN OPERANDO WITH RAMAN SPECTROSCOPY

Presented by: Killian MacFeely

Killian MacFeely, Thomas Denton, Collin Clay, Peter Bruggeman, Renee Frontiera*

macfe001@umn.edu, rrf@umn.edu

Atmospheric pressure, non-thermal plasma-liquid interactions have garnered interest in driving redox chemistry. These interactions have been shown to offer alternative chemical reaction pathways that can reduce the need for dangerous experimental conditions such as high temperatures, pressures, or harmful solvents frequently used in chemical synthesis. Plasma driven solution electrochemistry is facilitated by the generation of highly energetic species that can overcome energy barriers, in ambient conditions, to produce economically valuable products. Despite significant research into non-thermal plasma-liquid systems, many physical characteristics in solution during the two phase interaction are not well understood and present a barrier to fully understanding the mechanisms by which plasma-liquid redox chemistry takes place. As an applied electric field is used to drive this plasma-liquid chemistry, the magnitude of the electric field in solution near the interface is of particular interest and has not been experimentally quantified in this system. Here, we report on the construction of a Raman laser system to measure the solution’s interfacial electric field magnitude in operando. By using molecules sensitive to externally applied electric fields and tuning Columbic shielding by varying salt concentrations, we seek to quantify the electric field magnitude in solution within the nanometer scale length regions of the plasma-liquid interface. Our measurements suggest probe molecules near the interface experience an electric field an order of magnitude larger than current computational predictions. These measurements impact our current understanding about the range of reduction-oxidation reactions available to occur and will directly inform future modeling of these systems.

Room 101 | 9:35 a.m.

UNDERSTANDING THE EFFECTS OF COMPETING SPIN-PAIR DEPHASING PATHWAYS IN MOLECULAR SPINS

Presented by: Timothy J. Krogmeier

Timothy J. Krogmeier, James Bradley, Anthony W. Schlimgen, Kade Head-Marsden* 

krogm033@umn.edu, khm@umn.edu 

Molecular spins offer promise in emerging quantum technologies such as quantum sensing and computing. At low temperatures, nuclear spin-spin interactions affect electron spin coherence lifetimes through pure dephasing. Nuclear spin noise can originate from spin pairs within a molecule itself, pairs in a surrounding environment system, or pairs in which one spin is on the molecule and the other in the environment. Improving coherence times requires detailed knowledge of the dominant sources of dephasing. Here, we analyze the decoherence behavior of two molecular qubit candidates with various ligands and in different nuclear-spin containing solvents. We apply an electronic-structure enhanced, non-Markovian perturbative theoretical method to connect experimentally comparable dephasing times to individual spin pairs. This analysis allows the development of a computational workflow to strategically improve coherence lifetimes in spin systems where decoherence is dominated by spin-spin dephasing.

Room 101 | 10:00 a.m. 

CHARGE-TRANSFER-INDUCED NEUTRALIZATION OF SPONTANEOUS ORIENTATION POLARIZATION IN ORGANIC LIGHT-EMITTING DEVICES

Presented by: Abhinav Kapur

Abhinav Kapur, Bella Lutfiyya and Russell J. Holmes*

kapur056@umn.edu, rholmes@umn.edu 

Organic light-emitting devices (OLEDs) based on vapor-deposited organic semiconductor thin films are widely used in modern information display technologies. Despite their predominantly amorphous nature, these vapor-deposited films frequently show short-range order and preferential molecular orientation. For molecules possessing an appreciable permanent dipole moment (PDM), this anisotropy leads to the formation of large intrinsic built-in polarization fields, a phenomenon known as spontaneous orientation polarization (SOP). In OLEDs, the presence of SOP in charge transport layers results in charge accumulation at low-bias and exciton-polaron quenching, thereby reducing external quantum efficiency and operational lifetime. Various strategies have been explored to engineer SOP and suppress its effects in OLEDs, including tuning of deposition conditions (e.g., substrate temperature and deposition rate), dilution with nonpolar host materials, and blending with polar materials exhibiting SOP with opposite magnitudes. All of these strategies seek to alter the final distribution of PDM orientations to tune the magnitude of SOP. 

In this work, we instead focus on introducing an opposing field that can cancel SOP without actually adjusting molecular orientation. Our approach targets the SOP-induced polarization field by doping the SOP-forming transport layer with charge-donating conductivity dopants. The introduced charges lead to a counter field within the SOP-forming layer, neutralizing the bound polarization charge that would normally lead to exciton quenching and efficiency loss. We systematically vary dopant concentration and host material to understand how the introduced charge screens the SOP-induced field. OLEDs incorporating conductively doped transport layers show near-complete elimination of SOP-induced quenching, demonstrating the effectiveness of this approach.

Room 101 | 10:40 a.m. 

PROTON TRANSFER IN THE GAS PHASE DRIVEN BY A SUPERACID: THE MICROWAVE CHARACTERIZATION OF THE TRIMETHYLAMMONIUM FLUOROSULFATE ION PAIR.

Presented by: Victor Drewanz

Victor Drewanz, Luis R. Padilla, Jr., Aaron J. Reynolds, Kenneth J. Koziol,  Kenneth R. Leopold*

drewa003@umn.edu, *kleopold@umn.edu 

Proton transfer is one of the most ubiquitous of chemical reactions, and is typically assisted by solvation. To better differentiate between intrinsic features of the reactants and solvent effects, we aim to characterize proton transfer without solvation. In this work, we employ microwave spectroscopy to study the gas phase complex formed between fluorosulfonic acid (FSO₂OH) and trimethylamine (TMA). Our results provide information about the molecular and electronic structure of the dimer, the latter being particularly sensitive to the position of the proton within the complex. Experimental data are in good agreement with quantum chemical calculations, which predict transfer of the proton from FSO₂OH to TMA such that the system is best described as an ion pair. The ability of fluorosulfonic acid to undergo proton transfer without the stability afforded by near-neighbor interactions is likely due to its superacidity. Simple arguments based on gas phase ion energetics are employed to rationalize the preference for ion pair formation over hydrogen bonding. By comparison with other acid-TMA complexes, both structural and electronic metrics used to assess the degree of proton transfer are shown to correlate with the deprotonation energy of the acid. The ability of the anionic conjugate base to delocalize charge may play a role in some cases, but deprotonation energy appears to dominate in superacidic systems. Overall, our results indicate superacids provide a useful means of studying gas phase proton transfer in complexes amenable to high resolution spectroscopic methods.

Room 101 | 11:05 a.m.

INVESTIGATION OF THE INFLUENCE OF DNA DAMAGE ON LIPID DROPLET COMPOSITION IN AML12 CELLS USING RAMAN MICROSCOPY

Presented by: Claire Arnold

Claire Arnold, Mahima Devarajan, Douglas G. Mashek, Renee Frontiera*

arnol621@umn.edu, rrf@umn.edu

The efficacy of harsh cancer treatments often relies on the damage they inflict on cellular DNA, which can affect cancer cells and healthy cells indiscriminately.  Fasting, which is known to stimulate lipolysis – the breakdown of triacylglycerols stored in lipid droplets (LDs) – has been shown to increase the effectiveness of chemotherapeutic drugs against cancer cells while simultaneously reducing chemo-related toxicity.  The mechanism behind this finding remains unclear, however, and a full understanding requires a deeper knowledge of the connections that exist among LDs, lipolysis, and DNA damage and repair.  Spontaneous Raman scattering microscopy offers a uniquely specific and non-destructive approach to identifying the size and chemical makeup of subcellular structures such as LDs through its characterization of vibrational modes across spatial regions.  Using this technique, we have imaged LDs in murine hepatocytes that have been subjected to a DNA damaging agent and identified compositional differences from LDs in control cells.  A detailed analysis of these images reveals a greater degree of unsaturation and a higher relative concentration of triacylglycerols among the lipid species present in the DNA-damaged cells as compared to those of their non-damaged counterparts.  The insights gained from these experiments shed light on the role of LDs in DNA damage and repair and can ultimately aid in the development of novel cancer therapeutics with increased effectiveness and decreased toxicity.  

Room 101 | 11:30 a.m. 

INFLUENCE OF CHEMISORBED N-HETEROCYCLIC CARBENES ON INTERFACIAL SOLVENT DYNAMICS AND HYDROGEN EVOLUTION REACTION OVER PLATINUM(111) SURFACES

Presented by: Emmanuel Adeniyi

Emmanuel Adeniyi, Matthew Neurock*

adeni054@umn.edu, mnuerock@umn.edu

N-Heterocyclic carbenes (NHCs) are strong σ-donor ligands in molecular catalysis that have emerged as promising surface modifiers for tuning the catalytic properties of transition metal surfaces. In this work, we examine the role of NHC functionalization on Pt(111) surfaces, with a focus on driving the hydrogen evolution reaction (HER) by combining potential-dependent density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. Initial static calculations established trends in adsorption energetic stability and charge transfer for different classes of NHCs, including imidazolium and mesoionic carbenes. These trends are further connected to changes in the surface electronic properties, including work function modulation, which serves as descriptors for interfacial reactivity. To capture solvent effects, AIMD simulations are carried out to examine water structure and dynamics at the NHC-modified Pt(111) interface. Analysis of structural stability, radial distribution functions, and diffusion behavior showed that NHCs perturb the interfacial water organization and mobility. These modifications depend on the sterics and electronic properties of NHCs, indicating that NHCs can systematically tune the local solvent environment. Potential-dependent ab initio molecular dynamics simulations are carried out to determine the interfacial changes that occur at the water/Pt interface and their effects on the Volmer step under acidic as well as alkaline conditions. The results suggest that gas-phase adsorption trends provide a useful baseline descriptor and that solvent reorganization plays a critical role in determining reaction energetics, particularly in alkaline media. This work demonstrates that NHCs influence HER steps through intrplay of electronic effects and solvent structuring at the interface.

Room 101 | 11:55 a.m.

METALLIC CONDUCTION AND ANISOTROPIC CHARGE TRANSPORT IN TETRATHIAFULVALENE-BASED CONDUCTING COORDINATION POLYMERS.

Presented by: Saranya Velliyarat

Saranya Velliyarat, Jan-Niklas Boyn*

velli013@umn.edu , jboyn@umn.edu *

Conducting coordination polymers (CCPs) combine the structural tunability of coordination chemistry with advanced electronic properties, making them attractive for flexible electronics, spintronics, and thermoelectric applications. Among them, tetrathiafulvalene (TTF)-based CCPs exhibit extended π- conjugation and rich redox chemistry, enabling metallic conductivities comparable to traditional inorganic semiconductors. However, charge transport mechanisms remain unclear due to interplay of π-conjuga- tion, electron-phonon interactions, and structural disorder. Here, we employ density functional theory and Boltzmann transport calculations to study the electronic structure and transport in NiTTFtt and related metal-TTFtt systems. Our results reveal that, metallic character arises from π-π stacking within the con- jugated framework, largely independent of metal identity and resilient to structural perturbations. Fe- containing systems exhibit spin polarization, indicating that magnetic functionality can be introduced with- out strongly compromising conductivity. Transport in NiTTFtt is highly anisotropic, dominated by polymer chain and π-π stacking directions, while inter-chain direction acts as the bottleneck. Ideal crystalline models overestimate experimental conductivities, and electron-phonon interactions alone cannot explain this discrepancy. Instead, structural disorder, especially disruptions to π-π stacking emerges as the key limiting factor, driving a crossover from band-like to localized transport and reducing conductivity to ex- perimental values while retaining metallic character. These results confirm that while metallic conduction is intrinsic to the π-conjugated framework, bulk performance is determined by disorder and grain bound- aries. The combination of robust metallic behavior, tunable magnetism, and mechanical flexibility high- light TTFtt-based CCPs as promising multifunctional molecular conductors.

Room 101 | 1:35 p.m

Selective Li ion Transport via Interpenetrated Crystal Growth on ZIF-8 Seeded Nanocomposite Membranes.

Presented by: Benjamin Clayville

Benjamin Clayville, Ji Yong Choi, Christian Wagner, William Warren Jihye Park* 

clayv001@umn.edu | j-park@umn.edu

Expanding reliance on Li-ion battery materials and the pursuit of next generation materials for energy storage and conversion necessitate extended control over ion transport. Leveraging size-sieving effects observed in nano-porous materials, ion exchange, reverse osmosis, and ion rectifying membranes, have realized promising utility in selective ion transport. However, these traditionally polymeric materials lack structural modularity with molecular precision to investigate, tune, and optimize nanoporous ion transport phenomena. Metal-organic frameworks (MOFs), overcome these barriers, synergizing permanent nanoporosity with well-defined periodic structures. Zeolitic imidazolate frameworks (ZIFs) in particular have exemplified the intimate nature by which small molecules interact with their network structures realizing efficient molecular separations. The ZIF-8 establishes uniform pore apertures of 3.4 Å, coinciding with the hydrated diameters of alkali cations. Herein, we leveraged the ZIF-8 network to establish a series of mixed matrix membranes (MMMs) to realize and tune alkali ion transport selectivity. Poly(vinylidene) difluoride (PVDF) was employed to prepare ZIF-8 based nanocomposite MMMs (5s-MMMs). The microstructure of the 5s-MMM was subsequently controlled to produce densely interpenetrated ZIF-8 via post-synthetic seeded growth (5c-MMMs). The mass transport limited ion conductivities of the cells in different alkali electrolyte solutions of the MMMs were evaluated in an H-cell. The hydrophobic PVDF and nanocomposite 5s-MMMs exhibited no diffusional selectivity and ion conductivities on the order of 10−12 S cm−1. However, 5c-MMMs exhibited ion conductivities on the order of 10−8 S cm−1 and realized diffusional selectivity favoring Li over Na and K ions, owing to the densely interpenetrated morphology of ZIF-8 on the membrane.

Room 101 | 2:00 p.m. 

OPTIMIZATION OF POLYMERIC MEMBRANES FOR MINIATURIZED ION-SELECTIVE SENSORS FOR CONTINUOUS AND REAL-TIME MONITORING OF ELECTROLYTES IN INTERSTITIAL FLUID

Presented by: Maria Komal

Maria Komal, Faija Farjana, Kuzivakwashe Madungwe, Sarah Swisher*, Phil Bühlmann*,Andreas Stein* 

komal007@umn.edu, a-stein@umn.edu

For a healthy human body, the concentration of essential ions such as potassium and pH is delicately maintained at appropriate levels. Imbalance in the concentrations of these electrolytes leads to various diseases and can be life-threatening. Current point-of-care devices are invasive and provide discrete measurements, with testing results taking hours or sometimes days, which is not suitable for situations that require urgent interventions. Recent developments in point-of-care devices include wearable patches of ion-selective sensors, which require miniaturization of all-solid-state ion-selective electrodes. In this work, we are developing a miniaturized gold microneedle-based ion-selective sensor array that measures pH and potassium concentration with a Nernstian response within their relevant ranges, combined with a localized ionic-liquid-based microneedle reference electrode. The miniaturization requires optimizing both needle geometry and the concentrations of the ionophore and ionic site molecules in the polymeric membrane to achieve a stable Nernstian response to target ion concentrations in a background of other ions. The key challenge in this miniaturization is that fewer binding sites (ionophore) are present for the target ion on a smaller electrode, which are further limited by the adsorption of the ionophore onto the high-surface-area carbon solid contact, leading to sub-Nernstian response. Therefore, adjusting the initial composition of the sensing membrane to account for the loss in the adsorption process can ensure that a sufficiently high ionophore concentration remains at the sample–membrane interface. This optimization yields a Nernstian response with a good selectivity in a miniaturized, wearable sensor array for continuous monitoring of electrolytes.

Room 101 | 2:25 p.m.

ENABLING IONIC CONDUCTIVITY IN METAL-ORGANIC MATERIALS (MOMs)

Presented by: Liam Warren

William Warren, Brianna Check, Joe Santarelli, Jihye Park* 

warre522@umn.edu, j-park@umn.edu 

Electrochemical means of energy storage have been pioneered for their high renewability and effectiveness as mainstream opinions on natural gas have soured over its environmental and ethical concerns. Highly conductive materials, such as graphene and certain metal oxides, are well known as effective storage materials. However, reconciling electrical conductivity and ion transport in the same material is elusive due to their differing mechanisms, and material constraints. To address this gap in the literature, new materials are developed to investigate post-synthetic strategies to enable mixed ion-electron conductivity. Conductive metal-organic materials (MOMs) are a class of advanced materials with promising application in electrical conductivity and ion storage/transport. Two materials have been carefully designed for mixed conductivity. The first, Copper-Octadehydrobenzoannulene[OH] (Cu-ODBA[OH]) is a crystalline, alkyne-conjugated MOM with good electrical conductivity (6.9 x 10-4 S/cm) designed to use sp carbon-ion bonding interactions to promote ion conductivity and storage. The second, Cu-Truxone, which is part of a family of electrically conductive truxene-based MOMs, possesses functional carbonyl sites that can be used for further, post-synthetic, modification via amine reactions. Post-synthetic modification adding aliphatic carbon chains has successfully been shown to significantly increase hydrophobicity in the material, a necessary component for electronics in wet or humid environments. Further functionalizion will be explored to help elucidate the role polar functional groups, such as PEG, can play in promoting ion conductivity in MOFs. These materials will provide key insights into ion conductivity in crystalline conductive materials.

Room 101 | 2:50 p.m. 

3D MANGANESE-BASED ELECTRICALLY CONDUCTIVE METAL-ORGANIC FRAMEWORK WITH ELECTROCHROMIC PROPERTIES

Presented by: Kathryn Bairley

Kathryn Bairley, Joe Santarelli, Liam Warren, Jihye Park*

bairl001@umn.edu, j-park@umn.edu

Electrochromic materials exhibit a reversible, redox-driven change in optical properties (e.g., color, transmittance, reflectance) in response to an applied potential. This unique characteristic enables many practical applications, including electronic displays, smart dimming windows, and adaptive camouflage. Metal-organic frameworks (MOFs) are porous, crystalline materials composed of organic linkers coordinated to metal nodes. MOFs exhibit high intrinsic surface areas and form a dense array of active sites (i.e., metal nodes) with enhanced molecular accessibility. While most MOFs are inherently insulating, thus limiting electrochromic performance, d-π conjugation can be introduced through rational combinations of molecular building blocks to impart electrical conductivity with a narrow bandgap. To study the effect of redox-active metal centers on optical modulation, we have successfully synthesized a new Mn-based c-MOF. By combining a common redox-active linker (HHTP) with a redox-active metal node (i.e., Mn), we have achieved a 3D c-MOF with moderate conductivity (~10⁻⁶ S cm⁻¹ ). Based on the observed PXRD pattern and faceted crystal growth, we propose a 3D crystal structure with octahedrally- coordinated metal clusters. Mn-HHTP thin films have been synthesized via in-situ growth on FTO glass to study the electrochromic properties by cyclic voltammetry in 0.1 M KPF₆ in acetonitrile at a scan rate of 100 mV/s. We observe two distinct color changes from yellow to green and to black within a potential range of −1.5 V to +1.0 V. These results highlight the potential of redox-active metal centers for electro- chromic materials.