UCLA

Physical Chemistry Seminar 228: Robert Baker
2023-11-27 16:00 - 17:00 (America/Los_Angeles) | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Baker Flyer
Title: Observing Ultrafast Electron Motion in Catalytic Systems: New Ways to Visualize Charge and Spin Dynamics at Interfaces
Abstract: Understanding and controlling electron dynamics at interfaces is at the heart of numerous applications ranging from heterogenous catalysis to information processing. To directly observe these dynamics, we have developed ultrafast XUV reflection spectroscopy as a surface sensitive analog of time-resolved x-ray absorption. In these measurements, high harmonic generation of attosecond to femtosecond XUV pulses enables real-time observation of charge and spin dynamics with element specificity, ultrafast time resolution, and near atomic layer surface sensitivity. This talk will highlight recent studies of surface electron dynamics in materials ranging from photocatalysts to magnetic semiconductors to systems displaying chiral-induced spin selectivity (CISS). In addition to ultrafast electron transfer, we also study the interfacial solvation structure in electrocatalytic systems using in-situ sum frequency generation vibrational spectroscopy. This complimentary tool enables direct measurement of solvent-mediated electric fields at catalytic interfaces, which are found to significantly influence the kinetics of electrochemical CO2 activation and reduction. Last, I will briefly describe the National eXtreme Ultrafast Science (NeXUS) facility. This $10M infrastructure project provides attosecond and femtosecond pulses of XUV light with tailored bandwidth to a suite of experimental end-stations enabling molecular and material characterization with unprecedented temporal and spatial resolution. This facility, which is supported by the National Science Foundation, will soon become an international open-access user facility serving the entire chemical, physics, and materials communities.

Chem 248 Organic Chemistry Student Seminar: Elizabeth Croll
2023-11-27 15:00 - 16:00 | Collaboratory Yoo Seminar & Conference Hall YH4222

Physical Chemistry Seminar 228: Lu Wei
2023-11-20 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Wei Flyer
Title: Functional Bond-Selective Microscopy for Subcellular Bioanalysis
Abstract: Innovations in optical spectroscopy and microscopy have revolutionized our understanding in live biological systems at the sub-cellular levels. In this talk, I will present our recent advances in developing and applying functional bond-selective spectro-microscopy for investigating subcellular biological activities with rich chemical information. In the first part of my talk, I will present the novel coupling of the stimulated Raman scattering (SRS) imaging, a nonlinear Raman imaging modality, with the newly developed chemical strategies for Raman-guided intracellular metabolic mapping; quantitative subcellular analysis of cytoplasmic aggregates; photo-activatable and photo-switchable SRS spectral-imaging; intracellular sensing through alkyne-HDX; and toward super-resolution chemical imaging. In the second part of my talk, I will present a new mid-infrared near-infrared two-photon imaging technique for bond-selective fluorescence imaging with single-molecule sensitivity.

Chem 248 Organic Chemistry Student Seminar: Aris Rubio
2023-11-20 15:00 - 16:00 | Collaboratory Yoo Seminar & Conference Hall YH4222

Dickerson Biochemistry Seminar – Stuart Conway and Soumitra Athavale
2023-11-17 15:30 - 16:30 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States

Distinguished Lecture Series: Prof. David Christianson
2023-11-16 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Title: Directing Biosynthesis with Modular Architecture in Terpene Cyclases
Abstract: Terpene cyclases catalyze the most complex chemical reactions in biology, in that more than half of the carbon atoms in an isoprenoid substrate undergo changes in bonding or hybridization during a multi-step cyclization cascade that proceeds through multiple carbocation intermediates. Although the substrate pool for these enzymes is limited to only a handful of linear isoprenoids, more than 100,000 terpenoid natural products have been identified to date. Crystal structures of terpene cyclases reveal common, modular protein folds that direct unique catalytic strategies underlying this exquisite chemodiversity. Most recently, structural studies of bifunctional assembly-line terpene synthases using cryo-EM and other biophysical techniques show how the first two steps of terpene biosynthesis are combined in nanoscale oligomeric assemblies. Cluster channeling within the oligomer ensures efficient carbon management in wild-type and mutant enzymes.

Jeffrey I. Zink Inorganic Chemistry Seminar Series: Phillip J. Milner
2023-11-15 16:00 - 17:15 | Collaboratory Yoo Seminar & Conference Hall YH4222
Flyer:Prof. Phillip Milner Flyer
Title: “Simplifying Synthesis at the Interface of Organic and Materials Chemistry”
Abstract: Porous framework materials, including metal-organic frameworks (MOFs), are highly tunable materials with myriad potential applications ranging from chemical separations to gas storage to catalysis. This is due to the unusual local environment offered by their pores. Herein we will discuss how this tunability can be used to unlock new reactive species relevant to organic synthesis and catalysis, focusing on fluorination chemistry, which is critical to the pharmaceutical, polymer, and agrochemical industries. We will also draw inspiration from organic chemistry for the design of new chemical separations and electrocatalytically active materials.

Physical Chemistry Seminar 228: Lisa Fredin
2023-11-13 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Fredin Flyer
Title: Modeling Photoactive Organic Materials
Abstract: Chemical intuition is well developed for single molecules but the extent to which disorder in solid state molecular materials contributes to their properties is poorly understood. In particular, molecular materials move charges in some directions much more efficiently than others due to the packing of the molecules. Noncovalent interactions between the molecular components mean that dynamic disorder in these materials can have a large impact on the electronic properties of these materials at room temperature. This work explores how packing and vibrations in organic crystals affect charge transport in light driven devices. In particular, the size of dynamic disorder due to phonons or electronic excitation of molecules in the crystal is predicted for well-ordered high-mobility single crystals.

Chem 248 Organic Chemistry Student Seminar: Marcelo Mazariego
2023-11-13 15:00 - 16:00 | Collaboratory Yoo Seminar & Conference Hall YH4222

Houk-Jung Organic Colloquium 247: Prof. Abby Knight
2023-11-09 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Knight Flyer
Title: Biomimetic Hierarchical Structure in Synthetic Macromolecules
Abstract: The remarkable functions of proteins, from refined binding profiles to efficient catalysis, are currently unrivaled by synthetic macromolecules due to complex hierarchical structure in natural systems. Inspired by this grand challenge, the Knight group is at the interface of chemical biology and polymer science, developing synthetic strategies to control hierarchical structure and high-throughput platforms to understand fundamental design principles underlying macromolecule conformation. These research efforts are motivated by the need for innovative strategies to address global health and environmental challenges, where our foundational work informs the de novo design and development of functional polymeric materials.

Chem 218 Student Exit Seminar: Zisheng Zhang
2023-11-09 12:00 - 13:00 | Collaboratory Yoo Seminar & Conference Hall YH4222

Jeffrey I. Zink Inorganic Chemistry Seminar Series: Elizabeth Young
2023-11-08 16:00 - 17:30 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Flyer: Prof. Elizabeth Young Flyer
Title: From Photodynamic Therapy to Photovoltaics: Photophysics of Pd(II)biladiene and Charge Carrier Dynamics in Thin Films of Light Harvesting Sb2S3
Abstract: Solar light harvesting and interconversion of solar energy into either electricity or driving force for small molecule activation reactions are critical to the production of energy and other processes that our society requires to function. In this talk, I will discuss two project united by photochemistry, each with their own application. In the first vignette, I will discuss a porphyrinoid complex, called a Pd(II)biladiene, This Pd(II)biladiene moiety was designed for use as a photosensitizer drug for photodynamic therapy. Up until this point, the excited-state dynamics of such biladiene complexes have been virtually unexplored. During our work on this moiety, we discovered that while excitation into the lowest-energy absorption feature of the Pd(II)biladiene complexes produces expected photophysics, interestingly, excitation into higher-lying excited states resulted in an additional, unexpected lifetime. I will discuss our work to propose the cause of this unexpected behavior. In the second vignette, I will discuss our recent work on stibnite (Sb2S3), which can be employed as the photoactive layer in next generation thin-film solar cells. Sb2S3 is of particular interest due to the suitable band gap of 1.7 eV and high absorption coefficient (1.8 × 105 cm–1 at 450 nm). I will present our work using transient absorption spectroscopy to directly observe carrier diffusion, electron transfer, hole transfer and charge recombination through uniform ultra-thin (< 3 nm) layers of insulating or transport materials deposited by atomic layer deposition (ALD) that are coupled to photo-active materials. Our results will be used to correlate the structure and function of material thickness and transport type to develop a fundamental, detailed, quantitative understanding of photo-induced ET dynamics through thin films of materials.

Physical Chemistry Seminar 228: Franz Geiger
2023-11-06 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Geiger Flyer
Title: Photonic Electrochemistry
Abstract: Water’s oxygen is the electron source in the industrially important oxygen evolution reaction, but how water interacts with an electrode remains enigmatic. While much microscopic insight into the Stern layer comes from atomistic simulations or joint theory-experiment approaches, water’s strong absorber problem has clouded our view of how water aligns in response to applied potentials. Here, we employ nonlinear optics with a non-resonant pulse triplet at Ni:NiOx electrodes during cyclic voltammetry at pH 13 to quantify 𝒩water↓, the Stern layer water molecules pointing their oxygen atoms towards the electrode, and Ftot, the total interfacial potential. 𝒩water↓ varies sigmoidally with applied potential, U, but linearly with Ftot. While there is no net alignment at U=0.4 V, 3/4 of a water monolayer align at U=0.6 V and Eflip, the energy associated with water flipping, matches liquid water’s cohesive energy. At U=0.8 V, all Stern layer water molecules (1 x 10^15 cm^-2) align and Eflip matches the cohesive energy of ice. The current density is exponentially sensitive to 𝒩water↓ and Eflip. Our experiments provide new benchmarks for electrical double layer models and a diagnostic tool for molecular electrochemistry.

Dickerson Biochemistry Seminar – Jorge Torres and Roy Wollman
2023-11-03 15:30 - 16:30 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States

Houk-Jung Organic Colloquium 247: Prof. Joel Smith
2023-11-02 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Smith Flyer
Title: Dearomative Alkaloid Synthesis
Abstract: Biologically active alkaloids continue to serve as a means of biomedical discovery in addition to serving as forcing functions for the invention of new chemical transformations. Structurally, many of these natural products and rationally designed drugs also contain one or more piperidine rings, making it the most common nitrogenous heterocycle amongst approved small-molecule therapeutics. Thus, the concise redox-economic construction of these heterocycles in the context of target-oriented synthesis has become a recent research focus in our lab. In particular, leveraging controlled and selective dearomatization reactions has enabled the concise synthesis of several natural products and approved pharmaceuticals from simple feedstock pyridines. Our lab’s recent synthetic efforts related to alkaloids from the lupin, ergoline, aspidosperma, morphinan and manzamine families of alkaloids will be discussed, articulating the breadth of targets that can be accessed by this strategic approach. In addition, both fundamental and translational opportunities afforded by our work in this area will be highlighted.

Jeffrey I. Zink Inorganic Chemistry Seminar Series: Professor Prashant Jain
2023-11-01 16:00 - 17:30 | Collaboratory Yoo Seminar & Conference Hall YH4222
Flyer: Prof. Prashant Jain Flyer
Title: “The Chemical Potential of Light”
Abstract: The interaction of light with molecules can be used to access new modes of chemical reactivity; however, this interaction is often difficult to exploit in a universal manner. I will describe how plasmonics is proving to be a general strategy for interfacing photons with molecules and activating chemical transformations and even inducing emergent chemistry. In my laboratory, catalysts based on plasmonic nanoparticles are allowing light to be used as a redox equivalent in chemical reactions, for promoting non-equilibrium chemical processes, for modifying product selectivity, for photosynthesizing fuels, and for boosting electrochemical conversions. I will provide a deeper view of the excited-state structures, species, and mechanisms that underlie these phenomena at the nanoparticle–solution interface.

Jeffrey I. Zink Inorganic Chemistry Seminar Series: Prashant Jain
2023-11-01 16:00 - 17:30 | Collaboratory Yoo Seminar & Conference Hall YH4222

Physical Chemistry Seminar 228: Hannah Shafaat
2023-10-30 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Shafaat Flyer
Title: Model Metalloenzymes to Catalyze the Reactions of Early Life
Abstract: Metalloenzymes catalyze the challenging chemical reactions that lie at the core of vital life processes, from carbon and nitrogen fixation to photosynthesis and respiration. Native metalloenzymes use only earth-abundant transition metals and operate under mild conditions, accessing reactivity that remains largely out of reach for synthetic systems. Given the importance of these fundamental processes in the context of energy, environment, sustainability, and human health, gaining molecular-level understanding into how metalloenzymes work is of the utmost importance. To this end, we are developing protein-based models as structural, functional, and mechanistic mimics of naturally occurring metalloenzymes. Targets to be discussed in this presentation include hydrogenase, carbon monoxide dehydrogenase (CODH), and acetyl coenzyme A synthase (ACS). These nickel-containing enzymes are implicated in chemoautotrophic origins of life and play key roles in the metabolisms of ancient bacteria and archaea. However, while these enzymes are highly functional within their cellular environment, most are costly to isolate, sensitive to external conditions, and generally poorly suited for large-scale application. Additionally, the multimetallic active sites and auxiliary cofactors obscure distinguishing spectroscopic features and render detailed analyses challenging. As a result, the molecular mechanisms of catalysis remain relatively poorly understood, thwarting efforts to build biomimetic synthetic systems that act with the efficacy of native enzymes. By combining functional studies of our model proteins with diverse spectroscopic techniques and computational investigations, we can obtain a comprehensive understanding of how the electronic and geometric structures dictate reactivity in each system. Reconstructing functional metalloenzymes “from the ground up” offers direct insight into the fundamental chemical principles driving the natural systems. Looking forward, we hope to apply these principles towards engineering effective systems for energy conversion reactions while learning about fundamental chemical transformations that may underlie the evolution of prebiotic processes into early life.

Chem 248 Organic Chemistry Student Seminar: Daniel Turner
2023-10-30 15:00 - 16:00 | Collaboratory Yoo Seminar & Conference Hall YH4222

Dickerson Biochemistry Seminar – Ellen Sletten and Danielle Schmitt
2023-10-27 15:30 - 16:30 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States

Houk-Jung Organic Colloquium 247: Dr. Liela Romero
2023-10-26 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Romero Flyer
Title: Highly Selective Catalytic Platforms for Reduction and Interhalogenation Chemistry: Our Early Explorations in ZrH and Lewis Base Catalysis
Abstract: Research in the Romero group is centered on the development and mechanistic study of novel catalytic reactions, with applications in natural product synthesis and drug discovery. To this end, we are exploring new avenues for the catalytic halo- and hydrofunctionalization of simple π-systems. The first research program regards our efforts to develop a unified strategy for the interhalogenation of alkenes and alkynes via Lewis base activation of sulfinyl halides. This approach furnishes vicinal dihalides with pronounced chemo-, regio-, and stereocontrol. Notably, when 1–3 mol% of a chiral Lewis basic catalyst is employed, a novel enantioselective bromochlorination of chalcones is realized. The second part of this seminar will focus on the development of a general platform for zirconocene hydride catalysis utilizing hydrosilanes as mild reductants. This catalytic system enables a variety of chemoselective and redox-economic functional group interconversions, including the catalytic semi-reductive diversification of amides and esters, as well as the hydrofunctionalization of alkynes.

Chem 218 Student Exit Seminar: Benqian Wei
2023-10-26 12:00 - 13:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States

Jeffrey I. Zink Inorganic Chemistry Seminar Series: Professor Jinyong Liu
2023-10-25 16:00 - 17:30 | Collaboratory Yoo Seminar & Conference Hall YH4222
Flyer: Prof. Jinyong Liu Flyer
Title: “Photodegradation of PFAS: Mechanistic Insights and Technology Development”
Abstract: The list of PFAS pollutants is expanding rapidly. PFAS pollutants have various chain lengths and end functional groups. These structural features substantially impact the molecular reactivity under reductive and oxidative treatment. The efficacy and efficiency of PFAS degradation systems also depend on solution chemistry, such as pH and the source of reducing/oxidizing species. This presentation will summarize our recent findings from treating over 60 legacy and emerging PFAS structures. The structure-reactivity relationship and system performance improvement will benefit the design of remediation systems for most PFAS pollutants.

Special Physical Chemistry Seminar by Prof. Sandeep Sharma
2023-10-25 13:00 - 14:00 | Collaboratory Yoo Seminar & Conference Hall YH4222
Sandeep Sharma Flyer

Physical Chemistry Seminar 228: II-Doo Kim
2023-10-23 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Kim Flyer
Title: Innovation in Nanomaterials Synthesis: from Lab to Commercialization
Abstract: Nanoengineering plays a pivotal role in optimizing nanomaterials to achieve enhanced performance and impressive mechanical stability, especially in challenging environments. Recent research has been dedicated to the creation of various novel composite materials, encompassing high entropy and multi-elemental nanoparticles, as well as the integration of stable single-atom catalysts onto robust supporting nanomaterials to ensure highly efficient catalytic performance. Effective catalyst design is essential not only for the advancement of chemical sensors but also for energy devices like lithium-air batteries, water-splitting, and CO2 conversion, and more. These active nanomaterials, including catalysts, must resist agglomeration, maintain high thermal stability during repetitive reactions, and necessitate minimal catalyst content for maximal performance. This presentation delves into diverse applications employing electrospun polymer fibers, metal oxide fibers, and carbon fibers. The presentation also outlines an expedited and optimal process for catalyst attachment onto electrospun nanofiber backbone structures. Lastly, a case study traversing the journey from laboratory research to commercialization spotlights the utilization of custom-made electrospinning equipment, roll-to-roll machines with nozzle arrays spanning 35 cm and 1.2 m widths. As electrospinning relies on solution-based processing, we can create a range of fiber types, including colorimetric, thermochromic, and antivirus fibers. Finally, I will conclude by offering insightful perspectives on innovative material synthesis using electrospinning and highlighting interesting case studies of device application

Dickerson Biochemistry Seminar – Joe Loo and Michael Lawson
2023-10-20 15:30 - 16:30 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States

Jeffrey I. Zink Inorganic Chemistry Seminar Series: Professor Yong Yan
2023-10-18 16:00 - 17:30 | Collaboratory Yoo Seminar & Conference Hall YH4222
Flyer: Prof. Yong Yan Flyer
Title: “Perovskite Semiconductors For Photocatalytic Organic Synthesis”
Abstract: Heterogeneous catalysis is responsible for the vast majority of chemical transformations, yet the direct employment of chiral solid catalysts for asymmetric synthesis is mostly overlooked. Our lab proved that photophysical properties of lead halide perovskites already proved for photovoltaics, also should be of interest in photoredox organic synthesis. Because the key aspects of these two applications are both relying on charge separation and transfer. We demonstrated that perovskites nanocrystals are exceptional candidates as photocatalysts, not only for fundamental organic reactions but also active for elusive asymmetric organic synthesis. Chiral 1-phenylethylamine (PEA)-hybridized perovskite PEA/CsPbBr3 NC photocatalysts exhibit an enantioselective (up to 99% enantiomer excess) avenue to produce N–C axially chiral N-heterocycles, i.e., N-arylindoles from N-arylamine photo-oxidation. Mechanistic investigation indicated a discriminated prochiral binding of the N-arylamine substrates onto the chiral-NC surface with ca. −2.4 kcal/mol enantiodifferentiation. Our perovskite NC heterogeneous catalytic system not only demonstrates a promising strategy to address the long-term challenges in atroposelective pharmaceutical scaffold synthesis but also paves the road to directly employ chiral solids for asymmetric synthesis.

Physical Chemistry Seminar 228: Rodrigo Noriega
2023-10-16 16:00 - 17:00 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Noriega Flyer
Title: Study and Regulation of Biomolecular Interactions at Electrified Interfaces
Abstract: We seek to understand the role of electrostatic interactions in molecular recognition mechanisms that are sensitive to structure but not sequence. An interesting model system for these multifaceted interactions is Loquacious-PD (Loqs-PD), a co-factor protein with two RNA binding motifs that recognize double-stranded RNA (dsRNA) regardless of their terminus structure. Loqs-PD regulates the terminus-dependent binding of the endonuclease enzyme Dicer-2 and is crucial to the efficient processing of sub-optimal dsRNA targets with a 3’ overhang terminus for gene silencing in Drosophila melanogaster.
To identify the effects of electrostatics and local dynamics on the formation and stability of dsRNA:Loqs-PD complexes, we study their binding and dynamics at electrified interfaces with a combination of mid-infrared surface plasmonics, time-resolved ultrafast fluorescence, and in situ electrochemical experiments at the surface of a degenerately doped wide-gap metal oxide. In this way, we distinguish distinct stages in the binding event between an RNA-binding protein and its target and follow dynamic events over multiple time scales. Time-resolved fluorescence measurements show a high affinity interaction that is strongly affected by electric fields, while mid-infrared surface plasmon observations detect a lower affinity interaction with a reduced (but still substantial) sensitivity to electric fields. In both cases, fluctuations are dependent on protein binding and the presence of electric fields.
Multi-stage binding process that arise from non-specific interactions are common between nucleic acids and proteins, and studies that employ complementary observations under controlled perturbations are a powerful tool to interrogate the link between molecular recognition and biochemical function.

SoCal TheoChem 2023
2023-10-14 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
Explore theoretical and computational chemistry with talks and poster sessions. Organized by Profs. Anastassia Alexandrova and Benjamin Schwartz at UCLA. Featuring speakers from UCLA, California State University Northridge, UC Riverside, UCSD, and Caltech. Abstract submissions are now being accepted. Free attendance, register by September 14 at http://www.chem.ucla.edu/~ana/SoCalTheoChem/.

Dickerson Biochemistry Seminar – David Eisenberg and Bill Gelbart
2023-10-13 15:30 - 16:30 | Mani L. Bhaumik Centennial Collaboratory, 607 Charles E. Young Dr., East, Los Angeles, CA, 90095, United States
